History of botany (1530-1860)

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HISTORY OF BOTANY

SA CHS

HENRY FROWDE

Oxford University Press Warehouse
Amen Corner, E.C.

HISTORY OF BOTANY

(1530— 1860)

BY

JULIUS VON SACHS

PROFESSOR OF BOTANY IN THE UNIVERSITY OF WIJRZBURG

AUTHORISED TRANSLATION

HENRY E. F. GARNSEY, M.A.

Fdloiu of Magdalen College, Oxford
REVISED BY

ISAAC BAYLEY BALFOUR, M.A., M.D., F.R.S.

Professor of Botany in the University
And Keeper of the Royal Botanic Garden, Edinburgh

AT THE CLARExXDON PRESS
1 890

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PRINTED AT THE CLARENDON PRESS

BY HORACE HART. PRINTER TO THE UNIVERSITY

PREFACE.

Botanical Science is made up of three distinct
branches of knowledge, Classification founded on Mor-
phology, Phytotomy, and Vegetable Physiology. All
these strive towards a common end, a perfect under-
standing of the vegetable kingdom, but they differ en-
tirely from one another in their methods of research, and
therefore presuppose essentially different intellectual en-
dowments. That this is the case is abundantly shown by
the history of the science, from which we learn that up to
quite recent times morphology and classification have
developed in almost entire independence of the other two
branches. Phytotomy has indeed always maintained a
certain connection with physiology, but where principles
peculiar to each of them, fundamental questions, had to
be dealt with, there they also went their way in almost
entire independence of one another. It is only in the
present day that a deeper conception of the problems
of vegetable life has led to a closer union between
the three. I have sought to do justice to this historical
fact by treating the parts of my subject separately; but in
this case, if the present work was to be kept within suit-
able limits, it became necessary to devote a strictly limited
space only to each of the three historical delineations. It
is obvious that the weightiest and most important matter
only could find a place in so narrow a frame, but this I do

vi Preface.

not exactly regard as a misfortune, and in the interests of
the reader it is rather an advantage ; for, in accordance
with the objects of the 'General History of the Sciences,'
this History of Botany is not intended for professional
persons only, but for a wider circle of readers, and to
these perhaps even the details presented in it may here
and there seem wearisome.

The style of the narrative might have been freer, and
greater space might have been allotted to reflections on the
inner connection of the whole subject, if I had had before
me better preliminary studies in the history of botany ;
but as things are, I have found myself especially occupied
in ascertaining questions of historical fact, in distinguish-
ing true merit from undeserved reputation, in searching
out the first beginnings of fruitful thoughts and observing
their development, and in more than one case in pro-
ducing lengthy refutations of wide-spread errors. These
things could not be done within the allotted space without
a certain dryness of style and manner, and I have often
been obliged to content myself with passing allusions
where detailed explanation might have been desired.

As regards the choice of topics, I have given promin-
ence to discoveries of facts only when they could be
shown to have promoted the development of the science ;.
on the other hand, I have made it my chief object to dis-
cover the first dawning of scientific ideas and to follow
them as they developed into comprehensive theories, for
in this lies, to my mind, the true history of a science.
But the task of the historian of Botany, as thus conceived,
is a very difficult one, for it is only with great labour
that he succeeds in picking the real thread of scientific
thought out of an incredible chaos of empirical material.

Preface. vii

It has always been the chief hindrance to a more rapid
advance in botany, that the majority of writers simply
collected facts, or if they attempted to apply them to
theoretical purposes, did so very imperfectly. I have
therefore singled out those men as the true heroes of
our story who not only established new facts, but gave
birth to fruitful thoughts and made a speculative use of
empirical material. From this point of view I have taken
ideas only incidentally thrown out for nothing more than
they were originally ; for scientific merit belongs only to
the man who clearly recognises the theoretical importance
of an idea, and endeavours to make use of it for the pro-
motion of his science. For this reason I ascribe little
value, for instance, to certain utterances of earlier writers,
whom it is the fashion at present to put forward as the
first founders of the theory of descent ; for it is an in-
dubitable fact that the theory of descent had no scientific
value before the appearance of Darwin's book in 1859, and
that it was Darwin who gave it that value. Here, as in
other cases, it appears to me only true and just to abstain
from assigning to earlier writers merits to which prob-
ably, if they were alive, they would themselves lay no
claim.

J. SACHS.

AViJRZBURG, y«/j' 22, 1S75.

THE AUTHOR'S PREFACE

To the English translation of the History of Botany of
Julius von Sachs.

I AM gratefully sensible of the honourable distinction
implied in the determination of the Delegates of the
Clarendon Press to have my History of Botany trans-
lated into the world-wide language of the British Empire.
Fourteen years have elapsed since the first appearance of
the work in Germany, from fifteen to eighteen years since
it was composed, — a period of time usually long enough in
our age of rapid progress for a scientific work to become
obsolete. But if the preparation of an English translation
shows that competent judges do not regard the book as
obsolete, I should be inclined to refer this to two causes.
First of all, no other work of a similar kind has appeared,
as far as I know, since 1875, so that mine may still be
considered to be, in spite of its age, the latest history of
Botany ; secondly, it has been my endeavour to ascertain
the historical facts by careful and critical study of the
older botanical literature in the original works, at the cost
indeed of some years of working-power and of consider-
able detriment to my health, and facts never lose their
value, — a truth which England especially has always
recognised.

But the present work is not a simple enumeration of the

The Author's Preface. ix

names of botanists and of their writings, no mere list of
the dates of botanical discoveries and theories ; such was
not at all my plan when I designed it. On the contrary I
purposed to present to the reader a picture of the way in
which the first beginnings of scientific study of the veget-
able world in the sixteenth century made their appearance
in alliance with the culture prevailing at the time, and how
gradually by the intellectual efforts of gifted men, who at
first did not even bear the name of botanists, an ever
deepening insight was obtained into the relationship of all
plants one to another, into their outer form and inner
organisation, and into the vital phenomena or physio-
logical processes dependent on these conditions.

For the attainment of this end it was above all things
necessary for me to form a clear judgment respecting
the influence of the views and principles enunciated
by the different authors on the further development of
botanical science. This is to the historian of science
the central point round which all beside should be
disposed, and without which the entire work breaks up
into a collection of unmeaning details, and it is one which
demands knowledge of the subject, and capacity and
impartiality of judgment. On questions connected with
times long gone by the decision of the experts has in
most cases been already given, though I myself found to
my surprise that older authors had for centuries been
regarded as the founders of views which they had dis-
tinctly repudiated as absurd, showing how necessary it is
that the works of our predecessors should from time to
time be carefully read and compared together. But in
the majority of cases there is no dispute at the present
day respecting the historical value, that is the operative

X The Author's Preface.

influence on posterity, of works written three hundred or
even one hundred years ago.

But it is a very different matter when the author of a
book hke mine ventures, as I have done for sufficient
reasons but at the same time with regret, to sit in judg-
ment on the works of men of research and experts, who
belong to our own time and who exert a lively influence
on their generation. In this case the author can no longer
appeal to the consentient opinion of his contemporaries ;
he finds them divided into parties, and involuntarily be-
longs to a party himself But it is a still more weighty
consideration that he may subsequently change his own
point of view, and may arrive at a more profound insight
into the value of tlie works which he has criticised ; con-
tinued study and maturer years may teach him that he
overestimated some things fifteen or twenty years ago
and perhaps undervalued others, and facts, once assumed
to be well estabHshed, may now be acknowledged to be
incorrect.

Thus it has happened in my own case also in some but
not in many instances, in which I have had to express an
opinion respecting the character of works which appeared
after i860, and which to some extent influenced my judg-
ment on the years immediately preceding them. But this
was from fifteen to eighteen years ago when I was working
at my History. It might perhaps be expected that I should
remove all such expressions of opinion from the work
before it is translated. In some few cases, in which this
could be effected by simply drawing the pen through a few
lines, I have so done ; but it appeared to me that to alter
with anxious care every sentence which I should put into
a different form at the present day would serve no good

TJie Author's Preface. xi

purpose, for I came to the conclusion that my book itself
may be regarded as a historical fact, and that the kindly
and indulgent reader may even be glad to know what- one,
who has lived wholly in the science and taken an interest
in everything in it old and new, thought from fifteen to
eighteen years ago of the then reigning theories, repre-
senting as he did the view of the majority of his fellow-
botanists.

However, these remarks relate only to two famous
writers on the subjects with which this History is con-
cerned. If the work had been brought to a close with the
year 1850 instead of i860, I should hardly have found it
necessary to give them so prominent a position in it.
Their names are Charles Darwin and Karl Nageli. I
would desire that whoever reads what I have written on
Charles Darwin in the present work should consider that
it contains a large infusion of youthful enthusiasm still
remaining from the year 1859, when the 'Origin of
Species ' delivered us from the unlucky dogma of con-
stancy. Darwin's later writings have not inspired me
with the like feeling. So it has been with regard to
Nageli. He, like Hugo von Mohl, was one of the first
among German botanists who introduced into the study
that strict method of thought which had long prevailed in
physics, chemistry, and astronomy ; but the researches
of the last ten or twelve years have unfortunately shown
that Nageli's method has been applied to facts which,
as facts, were inaccurately observed. Darwin collected
innumerable facts from the literature in support of an
idea, Nageli applied his strict logic to obscr\'ations
which were in part untrustworthy. The services which
each of these men rendered to the science are still

xii The Author s Preface.

acknowledged ; but my estimate of their importance for
its advance would differ materially at the present moment
from that contained in my History of Botany. At the
same time I rejoice in being able to say that I may some-
times have overrated the merits of distinguished men, but
have never knowingly underestimated them.

Dr. J. VON SACHS,

Foreign Felloiv of the Royal Society.
WiJRZBURG, March 24, 1889.

NOTE BY THE TRANSLATOR.

No History of Botany in English has ever been
published, and it is to supply in some measure this want,
long felt by English-speaking students, that this trans-
lation of Professor Sachs' masterly sketch has been pre-
pared.

H. E. F. G.

CONTENTS,

FIRST BOOK.

History of Morphology and Classification.

1530-1860.

PAGE

Introduction 3

CHAPTER I.

The Botanists of Germany and the Netherlands from Brunfels to

Caspar Banhin, 1 530-1623 13

CHAPTER II.

Artificial Systems and Terminology of Organs from Cesalpino to

Linnaeus, 1583-1760 37

CHAPTER III.

Development of the Natural System under the Influence of the

Dogma of the Constancy of Species, 1 759-1S50. . . . ToS

CHAPTER IV.

Morphology under the Influence of the Doctrine of Metamorphosis

and of the Spiral Theory, 1 790-1850 ..... 155

CHAPTER V.

Morphology and Systematic Botany under the Influence of the
History of Development and the knowledge of the Cryptogams,
1840-1860 i8i

xiv Contents.

SECOND BOOK.

History of Vegetable Anatomy.
1671-1860.

PAGE

Introduction ........... 219

^ CHAPTER I.

Phytotomy founded by Malpighi and Grew, 1671-1682 . . . 229

CHAPTER H.
Phytotomy in the Eighteenth Century ...... 246

CHAPTER ni.

Examination of the Matured Framework of Cell-Membrane in Plants,

1 800-1 840 256

CHAPTER IV.

History of Development of the Cell, Formation of Tissues, Molecular

Stmcture of Organised Forms, 1840-1860 . . . .311

THIRD BOOK.

History of Vegetable Physiology.

1583-1860.

Introduction 359

CHAPTER I.

History of the Sexual Theory

1. From Aristotle to R. J. Camerarius 376

2. Establishment of the Doctrine of Sexuality in Plants by R. J.

Camerarius, 1691-1694 ....... 385

3. Dissemination of the New Doctrine ; its Adherents and

Opponents, 1700-1760 ....... 390

4. The Theory of Evolution and Epigenesis .... 402

Contents. xv

pacf;

5. Further Development of the Sexual Theory by J. G. Koel-

reuter and Konrad Sprengel, 1 761-1793 .... 406

6. New opponents of Sexuality and their refutation by Ex-

periments, 1 785-1849 . . . . . . .422

7. Microscopic Investigation into the Processes of Fertilisation

in the Phanerogams, the Pollen-Tube and Eggs, 1830-1850 431
S. Discovery of Sexuality in the Cr)'ptogams, 1837-1860 . 436

CHAPTER II.

History of the Theory of Nutrition of Plants, T 583-1 860 . . 445

1. Cesalpino, 1583 ......... 450

2. First Inductive Experiments and Opening of New Points of

View in the History of the Theory of the Nutrition of
Plants, to 1 730 453

3. Fruitless Attempts to Explain the Movement of the Sap in

Plants, 1 730-1 780 482

4. The Modem Theory of Nutrition Foimded by Ingen-Houss

and Theodore de Saussure, 1779-1804 .... 491

5. Vital Force. Respiration and Heat of Plants. Endosmose,

1804-1840 504

6. Settlement of the Question of Food-Material of Plants,

1 840-1 S60 . . . 524

CHAPTER III.

Histor}- of Phytodynamics

From end of 17th centurj' to about i860 .... 535

Index 565

ERRATA.

Page 1 8, line 3 from bottom, y^r Chini read Ghini
,, 20, „ 7, yiir Schmiedel rm^ Schmidel
„ 160, ,, 2 from bottom, y^r many rffl!(f some
,, 160, note, /or Robert read L,oms Marie Aubert
,, 201, line ii,yor asexually read sexna.\\y.

