Content uploaded by Peer Schilperoord
Author content
All content in this area was uploaded by Peer Schilperoord on Feb 17, 2015
Content may be subject to copyright.
CONCEPT OF MORPHOLOGICAL POLARITY AND ITS IMPLICATION
ON THE CONCEPT OF THE ESSENTIAL ORGANS* AND ON THE
CONCEPT OF THE ORGANISATION TYPE OF THE
DICOTYLEDONOUSPLANT
P. Schilperoord-Jarke
Hauptstrasse 16
CH-7492 Alvaneu Dorf, Switzerland
Received 12-V-1995
Acta Biotheoretica 45: 51-63, 1997
Kluwer Academic Publishers. Printed in the Netherlands.
ABSTRACT
Dicotyledons are polarly organised in several ways. In plant morphology polarity, a principle,
allowing comparison of different plant structures has until yet not been studied. A
division**.of the plant in shoot and root as polar structures leads to the distinction of four
instead of three basic organs: leaf, shoot axis, root axis and root cap together with the root
hairs. The flower is a1so polarly organised, its poles are formed by the carpels and the
stamens. The foliage leaves are also polarly organised which is reflected by the morphological
relationship of foliage leaf, stamen and carpel. The stamen uses the hypophyll*** as base of
construction and the carpel uses the epiphyll**** as base of construction. Hypophyll and
epiphyll are the two poles of the foliage leaf. Root and shoot, the polar entities of the
vegetative plant and stamen and carpel, the polar entities of the generative plant are,
morphologically correlated. Stamen and carpel can be understood as a combination of the
basic organs of vegetative and generative parts of the plant. The basic organs of the generative
plant are pollen grain and embryo sack with their gametophytes. The quantitative comparison
of variable proportions is supplemented by a qualitative comparison of polarities. The result is
that the organisation type of the Dicotyledons can yet be understood as constituted of
morphological related parts.
* in german Grundorgane
** in german: Gliederung
*** in german: Unterblatt
**** in german: Oberblatt
1. INTRODUCTI0N
Type and essential or basic organ are two fundamental concepts in plant morphology. In every
introduction to plant morphology these two terms are mentioned and explained (Troll, 1954;
Strasburger, 1993). Until now there was no need to question these concepts. If there are
features, which do not fit into these concepts, it is time to reconsider their content thoroughly.
The discussion of the basic concepts is subject of the present paper.
The method of plant morphology is comparing forms. The result is, for example, the
estab1ishing of basic organs, organisation types, construction types, homology and analogy.
Two fields for comparing are generally used in plant morphology: 1. The comparison of
structures, which have the same re1ative position in the overall configuration of the p1ants
(determination of homologous structures). 2. The comparison of structures, which have the
same function, i.e. belong to the same construction type (determination of analogous
structures) (Froebe & Classen-Bockboff, 1994).
The morphologist distinguishes in the vegetative plant a shoot and a root. The plant appears in
the first analysis as a bipolar entity. The shoot is divided in stem and fo1iage leaf. The three
organs: root, shoot axis and leaf are the so-called basic organs. Sitte (1993, p.170) defines
these as follows: "die Grundorgane sind nicht miteinander homologisierbar, und sie üben
verschiedene Basisfunktionen aus", ("the basic organs are not homologous and they perform
different basic functions"). The ground organs are distinguished by this definition.
In the present paper I examine in the dicots first the po1arity of root and shoot. Could polarity
not on1y be used in a positional, but also in a morphological sense? A concept of
morphological polarity in comparative morphology is until yet missing. A third field for
comparing is proposed to deepen our insight in plant morphology.
The consideration of root and shoot as polar structures leads to the characterization of four,
instead of three, basic organs: foliage leaf, shoot axis, root axis and root cap with the root
hairs. With these four basic organs it is possible to describe the vegetative plant. This
distinction is only limitedly app1icable to the generative plant. The basic organs of the
generative p1ant are the two sporangiums with their contents and the two gametangiums. The
form of the flower is the result of the cooperation of three pairs of polarly organised organs
(root and shoot, both sporangiums and the male and female gametangium). This cooperation
is shown: 1. by the differentiation of the fo1iage leaf in hypo- and epiphyll as basis for the
growth of stamen and carpel. The stamen is partially homologous with the hypophyll, the
carpel with the epiphyll. Another morphological relationship between the organs is: 2. the
consequence of a qualitative metamorphosis of the lateral vegetative organs (of the lateral
roots and shoots), which do not appear in the flower, and the basic organs for generative
propagation. From a quantitative metamorphosis bymeasuring the variabi1ity of proportions,
it is not possible to derive relationships between the vegetative and the generative way of
propagation. Without qua1itative metamorphosis it is impossible to relate vegetative and
generative propagation.
