Plant Morphology: Fundamental Issues

The Investigation of Plant Form

Rolf Sattler

Mainstream Plant Morphology (Classical Plant Morphology)
Continuum Morphology of Plants
Process Morphology of Plants
MorphoEvoDevo: The Evolution of Plant Form
Plant Morphology and Philosophy
The Importance of Questions
Plant Morphology and Spirituality
Plant Morphology in Relation to Integral Philosophy


“Plant morphology” literally means the logos - or I would say investigation - of plant form. According to Donald R. Kaplan, an influential American plant morphologist, “plant morphology is largely a German science” (Kaplan 2001). Such a statement appears very one-sided and incomplete. Although German plant morphologists have made great and comprehensive contributions to plant morphology and the term ‘morphology’ was coined by Goethe, Germany’s great poet and scientist, French and British plant morphologists have also made many very significant and important contributions. And plant morphologists of other countries such as Russia, India, Japan and Venezuela cannot be ignored. Gérard Cusset published an excellent article on the history of plant morphology that provides a much more comprehensive and balanced view than Kaplan’s because it includes and honours the contributions of many plant morphologists in many countries around the world (Cusset 1982).

Plant Morphology deals with plant form, including its development and evolution. It can be defined in a narrow sense as referring only to external form, in contrast to anatomy that refers to internal form. But plant morphology can also be defined in a wide sense that includes both internal and external form at all levels of organization from the molecular and cellular level to the organismal level (Sattler 1978, Introduction).

Since molecular genetics has become fashionable, plant morphology has been increasingly neglected and to some extent it has been integrated into
evolutionary developmental biology (evo-devo). Nonetheless, plant morphology remains fundamentally relevant to nearly all fields of plant biology such as molecular genetics, physiology, ecology, evolutionary biology and systematics. In these fields morphological concepts and/or theories are used or implied. Therefore, to some extent these fields are based on or reflect morphology (Kaplan 2001, Sattler and Rutishauser 1997).

Contrary to a widespread misconception, plant morphology is not a finished science, but, like any science, open to constant innovation. Such innovation may concern morphological details, concepts, theories, and even the disciplinary matrix (or paradigm). My contributions to plant morphology have been empirical and theoretical, involving a revision of some of the most basic assumptions and tenets in the disciplinary matrix of plant morphology.

With many undergraduate and graduate students, technicians, postdoctoral fellows, research associates, and colleagues I carried out research in plant morphology for nearly forty years in the second half of the 20
th century (see my Publications). One major focus of this research has been the dynamic form continuum in plants, especially flowering plants. A review of many aspects of this research can be found in my book chapter entitled “Homology, homeosis and process morphology in plants” (Sattler 1994). What follows is a general discussion of fundamental issues in plant morphology. References to our contributions can be found in the list of my publications. For a tour through what I consider some of my most important publications see my essay The Evolution of my Phytomorphological Research in my Publications and Plant Evo-Devo (Evolutionary Developmental Biology).

Mainstream plant morphology

Mainstream plant morphology (also called
classical plant morphology) emphasizes categorization. Thus, plants are said to consist of the organ categories root, stem (caulome), leaf (phyllome), and outgrowths of these organs such as hairs (trichomes). Then the whole diversity of plant form such as that of flowering plants is reduced to these categories. Hence, every organ that is encountered in flowering plants must be either a root, or a stem, or a leaf, or homologous to any one of them. Braun (1851) emphasized that the sharp and unambiguous distinction of roots, stems, and leaves is the very foundation of plant morphology and Troll (1935-1943) reiterated this dogma, which up to the present day represents the core of mainstream plant morphology despite much evidence to the contrary (for the references and a more detailed discussion of this subject see Sattler and Jeune 1992a).

Historical Comments: The root-stem-leaf categorization, which has become the dominant view or belief, is referred to as classical morphology because it was advocated at the end of the classical period by Goethe in his
Metamorphosis of Plants (1790, 1817) (see my essay on Philosophy of Plant Morphology). It should be noted, however, that in his Metamorphosis of Plants Goethe also accepted a phytonic view according to which the plant consists only of roots and phytons or phytomers. A phytomer comprises a leaf and the stem segment below the leaf. Thus the stem has become absorbed into the leaf and therefore the shoot consists only of leaves in the sense of phytomers. In other remarks (that are not contained in his Metamorphosis of Plants), he also questioned the basic premise of the Metamorphosis of Plants that all lateral appendages are homologous, that is, that all are leaves (phyllomes) or phytomers. He noted that compound leaves are more like branches or have the urge to become branches, an idea that foreshadowed Agnes Arber's partial-shoot theory of the leaf (see my essay on Philosophy of Plant Morphology). Therefore, Goethe went far beyond what has become the dominant view and what sometimes is referred to as classical morphology. It was Alexander Braun and especially Wilhelm Troll and other botanists who upheld the root-stem-leaf model as the only true representation of the diversity of plant form. Hofmeister and especially Goebel were less dogmatic. The latter accepted intermediate forms between the categories of root, stem, and leaf, and thus opened the way toward a continuum of forms, that is, continuum morphology (see Cusset 1982, p. 37).