FIRST BOOK

HISTORY OF MORPHOLOGY AND
CLASSIFICATION

( 1 530-1 860)

INTRODUCTION.

The authors of the oldest herbals of the i6th century',
Brunfels, Fuchs, Bock, MattioH and others, regarded plants
mainly as the vehicles of medicinal virtues ; to them plants
were the ingredients in compound medicines, and were there-
fore by preference termed ' simplicia,' simple constituents of
medicaments. Their chief object was to discover the plants
employed by the physicians of antiquity, the knowledge of
which had been lost in later times. The corrupt texts of
Theophrastus, Dioscorides, Pliny and Galen had been in many
respects improved and illustrated by the critical labours of the
Italian commentators of the 15th and of the early part of the
1 6th century ; but there was one imperfection which no
criticism could remove, — the highly unsatisfactory descriptions
of the old authors or the entire absence of descriptions. It
was moreover at first assumed that the plants described by
the Greek physicians must grow wild in Germany also, and
generally in the rest of Europe ; each author identified a
different native plant with some one mentioned by Dioscorides
or Theophrastus or others, and thus there arose as early as the
1 6th century a confusion of nomenclature which it was scarcely
possible to clear away. As compared with the efforts of the
philological commentators, who knew little of plants from their
own observation, a great advance was made by the first German
composers of herbals, who went straight to nature, described
the wild plants growing around them and had figures of them
carefully executed in wood. Thus was made the first begin-
ning of a really scientific examination of plants, though the
aims pursued were not yet truly scientific, for no questions

B 2

4 Introduction.

were proposed as to the nature of plants, their organisation or
mutual relations ; the only point of interest was the knowledge
of individual forms and of their medicinal virtues.

The descriptions were at first extremely inartistic and un-
methodical ; but the effort to make them as exact and clear as
was possible led from time to time to perceptions of truth, that
came unsought and lay far removed from the object originally
in view. It was remarked that many of the plants which
Dioscorides had described in his Materia Medica do not
grow wild in Germany, France, Spain, and England, and that
conversely very many plants grow in these countries, which
were evidently unknown to the ancient writers ; it became
apparent at the same time that many plants have points of
resemblance to one another, which have nothing to do with
their medicinal powers or with their importance to agriculture
and the arts. In the effort to promote the knowledge of plants
for practical purposes by careful description of individual forms,
the impression forced itself on the mind of the observer, that
there are various natural groups of plants which have a distinct
resemblance to one another in form and in other characteristics.
It was seen that there were other natural alliances in the veget-
able world, beside the three great divisions of trees, shrubs, and
herbs adopted by Aristotle and Theophrastus. The first per-
ception of natural groups is to be found in Bock, and later
herbals show that the natural connection between such plants
as occur together in the groups of Fungi, Mosses, Ferns,
Coniferae, Umbelliferae, Compositae, Labiatae, Papilionaceae
was distinctly felt, though it was by no means clearly understood
how this connection was actually expressed ; the fact of natural
affinity presented itself unsought as an incidental and indefinite
impression, to which no great value was at first attached. The
recognition of these groups required no antecedent philosophic
reflection or conscious attempt to classify the objects in the
vegetable world ; they present themselves to the unprejudiced
eye as naturally as do the groups of mammals, birds, reptiles,

Introduction. 5

fishes and worms in the animal kingdom. The real resem-
blance of the organisms in such groups is unconsciously
accepted by the mind through the association of ideas, and
it is not till this involuntary mental act, which in itself requires
no effort of the understanding, is accomplished, that any neces-
sity is felt for obtaining a clearer idea of the phenomenon, and
the sense of this necessity is the first step to intentional sys-
tematic enquiry. The series of botanical works published in
Germany and the Netherlands from 1530 to 1623, from
Brunfels to Kaspar Bauhin, shows very plainly how this per-
ception of a grouping by afifinity in the vegetable kingdom grew
more and more distinct ; but it also shows how these men
merely followed an instinctive feeling in the matter, and made
no enquiry into the cause of the relationship which they
perceived.

Nevertheless a great step in advance was thus taken ; all the
foreign matter introduced into the description of plants by
medical superstition and practical considerations was seen to be
of secondary importance, and was indeed altogether thrown
aside by Kaspar Bauhin ; the fact of natural affinity, the vivify-
ing principle of all botanical research, came to the front in its
place, and awakened the desire to distinguish more exactly
whatever was different, and to bring together more carefully all
that was like in kind. Thus the idea of natural affinity in
plants is not a discovery of any single botanist, but is a
product, and to some extent an incidental product, of the
practice of describing plants.

But before the exhibition of the natural affinity gave birth to
thefirst efforts at classification on the part of de I'Obel (Lobelius)
and afterwards of Kaspar Bauhin, the Italian botanist Ccsalpino
(1583) had already attempted a system of the vegetable king-
dom on a very different plan. He was led to distribute all
vegetable forms into definite groups not by the fact of natural
affinity, which impressed itself on the minds of the botanists of
Germany and the Netherlands through involuntary association

6 Introduction.

of ideas, but by philosophical reflection. Trained in the phi-
losophy which flourished in Italy in the i6th century, deeply
imbued with the doctrines of Aristotle, and practised in all
subtleties of the schools, Cesalpino was not the man to surren-
der himself quietly to the influence of nature on the unconscious
powers of the mind ; on the contrary, he sought from the first
to bring all that he learnt from the writings of others and from
his own acute observation of the forms of plants into subjection
to his own understanding. Hence he approached the task of
the scientific botanist in an entirely different way from that of
de rObel and Kaspar Bauhin. It was by philosophical reflec-
tions on the nature of the plant and on the substantial and
accidental value of its parts, according to Aristotelian concep-
tions, that he was led to distribute the vegetable kingdom into
groups and sub-groups founded on definite marks.

This difference in the origin of the systematic efforts of
Cesalpino on the one hand and of de I'Obel and Bauhin on the
other is unmistakably apparent ; the Germans were instinc-
tively led by the resemblances to the conception of natural
groups, Cesalpino on the contrary framed his groups on the
sharp distinctions which resulted from the application of pre-
determined marks ; all the faults in Bauhin's system are due
to incorrect judgment of resemblances, those of Cesalpino to
incorrectness in distinguishing.

But the main point of difference lies in the fact, that the
system is presented by de I'Obel and Bauhin without any state-
ment of the principles on which it rests ; in their account of it
the association of ideas is left to perfect itself in the mind of
the reader, as it grew up before in the authors themselves.
De I'Obel and Bauhin are like artists, who convey their own
impressions to others not by words and descriptions, but
by pictorial representations ; Cesalpino, on the other hand,
addresses himself at once to the understanding of his reader
and shows him on philosophic grounds that there must
be a classification, and states the principles of this classifi-

Introduction. 7

cation ; it was on philosophic grounds also that he made the
characters of the seed and the fruit the basis of his arrange-
ment, while the German botanists, paying little attention to the
organs of fructification, were chiefly influenced by the general
impression produced by the plant, by its habit as the phrase
now is.

The historians of botany have overlooked the real state of
the case as here presented, or have not described it with
sufficient emphasis ; due attention has not been paid to the
fact, that systematic botany, as it began to develope in the
17th century, contained within itself from the first two oppos-
ing elements ; on the one hand the fact of a natural affinity
indistinctly felt, which was brought out by the botanists of
Germany and the Netherlands, and on the other the desire, to
which Cesalpino first gave expression, of arriving by the path
of clear perception at a classification of the vegetable kingdom
which should satisfy the understanding. These two elements
of systematic investigation were entirely incommensurable ;
it was not possible by the use of arbitrary principles of
classification which satisfied the understanding to do justice
at the same time to the instinctive feehng for natural affinity
which would not be argued away. This incommensurability
between natural affinity and a priori grounds of classification
is everywhere expressed in the systems embracing the whole
vegetable kingdom, which were proposed up to 1736, and
which including those of Cesalpino and Linnaeus were not less
in number than fifteen. It is the custom to describe these
systems, of which those of Cesalpino, Morison, Ray, Bachmann
(Rivinus), and Tournefort are the most important, by the one
word 'artificial"; but it was by no means the intention of
those men to propose classifications of the vegetable kingdom
which should be merely artificial, and do no more than offer an

' It will be shown in a later chapter that Linnaeus' sexual system was
intended to be artificial.

8 Introduction.

arrangement adapted for ready reference. It is true that the
botanists of the 17th century and Linnaeus himself often spoke
of facility of use as a great object to be kept in view in con-
structing a system ; but every one who brought out a new
system did so really because he believed that his own was
a better expression of natural affinities than those of his pre-
decessors. If some like Ray and Morison were more influenced
by the wish to exhibit natural affinities by means of a system, and
others as Tournefort and Magnol thought more of framing a
perspicuous and handy arrangement of plants, yet it is plain
from the objections which every succeeding systematist makes
to his predecessors, that the exhibition of natural affinities was
more or less clearly in the minds of all as the main object of
the system ; only they all employed the same wrong means for
securing this end, for they fancied that natural affinities could
be brought out by the use of a few easily recognised marks,
whose value for systematic purposes had been arbitrarily de-
termined. This opposition between means and end runs
through all systematic botany from Cesalpino in 1583 to
Linnaeus in 1736.

But a new departure dates from Linnaeus himself, since he
was the first who clearly perceived the existence of this discord.
He was the first who said distinctly, that there is a natural
system, of plants, which could not be established by the use of
predetermined marks, as had been previously attempted, and
that even the rules for framing it were still undiscovered. In
his Fragments of the date of 1738, he gave a Hst of sixty-five
groups or orders, which he regarded provisionally as cycles of
natural affinity, but he did not venture to give their character-
istic marks. These groups, though better separated and more
naturally arranged than those of Kaspar Bauhin, were like his
founded solely on a refined feeling for the relative resemblances
and graduated differences that were observed in comparing
plants with one another, and this is no less true of the enumer-
ation of natural families attempted by Bernard de Jussieu in

Introduction. 9

1759. To such of these small groups of related forms as had
not been already named both Linnaeus and Jussieu gave names,
which they took not from certain marks, but from the name
of a genus in each group. But this mode of naming plainly
expresses the idea which from that time forward prevailed in
systematic botany, that there is a common type lying at the
foundation of each natural group, from which all its forms
though specifically distinct can be derived, as the forms of a
crystal may all be derived from one fundamental form, — an
idea which was also expressed by Pyrame de Candolle in 18 19.

But botanists could not rest content with merely naming
natural groups ; it was necessary to translate the indistinct
feeling, which had suggested the groups ot Linnaeus and
Bernard de Jussieu, into the language of science by assigning
clearly recognised marks ; and this was from this time forward
the task of systematists from Antoine Laurent de Jussieu and
de Candolle to Endlicher and Lindley. But it cannot be
denied, that later systematists repeatedly committed the fault
of splitting up natural groups of affinity by artificial divisions
and of bringing together the unlike, as Cesalpino and the
botanists of the 17th century had done before them, though
continued practice was always leading to a more perfect
exhibition of natural affinities.

But while natural relationship was thus becoming more and
more the guiding idea in the minds of systematists, and the
experience of centuries was enforcing the lesson, that prede-
termined grounds of classification could not do justice to natural
affinities, the fact of affinity became itself more unintelligible and
mysterious. It seemed impossible to give a clear and precise
definition of the conception, the exhibition of which was felt
to be the proper object of all efforts to discover the natural
system, and which continued to be known by the name of
affinity. A sense of this mystery is expressed in the sentence
of Linnaeus : ' It is not the character (the marks used to
characterise the genus) which makes the genus, but the genus

lo Introduction.

which makes the character;' but the very man, who first
distinctly recognised this difficulty in the natural system,
helped to increase it by his doctrine of the constancy of
species. This doctrine appears in Linnaeus in an unobtrusive
form, rather as resulting from daily experience and liable to be
modified by further investigation; but it became with his
successors an article of faith, a dogma, which no botanist could
even doubt without losing his scientific reputation ; and thus
during more than a hundred years the belief, that every
organic form owes its existence to a separate act of creation
and is therefore absolutely distinct from all other forms,
subsisted side by side with the fact of experience, that
there is an intimate tie of relationship between these forms,
which can only be imperfectly indicated by definite marks.
Ever}^ systematist knew that this relationship was something
more than mere resemblance perceivable by the senses, while
thinking men saw the contradiction between the assumption of
an absolute difference of origin in species (for that is what is
meant by their constancy) and the fact of their affinity.
Linnaeus in his later years made some strange attempts to
explain away this contradiction ; his successors adopted a way
of their own ; various scholastic notions from the i6th century
still survived among the systematists, especially after Linnaeus
had assumed the lead among them, and it was thought that the
dogma of the constancy of species might find especially in
Plato's misinterpreted doctrine of ideas a philosophical justifi-
cation, which was the more acceptable because it harmonised
well with the tenets of the Church. If, as Elias Fries said
in 1835, there is ' quoddam supranaturale' in the natural system,
namely the affinity of organisms, so much the better for the
system ; in the opinion of the same writer each division of
the system expresses an idea ('singula sphaera (sectio) ideam
quandam exponit'), and all these ideas might easily be explained
in their ideal connection as representing the plan of creation.
If observation and theoretical considerations occasionally

Introduction.

