Plant Evo-Devo and my Morphological Thinking
The Evolution of my Morphological Thinking in my Publications and Plant Evo-Devo (Evolutionary Developmental Biology)
On the Broader Context: The History of Plant Morphology
The history of
plant morphology has been comprehensively illustrated in an
excellent article by the late Gérard Cusset:
Cusset, G. 1982. The conceptual bases of plant morphology. In: Sattler, R. (ed.) Axioms and Principles of Plant Construction. The Hague/Boston/London: Martinus Nijhoff/ Dr. W Junk Publishers, pp. 8-86 (also published in Acta Biotheoretica, Volume 31A).
When I studied
botany in the 1950s, I was taught mainly what is referred to
as classical plant morphology - “classical” because it has
one of its major roots in Goethe’s famous booklet on the
metamorphosis of plants. But as I carried out my
morphological research, I became increasingly aware of the
limitations of this kind of plant morphology, and I realized
that a number of other botanists, especially in the
also critical of the classical doctrine. Even Goethe himself
entertained alternative views. But the simplicity of the
classical view, which is based on the root-stem-leaf trinity
of plant construction, seemed so appealing that alternative
views were ignored or suppressed. As a result, students of
plant biology received a very one-sided education and
indoctrination. This one-sidedness still persists today,
although there seems to be more awareness of the limitations
of the classical model of plant construction. Cusset’s
article, referred to above, makes it very clear that
classical plant morphology is only one view besides others.
Research in Plant Evo-Devo (evolutionary-developmental plant
morphology) that relies to a great extent on molecular
genetics has also shown that the rigidity of the
root-stem-leaf trinity needs softening and modification to
accommodate novel evidence.
In the following paragraphs I want to show how my morphological thinking evolved, how it anticipated some insights of plant evo-devo, how it is compatible with evo-devo, and how in some ways - scientifically, philosophically and spiritually - it went beyond plant evo-devo.
I end this article with Conclusions on Plant Evo-Devo and my Morphological Thinking.
Towards a Continuum Morphology of Plants
morphology, that is, classical plant morphology, appears
categorical. Any organ of flowering plants must be either a
root, or a stem, or a leaf, or a homologue of one of them. I
found that although many or most organs can be fitted into
these categories, others appear more or less intermediate
between these categories. As a result, one can see the
diversity of plant form as a continuum that spans all the
categories. I first proposed this idea in my paper:
Sattler, R. 1966. Towards a more adequate approach to
comparative morphology. Phytomorphology 16: 417-429.
provided a much more detailed elaboration of continuum
morphology, especially with regard to the shoot, that is,
stems, leaves, and emergences (outgrowths of the organs)
(roots were not completely ignored since they may also occur
Sattler, R. 1974. A new conception of the shoot of higher
plants. Journal of Theoretical Biology 47: 367-382.
In retrospect I
think that a more appropriate title for his paper would have
been “The continuum conception of plant morphology.” I
realized that - as I already mentioned in my paper - the idea
of a continuum was not totally new. Other authors in the
recognized intermediates between categories. But since their
findings and views had been largely ignored and suppressed by
the scientific community of plant biologists, I was not
sufficiently aware of all of my predecessors in continuum
morphology. I learned much about them during a stay in Prof.
Gérard Cusset's laboratory at the University of Paris in
In my Biophilosophy book (1986, p. 105) I presented the continuum model of the shoot in the form of a pyramid, that is, a tetrahedron in which shoots, stems, leaves, and emergences occupy the four corners of the tetrahedron and intermediate structures the space between the corners. Dr. Ming Anthony and I extended this model to pathological plant structures:
Finally, in 1992
I published a paper with Dr. Bernard Jeune that established
quantitatively by means of multivariate analysis the
continuum between the categories of root, shoot, stem, leaf,
emergence, and their homologues:
As far as I know,
this was the first quantitative confirmation of the
morphological continuum that spans not only the categories of
the three types of organs of classical plant morphology but
also three of its organizational levels: the organ system
(shoot), organs (roots, stems, and leaves), and outgrowths of
organs (emergences). I am most
grateful to Dr. Bernard Jeune for his collaboration on this
project. Without his mathematical expertise I could not have
accomplished this difficult undertaking. Its results went far
beyond my first paper on continuum morphology (1966) - cited
above - in which I used a very simple example to indicate the
continuum between the stem and leaf categories.
Using a different mathematical approach and mostly different plant species, Gérard Cusset corroborated the continuum view of plant form (Cusset, G. 1994. A simple classification of the complex parts of vascular plants. Botanical Journal of the Linnnean Society 144: 229-242). Jeune and Sattler (1992) also confirmed the continuum in terms of process morphology (see below).