Continuum Morphology

Although the fragmenting categorical approach of
mainstream morphology works to some extent, it tends to obscure the continuum of plant form. When we observe any one particular plant such as a flowering plant, we cannot find a clear-cut boundary between the root and the stem or the stem and the leaves. Furthermore, we cannot find a clear-cut boundary between the soil and the root or the leaves and the air. A close microscopic inspection reveals what has been called the Soil-Plant-Air Continuum (SPAC). Since animals and humans breathe in the air of this continuum, they are also included in it. With regard to various energies, this continuum extends into ecosystems, Gaia, and the whole universe. Thus, plant morphology and plant biology, although they may seem narrow fields, can become universal (see also my essay From Plant Morphology to Infinite Issues and Continuum and Discontinuum).

In spite of the continuum within plants, in textbooks and many research publications it is stated explicitly or assumed implicitly that plants such as flowering plants
consist of roots, stems, and leaves. This gives the impression that roots, stems, and leaves actually exist as entities. However, since there are no clear-cut boundaries between these organs, we have to construct them through our delimitations. Although these delimitations have a limited validity, they do not constitute absolute discontinuities. Other delimitations that divide plants in different ways can also be made. For example, the leaf with a continuous part of the stem below it can be considered a unit of plant construction (Cusset 1982; Rutishauser and Sattler 1985).

Units that result from different delimitations complement each other (Rutishauser and Sattler 1985). They illuminate different complementary aspects of plant construction and thus, together, provide a more comprehensive picture and understanding than any one single set of units such as the common root, stem and leaf units (for the concept of complementarity see my essays on Complementarity and Perspectivism and Complementarity: AQAL, the Big Tube, and the Dynamic Mandala).

When we compare organs of different plants, we find that although many of them can be grouped into categories such as root, stem (caulome) and leaf (phyllome), there are also intermediates between these categories. Thus, we find a structural continuum not only within plants but also between organ categories. This continuum even reaches beyond the organ level to include higher and lower levels of the structural hierarchy, thus leading to a new model of the shoot, referred to as the pyramid model of the shoot (
Anthony and Sattler 1990). According to this model, the typical shoot occupies the top corner of the pyramid and the typical stem (caulome), leaf (phyllome), and hair (trichome) the three bottom corners of the tetrahedral pyramid. Intermediate structures occur in the space between the four poles of the tetrahedron (see Sattler 1986, p.105). Using principal component analysis, we demonstrated a continuum between roots, shoots, stems, leaves, and hairs (Sattler and Jeune 1992). The same conclusions were reached by Cusset( 1994).

Nonetheless, as long as we consider only structures that fit the structural categories,
either/or thinking of our common Aristotelian logic is applicable. Thus, a structure belongs either to category A or B, an organ is either a stem (caulome), or a leaf (phyllome). However, if we consider the whole structural continuum, continuum or fuzzy logic is required because for intermediate structures it makes no longer sense to ask whether they are essentially A or B; they are neither A nor B; they represent partially A and B. In fuzzy logic we express to what degree they represent A and B. For example, the stamens of Commandra umbellata (that in mainstream plant morphology are interpreted as phyllomes, that is, leaf homologues), according to principal component analysis turn out as 51% phyllomes and 49% caulomes (stem homologues) (Sattler and Jeune 1992, Appendix 5, p. 261). For a general discussion of fuzzy logic see my essays Either/or Logic and Beyond and Healing Thinking through Fuzzy Logic. For scientific and philosophical issues of plant morphology see Sattler (1986, 1996, 2001).