II

suggested objections to such views, these objections were
usually little regarded, and in fact reflections of this kind
on the real meaning of the natural system did not often
make their appearance ; the most intelligent men turned
away with an uncomfortable feeling from these doubts and
difficulties, and preferred to devote their time and powers
to the discovery of affinities in individual forms. At
the same time it was well understood that the question
was one which lay at the foundation of the science. At
a later period the researches of Niigeli and others in mor-
phology resulted in discoveries of the greatest importance to
systematic botany, and disclosed facts which were necessarily
fatal to the hypothesis, that every group in the system represents
an idea in the Platonic sense ; such for instance were the re-
markable embryological relations, which Hofmeister discovered
in 185 1, between Angiosperms, Gymnosperms, Vascular Crypto-
gams and Muscineae ; nor was it easy to reconcile the fact,
that the physiologico-biological peculiarities on the one hand
and the morphological and systematic characters on the other
are commonly quite independent of one another, with the plan
of creation as conceived by the systematists. Thus an oppo-
sition between true scientific research and the theoretical views
of the systematists became more and more apparent, and no
one who paid attention to both could avoid a painful feehng of
uncertainty with respect to this portion of the science. This
feeling was due to rhe dogma of the constancy of species, and
to the consequent impossibility of giving a scientific definition
of the idea of affinity.

This state of things finally ceased with the appearance of
Darwin's first and best book on the origin of species in 1859 ;
from a multitude of facts, some new, but most of them long
well-known, he showed that the constancy of species was no
longer an open question ; that the doctrine was no result of
exact observation, but an article of faith opposed to observa-
tion. The establishment of this truth was followed almost as a

12 Introduction.

matter of course by the true conception of that which had been
hitherto figuratively called affinity ; the degrees of affinity ex-
pressed in the natural system indicated the different degrees of
derivation of the varying progeny of common parents ; out of
affinity taken in a figurative sense arose a real blood-relation-
ship, and the natural system became a table of the pedigree of
the vegetable kingdom. Here was the solution of the ancient
problem.

Darwin's theory has this special interest in the history of the
science, that it established clearness in the place of obscurity,
a scientific principle in place of a scholastic mode of thought,
in the domain of systematic botany and morphology. Yet
Darwin did not effect this change in opposition to the historical
development of our science or independently of it ; on the
contrary his great merit is that he has correctly appreciated the
problems long existing in systematic botany and morphology
from the point of view of modern research, and has solved
them.

That the constancy of species is incompatible with the idea
of affinity, that the morphological (genetic) nature of organs
does not proceed on parallel lines with their physiological and
functional significance, are facts which were known in botany
and zoology before the time of Darwin ; but he was the first to
show, that variation and natural selection in the struggle for
existence solve these problems, and enable us to conceive of
these facts as the necessary effects of known causes ; it is at
the same time explained, why the natural affinity first recog-
nised by de I'Obel and Kaspar Bauhin cannot be exhibited by
the use of predetermined principles of classification, as was
attempted by Cesalpino.

CHAPTER I.

The Botanists of Germany and the Netherlands from

BRUNFELS to KaSPAR BAUHIN^

1530-1623.

When those who are accustomed to modern botanical h'tpra-
ture take up for the first time the works of Otto Brunfels (1530),
Leonhard Fuchs (1542), Hieronymus Bock (Tragus), or of the
later authors Rembert Dodoens (Dodoniius), Charles de I'Ecluse
(Carolus Clusius), Matthias de I'Obel (Lobelius, 1576), or
even those of Kaspar Bauhin from the beginning of the 1 7th
centur)', they are surprised not only by the strange form,
the curious and unfamiliar accessories from which what is
really useful must be laboriously extracted, but still more by
the extraordinary poverty of thought which characterises these
composers of usually very thick fohos. If however instead of
travelling backwards from the present time they pursue the
opposite direction ; if they have previously occupied themselves
with the botanical views of Aristotle and the comprehensive
botanical works of his disciple Theophrastus of Eresus, with
Pliny's Natural History and the medical science of Dioscorides;

^ Kurt Sprengel in his * Geschichte der Botanik,' i. 1817, and Ernst
Meyer in his 'Geschichteder Botanik,' iv. 1857 have described the connection
between the first beginnings of modem botany and the general state of
learning in the 15th and 16th centuries ; a particularly interesting notice of
Valerius Cordus from the pen of Thilo Irmisch will be found in the ' Prii-
fungsprogramm ' of the Schwarzburg gymnasium of Sondershausen for 1862.
Here, as throughout, the present work will be confined to the investigation
and description of the development of strictly botanical ideas.

14 Botanists of Germany and the Netherlands [Book i.

if they have made themselves acquainted with the botanical
literature of the middle ages and noted how it continually
grows less and less valuable, and have proceeded through the
works of Albertus Magnus, as prolix as they are deficient in
ideas, to the ' Hortus Sanitatis ' (Garden of Health), the popu-
lar work on natural history before and after 1500, and similar
productions, then certainly they receive a very different and
almost imposing impression even from the first herbals, those
of Brunfels, Bock, and Fuchs. These books will appear to
them almost modern in comparison with the last-named pro-
ductions of medieval superstition, nor will they fail to perceive
that a new epoch of natural science commenced with these
men, and above all that they laid the foundations of modern
botany. They give us, it is true, nothing but separate descrip-
tions of the wild and cultivated plants of Germany, and these
for the most part of common occurrence, arranged by Fuchs
alphabetically, by Bock grouped under the heads of herbs,
shrubs, and trees, and following one another under each head
in the most motley order ; it is true that these descriptions are
so naive and inartistic as hardly to offer points of comparison
with modern scientifically correct diagnoses ; but the great
point is, that they are taken from the plants as they lay
before the writers, who had often seen and carefully examined
them. Woodcuts are added to supply any defects in the
description, and to give a clear idea of the plant intended
by the name ; and these figures, which always give the whole
plant and were drawn immediately from nature by the hands
of practised artists, are so true to nature that a botanist's eye at
once recognises in every case the object meant to be repre-
sented. These figures and descriptions (the latter are wanting
in Brunfels \ 1530) would have rendered a great service to the

' Otto Brunfels, born at Mainz before the year 1500, was at first a
student of theology and a monk ; becoming a convert to Protestantism he
was actively engaged at Strassburg first as a teacher and afterwards as a
physician; he died in 1534.

Chap. I.] jrom Brunfels to Kaspar Batihin 15

science, even if they had not been as good as they are ; for
botanical literature had sunk so low, that not only were the
figures embellished with fabulous additions, as in the ' Hortus
Sanitatis,' and sometimes drawn purely from fancy, but the
meagre descriptions of quite common plants were not taken
from nature, but borrowed from earlier authorities and eked
out with superstitious fictions. The powers of independent
judgment were oppressed and stunted in the middle ages, till
at last the very activity of the senses, resting as it does to a
great extent on unconscious operations of the understanding,
became weak and sickly ; natural objects presented themselves
to the eye even of those who made them their study in
grotesquely distorted forms ; every sensuous impression was
corrupted and deformed by the influence of a superstitious
fancy. In comparison with these perversions the artless
descriptions of Bock appear suitable and true, and are refresh-
ing from their immediate contact with nature ; while in the
more learned Fuchs criticism of other writers is already seen
united with actual examination of natural objects. Great was
the gain when men began once more to look at plants with
open eyes, to take pleasure in their variety and beauty. It was
not necessary for a while that they should speculate on the
nature of plants, or the cause of plant-life ; time enough
for that when sufficient practice had been gained in the percep-
tion of their resemblances and differences.

The German fathers of botany connected their labours with
the botanical literature of classical antiquity only so far as they
sought to recognise in the plants of their own country those
named by Theophrastus, Dioscorides, Pliny and Galen. The
attempt to do this indeed led to many mistakes, for the descrip-
tions of the ancient botanists were very imperfect and often
quite unserviceable for the recognition of the plants described.
In this point therefore the compilers of herbals found no
models worthy of imitation in the old writers. But in seeking
to recover a knowledge of the medicinal plants of the Greek

1 6 Botanists of Germany and the Netherlands [Book i.

physicians \ they were compelled to compare together a great
variety of native plants, and thus to exercise and perfect the
faculty of apprehending differences of form. This mode of
proceeding, arising out of medical requirements, directed the
attention entirely to the individual form, which was also the
chief thing required in the interest of pure science, and much
more was thus gained than if these men had only followed the
philosophical writings of Aristotle*^ and Theophrastus^. The
Greek authors built their views on the philosophy of botany on
very weak foundations ; scarcely a plant was known to them
exactly in all its parts ; they derived much of their knowledge
from the accounts of others, often from dealers in herbs. From
this scanty material and from various popular superstitions had
Aristotle formed his views on the nature of plants, and if
Theophrastus possessed more experimental knowledge, he still
saw facts in the light of his master's philosophical doctrines.
If we succeed in the present day in extracting much that is
accurate from the writings of Aristotle and Theophrastus, it was
nevertheless well that the first compilers of herbals ceased to
pay attention to them, and occupied themselves with accumu-
lating descriptions of individual plants worked out by them-

^ Beside the herbals mentioned in the text, which may be regarded as
scientific works on botany, a considerable number of books on the signature
of plants were written in the i6th and 17th centuries in the interests of
medicine or medical superstition. It was believed that certain external
marks and resemblances between parts of plants and the organs of the
human body indicated the plants and the parts of them which possessed
healing virtues. Pritzel mentions by name twenty-four works of the kind,
which appeared between 1550 and 1697. The herbals also noticed the sig-
natures, and even Ray has an enquiry into the subject.

^ The fragments of Aristotelian botany which have come down to us are
to be found translated from Wimmer's edition in Ernst Meyer's ' Geschichte
der Botanik,' i. p. 94.

^ Ernst Meyer (Geschichte der Botanik) gives a full account of Theo-
phrastus, who was bom at Lesbos A.c. 371 and died A.c. 286. An edition
of his work ' De historia et de causis plantarum ' was published by Theodor
Gaza in 1483. See also Pritzel's ' Thesaurus literarum botanicanim.'

Chap. I.] froui Briuifcls to Kasptt)' Baiihin. 1 7

selves with all possible exactness. History shows that in this
way a new science arose in the course of a few years, while the
philosophical botany of Aristotle and Theophrastus has led to
no important result. Moreover we shall see how even in the
hands of a philosophically gifted and scholarly man like
Cesalpino the teaching of Aristotle had only a mischievous
effect on the study of plants.

If the compilers of herbals did not aim at deducing general
conclusions from their observations, yet the continually accu-
mulating descriptions of individual forms gradually gave rise
of themselves to perceptions of an abstract and more compre-
hensive character. The feeling for resemblance and difference
of form especially was developed, and finally the idea of natural
relationship; and though this idea was as yet by no means worked
out with scientific precision, it was nevertheless, even in the in-
distinct form in which it appears in de I'Obel in 1576 and more
clearly in Kaspar Bauhin in 1623, a result of the highest value,
and one of which neither learned antiquity nor the middle ages
had ever caught a glimpse. The perception of a natural affinity
among plants could only be obtained from exact description a
thousand times repeated, never from the abstractions of the
Aristotelian school, which rested essentially on superficial
observation. It appears then that the scientific value of the
herbals of the i6th century lay mostly in the description of such
plants as every botanist found in a somewhat limited portion
of his native land, and considered worth his notice ; at the
same time the later compilers endeavoured to give a universal
character to each herbal by admitting plants which had not
been actually seen by the writer ; each as far as possible
gathered from his predecessors all that they had seen, and
added what he had himself seen that was new ; but in contrast
with the previous centuries the peculiar merit of each new-
herbal was held to depend not on what the compiler had
borrowed from his predecessors, but on what he had added
from his own observation. Hence every one was anxious to

c

1 8 Botanists of Germany and the Netherlands [Book i.

introduce into his work as many plants unknown till that time
or unnoticed as he possibly could, and the number of descrip-
tions of individual forms mounted rapidly up; in Fuchs in
1542 we find about five hundred species described and figured,
but in 1623 the number of species as enumerated by Kaspar
Bauhin had risen to six thousand. As the botanists were
spread over a large part of Germany, Fuchs in Bavaria and after-
wards at Tubingen, Bock on the middle Rhine, Konrad Gesner
at Zurich, Dodoens and de I'Obel in the Netherlands, a terri-
tory of considerable extent was thus examined ; it was enlarged
by the contributions which travellers brought or transmitted
to the botanists, and de I'Ecluse especially traversed a large
part of Germany and Hungary and even of Spain, and eagerly
collected and described the plants of those countries. During
this period also the number of known plants was increased
from Italy, partly by the exertions of Italian botanists, such as
Mattioli, and partly by travelling Germans. The first flora of
the Thiiringer-Wald was written by Thai, but not published
till after his death in 1588. Botanical gardens even, though in
more modest form than in our day, were already helping in the
1 6th century to add to the knowledge of plants ; the first were
formed in Italy, as at Padua in 1545, at Pisa in 1547, at
Bologna in 1567 under Aldrovandi, afterwards under Cesalpino.
Soon similar collections of living plants were made in the
north; in 1577 a botanic garden was founded at Leyden, over
which de I'Ecluse long presided, in 1593 at Heidelberg and at
Montpellier ; in the course of the next century the number of
these gardens was considerably increased.

The preserving of dried plants, the formation of the collec-
tions which we now call herbaria, dates from the i6th century;
at that time however the word herbarium meant a book of
plants. In this matter also the Italians led the way. Accord-
ing to Ernst Meyer, Luca Chini seems to have been the fir.st
who made use of dried plants for scientific purposes, and his
two pupils Aldrovandi and Cesalpino are said to have formed

Chap. I.] fvom Bnuifcls to Kaspav Baiihin. 19

the first herbaria in our sense of the word ; one of the first
collections of the kind, perhaps of the date of 1559, was the
herbarium formed by Ratzenberger, which was discovered in
the museum at Cassel a few years since and described by
Kessler.