The present-day type of the dicot plant is viewed as an organism, composed of several well
demarcated parts. This concept contradicts the tendency in morphology to stress the
interrelationship of the parts.
Methods: It is important to realise the direction of the cognitive process. One can descend
from a bigger level to a subordinate level, one can ascend from a lower to a higher level of
organisation, or one compares structures of the same level.
Starting with the morphological analysis of the vegetative plant, the first subordinated level is
the level of polarity. Sitte (1993,170): "Through the development of shoot and root pole (in
the embryo), a bipolarity is given, which designates further development.
1
The step after the
distinction of the plant in shoot and root is the description of the articulation Z in the different
organs, for example in axis and foliage leaf. The analysis has to answer the question of what
kind of morphological relationships of the distinguished structures gives rise to the unity of
the plant, in process; the synthesis of the distinguished structures giving 6 rise to the unity of
the plant. In the case of the concept of the three essential organs the analysis is incomplete,
the morphological interrelationship of the organs is not recognized (in contrast to the
physiological interrelationship) and so a synthesis is not possible.
2. THE VEGETATIVE DICOTYLEDONOUS HERHACEOUS PLANT
1
In the german language: "Durch die Ausbildung von Spross und Wurzelpol ist eine Bipolarität vorgegeben, die
für die weitere Entwicklung der Pflanze bestimmend bleibt."
2.1 Organic Disunion and Polarity
With organic disunion is indicated the process by which from an original unit a dual entity (or
two units) arises. In the course of embryogenesis differentiation of polar structures comes into
existence. I define polar structures as structures, that have complementarous opposite sites
and imply each other.
What does the polarity look like in the vegetative plant?
2.2 Root
I use the term axis similarly for the shoot and the root. So one can distinguish two root organs:
1. the root axis and 2. the root cap with the root hair zone. The lateral roots repeat the same
construction. Lateral organs originate endogenously, the root apex cannot branch. Axis, cap
and root hair zone arise from the primary meristem of the root apex. The border between root
hair zone and root axis is the hypodermis (also called exodermis). After the disappearance of
the rhizodermis the soil borders the hypodermis of the root axis. By elongational growth of
the axis new areas of the soil can be disclosed. The penetration of the root apex into the soil is
facilitated by the continuous formation of the root cap and its decay. The unicellular root hair
is ultimately close connected with the surrounding soil particles. The root hair zone follows
the root apex continuously, continually arising, continually decaying.
2.3 Shoot
It is well known, that one can distinguish two kinds of shoot organs: axis and foliage leaves.
Shoot axis and leaves arise from the primary meristem of the shoot apex. The lateral shoots
repeat this construction; they arise exogenously, in other words, from the outer parts of the
tissue. The shoot apex does not branch. The elder leaf primordia envelop the apex. The
growing leaves open gradually. They are bordered by the epidermis.
2.4 Polarity of Root and Shoot
Considering the plant as consisting of polar structures leads to the following order. First root
and shoot divided in:
root apex -shoot apex
root cap -envelope of the leaf primordiums
root hair zone -foliage leaves
root axis -shoot axis
lateral root primordium -lateral shoot primordium
The polarity becomes clear in the following. characteristics: 1. in root and shoot axis; a
Circular configuration of the vascular strands in the centre of the root axis, and a radial
configuration of the strands in the periphery of the shoot axis with respectively endogenous
and exogenous origin of the lateral organs. 2. in the leaves and in the root organ (root cap,
root hairs and rhizodermis): the root organ arises continually, only one organ arises, which is
continually decaying and built up. Several leaves arise, they are spatially separated. The root
organ has on1y one form. The leaf has many possible forms. The root organ is not clearly
detached from the root axis by its cylindrical shape. The leaf is clearly detached from the
shoot axis. Tissue layers of the root organ are spatially separated, the root cap becomes slimy,
the inner parts of the organ, the root hairs, are exposed. The tissue layers of the leaf constitute
a spatial unit, the inner part of the organ is not exposed, the leaf as a whole stays physically
intact.
In the same way as one can describe the leaf as apart of the shoot, it is possible to describe a
root organ as apart of the root. The latter organ is unique, homologous forms cannot be found.