Although I worked mainly at the levels of organs systems, organs, and outgrowths of organs, it must be pointed out that the morphological continuum is not restricted to these levels. It can also be found at other levels of organization such as the levels of tissues and cells. For example, we demonstrated a continuum between different types of perforation plates in the cells of vessels (the water-conducting structures in plants).
Muhammad, A.F. and
Sattler, R. 1982. Vessel structure of Gnetum
origin of angiosperms. American Journal of Botany
Homology in Plants
Homology has been
called the central concept of comparative morphology. In
classical morphology, homology is conceived in terms of
either/or. But in continuum morphology homology becomes a
matter of degree, and thus a structure may be partially
homologous to a stem, a leaf, and even a root. Such
homologization seems inconceivable in classical morphology
where an organ must be homologous to either a stem or a leaf
or a root. Because of this insistence on categorical
homology, homologization in classical terms gave rise to
endless debates about the homology of intermediate
structures. But, as I pointed out in the following two
publications, if homology is seen as a matter of degree,
these futile debates can be resolved:
Sattler, R. 1984. Homology – a continuing challenge. Systematic Botany 9: 382-394.
Sattler, R. 1994. Homology, homeosis, and process morphology in plants. In: Hall, B.K. (ed.) Homology: The Hierarchical Basis of Comparative Biology. New York: Academic Press, pp. 423-475.
Fuzzy Logic in Plant Morphology
partial homology and continuum morphology involve fuzzy
logic, whereas categorical homology and classical morphology
are based on Aristotelian either/or logic. According to fuzzy
logic, membership in a class is a matter of degree. Hence, a
structure may be, for example, a 50%, 80%, or 100% leaf. I
briefly mentioned the importance of fuzzy logic (or fuzzy
thinking) in my article on Agnes Arber for whom
thinking in terms of degree was of great importance:
For a much more
detailed discussion of Agnes Arber’s thinking in terms of
degree (that is, fuzzy thinking – a term she did not use, as
far as I know, because fuzzy logic was invented after her
death) see the excellent article by Rutishauser, R. and Isler, B. (2001).
Developmental genetics and morphological evolution of
flowering plants, especially bladderworts (Utricularia):
Fuzzy Arberian morphology complements classical
morphology. Annals of Botany 88:1173-1202.
For a general discussion of fuzzy logic and its importance in practically all aspects of life see the excellent book by Bart Kosko. 1993. Fuzzy Thinking. The New Science of Fuzzy Logic. New York: Hyperion.
The words ‘fuzzy’ and ‘fuzziness’ appear distasteful to many people and especially to many scientists, I guess because these words are often equated with inexactness and vagueness, and science is supposed to be exact. However, fuzzy logic, as a quantitative approach, offers more exactness and precision than either/or logic. And continuum morphology, which reflects fuzzy logic, offers more precision than categorical classical morphology because instead of forcing the whole diversity of structures into mutually exclusive categories, it captures the whole range of structural variation. I guess if Zadeh, the inventor of fuzzy logic, would have called it ‘continuum logic,’ it would have been more palatable to many people; but Zadeh chose the name 'fuzzy logic.'
My Critique of Essentialism
thinking and essentialism appear closely related. I became
aware of the pitfalls of essentialism early on in my
morphological work and pointed them out in my paper “A new
conception of the shoot of higher plants (1974, p. 369)” (see
above in the section on Continuum Morphology). Later on in
1977, I elaborated on them in a paper I presented at an
international congress in Japan:
Sattler, R. 1977. Essentialism in plant morphology.
Proceedings No. 3, XIVth International Congress of the
History of Science. Tokyo & Kyoto, pp. 464-467.
morphologists tend to embrace essentialism consciously or
more often subconsciously. When they encounter structures
that do not fit the classical categories, they often insist
that these “misfits” represent the essence of one of the
categories. For example, for a structure that appears
intermediate between a stem and a leaf they would argue that
it is essentially a stem or a leaf. They might not agree
which one it is, but they agree that it must be one or the
other. Thus, the underlying belief or philosophy of
essentialism that dates back to Plato and Aristotle is used -
consciously or subconsciously – to force the whole diversity
of structural variation into fixed categories or essences. To
my mind, this implies a disregard of empirical findings in
favor of the preconceived notion of categories or essences.
Can we still call it science when intermediate structures can
no longer question the general validity of the categorical,
Evolutionary biologists generally reject essentialism. I have shown, however, that to some extent evolutionary plant morphology may also be trapped in essentialism because evolutionary plant morphologists often use mutually exclusive morphological categories and the use of such categories may imply essentialism.