These are matters somewhat external to our immediate sub-
ject, but they show how lively an interest was taken in botany
in the latter half of the sixteenth century ; this is still more
shown by the great number of books of plants, published with
numerous and expensive plates and in some cases going through
several editions. But the artistic and scientific value of the
drawings, which were appended to the descriptions and in later
herbals were reckoned by thousands, did not keep equal pace
with their number ; Fuchs' splendid figures remained unap-
proached, and gradually, as the distance from Durers time
increased, the woodcut^ grew smaller and poorer', and some-
times even quite indistinct. The art of describing on the
contrary continually improved ; the descriptions became fuller,
and gradually a certain method appeared in assigning marks
and in estimating their value ; critical remarks on the identity
or non-identity of species, the separation of forms previously
considered to be alike, and similar matters occur more frequently.
The descriptions in de I'Ecluse may in fact claim to be called
scientific ; in Kaspar Bauhin they appear in the form of terse
and methodical diagnoses.

The most remarkable thing to us in these descriptions from
Fuchs and Bock to Bauhin is the striking neglect of the flowers
and fruit. The earliest descriptions, especially those of Bock,
endeavour to depict the form of the plant in words, to render
directly the impression on the senses ; special attention was
paid to the shape of the leaves, the nature of the ramification,
the character of the roots, the size and colour of the flowers.

* See L. C. Treviranus in his work, ' Die Anwendung des Ilolzschnitts
zur bildlichen Darstellung der Pflanzen,' Leipzig, 1855, and Choulant
' Graphische Incunabeln,' Leipzig, 1858.

C 2

20 Botanists of Germany and the Netherlands [Book i.

KoNRAD Gesner^ was the only one who bestowed a closer
attention on the flowers and parts of the fruits ; he figured them
repeatedly, and recognised their great value for the determina-
tion of affinity, as we learn from his expressions in his letters ;
but the much occupied and much harassed man died before
he could complete the work on plants which he had long been
preparing, and when in the i8th century Schmiedel pub-
lished Gesner's figures, which meanwhile had passed through
various hands, the work too long delayed remained useless to a
science which had already outstripped it.

It will be gathered from the above remarks, that we find
in these authors no approach to a system of morphology
founded on a comparative examination of the parts of plants,
and therefore no regular technical language. Still the more
learned among them felt the necessity of connecting the
words they used in describing a plant with a fixed sense,
of defining their conceptions ; and though their first efforts in
this direction were weak, they deserve notice, because they
show more than anything else how great has been the advance
in the study of nature from the i6th century to the present day.

The first attempt to establish a botanical terminology is to
be found as early as 1542 in the ' Historia Stirpium ' of
Leonhard Fuchs^. Four pages at the beginning of the work
are thus occupied. A considerable number of words are
explained in alphabetical order — the mode of arrangement
which he followed also in describing his plants. It is difficult

* Konrad Gesner, bom in Zurich in 15 16, became after many vicissitudes
of fortune Professor of Natural History in his native town, and died there
of the plague in 1565. See Ernst Meyer, ' Geschichte der Botanik,' iv.

- Leonhard Fuchs, bom at Membdingen in Bavaria in 1 501, was a student
of the classics under Reuchlin in Ingolstadt in 151 9, and became Doctor
of Medicine in 1524. Owing to his conversion to Protestantism he led
an unsettled life for some years, but was finally made Professor of
Medicine in Tubingen in 1535, and died there in 1566. See Meyer,
' Geschichte der Botanik,' iv.

Chap. I.] froni Bvnufcls to Kttspar Bauhin. 21

to give a clear idea of this the first botanic terminology- by
selected examples ; yet the attempt must be made, because it
is in this way only that we learn to see from what feeble
beginnings the later scientific terminology and morphology
has been developed. Thus we read : ' Acinus ' denotes
not merely, as many believe, the grains inside the grape, but
the whole fruit, which consists of juice, of a fleshy portion with
the stones (' vinaceis '), and of the outer skin. Galen is quoted
as authority for the following explanation : ' Alae ' are said to
be the hollows (angles) between the stem and its branches (the
leaves), from which new sprouts (' proles ') proceed. ' Asparragi,'
the germs of herbs which appear before the leaves and the
first edible shoots are developed. ' Baccae ' are smaller ' foetus '
of herbs, shrubs, and trees, which appear separate and isolated
on the plant, as for example laurel-berries ('partus lauri '), and
differ from acini, inasmuch as these are more crowded together.
' Internodium ' is that which lies between the articulations or
knees. ' Racemus ' is used for the bunch of grapes, but does not
belong to the vine only, but also to the ivy and other herbs and
shrubs which bear clusters of any kind. The majority of such
explanations of names concern the forms of the stem and the
branches, but the most remarkable thing about the whole list
is, that it does not include the words flower and root; yet
under the word ' julus^' occurs the statement, that it is that which
in the hazel ' compactili callo racematim cohaeret,' and may be
described as a long worm borne on a special pendent stalk
and coming before the fruit. Though the word flower is not
explained, yet some parts of the flower are mentioned ; thus it
is said, ' stamina sunt, qui in medio calycis erumpunt apices, sic
ditta quod veluti filamenta intimo floris sinu prosiliant.' The
explanation of the word fruit may be added : ' Fructus, quod
carne et semine compactum est ; frequenter tamen pro eo, (luod
involucro perinde quasi carne et semine coactum est, accipi
solet.'

Progress in this direction was slow but still recogni.sable. In

22 Botanists of Germany and the Netherlands [Book i.

the last edition of the ' Pemptades ' of Dodoens^ of the year
1616, a foho volume of 872 pages, only one page and a third
are devoted to the explanation of the parts of plants ; but the
selection of the words explained and the substance of the
explanations hit the essential points better than in Fuchs.
We find for instance : Root (' radix, p'l^a ') is the name
given in the tree and in every other plant to the lower part,
by which it penetrates into the earth and cleaves to it, and
by which it draws its nourishment. This part, unlike the
leaves which are usually deciduous, is common to all plants,
a few only excepted which live and grow without roots, such
as Cassytha, Viscum, and the plant called ' Hyphear,' Fungi,
Mosses, and Fuci, all which are however usually reckoned
among <^vra. 'Caudex ' is in trees and shrubs that which springs
from the root and rises above the ground, and by which the
nourishment is carried upwards ; the same part is called in
herbs caulis or cauliculus. Leaf ('fohum') is in every plant
that which clothes and adorns it, and without which trees and
other plants appear naked. The definition of a flower would
lose in a translation : ' flos, av6oi, arborem et herbarum gaudium
dicitur, futurique fructus spes est ; unaquaeque etenim stirps pro
natura sua post florem partus ac fructus gignit.' The parts of the
flower are with him the calyx (' calyx '), in which the blossom is
at first enclosed and with which the ' foetus ' is soon surrounded,
stamens (' stamina ') which arise Hke threads from the depth of
the blossom and from the calyx, and ' apices ' (anthers), certain
thickish appendages on the summit of the stamens. 'Julus'
(catkin) is that which hangs down round and long in place of
the flower, as in the walnut, hazel, mulberry, beech, and other

* Rembert Dodoens (Dodonaeus), born at Malines in 151 7, was a physi-
cian, and a man of varied culture ; he published a number of botanical works,
some of them in Flemish, after 1552, and finally in 1583 his 'Stirpium His-
toriae Pemptades vi ' (Antwerp). From 1574 to 1579 he was physician to the
Emperor Maximilian II. In 1582 he became Professor in Leyden and died
in 1585. See Ernst Meyer, 'Geschichte der Botanik,' iv. p. 340.

Chap. I.] from Bnoifels to Kaspar Baithin. 23

trees. ' Fructus ' is that in which the seed is formed, but fre-
quently it is itself the seed, as where the latter is not enclosed
in anything else and is formed naked. We must not be led by
these words to think ot our Gymnosperms, but must under-
stand that here, as with all botanists till the time of A. L.
de Jussieu and Joseph Gartner (1788), naked seeds mean dry
indehiscent fruits.

De rObel, from whom especially we might have looked for
similar explanations, has given none.

The absence of more profound comparative examination of
the parts of plants, as shown in the examples of terminology
here adduced, may serve as an additional support of the asser-
tion, that natural affinity was not inferred from exact comparison
of the form of organs, but was the result of a feeling arising
from the likeness of habit directly apprehended by the senses,
that is by the collective impression produced by the whole
plant.

Passing to the consideration of the attempts in systematic
botany made by the Germans in this period, the chief thing to
notice is, that the division into the main groups of trees,
shrubs, undershrubs, and herbs was the one generally
adopted ; these groups were borrowed from antiquity and
were maintained even by the special systematists, from Cesal-
pino to the beginning of the i8th centur)' ; nor was any
change made in principle when these four groups were
reduced to three or two (trees and herbs). It was moreover
considered to be self-evident that trees were the most perfect
plants. Hence when relationship is spoken of in subsequent
remarks, it must be understood that this holds good only
within the groups just mentioned. The classifications of the
German and Dutch botanists not only sprang from the de-
scribing of individual plants, but they were originally in a
certain sense identical with it. In undertaking to describe
individual forms, the first task was to sei)arate those which
closely resembled one another, for the resemblance of syste-

24 Botanists of Germany and the Netherlands [Book i.

matically-allied plants is often so great, that to distinguish
them specifically requires consideration and careful com-
parison. The resemblance is more obvious than the difference.
There are moreover many plants which are entirely distinct from
one another in their inner nature, but which appear strikingly
alike if we regard the impression produced immediately on
the senses, and the converse of this statement is equally true.
Hence the attempt to circumscribe and fix individual forms
in the act of describing was at once found to involve diffi-
culties, the solution of which leads directly to the conception
of some kind of arrangement. A comparison of the herbals
of Fuchs and Bock up to Kaspar Bauhin shows very plainly
how these difficulties were gradually overcome, how the
describing of single species led necessarily, and without the
intention of the describer, to considerations of a distinctly
systematic character. Where the species in a group of forms,
which we now designate as a genus or family, closely resemble
each other in habit, there arose of itself the instinctive feeling
that such forms belong to one another. This feeling asserted
itself in words when, as was done from the first, a number
of such forms were without conscious reflection designated by
the same name ; thus, to mention one of many examples, w^e
find Bock applying the name Wolfsmilk, Euphorbia, not to one
species of the genus, but to several, which he then distinguishes
by epithets (common, least, cypress, sweet).' The customary
mode of expression in the herbals is very instructive on this
point ; there are, they say, two or more of this or that plant
which have not been hitherto distinguished. But this feeling
of connection and similarity of kind was produced not only by
forms that were closely allied, but also by such as belong to
extensive groups of the system ; thus the words moss, lichen,
fungus, alga, fern, had long served to include a great number
of distinct forms, though the separation of these groups had
nowhere in truth been carried out with logical precision.
These remarks are important as serving to show in the most

Chap. I.] from Bninfcls to Kaspar Bauhin. 25

decisive manner the incorrectness of the assertion, that the
study of organisms sprang from the recognition of individual
species ; that it is this which is directly given, and that without
it no advance in the science is possible. The historical fact
rather is, that descriptive botany began often, perhaps most
often, not with species but with genera and families, that very
often at first whole groups of forms were conceived of as unities,
which had to be divided later and of set purpose into separate
forms ; and up to the present day one part of the task of the
systematist is to undertake the splitting up of forms previously
regarded as identical. The notion that the species is the
object originally presented to the obser\-er, and that certain •
species were afterwards united into genera, is one that was
invented in post-Linnaean times under the dominion of the
dogma of the constancy of species ; it happened so sometimes,
but just as often the genus was the object first presented, and the
task of the describer was to resolve it into a number of species.
In the 1 6th century the conception neither of genus or species
had yet been defined ; for the botanists of that period genera
and species had the same objective reality. But, in the process
of continually making the descriptions of individual plants
more exact, forms once separated were united, and those before
assumed to be identical were separated, till it gradually became
apparent that both operations must be pursued with system and
method. It cannot therefore be exactly said that somebody
first established the species, another the genus, and a third
person again the larger groups. It is more correct to say that
the botanists of the i6th century carried out this process of
separation up to a certain point without intending it, and in
the effort to give the greatest possible preciseness to their
descriptions of individual forms. It lay therefore in the nature
of the case, that those groups which we call genera and species
should first be cleared up, and we find in fact at the end
of this period in Kaspar Bauhin the genera already distin-
guished by names, if not by characters ; the species by names

26 Botanists of Germany and the Netherlands [Book i.

and characters. Together with these smaller groups, many
more comprehensive ones, which we now designate families,
were also marked off and supphed with names, which are still
in use. The i6th century established the groups and names
of Coniferae, Umbelliferae, Verticillatae (Labiatae), Capillares
(Ferns), and others. It is true that the determination of the
limits of these groups by distinct marks was not yet attempted,
but the plants belonging to these groups were again and again
treated of in special chapters or ranged in due succession one
after another. But as long as this was done to some extent
without design, and the real meaning of this relationship was
not yet recognised, other considerations of very various kinds
influenced the composition of the books and disturbed the
natural arrangement. The feeling for natural affinity supplants
all other considerations in de I'Obel first, and after him much
more completely in Kaspar Bauhin.