The ways of examining the shoot and the root are identical. The concept of polarity shows the
morphological relationship.
2
2.5 The Hypocotyl as Intermediary
The hypocotyl has neither the ability to produce leaves nor a hypodermis with root hairs.
Lateral roots and lateral shoots can arise from the hypocotyl, like they both can arise from the
root axis and the shoot axis. The transitional configuration between the vascular bundles of
the root axis and the shoot axis is localised in the hypocotyl. The hypocotyl reveals how at
this site in the plant two different organs are connected. Both organs are essential organs, and
neither homologous nor analogous. Nevertheless it is possible to transform theoretical1y one
organ into the other, by gradual1y changing the configuration of the vascular system. The
hypocotyl is the intermediate stage. The relativity of the distinction of the essential organs
becomes obvious, when considering that the root axis and the shoot axis become alike by
secondary thickening. To speak of different organs is then itself cannot become a root in the
course of its further development. The same is true for the root. One bas to distinguish
between two kinds of metamorphosis: 1. metamorphosis as a process of differentiation and 2.
metamorphosis as a process of transformation. The existing theory of the basic organs
considers on1y the second type of metamorphosis.
2.6 Root and Shoot, Their Morphological Relationship
The polar vegetative plant is a unit. The meristem of root and shoot arise from one zygote.
The relationship between both meristems is continuous in time. The root and shoot axis
connect both meristems. The relationship between foliage leaf and root organ is spatially
discontinuous. There is no gradual metamorphosis between root organ and foliage leaf. By
comparing different types of foliage leaves, one uses the principle of the variability of
proportions. According to this principle one can theoretically change one form of foliage leaf
into another by gradually changing the different proportions of the leaf. With this principle it
is impossible, to describe the morphological relationship between root organ and foliage leaf.
If on I y this principle is admitted as a criterium to establish morphological relationships, then
the relationships between root organ and foliage leaf must be denied.
In "Vorarbeiten zu einer Physiologie der Pflanzen" Goethe (1975,98-99) has introduced the
concept of "organische Entzweiung" (organic disunion)
3
3. This concept leads to the concept
of polarity, with this concept is the unveiling of the morphological relationship of root organ
and foliage leaf possible. In the third chapter "organische Einheit" of his draft he outlines the
concept of organic unity and then in the fourth chapter "organische Entzweiung" he outlines
his concept of organic disunion:
"Before, we looked at the plant as a unity. We can see the empirical unity with our eyes. It
arises by the association of many different parts of the greatest variety as an apparent
individual. A one year old completed plant tom out. Ideal unity: When these different parts
are thought to have arisen from an ideal body, and have developed sequentially. From the
very beginning we have to consider this ideal body as simple as possible, and to look at it as
disunited, for without the process of disuniting of an entity, a third one cannot develop.
4
2
The distinction of the root organ is based on the idea of linkage of two parts in the entire vegetative plant.
Histological1y, there is no need to distinguish root axis and root organ.
3
Goethe has not published himself the text "Vorarbeiten..." in contrast to his "Versuch die Metamorphose der
Pflanzen zu erklären". The text "Vorarbeiten..." is not a scientific publication, it is a preparatory work.
4
The german text: "Vorher ward die Pflanze als Einheit betrachtet. Die empirische Einheit können wir mit den
Augen sehen. Sie entsteht aus der Verbindung vieler verschiednen Teile von der grössten Mannigfaltigkeit zu
einem scheinbaren Individuum. Eine einjährige vollendete Pflanze ausgerauft.
3. FOLIAGE LEAF, STAMEN AND CARPEL
In the previous chapter we dealt with the morphological polarity of root and shoot. In this
chapter the morphological relationships between foliage leaf, stamen and carpel are examined.
The morphological structures of stamen and carpel can be understood as polar structures.
3.1 The Limits of Determining Homologies I
The present-day preferred interpretation considers foliage leaf, stamen and carpel, on account
of their relative position in the configuration of the plant, as homologous organs
5
The criterion
of the similar position of foliage leaf, stamen and carpel (homotopy) describes only a partial
homology between the mentioned structures. The stamens release pollen
grains, the embryo sacks arise on the carpels, comparable structures are not found on foliage
leaves. Although the position of stamens and carpels is similar with the position of the foliage
leaves, the qualitative differences between these organs are enormous. The criterion of
topography has only a limited value. Sachs (1882, 15) distinguishes in his "Vorlesungen über
Pflanzenphysiologie" three categories of organs: 1) the vegetative
organs: root and shoot. Among the reproductive organs: 2) the asexual sporangiums with
spores and 3) the sexual archegonia and antheridia. According to him are the resting types of
organs rudimentary or partially developed organs of these categories. Stamen and carpel are
on one hand shoot organs; on the other hand they are sexual organs. The foliage leaf belongs
to one categorie of organs. Stamen and carpel are partially homologous with the foliage leaf.