I never denied that morphological categories have a limited usefulness because many, if not most, structures fit more or less the categories. However, intermediate structures don’t fit, and therefore continuum morphology appears more encompassing than categorical morphology. Categorical morphology can be seen as a special case of continuum morphology that seems appropriate for the extremes in the continuum.
As noted below, molecular genetics also supports the continuum view. For example, James (2009, p. 17) stated that "it is now widely accepted that... radiality [characteristic of most stems] and dorsiventrality [characteristic of typical leaves] are but extremes of a continuous spectrum. In fact, it is simply the timing of the KNOX gene expression!"
Fusion in Plant Morphology
The concept of
fusion plays an important role in plant morphology. Classical
plant morphologists distinguish two kinds of fusion: 1.
Fusion that can be observed (post-genital fusion), and 2.
Fusion that by definition cannot be observed (congenital
fusion). The latter is often used to make aberrant
configurations fit into the positional relationships required
by classical morphology. For example, according to classical
morphology, lateral shoots are supposed to arise in the axils
of leaves. If they arise on the leaf, they are said to be
congenitally fused with the leaf so that in reality they
would have arisen in the axil. But this fusion cannot be
observed. The observable processes were elucidated in two
epiphyllous species by Dickinson and Sattler (1974) and
(1975) (see my list of
Dickinson, who is professor at the University of Toronto
and the Royal Ontario Museum, also published an excellent
review article on the phenomenon of epiphylly (structures
on leaves): Dickinson, T. A. 1978. Epiphylly in
Angiosperms. Botanical Reviews 44:181-232.
In 1978, I published the following paper:
Sattler, R. 1978. ‘Fusion’ and ‘continuity’ in floral
morphology. Notes from the Royal Botanic Gardens Edinburgh
In this paper I tried to elucidate the observable processes that underlie the so-called congenital fusions. In this way I recovered the empirical basis where it had been lost or obscured through classical plant morphology.
Heterotopy in Plant Morphology
has been lost or obscured through the concept of congenital
fusion: heterotopy, which is a change in the position of
structures. Together with my
students and collaborators, I provided empiriral evidence for
heterotopy in several publications, and I
discussed the significance and implications of heterotopy,
especially for homologization and our conception of plant
construction (see, for example, the above paper on "A new
conception of the shoot of higher plants," 1974).
occur anywhere in the plant body. However, it is especially
important in the gynoecium of flowers, where it has often
been obscured through the application of the concept of
congenital fusion. In 1974, I published a paper in which I
introduced a gynoecial morphology that does not rely on
unobservable congenital fusions:
Sattler, R. 1974. A new approach to gynoecial morphology.
In retrospect, I
would prefer the title “An empirical approach to gynoecial
morphology” because this title would underline that this
approach is based on observable data. As a result of these
data, the floral concept of classical morphology had to be
revised in a rather fundamental way. My students and I
provided much empirical evidence for this revision (see my
list of publications for my
of Flowers (1973),
Macdonald and Sattler (1973), Posluszny and Sattler
(1976), Pauzé and Sattler (1979), Sattler and Perlin
(1882), and Sattler and Lacroix (1988)).
Homeosis in Plants
that at the site of one part of a plant another part or
feature(s) of another part of that plant are expressed. Thus,
for example, an axillary branch may be replaced by a leaf or
a structure with some features of a leaf and a branch. Such
cases cannot be understood in classical terms but require a
broader framework of continuum morphology and the notions of
partial or quantitative homology. I have discussed these and
other implications of homeosis in the following papers:
Sattler, R. 1988. Homeosis in plants. American Journal of
Sattler, R. 1994. Homology, homeosis, and process morphology in plants. In: Hall, B.K. (ed.) Homology: The Hierarchical Basis of Comparative Biology. New York: Academic Press, pp. 423-475.
and Sattler (1987) and Lehmann and Sattler (1992, 1993, 1994,
1996, 1997) investigated many cases of homeosis and
demonstrated their significance for plant development and
evolution (see my list of publications).
Developmental Hybridization in Plants
hybridization, leading to developmental mosaics, can be
considered a special case of homeosis in which features of
different structures are combined. If the different
structures are homologous in the classical sense (that is, if
they belong to the same category), the hybridization can be
understood within the framework of classical morphology.
However, if the different structures are not homologous in
the classical sense (that is, if they belong to different
categories or do not fit categories), then the hybridization
can be only understood in terms of continuum morphology and
its associated concepts of partial or quantitative homology.
Examples of this type of developmental hybridization are
compound leaves such as pinnate leaves that combine features
of leaves and branches and thus become mosaics. The following
papers present evidence for this phenomenon (see also
Rutishauser et al.