The existence of intermediate structures has often been overlooked or denied because of excessive and overriding weighting of the position criterion of homology. According to this criterion, structures are considered homologous if they occupy the same relative position within the plant. Thus, what occurs in the axil of a leaf is considered a shoot, and what subtends a shoot is interpreted as a leaf. However, this kind of reasoning can lead to absurd conclusions: for example, in Nasturtium officinale
roots may occur in the axils of leaves (Champagnat et Blatteron 1966). Obviously, this is not a case of homology, but only homotopy (same position). Similarly, intermediate structures that we have found to occur in the axil of leaves are not essentially shoots, nor are they derived from shoots only; they are derived from the organs whose traits they share. For example, if they combine leaf and stem traits, they are derived from both leaves and stems: they represent hybrid structures or mosaics (Sattler 1988).

We have much evidence that not only the quality but also the relative position of structures may change, which means that one structure can be totally or partially replaced by another structure that may or may not be homologous. This phenomenon is called homeosis. Examples of total homeosis: the replacement of a stamen by a petal, or an axillary shoot by a leaf (Sattler 1988). Examples of partial homeosis: certain compound leaves that show a combination of leaf and shoot features (
Rutishauser and Isler 2001) and therefore can be considered partially leaves and shoots as Agnes Arber has pointed out long ago in her Philosophy of Plant Form (1950) whose nearly 50th anniversary was celebrated in a symposium at the International Botanical Congress in 1999. In this symposium, Rutishauser and Isler (2001) contrasted Fuzzy Arberian Morphology (FAM) with the more restricted Classical Morphology (CLAM). Serge Meyen's work also went far beyond the limitations of classical morphology (see, e.g., Meyen 1987). Like Arber's work, the contributions of Meyen (that focus on evolutionary plant morphology) have not received the attention they deserve. However, my own work has been much inspired by that of Serge Meyen (whom I once met in Moscow at the International Botanical Congress), Agnes Arber (whom I never met), and many others.

In Fuzzy Arberian Morphology or continuum morphology the concept of homology becomes also fuzzy. The question then is not whether an intermediate structure is homologous with A or B, but to what degree it appears homologous with A and B (see Sattler 1994). However, for structures that fit the categories, the common homology concept based on either/or logic seems still applicable.

The claims of continuum morphology have been supported by many detailed empirical investigations of shoot, leaf, and flower development in a great diversity of flowering plants (see my
publications and those of other authors such as Rutishauser and Isler 2001 and Rutishauser 2016). The complexity of developmental patterns that we presented in my book Organogensis of Flowers (1973) can also be understood in terms of continuum morphology.

Investigations in molecular genetics have provided support for continuum morphology. For example, it has been shown that certain compound leaves combine gene activity that is typical for shoot and leaf development (see below). Therefore, these compound leaves are not only morphological but also genetic mosaics, that is, intermediates between leaves and shoots as postulated by Agnes Arber’s partial-shoot theory of the leaf and demonstrated by detailed morphological investigations (see, for example,
Rutishauser and Sattler 1997; Lacroix et al. 2003).

Process Morphology

It can be useful to make a distinction between structure and process: for example, between the structure of a leaf and the processes that occur within the leaf. However, upon close inspection, we can see that the structure of the leaf changes and therefore can be seen as a process. Since it changes very slowly, this process is not easily noticeable, especially in later developmental stages as the leaf approaches maturity. But the leaf, like other structures, is never completely static. It always undergoes a process of growth and/or decay, differentiation and/or dedifferentiation. Within these four basic morphogenetic processes, subprocesses can be distinguished such as branching or symmetrisation. A whole structure such as a leaf can then be seen as a combination of processes, and the diversity of plant form can be understood as a diversity of process combinations (Sattler 1994,

Many of the process combinations correspond to the typical organ categories. However, since there are intermediates that do not fit the categories, a continuum of process combination occurs (Jeune and Sattler 1992).

The result: the dynamic form continuum of plants that I referred to above.

I called this dynamic approach to the study of plant form process morphology or dynamic morphology (Sattler, 2019, cited above). And I applied it not only to plant development but also to the evolution of plants (see below).

Most of my publications deal with processes, but, like almost all research in developmental and evolutionary plant biology, still imply a structure/process dichotomy. Process morphology goes beyond this dichotomy and therefore is more radically and more profoundly dynamic than most so-called dynamic morphology (see
Sattler 2019).

One reason, maybe the main reason, why we imply so easily a structure/process dualism resides in the structure of our language. Most languages, including the English language, have a noun-verb or subject-verb-object structure in which nouns refer to things such as leaves and verbs to processes such as the processes of leaves (Sattler 1993).
If we could devise a language that is based on verbs only, we would have a pure process language that would no longer imply a structure/process dualism. Then we could easily recognize that what we call a leaf constitutes leafing, only activity (see my essay on
Process Language).