Enough perhaps has now been said to render the main
result of the botanical efforts of the period, which we are
considering, intelligible to the reader ; but a clear view of the
method of describing plants at that time, and of the way in
which systematic botany came into being, can only be shown
by examples ; and if we proceed to give some here, it is with
the purpose with which figures copied as exactly as possible
from nature are added to treatises on natural history, because
a real understanding is only to be gained in this way. The
botanical literature of the i6th century is so different from that
of the 19th, that a very indistinct idea of it could be obtained
from a statement of results expressed in modern terms.

Fuchs, Historia Stirpium, 1542.

The common plant now known as Convolvulus arvensis is
there called Helxine cissampelos, and is described in the
following manner :

''Nomina. — 'EXIivi) ^to-crd/iTrfXor Graecis, Helxine cissampelus
et Convolvulus Latinis nominatur. Vulgus herbariorum et

Chap. I.] froiH Briinfcls to Kaspar Bauhin. 27

officinae Volubilcm mediam et vitealem appellant, Germani
Mittelwinden oder Weingartenwinden, Recte autem Cissam-
pelos dicitur, in vineis enim potissimum nascitur et folio
hederaceo. Convolvulus vero quod crebra revolutione vici-
nos frutices et herbas implicet.

Forma. — Folia habet hederae similia, minora tamen, ramulos
exiguos circumplectentes quodcumque contigerint. Folia
denique ejus scansili ordine alterna subeunt. Flores primum
candidos lilii efifigie, dein in puniceum vergentes, profert.
Semen angulosum in folliculis acinorum specie.

Locus. — In vineis nascitur, unde etiam ei appellatio cissam-
peli, ut diximus, indita est.

Tempus. — Aestate, potissimum autem Julio et Augusto men-
sibus, floret.'

HiERONVMUS BocK^, at page 299 of his ' Herbal,' published
at Strassburg in 1560, describes the same plant and Convolvu-
lus sepium as follows :

' Of the white wind-bell.

' Two common wind-plants grow ever) where in our land
with white bell-flowers. The larger prefers to dwell by hedges,
and creeps over itself, twists and twines, etc. The little wind-
er bell-flower (Convolvulus arvensis) is like the large one with
its roots, round stems, leaves and bell-flowers, in all things
smaller, thinner, and shorter. Some flowers on this plant are
quite white, some of a beautiful flesh colour, painted with red
dish brown streaks. It grows in dry meadows, in herb- and
onion-gardens, and does harm therein, because with its creeping
and twining it oppresses other garden herbs, and is also bad to
exstirpate, because the thin white rootlets make their way deep

^ Hieronymus Bock (Tragus) was born at Heiderbach in the Zwei-
briicken in 1498; he was destined to the cloister, but embraced Protest-
antism and became a schoolmaster in Zweibriicken and superintendent of
the Prince's garden ; he was aftei-wards preacher in Hombach, where he
practised also as a physician and pursued his botanical studies ; he died in
1554. See Ernst Meyer, ' Geschichte der Botanik,' iv. p. 303.

28 Botanists of Germany and the Netherlands [Book i.

downwards, spread very widely, and are continually putting
forth new and young clusters like hops.'

Then follows a long paragraph on the names, that is, a
critical review of the opinions of different writers on the ques-
tion, which of Dioscorides' or Pliny's names should be applied
to the plant described. ' I must think,' says Bock, ' that this
flower is a wild sort, Scammonia Dioscoridis (but harmless),
which herb Dioscorides also calls colophonia, dactylion,
apopleumenon, sanilum, and colophonium,' and so on. Then
follows a chapter on its virtue and effect externally and
internally.

As regards the arrangement of the 567 species described
by Bock, he divides his book into three parts, the first
and second containing the smaller herbs, the third the
shrubs and trees. In each part closely allied plants are
generally described in larger or smaller numbers one imme-
diately after another, though the compiler is all the
time under the influence of very various considerations, and
follows no general principle. For instance, our Convolvu-
lus stands in the midst of a number of other very different
plants, which either climb as the ivy, or twine with tendrils as
Smilax ; then follows Lysimachia Nummularia, which simply
runs along the ground, then the hop, Solanum Dulcamara,
Clematis, Bryonia, Lonicera, and different Cucurbitaceae ;
immediately after come the Burdocks, Teasels, and Thistles,
and these are followed by some Umbelliferae. The whole work
is conceived in a similar spirit ; the feeling for relationship is
clearly to be traced within very narrow circles, but it finds im-
perfect expression and is frequently disturbed by reference to
biological habit ; this appears especially in the beginning of
the third part, which treats of shrubs generally, shrubs which
form hedges, and trees, ' as they grow in our German land ' ;
the first chapter is on the fungi which grow on trees, the second
on some mosses, and these are followed immediately by the
mistletoe. Then come the heather and some smaller shrubs,

Chap. I.] from Bruufcls to Kaspar Baiihin. 29

and finally larger and the largest trees. The chapter on Fungi
under the section ' Of names ' contains a statement of views on
the nature of fungi, such as are often repeated even into the
1 7th century : ' Mushrooms are neither herbs nor roots, neither
flowers nor seeds, but merely the superfluous moisture of the
earth and trees, of rotten wood and other rotten things. From
such moisture grow all tubera and fungi. This is plain from
the fact that all the above-mentioned mushrooms, those especi-
ally which are used for eating, grow most when it will thunder
or rain, as Aquinas Ponta says. For this reason the ancients
paid peculiar regard to them, and were of opinion that tubera,
since they come up from no seed, have some connection with
the sky ; Porphyrius speaks also in this manner, and says that
fungi and tubera are called children of the gods, because they
are born without seeds and not as other kinds.'

We pass over Valerius Cordus, Conrad Gesner, Mattioli ',
and some other unimportant writers, and turn to Dodoens,
de I'Ecluse, and Dalechamps, in whom a marked tendency to
orderly arrangement appears, though the principle of arrange-
ment in all three lies essentially in points external and accidental,
and above all in the relations of the plant-world to mankind.
Within the divisions thus artificially formed a constantly
increasing attention is paid to natural afifinities, but at the same
time allied forms are separated without scruple in deference to
the artificial principle of classification. It can also be plainly
seen, that these writers think more of giving some order to
their matter than of discovering the arrangement that will be
in conformity with nature. It is impossible to give the reader
a good idea of these classifications in our scientific language ;

' Pierandrea Mattioli, who was bom at Siena in 1501 and died there in
1577, was for many years physician at the court of Ferdinand I. He wrote
rather in the interests of medicine than of botany; his herbal, originally a
commentary on Dioscorides, was gradually enlarged and went through
more than sixty editions and issues in different languages. See Meyer,
* Geschichte der Botanik,' vi.

30 Botanists of Germany and the Netherlands [Book i.

it would be necessary to transcribe them. For brevity's sake we
will here quote de l'^Scluse only \ the best of the three writers
named above. In his ' Rariorum plantarum historia,' which
appeared as early as 1576, but which lies before the writer of
these pages in the edition of 1601, the first book treats of trees,
shrubs, and undershrubs ; the second of bulbous plants ; the
third of sweet-smelling flowers ; the fourth of those without
smell ; the fifth of poisonous, narcotic, and acrid plants ; the
sixth of those that have a milky juice, and of Umbelliferae,
Ferns, Grasses, Leguminosae, and some Cryptogams.

A similar arrangement is found in Dalechamps^; that of
Dodoens in his ' Pemptades ' is more perplexed and unnatural ;
but the design in both of them is evidently much the same as
that of de I'Ecluse. This design is best seen from the intro-
ductory observations to each book ; de I'Ecluse, for instance, says
at page 127, ' Having treated of the history of trees, shrubs, and
under-shrubs, and put these together in the preceding book, we
will now in this second book describe such plants as have a
bulbous or tuberous root, many of which attract and delight the
eyes of all persons in an extraordinary degree by the elegance
and variety of their flowers, and which therefore ought not to have
the lowest place assigned to them among garland-plants (' inter
coronarias '). We will begin with the plants of the lily kind, on
account of their size and the beauty of their flowers, etc. etc'
The introductions to the several books of the ' Pemptades ' of
Dodoens are more learned and more diffuse. It is plain that
the composers of these works had no thought of arranging

* Charles de I'Eeluse (Carolus Clusius) was born in Arras in 1526, His
family suffered from religious persecution in France, and he spent the greater
part ofhis life in Germany and the Netherlands ; in i573he removed to Vienna
by the invitation of Maximilian II; in 1593 he became professor in Leyden
and died there in 1609. See Meyer, ' Geschichte der Botanik,' iv, who
gives full information respecting the eventful life of this distinguished man.

^ Jacques Dalechamps, a native of Caen, who died in 1588, was a philolo-
gist rather than an original investigator of nature, as is remarked by Meyer
in his ' Geschichte der Botanik,' vi. p. 395.

Chap. I.] from Bnuifcls to Kaspar Batthtn. 31

their matter on the principles of a true natural system, but
were only anxious to give some kind of order to their descrip-
tions of individual plants. Hence their divisions do not
appear under the names of classes and subdivisions ('genera
majora et minora,' as they would have been called at that time),
but they are sections of the whole work kept as symmetrical as
was possible. If we would discover in these works whatever
may really lay claim to systematic value, we must not rely on
the sections as they are typographically distinguished, but
must observe within each of them the order in which the
plants are given, and then it becomes apparent that within the
frame once established forms naturally allied are, as far as may
be, grouped together. For instance, we find in the second
book of de I'Ecluse's work first of all a long list of true Liliaceae
and Asphodeleae, Melanthaceae, and Irideae described in
unbroken succession ; then comes Calamus, and then without
any explanation a number of the Ranunculaceae, among which
the genera Ranunculus and Anemone are very well
distinguished ; but then follows the genus Cyclamen with
several species, and next a number of Orchideae, in the middle
of which appear Orobanche and Corydalis, followed by Helle-
borus niger, Veratrum album, Polygonatum, and others. So it
is in the other sections, though in general the species of a
genus stand together, and even the genera of a family are not
unfrequently united ; but with all this there are no proper
breaks, because other considerations are perpetually disturbing
the feeling for natural relationship. The descriptions of
de rficluse are generally commended, and they deserve to be
commended for their fulness of detail and their attention to
the structure of the flowers, though he, like de I'Obel and
Dodoens, describes the leaves more minutely than any other
part of the plant.

With DE l'Obel^ as has been already observed, the feeling

Mathias de I'Obel (Lobelius^, the friend and fellow-countryman of

32 Botanists of Germany and the Netherlands [Book i.

for natural afifinity declares itself for the first time so decidedly
as to outweigh if not entirely to set aside all other considera-
tions. The fact is disclosed to us in the preface to his
'Stirpium adversaria nova' of 1576, where these words occur:
' proinde adversariorum voce novas veteribus additas plantas et
novum ordinem quadantenus innuimus. Qui ordo utique
sibi similis et unus progreditur ducitque a sensui propinquiori-
bus et magis familiaribus ad ignotiora et compositiora, modum-
que sive progressum similitudinis sequitur et familiaritatis, quo
et universim et particulatim, quantum licuit per rerum varie-
tatem et vastitatem, sibi responderet. Sic enim ordine, quo
nihil pulchrius in coelo aut in sapientis animo, quae longe
lateque disparata sunt unum quasi fiunt, magno verborum
memoriae et cognitionis compendio, ut Aristoteli et Theo-
phrasto placet.'

We must not indeed expect to find that de I'Obel really
produced a natural system of plants ; but his ' Observationes '
still more than his ' Adversaria ' attest his efforts to arrange
plants according to their resemblances in form ; and in these
efforts he is guided not by instinct merely and the general
habit, but mainly and with evident purpose by the form of the
leaves ; thus beginning with Grasses, which have narrow, long,
and simple leaves, he proceeds to the broader-leaved Liliaceae
and Orchideae ; then passing on to the Dicotyledons he
exhibits the main groups in fairly well limited masses. Still
the Ferns appear in the middle of the Dicotyledons on account
of the form of their leaves, while on the other hand, the
Cruciferae, Umbelliferae, Papilionaceae and Labiatae remain
but little disturbed in their continuity by secondary con-
siderations.

The progress of botanical science in the period which we have
been considering reaches its highest point in the labours of

Dodoens and de I'^lfecluse, was born at Lille in 1538 and died in England in
1616. A full account of this botanist will be found in Meyer.

Chap. I.] froiii Briiufels to Kaspar Bauhin. 33

Kaspar Bauhin', as regards both the naming and describing of
individual j^lants and their classification according to likeness
of habit. In Bauhin all secondary considerations have dis-
appeared ; his works may be called botanical in the strict
scientific meaning of the word, and they show how far it is
possible to advance in a descriptive science without the aid of
a general system of comparative morpiiology, and how far the
mere perception of likeness of habit is a sufficient foundation
for a natural classification of plants ; it was scarcely possible to
make greater advances on the path pursued by the botanists of
Germany and the Netherlands.

The descriptions of species in the ' Prodromus Theatri
Botanici ' of Kaspar Bauhin (1620) notice all obvious parts of
the plant with all possible brevity and in a fixed order ; the
form of the root, height and form of the stem, characters of the
leaves, flowers, fruit, and seed are given in concise sentences
seldom occupying more than twenty short lines ; the descrip-
tion of a single species is here in fact developed into an art
and becomes a diagnosis.