Sattler, R. and Rutishauser, R. 1992. Partial homology of pinnate leaves and shoots. Orientation of leaflet inception. Botanische Jahrbücher für Systematik 114: 61-79.
Lacroix, C.R. and Sattler,R. 1994. Expression of shoot
features in early leaf development of
(Rutaceae). Canadian Journal of Botany 72:678-687.
Rutishauser, R. and Sattler, R. 1997. Expression of shoot processes in leaf development of Polemonium caeruleum. Botanische Jahrbücher für Systematik 119:563-582.
I consider the
above publications important for several reasons: 1. They
illustrate the much neglected phenomenon of developmental
hybridization (although that term was not used in all of
these publications), 2. They support Agnes Arber’s partial
shoot theory of the leaf that has not received the
recognition it deserves, and 3. They show that developmental
hybridization is not restricted to rare "misfits" but occurs
also in common structures such as compound leaves.
Investigations of the molecular genetics of compound leaves also support our morphological conclusions. Eckardt and Baum (2010) stated that “it is now generally accepted that compound leaves express both leaf and shoot properties.”
Process Morphology of Plants
I have been
interested in plant development for a long time. Already for
my doctoral thesis, I chose to study floral development.
Subsequently, I continued developmental research. But, like
my colleagues, I did not realize that the way we studied
development was dynamic only to a limited extent. It still
involved some static presuppositions because although we
recognized that structures change during development, we
tacitly assumed that they retain their categorical status.
For example, we could see that a leaf changes as it develops,
but we took it for granted that it must remain a leaf. Thus,
we were locked into a dualism of something that could change
versus something – the category or essence – that remained
The process morphology that I began to develop in the late 80s is meant to eliminate this dualism that perpetuates static categorical assumptions. Therefore, this approach is not based on structural categories such as root, stem, and leaf. It is based on processes, and the diversity of plant form is seen as a diversity of process combinations. Ontogenetic as well as phylogenetic change is seen as a change in process combinations, not as a change in the properties or processes of structures.
It seems that many people find it difficult to see the difference between traditional ordinary developmental and evolutionary studies and process morphology. One way of emphasizing this difference is the following: According to the common way of thinking, structures have processes, hence there are structures and processes, whereas according to process morphology structures are seen as process(es), hence the structure/process dualism is overcome.
I first developed process morphology for floral development in a short paper that I presented in a symposium at the 14th International Botanical Congress in Berlin, Germany:
Sattler, R. 1988. A dynamic multidimensional approach to floral morphology. In: Leins, P. , Tucker, S,C. and Endress, P.K. (eds) Aspects of Floral Development. Stuttgart: Cramer, pp. 1-6.
generalized the process-morphological approach for all plant
Sattler, R. 1990. Towards a more dynamic plant morphology. Acta Biotheoretica 38:303-315.
Sattler, R. 1992. Process morphology: structural dynamics in development and evolution. Canadian Journal of Botany 70: 708-714.
with Prof. Rolf Rutishauser I showed how it works in
challenging concrete situations:
Dr. Bernard Jeune
and I demonstrated quantitatively that the diversity of
process combinations forms a dynamic continuum. Hence,
process morphology is also a continuum morphology:
In my last
morphological publication I used process morphology to
reconcile and transcend two very different views on the
evolution of plant form, namely Wolfgang Hagemann’s view and
Walter Zimmermann’s telome theory:
Sattler, R. 1998. On the origin of symmetry, branching and
phyllotaxis in land plants. In: Jean, R.V. and Barabé, D.
Symmetry in Plants.
Singapore: World Scientific, pp. 775-793.
In the following
book chapter I presented a summary and synthesis of continuum
and process morphology, homeosis and homology, including
partial homeosis, partial and quantitative homology:
Sattler, R. 1994. Homology, homeosis, and process morphology in plants. In: Hall, B.K. (ed.) Homology: The Hierarchical Basis of Comparative Biology. New York: Academic Press, pp. 423-475.
Plant Morphology, Language and Linguistics
Towards the end
of my career I became increasingly aware of how much the
language we use influences the results of morphological
research and scientific research in general. For example,
most languages have a noun-verb structure. Thus, we say ‘This
leaf branches.’ Since nouns often refer to categories, as we
employ nouns, we implicitly endorse categories, and as a
result, whether we like it or not, the continuum is obscured
or negated. For example, when we refer to leaves or stems we
endorse categories, unless we stipulate that a structure
is more or
less like a leaf
and more or
less like a stem, or
unless we specify a structure quantitatively as, for example,
a 40% leaf or a 60% stem.