In his
Biological Principles (1967, p. 330), J. H. Woodger characterized the aim of process morphology very succinctly in very general terms when he wrote: "what is required is an enlargement of our concept of 'structure' so as to include and recognize that in the living organism it is not merely a question of spatial structure with an 'activity' as something over it, but that the concrete organism is a spatio-tempotal structure and that this spatio-temporal structure is the activity itself." In other words: a structure is not only seen as having processes (or processes belonging to a structure), a structure is seen as process(es). Hence, no structure/process dualism. Nonetheless, the structure/process dualism remains a convenient perspective on biological phenomena, but its transcendence through process morphology reveals the dynamics of organic form more completely than the structure/process dualism inherent in mainstream biology (see also Nicholson and Dupré 2018).


Although continuum and process morphology have not yet become mainstream because they are too different from deeply ingrained modes of thinking in our culture and science, they remain an active area of research in the 21
st century. Christian Lacroix, Rolf Rutishauser, and others continue research on the dynamic continuum of plant form. Furthermore, the dynamic continuum is validated by investigations in molecular genetics. For example, Hirayama et al (2007) showed that the phylloclade in Ruscus aculeatus "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 and Sattler (1987)). Eckardt and Baum (2010) concluded that "it is now generally accepted that compound leaves express both leaf and shoot properties." (Some morphologists, including myself, reached this conclusion long ago by purely morphological investigations (see Rutishauser and Isler 2001). James (2009, p. 17) stated that "it is now widely accepted that... radiality [characteristic of most stems] and dorsiventrality [characteristic of leaves] are but extremes of a continuous spectrum. In fact, it is simply the timing of the KNOX gene expression!" Finally, continuum and process morphology also play a role in plant evo-devo (evolutionary developmental biology) (see, e.g., Vergara-Silva 2003). Emphasizing the relevance and importance of morphology, the term MophoEvoDevo has been suggested (Wanninger 2015; see also Minelli 2018).

MorphoEvoDevo: The Evolution of Plant Form

According to MorphoEvoDevo, the evolution of plant from resides in the change of plant development. In terms of process morphology, this means a change in process combinations, which form a dynamic continuum.
The recognition of the dynamic continuum may provide a different perspective of morphological evolution (Sattler 1992). For example, it has far-reaching consequences for the origin and evolution of land plants (Sattler 1998). It allows a synthesis of two opposite views: Zimmermann’s telome theory and Hagemann’s opposite view. According to the telome theory, land plants originated from radially symmetrical axes, called telomes, whereas according to Hagemann’s view, they arose from dorsiventrally flattened structures. Thus, either axes or flattened (leaf-like) structures are taken as the ancestral pattern of land plants. This opposition is overcome through the dynamic continuum that recognizes a continuum between radially symmetrical axes and dorsiventrally flattened structures, which according to process morphology constitute process combinations. The fossil record supports this view of a dynamic continuum at the origin of land plant evolution (for references see Sattler 1998).

Plant Morphology and Philosophy

Many plant morphologists and other scientists believe that science operates independently of philosophy. But it has been shown that science and philosophy remain intertwined: science includes philosophical assumptions and receives input from philosophy. Journals such as Biology and Philosophy are devoted to the relation between biological science and philosophy.

One philosophical assumption in mainstream plant morphology (classical plant morphology) involves essentialism or, if not essentialism, at least Aristotelean either/or logic, the belief that any organ of plants such as flowering plants must be either a root, a stem (caulome) or leaf (phyllome), which means that even if an organ does not clearly fit these categories, it belongs nonetheless to one or the other (Sattler 1986). The insistence on either/or supposedly has been justified by the phylogenetic interpretation of homology. It is argued, for example, that even if a structure appears to be an intermediate between a stem and a leaf, it evolved from either one or the other. However, in a strict sense, structures do not evolve from each other, that is, there is not direct phylogenetic connection between structures (Sattler 1984, p. 386). The phylogenetic connection or lineage is between organisms or populations. As has been known for a long time and as it is emphasized in evolutionary developmental biology, the development of organisms may change during evolution in such a way that elements of different developmental pathways may be combined. For example, it has been shown that certain compound leaves combine leaf and shoot processes, including genes that are associated with these processes (see, e.g.,
Rutishauser and Isler, 2001). Therefore, these compound leaves can be seen as partially homologous with leaves and shoots. The insistence in mainstream plant morphology that they are essentially leaves obscures their partial homology.