It happens, that it is impossible to determine the morphological status of an organ. Then the
auxiliar criterion, the formation of a sequence of gradual metamorphoses, can give arguments
for a decision, e.g. to establish the relationship between foliage leaf and stamen, we can also
use this criterium. It is easy to find intermediate forms which show, that the stamen is
(partially) homologous with the hypophyll. I refer again to Sitte (1933, 214) who says, that "a
comparison of the different leaves in a sequence shows, that more simple forms of leaves like
cataphylls, protective scales, floral bracts and floral leaves develop by inhibition of the
epiphyll and promotion of the hypophyll, i.e., by reduced growth. The sequence of the leaves
is an impressive demonstration of the ability of the metamorphosis of one organ type -in this
case the phyllom by shifting proportions.
6
With this quantitative comparison one can show the
homology of the hypophyll with the floral leaves, Sitte (1993, 161) gives as an example the
well known sequence of leaves of hellebore (Helleborus foetidus ) .He gives as an example of
intermediate forms of petals and stamens the rose (1993, 161). One can find many
intermediate forms between bracts, tepals and stamens in Magnoliidae and Ranunculidae.
Intermediate forms of tepals have sometimes more characteristics of the floral bracts
sometimes more characteristics of the stamens (Hiepko, 1965). Cronquist (1988) and also
Takhtajan (1991) both describe continuous sequences of intermediate forms between bracts
Ideale Einheit: Wenn diese verschiednen Teile aus einem idealen Urkörper entsprungen und nach und nach in
verschiedenen Stufen ausgebildet gedacht werden. Diesen idealen Urkörper, mögen wir ihn in unsern Gedanken
so einfach konzipieren als möglich, müssen wir schon in seinem Innern entzweit denken, denn ohne vorher
gedachte Entzweiung des einen lässt sich kein drittes Entstehendes denken."
5
For example Weberling (1981, 16) in his "Morphologie der Blüten und der Blütenstände".
The modified theory of the euanthium (according to Ehrendorfer, 1993, 760) is based too on the premise, that in
the course of the evolution stamen and carpel has assumed the characteristic shape of angiosperm leaves and
therefore they are homotopic with the foliage leaves.
6
The original german text: "Ein Vergleich der verschiedenen Blätter in der Blattfolge 7l:,igt, dass einfachere
Blattformen wie Niederblätter Tegmente, Hoch- und Blütenblätter durch Hemmung des Oberblattes und
Förderung des Unterblattes entstehen, also durch gekürzte Entwicklung. Die Blattfolge ist eine eindrucksvolle
Demonstration der Wandlungsfähigkeit eines Organtyps - hier des Phylloms - durch Verschiebung der
Proportionen.“
and stamens. However, they do not find; such a continuous sequence in one family. First, a
survey of all the families shows a ~ continuous sequence of intermediates. Each species can
show only apart of the total leaf sequence of its genus and in its turn the leaf sequence of a
genus is part of the leaf sequence in a higher taxonomic unit. In spite of the clear relationship
between the hypophyll of the foliage leaf and the stamen, no author considers the hypophyll
homologous with the stamen.
The abundance of intermediate forms, which exists between stamens and foliage leaves,
doesn’t exist between carpel and foliage leaf. Nevertheless, the relationship between foliage
leaf and carpel are easily recognizable, as Goethe in 1790 already found out (1975 § 78). He
denoted the carpel as a fo1iage leaf with a folded lamina of which the borders were fused.
This description fits for the epiphyllous part of the fo1iage leaf. Hagemann (1984, ~~ 339)
came to the same conclusion: "Because the carpel has lost its vegetative functions, it no
longer needs to be exposed, and hence, the leaf base and leaf petiole may be extremely
reduced. As a result, the leaf blade comes into close contact with the shoot apical meristem".
It is possible to derive the carpel by varying the proportions of the leaf blade, if one does not
take into consideration the existence of the ovules. One could say that the carpel is
homologous with the epiphyll, but it is better, what is already mentioned, to speak of a partial
homology. Stamen and carpel comprise more than the hypo- and epiphyll of the foliage leaf.