Another consequence of the noun-verb structure: the structure-process dualism I referred to above in the section on process morphology. Verbs refer to action, to process, but nouns imply static. For example, a leaf may undergo all sorts of processes referred to by verbs, but it remains a leaf. Thus, the noun-verb structure imposes a static element on our description that does not seem to exist in nature. To eliminate this distortion we would need a language based on verbs only. According to Benjamin Lee Whorf and others such languages actually exist (see, for example, Carroll 1956). Some Amerindian languages such as Nootka consist only of verbs, according to Whorf, and others such as Hopi use predominantly verbs where we use a noun-verb structure. Many linguists deny Whorf’s assertion. However, one can have intelligent sentences without a noun. For example, instead of saying ‘The sun shines’, a Hopi would simply say ‘shining’, and thus would only refer to a process, not to an agent, the sun, that does the shining. Similarly, one need not postulate a creator for organic evolution and the evolution of the universe. Thus, as Whorf and others have pointed out, a process language gives us a very different perception of the world: not a world that is fragmented into agents (objects or entities) or a creator to whom processes are ascribed, but a world that appears simply dynamic. David Bohm referred to holomovement (movement within the whole). I briefly discussed these issues on my website and in the following publication:
Sattler, R. 1993. Why do we need a more dynamic study of morphogenesis? Descriptive and comparative aspects. In: Barabé, D. et Brunet, R. (eds) Morphogenèse et Dynamique. Frelighsburg: Orbis, pp. 140-152.
concerning language has been much emphasized by
and yet only few people have taken note of it. Korzybski
pointed out that language conveys an abstraction from
reality, not reality itself. Therefore, “whatever you
not” (which is
explained through his Structural
example, whatever we might say a leaf is, it is not. What
is it then? It is the unnamable, un-speakable mystery.
Thus, an understanding of language and its limitations
leads us beyond science into the unnamable,
which is beyond thinking (see also below the section on Plant
Morphology and Spirituality).
Nowadays at most
universities plant morphology is no longer taught as a
separate major discipline. It has been integrated into what
is called Evo-Devo (evolutionary developmental biology).
According to Plant Evo-Devo, the evolution of plants is seen
as the evolution of plant development. Long ago, in
der Planzen (1959), which as
far as I know has not yet been translated into English,
Walter Zimmermann referred to this process as hologeny, the
evolutionary succession of more or less modified ontogenies.
In his Fundamentals
of Palaeobotany (1987), Serge V.
Meyen provided profound insights into the relation of plant
development and evolution.
Plant Evo-Devo "involves a synthesis of molecular developmental genetics, evolutionary biology and plant morphology" (Cronk 2008). The emphasis is on the elucidation of the role of genes in the organism’s development and evolution. Researchers want to know which genes are turned on or off during the development of body parts. For example, which genes are turned on or off during leaf development? According to classical plant morphology, one might postulate that there are at least some unique genes involved in the development of roots, stems, and leaves, or, in other words, that the mutual exclusivity of the three major organ types is reflected in the mutual exclusivity of gene activity. However, so far molecular genetics has not confirmed this postulate. On the contrary, molecular genetics has provided evidence in support of continuum morphology and partial homologies. Rutishauser and Isler (2001:1190-1193) reviewed molecular genetic evidence in support of the continuum between leaf and shoot categories. Molecular genetic investigations by Hirayama et al (2007) showed that the phylloclade of Ruscus aculeata "is not homologous to either the shoot or the leaf, but that it has a double organ identity," which means that it combines shoot and leaf processes (as has been documented on purely morphological grounds by Cooney-Sovetts, C. and Sattler, R. 1987. Phylloclade development in the Asparagaceae: an example of homeosis. Botanical Journal of the Linneean Society 94:327-371). James (2009, p. 17) stated that "it is now widely accepted that... radiality [characteristic of most shoots] and dorsiventrality [characteristic of leaves] are but extremes of a continuous spectrum. In fact, it is simply the timing of the KNOX gene expression!" Also on the basis of molecular genetic research, Eckardt and Baum (2010) concluded that "it is now generally accepted that compound leaves express both leaf and shoot properties” (see also Uchida et al. (2010)).
In conclusion, results of evo-devo research support continuum morphology, the idea of partial homology, and partial homeosis. Evo-devo emphasizes process, but as far as I can see it has not yet completely overcome the structure-process dualism that implies a static element. As noted above, according to process morphology - that transcends this dualism - structures do not have processes, they are seen as processes.