Most philosophers of science and biologists deny that essentialism still plays a role in mainstream thinking. However, listening to colleagues, I have heard again and again expressions such as "but essentially it is this." Similar expressions one can often hear in everyday life, which to me indicates that essentialism is still deeply rooted in our culture.

Continuum morphology also freed itself from the constraints of Aristotelian
either/or logic that is still taken for granted to a great extent in science and society. The logic of continuum morphology is fuzzy logic, or at least a more-or-less logic instead of or in addition to either/or logic.

Process morphology has incorporated ideas of
process philosophy and contextualism. According to process philosophy, reality is seen as dynamic as in Buddhism that emphasizes impermanence. Contextualism also implies change: events are placed into the context of other events that may reach universal dimensions. For example, events (processes) that constitute a leaf (leafing), are intertwined with solar and cosmic radiation. Thus, the leaf (leafing) reaches cosmic dimensions. Since the integration is not limited to physical events but includes also subtle and very subtle events, it reaches even kosmic dimensions - kosmic, in contrast to cosmic, comprises matter, mind, and spirit (see Wilber 2000, p. 45). Because of the emphasis on integration, contextualism tends towards organicism and holism (Sattler 1986, p. 245; see also my essay Ways of Thinking).

Agnes Arber, the eminent plant morphologist of the 20th century, pointed out, plant morphology “may seem a narrow road, but rightly conceived, it should, like other biological paths, lead us to infinite issues” (Arber 1950, p. 1). I explored these infinite issues in a separate essay: From Plant Morphology to Infinite Issues (including Ken Wilber and Korzybski). For a more comprehensive discussion of philosophical issues relating to plant morphology see my essay Philosophy of Plant Morphology.

The Importance of Questions

In a sense, questions seem more important or more fundamental than answers because the questions we ask determine to a great extent the kind of answers we obtain. If we ask an either/or question as it is typical for mainstream plant morphology and much thinking in science and society, the answer, if any, is in terms of a category. For typical structures, this kind of question seems appropriate. However, if we ask an either/or question for an intermediate structure, we cannot find a satisfactory answer because the question seems inappropriate in this particular situation. Therefore, before asking a question, one has to examine whether it appears appropriate.

Inappropriate questions have been called pseudo-questions because we cannot obtain satisfactory answers to these questions. Such questions obstruct progress. Recognizing pseudo-questions and posing new meaningful questions has led to great innovations in science and society.

Plant Morphology and Spirituality

I hesitate very much to refer to spirituality because it could be misconstrued as if I would promote a spiritualistic morphology. Not at all. To me spirituality does not imply a dogma or belief. It just implies a knowledge and experience of interconnectedness or oneness and thus it means ending the story of separateness (see my essay on The Human Condition and its Transcendence).

A number of books on the relation between science and spirituality have been published, and symposia have been organized around this topic. In a symposium entitled "Divergence and Convergence of Sciences and Spirituality" that was dedicated to the Dalai Lama on the occasion of his 60th birthday on July 6, 1995, I discussed the relation of life science and spirituality (Sattler 1999). Already in 1976, I taught a summer course on "Modern Biology and Zen" at Naropa Institute in Boulder, Colorado. In this course, I explored no-thingness in biology, including plant morphology, and its relation to
nothingness or emptiness in Buddhism, especially Zen. No-thingness means that there are no separate things but a continuum, undivided wholeness. As I pointed out above, a plant does not consists of things or entities such as organs. We create these things through our delimitations. Without these delimitations, there is no-thing, no separate thing. Also, the plant itself is no-thing, since it is fully integrated with its environment (see SPAC above).

Instead of no-thingness, we could refer to undivided wholeness, unity, or oneness, all of which play a central role in
holistic science and spirituality, especially mysticism - hence a convergence of science and spirituality. Barbara McClintock, the 1983 Nobel Laureate in Physiology or Medicine, as a plant geneticist and mystic, exemplified this convergence when she wrote: "Basically, everything is one. There is no way in which you draw a line between things. What we [normally] do is to make these subdivisions, but they're not real. Our educational system is full of subdivisions that are artificial, that shouldn't be there" (quoted in Evelyn Fox Keller 1983, p. 204).

There remains, however, also a difference between science and spirituality as mysticism. The scientist, especially the holistic scientist, has intellectual knowledge of nothingness, undivided wholeness, unity and oneness. The mystic experiences or
is nothingness, undivided wholeness, unity, and oneness.