The disunion of the sexes ("die Trennung der Geschlechter" according to Goethe), in stamen
and carpel, is related with the articulation of the foliage leaf in hypo- and epiphyll.
7
Stamen
and carpel are polar structures, which are related with the articulation of the foliage leaf.
There are no gradual and regularly ordered sequences of intermediate forms between stamens
and carpels. There are many forms, but in some cases the pollen sacs are situated above the
ovules, and in other cases below the ovules. An intermediate stable form between stamen and
carpel has not been estab1ished in the course of evolution. The contrasts cannot be over
bridged. Thus polarity of stamen and carpel is real.
The above presented relationship of foliage leaf, stamen and carpel is based on the articulation
of the foliage leaf in hypo- and epiphyll. This articulation is in many cases not clear, for
example in the case of the Dipsacaceae or in the case of the Compositae. Such types of leaves,
where the distinction between hypo- and epiphyll is not clear, are derived types. If one would
only consider these types of leaves, it would not be possible to detect the mentioned
relationships, they are hidden. The more simple dicots show these relationships in a clear way.
Hagemann (1970, 382-390) bas shown that full grown fo1iage leaves, which show no
articulation, show in their ontogenesis an articulation in hypo- and epiphyll. Hagemann
demonstrated in his article the polarity of hypo- and epiphyll in a morphogenetic sense.
The conclusion, that foliage leaf, stamen and carpel are homotopic organs, is reached by
studying serial leaf sequences. The comparison of the different organs, with on1y the purpose
to determine the relative position of these organs, does not take into consideration, with what
part of the leaf the organs are compared. The fo1iage leaf with his blade, stalk and base is an
entity, which has the potential to let each of the parts grow independently, e.g., the blade is
directly inserted on the axis when the petiole and the leaf base are completely reduced.
3.2 The Polar Structure of Stamen and Carpel
To compare stamen and carpel, I have made the following 1ist of paired characteristics, most
of them are not morphological:
stamen carpel
solid -with internal cavity
7
Goethe (1975, § IX) did not compare the complete structure of the carpel with the stamen, be considered on1y
style and stigma as the female parts.
dissimilating -assimilating
short-lived -long-lived
dying away -further growing, developing
dismissing -receiving
The pol1en grains arise in the pol1en sacks, they arise “endogenously”. The pol1en sacks
rupture when they ripen and the pol1en is set free. The embryo sacks arise on the leaf blade,
i.e., “exogenously”. They appear to be enveloped by the integuments 1ike the apical meristem
of the shoot is enclosed bud1ike in young leaves.
The poles of stamen and carpel are founded on the one side on hypo- and epiphyl1, on the
male and female gametophytes. Pol1en grain and embryo sack are basic organs, as Sachs
(1882, 15) already concluded. The polarity of the vegetative plant is linear, that of the f1ower
radial, within the centre the carpel pole and in the periphery the stamen pole.
3.3 Criterions of Polarity
The comparison of root and shoot gave the fol1owing results:
1. These structures are parts of a superimposed entity , they arise by the process of organic
disunion and imply each other .
2. Their positions are expressions of spatial polarity. 3. They have opposite structures and
qua1ities.
4. They cannot be related by a sequence of intermediate forms.
If one app1ies a similar comparison to the f1ower, then it is correct to speak of a polarity in
the structures of the f1ower:
1. The nature of the leaf of stamen and carpel is founded on the organic disunion of the
fo1iage leaf in hypo- and epiphyl1. The formation of the gametophytes is based on the
meiotic cel1 division (criterion of disunion and its imp1ication).
2. The stamens surround the carpels, which are inserted in the middle of the receptacle (spatial
criterion).
3. The third criterion (opposite structures and qua1ities) and the fourth criterion (the absence
of intermediates) are also fulfil1ed.
3.4 Different Kinds of Propagation
The question what the relation is between the pol1en grain and the embryo sack on the one
hand and the vegetative plant on the other remains. The vegetative plant can reproduce by
lateral organs (1ateral shoots and lateral roots). The f1ower does not have this abi1ity. In spite
of that, propagation in the f1ower is obviously possible by the growth of the gametophytes
and then as germ.
8
Following the descriptions of the vegetative plant and the flower, the
relationships between the root pole and the stamen pole and the shoot pole and the carpel pole
are obvious.