The Fundamental Relevance of Plant Morphology
plant morphology – and morphology in general – is no longer
taught at most universities, it remains fundamentally
relevant to practically all disciplines of plant biology,
including plant evo-devo, because all disciplines rely and
refer to morphological concepts, if not explicitly at least
implicitly. In the following publication we pointed out this
relevance and showed how a lack of morphological knowledge
can be detrimental to research in other areas such as
Plant Morphology and Philosophy
could also benefit from a greater awareness of its
philosophical assumptions (see, e.g., Vergara-Silva, F. 2003.
Plants and the conceptual articulation of evolutionary
developmental biology. Biology and Philosophy 18: 249-284;
Tauber, A. I. 2010. Reframing developmental biology and
building evolutionary theory's new synthesis. Perspectives in
Biology and Medicine 53:257-270).
Like any other science, plant morphology relies on philosophical assumptions. Often we are unaware of these assumptions. But as we render them explicit, we can examine them:
Sattler, R. 1986. Biophilosophy. New York: Springer, Chapter 5.
One concept of
central importance: the type concept. Morphologists, other
scientists, and laypersons often refer to types. It seems
that they often imply classificatory types, which are
mutually exclusive, that is, they imply either/or logic. In
contrast, extreme types have fuzzy edges, that is, they imply
fuzzy logic. If we use extreme types, we can see the
continuum between morphological categories, and furthermore
we can bridge the gap between classical morphology and
continuum morphology as pointed out in the following paper:
Sattler, R. 1996. Classical morphology and continuum morphology: opposition and continuum. Annnals of Botany 78:577-581.
In a review of
the evolution of my morphological thinking, I have to
acknowledge that many morphologists and philosophers have
influenced me. If I had to single out one of them, which
seems difficult, if not impossible, I would name
Agnes Arber, especially
her books The
Philosophy of Plant Form (1950),
and the Eye (1954), and
and the One (1957). Some
of her most basic ideas characterize also my thinking. In
a short article – my last botanical publication – I
summarized these ideas:
Sattler, R. 2001. Some comments on the
morphological, scientific, philosophical and spiritual
significance of Agnes Arber’s life and work. Annals of
Complementarity in Plant Morphology
has a very rich history. Many different concepts and theories
have been proposed (see, for example, Cusset, G. 1982. The
conceptual bases of plant morphology. In: Sattler, R.
(ed.) Axioms and
Principles of Plant Construction. The
Hague/Boston/London: Martinus Nijhoff/ Dr. W Junk Publishers,
pp. 8-86; also published in Acta Biotheoretica, Volume 31A).
As I mentioned already, I think that evo-devo research could
greatly benefit from a knowledge of these concepts and
theories. They have often been perceived as antagonistic to
each other: it has been assumed that one must be right and
the others wrong. However, they can also be seen as
complementary to each other, illuminating different aspects
of plant form. Prof. Rolf
working in my laboratory, explored complementarity in
plant morphology in great depth and published three papers
on this topic with me, demonstrating how different and
even contradictory morphological theories complement each
other because they capture different aspects of plant
Rutishauser, R. and
Sattler, R. 1985. Complementarity and heuristic value of
contrasting models in structural botany. I. General
considerations. Botanische Jahrbücher für Systematik und
Rutishauser, R. and Sattler, R. 1987. Complementarity and heuristic value of contrasting models in structural botany. II. Case study on leaf whorls: Equisetum and Ceratophyllum. Botanische Jahrbücher für Systematik und Pflanzengeographie 109: 227-255.
Rutishauser, R. and Sattler, R. 1989. Complementarity and heuristic value of contrasting models in structural botany. III. Case study on shoot-like "leaves" and leaf-like "shoots" in Utricularia macrorhiza and U. purpurea (Lentibulariaceae). Botanische Jahrbücher für Systematik und Planzengeographie 111: 121-137.
both/and logic. Different, and
even contradictory statements are accepted as different
perspectives of the situation. Therefore, both/and logic and
complementarity represent what is called perspectivism that
underlines the many-sidedness of everything. The idea
of many-sidedness has been
Jain logic more than two
thousand years ago and yet it has been barely incorporated
into mainstream science and society. Increased awareness of
many-sidedness could have the most beneficial effects on
science and society: it could reduce conflicts and wars and
thus lead to a more peaceful world (see, for example, Aidan
Rankin. 2010. Many-sided
Plant Morphology and Spirituality
last book is entitled The Manifold
and the One (1957). In this
book she beautifully examines the relation and the oneness of
the manifold and the one. As a plant morphologist, I
investigated the manifold of plant form, and I also
recognized that, as Nobel laureate Barbara McClintock put it,
everything is one.” Any plant
form is connected to everything else. This is especially
evident when we recognize plant form as process, that is,
process combinations. The process combinations that
constitute, for example, a leaf are combined with the
process combinations of the whole plant, which are
combined with process combinations of the environment that
includes animals and humans. Ultimately, these process
combinations are combined with cosmic processes such as
solar radiation and cosmic radiation. Therefore, we may
say that a leaf or a plant is a cosmic event.