Nothingness, undivided wholeness, unity and oneness in science as well as in process philosophy and process morphology refer to manifest reality that can be investigated through our senses and the thinking mind. However, beyond manifest reality - but not separate from it - we can find the unmanifest source, the unnamable. Since it cannot be named, one cannot say that it is dynamic or static, discontinuous or continuous, fragmented or whole. We cannot even say that it is both dynamic and static, discontinuous and continuous, fragmented and whole. It is beyond words and concepts, and therefore it appears mysterious... "The Tao that can be told is not the eternal Tao...The unnamable is the eternally real" (Tao Te Ching, translated by Stephen Mitchell. HarperPerennial, 1992).

Most scientists, especially mechanistic mainstream scientists, including mainstream plant morphologists, shy away from or denigrate mystery. However, some of the greatest scientists recognize that beyond that which can be grasped by the intellect lies the unfathomable mystery that transcends science but can inspire scientists. For example, Albert Einstein, the great physicist, wrote: "The most beautiful thing we can experience is the mysterious. It is the source of all true art and science"(quoted by Ravindra 2000; see also my essay
From Plant Morphology to Infinite Issues (including Ken Wilber and Korzybski).

Some Concluding Remarks

1. Ken Wilber severely criticized the myth of the given, “the belief that reality is simply given to me…instead of a world that is con-structured in various ways before it ever reaches my empirical or phenomenal awareness” (Wilber 2006. p. 176). We find an expression of this myth of the given in mainstream plant morphology where it is often taken for granted that plants such as flowering plants consist of roots, stem(s), and leaves. But as I have pointed out, these organs are constructed through our delimitations – they are not given by nature. As Ken Wilber and others, especially postmodern authors, have emphasized, our constructions reflect our culture. Since Aristotelian either/or logic constitutes still a fundamental part of our mainstream culture, it is reflected in mainstream plant morphology and its central concept, the concept of homology. However, for a long time, at least a few plant morphologists have gone beyond either/or thinking (see, for example, Cusset 1982 and Rutishauser and Isler 2001). Unfortunately, their innovations have not yet been sufficiently incorporated into mainstream plant morphology.

2. In Chinese medicine health means
balance. This notion is applied to our physical, emotional, and spiritual health. It can also be applied to plant morphology. Recognizing only the root-stem-leaf delimitations of plants such as flowering plants and treating them as given appears one-sided and unbalanced. But recognizing complementary delimitations creates more balance and thus a healthier plant morphology. Furthermore, recognizing and applying healing ways of thinking (healing logic) can heal the wounds and conflicts that have been inflicted by an exclusive insistence on Aristotelian either/or logic, especially in cases of a continuum where it does not apply.

3. Plant morphologists who embrace the root-stem-leaf delimitations of plants such as flowering plants often seem dead serious, and sometimes even aggressive and nasty in its defence. Unfortunately, such behaviour is not restricted to plant morphology but occurs also in many other areas of science, philosophy, ideology, and religion. If we could go beyond the myth of the given and recognize the relativity of different views (which does not mean that they are necessarily equally valid), we could inject
lightness, humour and laughter into this exaggerated seriousness, which would be healing not only for individuals but also for the scientific community, society and the planet.


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Troll, W. 1935- 1943. Vergleichende Morphologie der höheren Planzen. 3 volumes. Berlin: Borntraeger.

Vergara-Silva, F. 2003. Plants and the Conceptual Articulation of Evolutionary Developmental Biology. Biology and Philosophy 18: 249-284.

Wanninger, A. 2015. Morphology is dead - long live morphology! Integrating MorphoEvoDevo into molecular EvoDevo and phylogenomics. Frontiers in Ecology and Evolution 3, Article 54.

Wilber, K. 2000. Sex, Ecology. Spirituality. Boston& London: Shambhala.

Wilber, K 2006. Integral Spirituality. Boston & London: Shambhala

Woodger, J. H. 1967. Biological Principles. Reissued with a new Introduction. New York: Humanities Press.

See also The Evolution of my Phytomorphological Research in my Publications and Plant Evo-Devo (Evolutionary Developmental Biology), Morphological Development (Organogenesis) of Flowers, From Plant Morphology to Infinite Issues (including Ken Wilber and Korzybski), Philosophy of Plant Morphology, and Science: its Power and Limitations

Latest update of this webpage on January 21, 2021.