A still higher value must be set on the fact, that in Kaspar
Bauhin the distinction between species and genus is fully and
consciously carried out ; every plant has with him a generic
and a specific name, and this binary nomenclature, which
Linnaeus is usually thought to have founded, is almost per-
fectly maintained by Bauhin, especially in the ' Pinax ' ; it is
true that a third and fourth word is not unfrequently appended
to the second, the specific name, but this additional word is
evidently only an auxiliary. It is remarkable on the other
hand, that he has added no characters to the names of the

* Kaspar Bauhin was bom at Basle in 1550, and like his elder brother
John studied under Fuchs ; he collected plants in Switzerland, Italy, and
France, and became professor in Basle; he died in 1624. Some account is
given of him and of his brother by Hallcr in the preface to his ' Histoiia
Stirpium Helvctiae' (1768), and by Sprengel in his * Geschichte der
Botanik,' i. p. 364 (1818).

D

34 Botanists of Germajiy and the Netherlands [Book i.

genera ; it is only from the name that we know that several
species belong to one genus ; we might almost believe that the
characters of the genus are intended to be supplied by the
strange etymological explanation appended in italics to the
generic name. These fanciful etymologies maintained them-
selves to the end of the 17th centur)^, when Tournefort did
battle with them ; they were an evil which sprang in a great
measure from Aristotelian and scholastic modes of thought,
and from the belief that it was possible to conceive of the
nature of a thing from the original meaning of its name.

Nothing shows better the earnestness of Bauhin's research
than the fact, that he devoted the labour of forty years to his
' Pinax,' in order to show how each one of the species given by
him was named by earlier botanists. The example already
given from Fuchs shows how many names a plant had received
by the middle of the i6th century ; even in Dioscorides and.
Pliny we find a whole row of names given for a single plant,
and the botanists of Fuchs' time used their utmost endeavours
to attach the names in Dioscorides and other ancient writers
to particular plants found in central Europe. Dioscorides,
Theophrastus, and Pliny either add no descriptions to the names
of their plants, or they describe them in so unsatisfactory a man-
ner, that it was a very difficult task for the science of that day, as
it is still for us, to recognise the plants of the ancient writers ;
hence arose such a confusion of names that the reader of a
botanical work can never be sure whether the plant of one
author is the same as that of another with the same name. A
description of a plant is therefore usually accompanied in the
1 6th century by a critical enquiry how far the name used agrees
with that of other authors. Kaspar Bauhin sought to put an
end to this condition of uncertainty by his ' Pinax,' in which he
showed in the case of all species known to him what were the
names given to them by the earlier writers, and he has thus
enabled us to see our way through the nomenclature of the
period of which we are speaking ; the ' Pinax ' is in a word the

Chap. I.] from Brunfcls to Kaspar Banhin. 35

first and for that time a completely exhaustive book of syno-
nyms, and is still indispensable for the history of individual
species — no small praise to be given to a work that is more
than 250 years old.

It would not have been unsuitable to the purpose of the
author of the * Pinax,' if he had allowed himself to give the
plants in alphabetical order, but instead of this we find a care-
ful arrangement according to natural affinities. This directly
proves what is also confirmed by the ' Prodromus,' that Bauhin
regarded such an arrangement as of the greatest importance.
In this point, as in others, he goes far beyond his predecessors ;
he pursues the same method as de I'Obel had pursued forty
years before, but he carries it out more thoroughly. At the
same time he shares with his predecessors the peculiarity of
not distinguishing the larger groups, which with some excep-
tions answer to our present families, by special names or by
descriptions ; it is only from the order in which the species
follow one another that we can gather his views on natural
relationship. It follows therefore that the natural families, so
far as they are distinguishable in Bauhin's works, have no sharp
bounding lines ; we might almost conclude that he purposely
avoided assigning such limits, that he might be able to pass
without interruption from one chain of relationship to another.

Like de I'Obel, Bauhin proceeds in his enumeration from the
supposed most imperfect to the more perfect forms, beginning
with the Grasses and the majority of Liliaceae and Zingibe-
raceae, passing on to dicotyledonous herbs, and ending with
shrubs and trees.

The Cryptogams that were known to him stand in the middle
of the series of dicotyledonous herbs, between the Papiliona-
ceae and the Thistles, the Equisetaceae being reckoned among
the Grasses. On the great distinction between Cryptogams
and Phanerogams the views of Bauhin were evidently less
clear than those of many of his predecessors ; but it will not
seem strange that he should place some Phanerogams, as for

D 2

36 Botanists of Germany and the Netherlands.

instance the Duckweeds, among the Cryptogams and the
Salviniaceae among the Mosses, and unite the Corals, Alcio-
nieae, and Sponges with the Seaweeds, when we consider that
it was not till the middle of the iSth century that more correct
views arose in respect to these forms, and that Linnaeus himself
could not decide whether the Zoophytes should be excluded
from the vegetable kingdom and ranked with animals. The
knowledge of plants in the scientilic sense of the word was till
the beginning of the 19th century limited to the Phanerogams ;
and in speaking of principles and methods in descriptive
botany before that time we must think only of the Phanero-
gams, or at most of the Phanerogams and the Ferns. The
methodical examination of the Cryptogams belongs to quite
recent botanical research. The matter is here alluded to only
in connection with the fact, that it is from the works of Kaspar
Bauhin, a writer of ability, in whom the first period of scien-
tific botany culminates, that we most clearly see how great the
advance has been since his time.

CHAPTER II.

Artificial Systems and Terminology of Organs from
Cesalpino to Linnaeus.

15S3-1760.

While botany was being developed in Germany and the
Netherlands in the manner described in the previous chapter,
and long before this process of development reached its furthest
point in Kaspar Bauhin, Andrea Cesalpino in Italy was
laying down the general plan, on which the further advance of
descriptive botany was to proceed in the 1 7th and till far into
the i8th century; all that was done in the 17th century in
Germany, England, and France towards furthering morphology
and systematic botany was done with a reference to Cesal-
pino's principles, whether these were accepted and made use of,
or whether it was sought to refute them. This connection
with Cesalpino became gradually less close and less obvious,
being concealed by new points of view and by the increase of
material for observation ; but Cesalpino's ideas on the theo-
retical principles of systematic botany and the nature of
plants appear so plainly, even in the views of Linnaeus, that
no one can read both authors without lighting not unfrequently
, upon passages in Linnaeus' 'Fundamenta' or in his 'Philosophia
Botanica,' which remind him of Cesalpino, and even upon
sentences borrowed from him. As we saw in Kaspar Bauhin
the close of the course of development commenced by Fuchs
and Bock, so we may regard Linnaeus as having built up and
completed the edifice of doctrine founded by Cesalpino.

38 Artificial Systems mid Terminology of Organs [Book i.

Cesalpino comes before us, in strong contrast with the
simple-minded empiricism of the German fathers of botany, as
the thinker in presence of the vegetable world. Their main
task was the amassing descriptions of individual plants. Ces-
alpino made the material gathered by experience the subject of
earnest reflection; he sought especially to obtain universals from
particulars, important principles from sensuous perceptions ; but
as his forms of thought were entirely Aristotelian, it was inevit-
able that his interpretation of the facts should introduce into
them much that would have to be got rid of subsequently by
the inductive method. Cesalpino differs also from the German
botanists in another respect ; he did not rest satisfied with the
general impression produced by the plants, but carefully
examined the separate parts and paid attention to the small
and concealed organs ; he was the first who converted observa-
tion into real scientific research ; and thus we find in him a
remarkable union of inductive natural science and Aristotelian
philosophy, a mixture which gives a peculiar character to the
theoretical efforts of his successors down to Linnaeus.

Cesalpino was moreover much before his time in his mode
of contemplating the vegetable kingdom, seeking always for
philosophical combinations and comprehensive points of view.
His work which appeared in 1583 exercised no perceptible
influence on his contemporaries ; a trace of such influence
only may be seen in Kaspar Bauhin thirty or forty years
later, while the work of the botanists who followed Bauhin
down to 1670 was confined everywhere to increasing the
knowledge of individual plants. With this object travels were
undertaken after 1600 to all parts of the world; many new
botanic gardens were added to the few which had been,
founded in the i6th century — as at Giessen in 161 7, at Paris in
1620, at Jena in 1629, at Oxford in 1632, at Amsterdam
in 1646, at Utrecht in 1650, Instead of endeavouring to
embrace with their labours the whole vegetable kingdom,
botanists preferred to devote themselves to the examination of

Chap. II.] from Ccsalpiuo to Linnaeus. 39

single districts. This gave rise to the first local floras (the
word flora, however, was first introduced by Linnaeus in the
next century), and of these Germany especially soon produced
a considerable number ; a flora of Altorf was published by
Ludwig Jungermann in 16 15, of Ingolstadt by Albert Menzel
in 1618, of Giessen by Jungermann in 1623, of Dantzic by
Nicolaus Oelhafen in 1643, of Halle by Carl Scheffer in 1662,
of the Palatinate by Frank von Frankenau in 1680, of Leipsic
by Paul Ammann in 1675, of Nuremberg by J. Z. Volkamer in
1700.

But though travel, catalogues in local floras, and the cultiva-
tion of plants in botanic gardens promote knowledge of very
varied kind, yet this remains scattered about among descrip-
tions of plants, until at last a writer with powers of combination
and wider and deeper glance endeavours to gain some general
conclusions from them. Such attempts we first meet with late
in the second half of the 17th century in JMorison, Ray,
Bachmann (Rivinus), Tournefort, and others, who took up
Cesalpino's principles after they had lain neglected for almost
a hundred years, and indeed were almost forgotten by botanists.

In the dearth of higher scientific efforts during this period,
the describing of plants and cataloguing of species prolonged
a somewhat pitiful existence. This describing, a work of great
usefulness in the fathers of German botany, was now become
by perpetual repetition a mechanical labour ; all that was to be
gained in this way had already been gained by de I'Obel and
Bauhin. This sterility which followed upon the fruitful
beginnings of the i6th century was general ; neither in Ger-
many nor Italy, neither in France nor England, did the
botanists produce anything of importance. The representa-
tives of the science did not count among the more highly
gifted or among the thinkers of their time ; and so content
with the minor work of collecting and cataloguing plants, and
with endeavouring to know all jjlants as far as possible by
name, they lost whatever capacity they may have possessed for

40 Artificial Systems and Terminology of Organs [Book i.

more difficult operations of the mind simply by not attempting
them.

There was one man indeed in Germany who studied the
vegetable kingdom in thefirst half of the 17th century in the spirit
of Cesalpino before him, but who, like Cesalpino, found no
honour among contemporary botanists. This man was the
well-known philosopher Joachim Jung, who invented a com-
parative terminology for the parts of plants, and occupied
himself with critical enquiries into the theory of the system,
the naming of species and other subjects, embodying their
results in a long array of aphorisms. Free from the genius-
stiiling burden which the knowledge of individual species had
become, a man possessed of varied accomplishments and a
well-trained mind, Jung was better qualified than the pro-
fessed botanists to see what was wanted in botany and would
advance it — a phenomenon more than once repeated in the
history of the science. But his results remained unknown to
all except his immediate pupils, till Ray admitted them into his
great work on plants in 1693, and made them the foundation
of his own theoretical botany. Enriched by Ray's good mor-
phological remarks, Jung's terminology passed to Linnaeus,
who adopted it as he adopted every thing useful that literature
offered him, improving it here and there, but impairing its
spirit by his dry systematising manner.

The labours of the botanists of Germany and the Netherlands
during the 17th century, which culminated in Kaspar Bauhin,
were not without important influence upon the development of
systematic botany which began with Cesalpino. When CesaU
pino wrote the work which forms an epoch in the science, he
was perhaps unacquainted with the natural classification of
de rObel (1576) ; at least there is nothing in his book which
shows that he had seen it ; it appears even as though he had
made the discovery independently, that there is an actual
connection of relationship among plants expressed in their
organisation as a whole ; it is at any rate certain that this fact

Chap. II.] froui Ccsalpuio to Liuuacus. 41

assumed from the first an entirely different expression in his
system from that which it received at the hands of de I'Obel
and Bauhin, inasmuch as he was not guided by an indistinct
feehng for resemblances, but believed that he could establish
on predetermined grounds a system of marks, by which the
objective relationship must be recognised. If Cesalpino was
thus in advance of the German botanists, since he endeavoured
to express with clearness and on principle that which they only
felt indistinctly, he was at the same time treading a dangerous
path, and one which led succeeding botanists astray till the
time of Linnaeus, — the path which must always lead to artificial
classifications, since the natural system can never be laid down
upon a priori principles of division. Through this labyrinth,
in which botanists down to Linnaeus wandered fruitlessly
hither and thither, there remained one guide consistently
pointing to the goal to be attained, namely, the feeling for
natural afiinity first vividly apprehended by the German
botanists, and expressed by them to some extent in their
classifications. And when at last Linnaeus and Bernard de
Jussieu made the first feeble attempts at a natural arrangement,
it was the same indistinct perception which asserted itself in
them as in de I'Obel and Bauhin, and enabled them to see
that the path hitherto trodden could only lead astray.

The period in the development of descriptive botany which
begins with Cesalpino and reaches to Linnaeus may accordingly
be perhaps best characterised by saying, that botanists sought
to do justice to natural affinities by means of artificial classifica-
tions, till at length Linnaeus clearly perceived the contradiction
involved in this method of proceeding. But inasmuch as
Linnaeus left it to the future to work out the natural system,
and arranged the plants which he described in a confessedly
artificial manner, he so far marks rather the close of a previous
condition of the science than the beginning of modern botany.