How does this cosmic event that includes me relate to spirituality? To many people spirituality is communion with spirit, and spirit is often seen as opposed to matter and form. From this perspective, morphology, the study of material form, cannot be related to spirituality. However, to non-dualists such as, for example, Ken Wilber, spirit includes matter, or more precisely, it includes and transcends matter. This integral spirit and spirituality do not exclude form. They allow us to see the divine in form. Form becomes sacred.
But in whichever way we refer to spirit, we must remember Korzybski’s insight that “whatever you might say something "is", it is not.” Therefore, whatever we might say spirit is, it is not. And whatever we might say a plant, a leaf, or a flower is, it is not. A plant, a leaf, a flower, and spirit are not the speakable, hence the un-speakable, the mystery that cannot be named.
Another way of relating plant morphology to spirituality is through Buddhism, especially the Hear Sutra. According to the Heart Sutra, form is emptiness and emptiness is form (see, for example, Tenzin Gyatso, the Fourteenth Dalai Lama. 2005. Essence of the Heart Sutra). "Form is emptiness" means that form lacks independent, intrinsic existence and therefore remains one with everything, with the whole universe. For example, a leaf or a plant have no independent, intrinsic existence. If they are seen as process combinations, these process combinations remain one with process combinations of the whole universe as noted above. Thus, morphological insight can be a path to oneness and wholeness. And wholeness is related to holiness, the sacred. We may talk about this. But rational, conceptual understanding has limits. We also have to feel it and be it. What is it? We may say: emptiness and form, or the one and the manifold. But as Korzybski indicated through his Structural Differential, whatever we might say it is, it is not because ultimate reality or ultimate truth remain unnamable, awe-inspiring mystery, source of mystical spirituality that may be acquired through spiritual practice such as meditation or sometimes may arise spontaneously.
English translations of the Heart Sutra vary. Lim Peng Eok (personal communication) translated the above passage as "The seen is the unseen. The unseen is the seen." Ordinarily, form is seen. But according to the Hear Sutra, it is also the unseen (emptiness), beyond our sensual perception and our linguistic representation. Experiencing and being the unseen in the seen seems the greatest challenge as it transcends and yet includes morphological research on the way to awakening and liberation.
I published two papers that include a discussion of the relation between plant morphology and spirituality:
Sattler, R. 1977. On “understanding” organic form. Sophia Perennis III:29-50.
Sattler, R. 1999. Divergence and convergence of sciences and spirituality: life science and spirituality. Holistic Science and Human Values, Transactions 4:41-48.
Professor T. Izutsu, author of Toward a
Philosophy of Zen Buddhism (1977) invited me
to write the first of the above two papers. The second paper
is based on a talk in a symposium on "Divergence and
Convergence of Sciences and Spirituality" at the 65th
birthday celebrations of the Dalai Lama.
Conclusions on the Evolution of my Morphological Thinking
thinking began with my indoctrination into classical plant
morphology. But already in the 60s my research led me to
continuum morphology and in he 80s to process morphology. And
all along since the 70s, as I became more familiar with
Buddhism and especially the Heart Sutra, I realized that form
has no intrinsic, separate existence because of dependent
origination that implies wholeness and oneness that
ultimately cannot be conceptualized.
In other words, my investigations of the manifold of form, first in categorical terms and then in holistic dynamic ways, led me to the awareness of oneness and the recognition that the manifold and the one are not two but one as Agnes Arber so beautifully explained in her book The Manifold and the One, Chapter 5: The Coincidence of Contraries (1957).
Conclusions on Plant Evo-Devo and my Morphological Thinking
relies to a great extent on concepts of classical plant
morphology. However, some evo-devo research supports
continuum morpology. For example, it has been shown that
radiality [characteristic of typical stems] and
dorsiventrality [characteristic of typical leaves] are but
extremes of a continuous spectrum that is due to the timing
of the KNOX gene expression (James 2009, p. 17). I think
that in principle evo-devo is also compatible with process
morphology, but in practice it still tends to be caught in
a structure-process dualism that implies static elements.