4. REFORMULATION OF THE CONCEPT OF THE ESSENTIAL
ORGANS AND OF THE TYPE OF THE PLANT
4.1 The Vegetative Plant
The significance of the theory of the basic or essential organs is that it leads to the knowledge
that root, (shoot) axis .and foliage leaf are different organs. The comparison. of morphological
equivalent organs is founded by this concept. The type of the vegetative plant is a model,
which shows the kind of articulation of the different organs, which have ~ a non
8
The first step is of course that the haploid spores arise. The spores of the spermatophytes germinate already in
the stamen and in the carpel, the gametophyte of the pollen grain and the embryo sack are the result of the
growing and ripening of these spores.
interchangeable position in the configuration of the plant. It is possible to determine to which
type of ground organ a specific organ belongs on account of his relative topography (main
criterion) or, when the relative position is concealed, on account of a sequence of gradual
metamorphoses (auxiliar criterion) (Froebe, 1981): The determination of homologies and
remains for the science of plant morphology an Important method.
The weakness of this theory is, that the morphological relationships between the ground
organs are negatively defined. According to Sitte (1993: 170) the basic organs cannot be 1
homologous and they perform different basic functions. The basic organs are conceptually
separated from each other in spite of being related to each other .
I propose to widen the number of possibilities to compare organs to determine the
morphological relationship of the basic organs. The first articulation of the plant is the
division of root and shoot poles. The process of understanding morphological structures and
sampling morphological knowledge should therefore start by the comparison of polar
structures. The second step is a further articulation of the polar structures. According to this
consequent process of cognition, i.e., awareness of the quality of every next step in
distinguishing structures, it becomes obvious, that one should distinguish between four
ground organs: shoot axis and root axis on the one side and foliage leaf and root organs ( (root
cap and rhizoderm with root hairs
9
on the other side. Both axes connect the leaves with the
root organ. This implies for the organisation type of the vegetative plant, that it should be
understood at first as a bipolar organism, every pole being articulated too. Both axis connect
the morphological polarities of leaf and root organ.
4.2 The Generative Plant
With the proposed four ground organs it is possible to describe the vegetative type of the
plant. The extension of this concept on the flower is only partly possible. Neither Troll (1973)
nor Sitte (1993) call attention to this problem by their discussion of the theory of the (three)
ground organs. The well known and slightly modified scheme of Sachs (1882, 48), which
Sitte and Troll present as type of the dicotyledonous plant, is not sufficient at all. Troll
(1967,53, first annotation) refers to Goethe, when he claims, that Goethe in regard of the
"Urpflanze”
10
had spoken of a vegetative type. If one reads the text in Troll’s edition of
Goethe’s morphological work (Troll, 1926, l19)
11
, than it is clear that Goethe on1y writes
about the vegetative type. The "Urpflanze" is not mentioned
12
at all. The concept of a
vegetative type makes on1y sense, when also a generative type is distinguished.
13
The concept of the generative type includes both pollen grain and embryo sack with their
gametophytes. The type of the dicot spermatophyte is articulated in a vegetative and ~ a
generative type with their specific ground organs.
4.3 Consequences for the Determination of Homologies
The concept to determine whether structures are homologous or not, which is based on the
main criterion of the relative topography and the auxiliar criterion of a sequence of gradual
metamorphoses, is in this form only partially suitable for the comparison of floral organs with
9
According to Hansen (1907, 8) Hofmeister, Nägeli and Sachs (1881) have distinguished four ground organs in
the vegetative plant. They distinguished between root, shoot axis, foliage leaf and trichoms. Hansen himself
interpreted only shoot and root as ground organs.
10
Troll (1967, 177) understands Goethe’s concept of the "Urpflanze" as a concept of the type of the
spermatophytes.
11
Troll refers to the before last passage of Goethe’s "Die Absicht eingeleitet", Jena, 1807 (Goethe, 1975, 11).
12
Troll’s annotation (1967,53) is also Hansen mentioned. Hansen (1907,275-285) refers in the context of the
"Urpflanze " also to the scheme of Sachs as a visualisation of the idealistic concept of Goethe’s "Urpflanze"
(Hansen, 1907,281 and plate XVI). The same scheme is used by Troll and Sitte.
13
A more suitable scheme of the type of the dicots is a scheme of the development of the plant, in which is
referred to the alternation of generations
organs of the vegetative shoot. In combination with the concept of the essential organs of the
vegetative and generative plant the concept of homology becomes its necessary framework.
5. METHODOLOGICAL ASPECTS
5.1 The Direction of the Cognitive Process
It is possible to connect different levels of plant structures. The question is how we do this.