These introductory observations will have supplied the
reader with the thread which will guide him through the

42 Atiiftcial Systems and Terminology of Organs [BookI.

following account of the more prominent points in the history
of botanical science from Cesalpino to Linnaeus.

The often-quoted work of Andrea Cesalpino \ ' De plantis
libri XVI,' appeared in Florence in the year 1583. If the
value of the contemporary German botanists lies pre-eminently
in the accumulation of descriptions of individual plants, and
these, it is true, occupy fifteen books of Cesalpino's work, it is
on the contrary the introduction in the first book, a discussion of
the general theory of the subject, which in his case is of much
the higher importance for the history of botany. This contains
in thirty pages a full and connected exposition of the whole of
theoretical botany, and though based on broad and general
views is at the same time extremely rich in matter conveyed in
a very concise form. The different branches into which the
subject has since been divided are here united into an insepar-
able whole ; morphology, anatomy, biology, physiology, syste-
matic botany, terminology are so closely combined, that it is
difficult to explain Cesalpino's views on any one more general
question without at the same time touching on a variety of
other matters. Three things more especially characterise this
introductory book ; first, a great number of new and delicate
observations ; secondly, the great importance which Cesalpino
assigns to the organs of fructification as objects of morpho-
logical investigation ; lastly, the way in which he philosophises
in strictly Aristotelian fashion on the material thus gained from
experience. If this treatment has produced a work beautiful
in style and fascinating to the reader, if the whole subject is
vivified by it while each separate fact gains a more general
value, it is on the other hand apparent that the writer is often
led astray by the well-known elements of the Aristotelian
philosophy, which are opposed to the interests of scientific
investigation. Mere creations of thought, the abstractions of

^ Andrea Cesalpino (Caesalpinus) of Arezzo was born in 15 19. He
was a pupil of Ghini and professor at Pisa, and afterwards physician to
Pope Clement VIII. He died in 1603.

Chap. II.] from CcsalpiHo to Linnaeus. 43

the understanding, are treated as really existent substances, as
active forces, under the name of principles ; final causes
appear side by side with efficient; the organs and functions of the
organism exist either alicujus gratia or merely ob necessitaiem ;
the whole account is controlled by a teleolog)', the influence of
which is the more pernicious because the purposes assumed
are supposed to be acknowledged and self-evident, plants and
vegetation being conceived of as in every respect an imperfect
imitation of the animal kingdom. It was moreover a neces-
sary consequence of the treatment of his material adopted by
Cesalpino, that his ignorance of the sexuality of plants and of
the use of leaves as organs of nutrition led him to false and
mischievous conclusions ; this defect of knowledge would have
been of less importance in a purely morphological consideration
of plants, as we shall see presently in Jung ; but with Cesal-
pino morphological and physiological considerations are so
mixed up together, that a mistake in the one direction neces-
sarily involved mistakes in the other.

These remarks on Cesalpino's method may be illustrated by
some examples tending to show how closely he attaches himself
to Aristotle, and how certain Aristotelian conceptions, the
origin of which has not been sufficiently regarded, passed
through him into later botanical speculation. We shall recur
in the History of Physiology to Cesalpino's views on nutrition,
and to his rejection of the doctrine of sexuality in plants.

' As the nature of plants,' so begins Cesalpino's book,
' possesses only that kind of soul by which they are nourished,
grow, and produce their like, and they are therefore without
sensation and motion in which the nature of animals consists,
plants have accordingly need of a much smaller apparatus of
organs than animals.' This idea reappears again and again in
the history of botany, and the anatomists and physiologists of
the 1 8th centur}' were never weary of dilating on the simplicity
of the structure of plants and of the functions of their organs.
' But since,' continues Cesalpino, * the function of the nutritive

44 Artificial Systems and Terminology of Organs [Book i.

soul consists in producing something like itself, and this like has
its origin in the food for maintaining the life of the individual,
or in the seed for continuing the species, perfect plants have at
most two parts, which are however of the highest necessity ;
one part called the root by which they procure food ; the other
by which they bear the fruit, a kind of foetus for the continua-
tion of the species ; and this part is named the stem (' caulis ')
in smaller plants^ the trunk (' caudex ') in trees.'

This in the main correct conception of the upright stem as
the seed-bearer of the plant was also long maintained in
botany. We should observe also that the production of the
seed is spoken of as merely another kind of nutrition, a notion
which afterwards prevented Malpighi from correctly explaining
the flower and fruit, and in a modified form led Kaspar Fried-
rich Wolff in 1759 to a very wrong conception of the nature of
the sexual function. The next sentence in Cesalpino takes us
into the heart of the Aristotelian misinterpretation of the plant,
according to which the root answers to the mouth or stomach,
and must therefore be regarded in idea as the upper part
although it is the lower in position, and the plant would have
to be compared with an animal set on its head, and the upper
and lower parts determined accordingly : ' this part (the root)
is the nobler (' superior') because it is prior in origin and sunk
in the ground ; for many plants live by the roots only after the
stem with the ripe seeds has disappeared ; the stem is of less
importance (' inferior ') although it rises above the ground ; for
the excreta, if there are any, are given off by means of this
part ; it is, therefore, with plants as with animals as regards the
expressions ' pars superior ' and ' inferior.' When indeed we take
into consideration the mode of nourishment, we must define the
upper and the lower in another way ; since in plants and animals
the food mounts upward (for that which nourishes is light
because it is carried upwards by the heat), it was necessary to
place the roots below and to make the stem go straight upwards,
for in animals also the veins are rooted in the lower part of the

Chap. II.] from Ccsalpuio to Linnaeus. 45

stomach, while their main trunk ascends to the heart and the
head.' Here, in genuine AristoteHan fashion, the facts are
forced into a previously constructed scheme.

Cesalpino's di.scussion of the seat of the soul in plants is of
special interest in connection with certain views of later
botanists. ' Whether any one part in plants can be assigned
as the seat of the soul, such as the heart in animals, is a matter
for consideration — for since the soul is the active principle
(' actus ') of the organic body, it can neither be ' tota in toto '
nor ' tota in singulis partibus,' but entirely in some one and chief
part, from which life is distributed to the other dependent
parts. If the function of the root is to draw food from the
earth, and of the stem to bear the seeds, and the two cannot
exchange functions, so that the root should bear seeds and the
shoot penetrate into the earth, there must either be two souls
different in kind and separate in place, the one residing in the
root, the other in the shoot, or there must be only one, which
supplies both with their peculiar capabilities. But that there
are not two souls of different kinds and in a different part in
each plant may be argued thus ; we often see a root cut off
from a plant send forth a shoot, and in hke manner a branch
cut off send a root into the ground, as though there were a soul
indivisible in its kind present in both parts. But this would
seem to show that the whole soul is present in both parts, and
that it is wholly in the whole plant, if there were not this objec-
tion that, as we find in many cases, the capabilities are distri-
buted between the two parts in such a way that the shoot,
though buried in the ground, never sends out roots, for example
in Pinus and Abies, in which plants also the roots that are cut
off perish.' This, he thinks, proves that there is only one soul
residing in root and stem, but that it is not present in all the
parts ; in a further discussion he seeks to discover the true scat
of the soul. He points out an anatomical distinction between
the shoot and the root ; the root consists of the rind and an
inner substance which in some cases is hard and woody, in

46 Artificial Systems and Terminology of Organs [Book i,

others soft and fleshy. In the stem on the other hand there
are three constituent parts ; outside the rind, inside the pith,
between the two a body which in trees is called the wood.
This, on the whole, correct distinction between stem and root
is followed by a thoroughly Aristotelian deduction.

' Since then in all creatures ' (we must remark, that this
is assuming a point which has yet to be proved in the case of
the half of living creatures) 'nature conceals the principle of
life in the innermost parts, as the entrails in animals, it is
reasonable to conclude that the principle of life in plants is not
in the rind, but is more deeply hidden in the inner parts, that
is, in the pith, which is found in the stem and not in the root.
That this was the opinion of the ancients we may gather from
the name, for they called this part in plants the heart (' cor '), or
brain (' cerebrum ' or ' matrix '), because from this part in some
degree the principle of foetification (the formation of the seed)
is derived.' Here we see why the seed must, according to
Cesalpino, have its origin in the pith ; the idea was loyally
repeated after him by Linnaeus, as we shall see hereafter. The
argument, which is a long one, ends with the sentence : 'There
are then two chief parts in plants, the root and the ascending
part ; therefore the most suitable spot for the heart of plants
seems to be in the central part, namely, where the shoot joins
on to the root. There appears also at this spot a certain sub-
stance differing both from the shoot and from the root, softer
and more fleshy than either, for which reason it is usually
called the cerebrum ; it is edible in many plants while they are
young.' We shall see below how important a part this seat of
the soul of the plant, brought to light with such difficulty and
with all appliances of scholasticism, is intended to play in
Cesalpino's system, and how by this a priori path he was led to
the use of the position of the embryo in the seed as his principle
of division. It may be remarked here that the point of union
between the root and the stem, in which Cesalpino placed the
seat of the plant-soul, afterwards received the name of root-

Chap. II.] froui Ccsalpiuo to Linnaeus. 47

neck (collet); and though the Linnaean botanists of the 19th
century were unaware of what Cesalpino had proved in the
1 6th, and did not even believe in a soul of plants, they still
entertained a superstitious respect for this part of the plant,
which is really no part at all ; and this, it would seem, explains
the fact, that an importance scarcely intelligible without reference
to history was once attributed to it, especially by some French
botanists. To return once more to Cesalpino's ' cor,' he is not
much troubled by the circumstance that plants can be repro-
duced from severed portions ; in true Aristotelian manner he
says that although the principle of life is actually only one, yet
potentially it is manifold. Ultimately a ' cor ' is found in the
axil of ever)' leaf, by which the axillary shoot is united with
the pith of the mother-shoot, and finally, in direct contradiction
to the previous proof that the crown of the root is the seat of
the plant-soul, it is distinctly afifirmed in Chapter V that the
soul of plants is in some sense diffused through all their
parts.

The theoretical introduction to his excellent and copious
remarks on the parts of fructification may supply another
example of Cesalpino's peripatetic method : 'As the final cause
(' finis ') of plants consists in that propagation which is effected
by the seed, while propagation from a shoot is of a more imper-
fect nature, in so far as plants do exist in a divided state, so the
beauty of plants is best shown in the production of seed ; for
in the number of the parts, and the forms and varieties of the
seed-vessels, the fructification shows a much greater amount of
adornment than the unfolding of a shoot ; this wonderful beauty
proves the delight (* delitias ') of generating nature in the bring-
ing forth of seeds. Consequently as in animals the seed is an
excretion of the most highly refined food-substance in the heart,
by the vital warmth and spirit of which it is made fruitful, so
also in plants it is necessary that the substance of the seeds
should be secreted from the part in which the principle of the
natural heat lies, and this part is the pith. For this reason,

4^ Artificial Systems and Terminology of Organs [Book i.

therefore, the pith of the seed (that is, the substance of the
cotyledons and of the endosperm) springs from the moister and
purer part of the food, while the husk which surrounds the
seed for protection springs from the coarser part. It was
unnecessary to separate a special fertilising substance from
the rest of the matter in plants, as it is separated in animals
which are thus distinguished as male and female.'

This last remark and some lengthy deductions which follow
are intended to prove, after the example of Aristotle, the
absence and indeed the impossibility of sexuality in plants, and
accordingly Cesalpino goes on to compare the parts of the
flower, which he knew better than his contemporaries, with the
envelopes of the ova in the foetus of animals, which he regards
as organs of protection. Calyx, corolla, stamens, and carpels
are in his view only protecting envelopes of the young seed,
as the leaves are only a means of protecting the young shoots.
Moreover by the word flower ('flos') Cesalpino understands only
those parts of the flower which do not directly belong to the
rudiment of the fruit, namely, the calyx, the corolla, and the
stamens. This must be borne in mind if we would understand
his theory of fructification, and especially his doctrine of meta-
morphosis. We must also note, that by the expression pericarp
he understands exclusively juicy edible fruit-envelopes, though
at the same time pulpy seed-envelopes inside the fruit pass
with him for pericarps. The parts of his flower are the ' folium,'
which evidently means the corolla, but in certain cases includes
also the calyx ; the ' stamen,' which is our style ; and the 'flocci,'
our stamens. We see that Cesalpino uses the same word
' folium ' without distinction for calyx, corolla, and ordinary
leaves ; just as he, and Malpighi a hundred years later, unhesi-
tatingly regarded the cotyledons as metamorphosed leaves.
In fact the envelopes of the flower and the cotyledons approach
so nearly to the character of leaves, that every unprejudiced
eye must instinctively perceive the resemblance ; and if doubts
arose on this point in post-Linnaean times, it was only a conse-

Ciup. II.] from Ccsalpino to Linnaeus. 49

quence of the Linnaean terminology, which neglected all
comparative examination.