Besides process morphology, other findings and ideas of
morphology have not been sufficiently integrated into
evo-devo research. The rich morphological literature
offers much that could be relevant to evo-devo. For
example, phytonic theories (see Cusset 1982) and repeating
polymorphic sets or refrains (Meyen 1987) could provide
additional interesting frameworks for investigation. More
awareness of philosophical assumptions underlying evo-devo
research could provide more profound understanding. For
example, an awareness of the phenomenon of emergence could
enlarge the scope of the molecular genetic reductionism
that tends to prevail in evo-devo research. Investigations
into the role of self-organisation and morphogenetic or
morphic fields could also be beneficial. Morphogenetic
fields may be understood in terms of a physical basis as a
chemical pattern, an electromagnetic field, or an
attractor pattern of a complex, non-linear process, or
they may be conceived as having no physical basis
101-106). The latter view has been elaborated by
Rupert Sheldrake (2009, 2012).
Although not materialistic and mechanistic as mainstream
biology, it is scientific in the sense that it is testable
and has been confirmed through many observations and
experiments. Inclusion of the environment would expand
evo-devo to eco-evo-devo (Tauber 2010). Recognition
of the complementarity principle (both/and logic) could
enlarge evo-devo perspectives. It could lead to a very
inclusive vision that has been referred to as
inclusionality. Finally, an
awareness of the limitations of language could open vistas
beyond evo-devo and science towards the unnamable, the
mysterious, the spiritual, the sacred. For “whatever you
whatever we might say spirit is, it is not. And whatever
we might say a plant, a leaf, or a flower is, it is not.
Ultimately a plant, a leaf, a flower, and spirit "are" the
mystery that cannot be named. (I placed
"are" in quotation marks to avoid a logical contradiction.
But, in any case, the unnamable transcends logic and
1950. The natural
philosophy of plant form. Cambridge:
Cambridge University Press.
Arber, Agnes. 1954. The mind and the eye. Cambridge: Cambridge University Press.
Arber, Agnes. 1957. The manifold and the one. London: John Murray.
Carroll, J.B. 1956. Language, thought, and reality. Selected writings of Benjamin Lee Whorf. New York: Technology Press of MIT and Wiley.
Cusset, G. 1982. The conceptual bases of plant morphology. In: Sattler, R. (ed.) Axioms and Principles of Plant Construction. The Hague/Boston/London: Martinus Nijhoff/Dr. W. Junk Publishers, pp. 8-86 (also published in Acta Biotheoretica, Vol. 31A).
Eckardt, N. A. and Baum, D. 2010. The Podostemad puzzle: The evolution of unusual morphology in the Podostemonaceae. The Plant Cell 22:2131-2140.
Flannery, M. C. The many sides of Agnes Arber. http://www1.umn.edu/ships/gender/arber.htm
Gyatso, Tenzin, the Fourteenth Dalai Lama. 2005. Essence of the Heart Sutra. Boston: Wisdom Publications
Hirayama et al. 2007. Expression patterns of class 1 KNOX and YABBY genes in Ruscus aculeatus (Asparagaceae) with implication for phylloclade homology. Development Genes and Evolution 217:363-372. Epub 2007 Apr 12.
James, P. J. 2009. 'Tree and Leaf': A different angle. The Linnean 25: 13-19.
Kosko, B. 1993. Fuzzy thinking. The new science of fuzzy logic. New York: Hyperion.
Meyen, S.V. 1987. Fundamentals of palaeobotany. London: Chapman and Hall (see chapters on plant morphology).
Pietak, A. M. 2011. Life as Energy. Opening the Mind to a New Science of Life. Edinburgh: Floris Books.
Rankin, A. 2010. Many-Sided Wisdom. Winchester,UK/Washington, USA: O Books.
Rutishauser, R. and B. Isler. 2001. Developmental genetics and morphological evolution of flowering plants, especially bladderworts (Utricularia): Fuzzy Arberian morphology complements classical morphology. Annals of Botany 88:1173-1202.
Rutishauser, R., Grob, V. & Pfeifer, E. 2008: Plants are used to having identity crises. Pages 194 – 213 in A. Minelli & G. Fusco (eds.) Key Themes in Evolutionary Developmental Biology. Cambridge University Press, Cambridge.
Sheldrake, R. 2009. A New Science of Life. 3rd edition. London: Icon Books.
Sheldrake, R. 2012. The Science Delusion. Freeing the Spirit of Enquiry. London: Coronet of Hodder & Stoughton.
Tauber, A. I. 2010. Reframing developmental biology and building evolutionary theory's new synthesis. Perspectives in Biology and Medicine 53:257-270.
Uchida, N. et al. 2010. Coordination of leaf development via regulation of KNOX1 genes. Journal of Plant Research 123: 7-14.
Vergara-Silva, F. 2003. Plants and theConceptual Articulation of Evolutionary Developmental Biology. Biology and Philosophy 18: 249-284.
Zimmermann, W. 1959. Die Phylogenie der Planzen. 2nd edition. Stuttgart: Gustav Fischer Verlag.