According to Rutishauser & Sattler (1985) it is not possible, to find cytological and
histological. characteristics which have a diagnostic value to distinguish, for example between
axis and foliage leaf. The leaf can be axis-like, the axis can be leaf-like The axis concept and
the leaf concept cannot be defined on a cytological or histological level of organisation.
Starting from the superimposed organisation level of the shoot we analyze the shoot, we
observe the shoot as an articulated entity, and so we come to the subordinate level of
organisation, on which we distinguish between axis and leaf, consequently when, the axis is
leaf-like and conversely.
5.2 The Phytomer or Metamer Concept.
The essential organs of the vegetative plant are specifically interrelated. To understand the
change from the vegetative parts of the plant into the generative parts of the plant, it is
necessary to regard these interrelationships for these are changed too. The phytomer or
metamer concept provides a useful tool to understand these morphological changes. In his
metamorphosis Goethe describes the development of the plants. He starts with the seedling
and proceeds with the description of the sprouting, flowering and fruiting plant. He considers
both shoot axis, foliage leaf and bud. He describes in § ll3 how the plant "from node to node,
from leaf to leaf succeeds itself, that when it sprouts a kind of propagation takes place, which
differs from the propagation by the flower and fruit, which happens at once, only in the way
of being successive, for its shows itself in a sequence of separated, developing steps. This
sprouting manifests its power successively and continuously and is the same, with the one
which at once develops a considerable propagation.
14
Goethe describes in his text an
articulation of the plant in subunits. Such a subunit is also called phyton. Here in this context,
I define phyton as that subunit of the plant which includes fo1iage leaf, node, the internode
below the insertion of the leaf and the buds of the lateral root(s) and shoot(s).
The first phyton is the seedling, the following parts, which arise from the apical meristem,
metamorphose this first phyton. It is not possible to find anatomical boundaries between the
succeeding phytons. The phyton is not a basic organ. The phyton is a subunit of the plant,
which encloses all the essential organs. It is a general cognitive concept above the level of the
distinction of essential organs. One could agree to Troll, when he cites Eichler: "One could
imagine at last, (that the shoot is a sympodium of parts of the shoot: nodes, internodes, and
leaves PS), I still do not know, how this concept enriches our understanding of the plant
15
and
14
In german: "... von Knoten zu Knoten, von Blatt zu Blatt fortsetzt, indem sie sprosst, gleichfalls eine
Fortpflanzung geschehe, die sich von der Fortpflanzung durch die Blüte und Frucht, welche auf einmal
geschieht, darin unterscheidet, dass sie sukzessiv ist, dass sie sich in einer Folge einzelner Entwicklungen zeigt.
Diese sprossende, nach und nach sich äussernde Kraft ist mit jener, welche auf einmal eine grosse Fortpflanzung
entwickelt, auf das genauste verwandt".
15
In german: "Wenn es sich ja schliesslich auch vorstellen lässt, (dass der Stengel ein Sympodium von
Sprossgliedern ist PS), so weiss ich doch nicht, was mit dieser Vorstellung eigentlich gewonnen wäre."
Troll himself: “Then it is not the aim of morphology to dissect a structure (Gestalt), which is
always a wholeness, in artificial parts and then to
build up schematically the previous entity out of these parts; …”
16
(Troll, 1937, 172 ff.). The
concept of the phyton is here restricted to the vegetative plant. If one extends this concept
onto the flower, the case becomes interesting.
17
How can the transition from the vegetative
phyton to the phytons of the flower be characterised and the transitions between the different
phytons (whorls) in the flower? Following Goethe’s interpretation of the close relationship
between the vegetative and the generative propagation, it is clear, that we should not restrict
the concept of the phyton to the level of the vegetative plant. In the foregoing chapters I have
tried to show the different relations.
5.3 Spatial Discontinuity of the Metamorphosis
If one tries to look at the serial sequence of the leaf organs from the cotyledon up to the carpel
as a continuing metamorphosis of one and the same organ, one gets problems at the transition
from stamen to carpel. The spatial, linear sequence of the leaves is not identical with the
sequence of leaf metamorphosis. In the metamorphosis of the leaves there is, after the foliage
leaf, a bifurcation. For the stamen is partially homologous with the hypophyll of the foliage
leaf, the carpel is partially homologous with the epiphyll of the foliage leaf.
5.4 Quantitative and Qualitative Metamorphosis
The phyton looses its ability to give rise to lateral organs after the transition from the
vegetative to the generative plant. The phyton looses its force of propagation. This ability of
propagation must be found in a changed way in the flower. In the flower the force of
propagation is disunited. In the stamen (microsporophyll) the pollen grains mature, in the
carpel (macrosporophyll) the embryo sacks mature. The phyton of the vegetative plant
represents the whole vegetative plant, on the one hand there is the ability to give rise to lateral
roots, on the other hand to give rise to the lateral shoots. The vegetative way of propagation is
also divided into two parts. Is it possible to compare both the vegetative and the generative
way of propagation.
ACKNOWLEDGEMENTS
This study was supported by the government of the canton Graubünden in Switzerland, by the
Swiss Anthroposofic Society, and private persons. I wish especially to thank Prof. H.A.
Froebe (Botanisches Institut der RWTH, Aachen) for his support and critical remarks.
REFERENCES
Cronquist, A. (1988). The evolution and classification of flowering plants. New York, New York Botanical
Garden.
Ehrendorfer, F. (1993). Dritte Abteilung: Spermatophyta, Samenpflanzen. In: Strasburger Lehrbuch der Botanik
für Hochschulen. 33rd edition. Stuttgart, Gustav Fischer.
Froebe, H.A. and R. Classen-Bockboff (1994). Das trialektische Typuskonzept der botanischen Morphologie.
Senckenberg-Buch 70: 143-167. Frankfurt am Main, Waldemar Kramer.
Froebe, H.A. (1982). Homologiekriterien oder Argumentationsverfahren? Her. Deutsch. Bot. Ges. 95: 19-34.
Goethe, I.W. (1975). Schriften zur Botanik und Wissenschaftslehre. München, DTV Gesamtausgabe 39.
16
In german: “Denn es kommt ja in der Morphologie nicht darauf an, eine Gestalt, die ja immer ein Ganzes ist,
durch künstliche Einschnitte zu zerlegen um sodann dieses Ganze aus den Teilen in schematischer Weise wieder
zu erbauen;…“.
17
Nowadays the concept of the phyton plays a very important role in plant morphology, although this is not
always recognized. The investigations to reveal the morphogenetic processes are based on a metameric concept
(phytonistic concept) of the sprouting and flowering plant (see Meyerowitz et al, 1991; Talbert et al. 1995).
Hagemann, W. (1970). Studien zur Entwicklungsgeschichte der Angiospermenblätter. Bot Ib. 90: 297- 413.
Hagemann, W. (1984). Morphological aspects of leaf development in ferns and angiosperms. ln: R.A. White and
W.C. Dickinson, eds. Contemporary Problems in Plant Anatomy, 301-349. Orlando, Acad. Press.
Hansen, A (1907). Goethe’s Metamorphose der Pflanzen. Giessen, Alfred Töpelmann Verlag.
Hiepko, P. (1965). Vergleichend-morphologische und entwicklungsgeschichtliche Untersuchungen über , das
Perianth bei den Polycarpicae Teil 1 & 2. Bot Ib. 84: 350-426 & 427-508.
Meyerowitz, E.M. et al. (1991). Genetic interactions among floral homeotic genes of Arabidopsis. Development
ll2: 1-20.
Rutishauser, R. and R. Sattler (1985). Complementary and heuristic value of contrasting models in structural
botany. Bot Jahrb. Syst. 107: 415-455.
Sachs, I. (1882). Vorlesungen über Pflanzenphysiologie. Leipzig, Wilhelm Engelmann Verlag.
Sitte, P. (1993). Einleitung und Morphologie. In: Strasburger Lehrbuch der Botanik für Hochschulen. 33rd
edition. Stuttgart, Gustav Fischer.
Takhtajan, A. (1991). Evolutionary Trends in Flowering Plants. New York, Columbia University Press. Talbert,
P.B. et al. (1995). The REVOLUTA gene is necessary for apical meristem development and for limiting
cell-divisions in the leaves and stems of Arabidopsis thaliana. Development 121: 2723-2735.
Troll, W. (1926). Goethes morphologische Schriften. Jena, Eugen Diederichs Verlag.
Troll, W. (1967). Vergleichende Morphologie der höheren Pflanze. Teil1. Nachdruck. Königstein/T, Otto
Koeltz.
Troll, W. (1973). Praktische Einführung in die Pflanzenmorphologie, der vegetative Aufbau- Nachdruck,
Königstein/T, Otto Koeltz.
Weberling, F. (1981). Morphologie der Blüten under der Blütenstände. Stuttgart, Verlag Eugen Ulmer.