Moreover the doctrine of metamorphosis appears in a more
consistent and necessary form in Cesalpino than in the botanists
of the 19th century before Darwin; it flows more immediately
from his philosophical views on the nature of plants, and
appears therefore up to a certain point thoroughly intelligible.
We may also consider as part of this doctrine in Cesalpino the
view that the substance of the seed (embryo and endosperm)
arises from the pith, because the pith contains the vital
principle \ and as the pith in the shoot is surrounded for pro-
tection by the wood and the bark, so the substance of the seed
is surrounded by the woody shell, and by the bark-like pericarp
or by a fruit-envelope answering to a pericarp. According to
Cesalpino therefore the substance of the seed with its capa-
bility of development springs from the pith, the woody shell
from the wood, the pericarp from the rind of the shoot. The
difficulty which arises from this interpretation, namely, that
in accordance with his theory the parts of the flower also, the
calyx, the corolla, and the stamens ought to spring from the
outer tissues of the shoot, he puts aside with the remark (p. 19)
that these parts of the flower are formed when the pericarp is
still in a rudimentary state ; that the pericarp is only fully
developed after these parts have fallen off", and that they are
so thin that there is nothing surprising in this view of the matter.
We see in Cesalpino's doctrine of metamorphosis without doubt
the theory of the flower afterwards adopted by Linnaeus,
though in a somewhat different form. That Linnaeus himself
regarded the theory ascribed to him on the nature of the flower

* We find it stated in Theophrastus that if the pith of the vine is de-
stroyed the grapes contain no stones ; this evidently points to a still higher
antiquity for the view that the seeds arc formed from the pith ; see the De
causis plantarum, v. ch. 5, in the ' Theophrasti quae supersunt opera' of
Schneider, Leipzig, 1818.

E

50 Artificial Systems and Terminology of Organs [Book t.

as the opinion of Cesalpino also, is shown in his 'Classes Plan-
tarum,' where in describing Cesalpino's system he says : ' He
regarded the flower as the interior portions of the plant,
which emerge from the bursting rind ; the calyx as a
thicker portion of the rind of the shoot ; the corolla as an
inner and thinner rind ; the stamens as the interior fibres of
the wood, and the pistil as the pith of the plant.' It may be
observed however that this was not exactly what Cesalpino
says ; but it is nevertheless certain that Linnaeus' own view as
given in these words was intended to reproduce that of Cesal-
pino ; and if it does not do this exactly, there is no essential
difference in principle between the two, Linnaeus' conception
being perhaps a more logical statement of Cesalpino's meaning.
Cesalpino's doctrine of metamorphosis appears plainly on
another occasion also ; he says, that we do not find envelopes,
stamens, and styles in all flowers ; the flowers change in some
cases into another substance, as in the hazel, the edible chest-
nut, and all plants that bear catkins ; the catkin is in place of
a flower, and is a longish body arising from the seat of the
fruit, and in this way fruits appear without flowers, for the styles
(' stamina') form the longer axis of the catkin {' in amenti longi-
tudinem transeunt '), while the leafy parts and the stamens are
changed into its scales. All this shows that the notion of a
metamorphosis, of which we find intimations as early as
Theophrastus, was a famfliar one to Cesalpino, and it fitted in
perfectly with his Aristotelian philosophy, while Goethe's
doctrine on the same subject is equally scholastic in its charac-
ter, and therefore looks strange and foreign in modern science.
It has already been observed that Cesalpino includes only the
envelopes and stamens under the word flower, and distinguishes
the rudiments of the fruit from them ; therefore he says that
there are plants which produce something in the shape of a
catkin, without any hope of fruit, for they are entirely unfruit-
ful ; but those which bear fruit have no flowers, as Oxycedrus,
Taxus, and among herbs Mercurialis, Urtica, Cannabis, in which

Chap. II.] fvom Ccsalpiuo to Linnaeus. 51

the sterile pbnts are termed male, the fruitful female. Thus
he distinguished the cases which we now call dioecious from
the previously mentioned monoecious plants, among which he
reckons the maize.

All this may serve to give the reader some idea, though a
very incomplete one, of Cesalpino's theory ; to do him justice,
it would be necessary to give a full account of his very numerous,
accurate, and often acute observations on the position of leaves,
the formation of fruit, the distribution of seeds and their posi-
tion in the fruit, of his comparative observations on the parts
of the fruit in different plants, and above all of his very excel-
lent description of plants with tendrils and climbing plants, of
those that are armed with thorns and the like. Though there
is naturally much that is erroneous and inexact in his accounts,
yet we have before us in the chapters on these subjects the first
beginning of a comparative morpholog)', w'hich quite casts into
the shade all that Aristotle and Theophrastus have said on the
subject. But the most brilliant portions of his general botany
are contained in the 12th, 13th, and 14th chapters, in which he
gives the outlines of his views on the systematic arrangement
of plants ; to prepare the way for what is to follow, he shows
first that it is better to give up the four old divisions of the
vegetable kingdom, and to unite the shrubs with the trees and
the undershrubs with the herbs. But how these genera are to
be distinguished into species is, he says, hard to conceive, for
the multitude of plants is almost innumerable ; there must be
many intermediate genera containing the ' ultimae species,' but
few are as yet known. He then turns to the divisions founded
on the relations of plants to men. Such groups, he says, as
vegetables and kinds of grain, which are put together under the
name of ' fruges ' and kitchen-herbs (' olera '), are formed more
from the use made of them than from the resemblance of form,
which we require ; and he shows this by good examples. The
discerning of plants, he continues, is very difficult, for so long
as the genera (larger groups) are undetermined, the species must

£ 2

53 Artificial Systems and Terminology of Organs [Book i.

necessarily be mixed up together^; the difficulty arises from our
uncertainty as to the rules by which we should determine the
resemblances of the genera. While there are two chief parts
in plants, the root and the shoot, we cannot, as it seems, deter-
mine the genera and species from the likeness or unHkeness
either of the one or of the other ; for if we make a genus of
those plants which have a round root, as the turnip, Aristolo-
chia, Cyclamen, Arum, we separate generically things which
agree together in a high degree, as rape and radish which
agree with the turnip, and the long Aristolochia which agrees
with the round, while at the same time we unite things most
dissimilar, for the Cyclamen and the turnip are in every other
respect of a quite different nature ; the same is the case with
divisions which rest merely on differences in the leaves and
flowers.

In pursuing these reflections, w'hich have the conception of
species chiefly in view, he arrives at the following proposition :
That according to the law of nature like always produces like,
and that which is of the same species with itself.

All that Cesalpino says on systematic arrangement shows
that he was perfectly clear in his own mind with regard to the
distinction between a division on subjective grounds, and one
that respects the inner nature of plants themselves, and that he
accepted the latter as the only true one. He says, for instance,
in the next chapter : ' We seek out similarities and dissimilari-
ties of form, in which the essence ('substantia') of plants consists,
but not of things which are merely accidents of them ('quae
accidunt ipsis ').' Medicinal virtues and other useful qualities
are, he says, just such accidents. Here we see the path opened,
along which all scientific arrangement must proceed, if it is to
exhibit real natural affinities ; but at the same time there is a
warning already of the error which beset systematic botany up

* These words are quoted by Linnaeus in the 'Philosophia Botanica,'
par. 159.

Chap. II.] froui Ccsalpiuo to Linnaeus. 53

to Darwin's time ; if in the above sentence we substitute the
word idea for that of substance, and the two expressions have
much the same meaning in the Aristotehan and Platonic view
of nature, we recognise the modern predarwinian doctrine, that
species, genera, and famihes represent ' ideam quandam ' and
' quoddam supranaturale.'

Pursuing his deductions, Cesalpino next shows, that the most
important divisions, those of woody plants and herbs, must be
maintained in accordance with the most important function of
vegetation, that of drawing up the food through root and shoot ;
this division passed from the first and later on up to the time
of Jung for an unassailable dogma, to which science simply
had to conform. The second great function of plants is the
producing their like, and this is effected by the parts of fructi-
fication. Though these parts are only found in the more perfect
forms, yet the subdivisions ('posteriora genera') must be derived
in both trees and herbs from likeness and unlikeness in the fructi-
fication. And thus Cesalpino was led, not by induction but by
the deductive path of pure Aristotelian philosophy, to the con-
clusion, that the principles of a natural classification are to be
drawn from the organs of fructification ; for which conclusion
Linnaeus declared him to be the first of systematists, while he
thought de I'Obel and Kaspar Bauhin, who founded their
arrangements on the habit only, scarcely deserving of notice.

It appears, then, that Cesalpino obtained the subdivisions
which he founded on the organs of fructification from a priori
views of the comparative value of organs, such as run through
all Aristotelian philosophy. Of much interesting matter in the
remainder of his introduction we must mention only that he
makes the highest product of plants to be the fructification, of
animals sense and movement, of man the intellect ; and because
the latter stands in need of no special bodily instruments, there
is no specific difference in men, and therefore only one species
of man.

In his 14th chapter he gives in broad outline a view of the

54 Artificial Systems and Terminology of Organs [Book i,

system of plants which he founded on the fructification, begin-
ning with the least perfect ; no one who knows the botanical
writers of the 17th and i8th centuries will be surprised to find
that Cesalpino admits the doctrine of ' generatio spontanea ' in
the case of the lower plants, and in a somewhat crude form ;
this came from the teaching of Aristotle, and even a hundred
years later Mariotte endeavoured to set up a plausible defence
of spontaneous generation on physical grounds even in highly
developed plants.

' Some plants,' says Cesalpino, * have no seed ; these are the
most imperfect, and spring from decaying substances ; they
have only therefore to feed themselves and grow, and are
unable to produce their like ; they are a sort of intermediate
existences between plants and inanimate nature. In this
respect Fungi resemble Zoophytes, which are intermediate
between plants and animals, and of the same nature are the
Lemnae, Lichenes, and many plants which grow in the sea.'

Some on the other hand produce seed, which they form
after their peculiar nature in an imperfect condition, as the
mule among animals ; these are of the same nature as mere
monstrosities or diseased growths of other plants, and many
occur in the class of grain and bear empty ears. Cesalpino is
evidently speaking of the Ustilagineae, but he includes also the
Orobancheae and Hypocystis, which instead of seed contain
only a powder; and he adds that some of the more perfect
plants are sterile, but they do not belong to this division,
because the peculiarity is confined in their case to individuals.

Some plants bear a substance, a kind of wool, on the leaves,
which to some extent answers to seed, because it serves to
propagate the plant; such plants have neither stem, flower,
nor true seed, and the Ferns are of this kind. We should
notice this conclusion from Cesalpino's morphology, that plants
without true seeds have also no stem ; the view that ferns have
no stems continued to be held by later botanists, though the
original reason for it was gradually lost ; and those who in the

Chap. II.] from Ccsalpuw to Linnaeus. 55

middle of the 19th century argued still in favour of this opinion,
little suspected that they were endeavouring to establish a dogma
of the Aristotelian philosophy. It is a similar case to that of
the crown of the root mentioned above. But other plants,
continues Cesalpino, produce true seeds ; and he proceeds to
treat of this division first, on account of its great extent as
comprising all perfect plants. Three things, he says, contribute
especially to the constitution of organs, the number, position,
and shape of the parts ; the play of nature in the composition
of fruits varies according to their differences, and hence arise the
different divisions of plants. He then shows how he proposes
to apply these relations to the framing of his system, but his
various points of view may be omitted here, as they can be
better and more shortly gathered from the table below.

Other marks to be derived from roots, stems, and leaves,
may be used, he says, for forming the smaller divisions.
Lastly, some marks which contribute to the constitution neither
of the whole plant nor of the fruit, such as colour, smell, taste,
are mere accidents and are due to cultivation, place of growth,
climate, and other causes.

The first of Cesalpino's sixteen books ends with this general
view of his system. The remaining fifteen books contain
about 600 pages of descriptions of individual plants arranged
in fifteen classes ; some of the descriptions are exceedingly
minute ; the trees come first, and are followed by the shrubs
on account of their affinity ('ob afifinitatem'). Two things have
interfered with the recognition and acceptance of this system ;
the omission of a general view to precede the text, and its
appearance in the traditional form of books and chapters, such
as we find in de I'fxluse, Dodoens, and Bauhin, instead of in
classes and orders, though it is true that the headings and
introductions to the several books contain the designations and
general characteristics of the classes described in them. Lin-
naeus has done good service by giving in his 'Classes Plantarum'
a general view of all the systems proposed before his time.

56 Artificial Systems and Terminology of Organs [book i.

among which he gives the first rank to that of Cesalpino ; he
has also pointed out the pecuHar characteristics of each system,
and has appended to the old names of the genera those with
which he has himself made us familiar. This invaluable work,
which is a key to the understanding of the efforts that were
made in systematic botany from Cesalpino to Linnaeus himself,
will often be referred to in later pages of this history ; it
will supply us here with a tabular view of Cesalpino's main
divisions as precisely formulated by Linnaeus, which is well
worth the space it will occupy, as presenting the first plan pro-
posed for a systematic arrangement of the vegetable kingdom,
with characters for each division. For the better understanding
of these diagnoses it should be remembered that the ' cor ' (heart)
is the important point in the seed with Cesalpino, and that it
is the place in the embryo where the radicle and the plumule
unite, as has been said in a former page ; Cesalpino himself
says somewhat inexactly, the place from which the cotyledons
spring.

The characters of the classes are given, for brevity's sake, in
Latin.

Arboreae

(Arbores et frutices).

L Corde ex apice seminis. Seminibus saepiussolitariis (e.g.
Quercus, Fagus, Ulmus, Tilia, Laurus, Prunus).

IL Corde e basi seminis, seminibus pluribus (e.g. Ficus,
Cactus, Morus, Rosa, Vitis, Salix, Coniferae, etc.).

Herbaceae
(Suffrutices et herbae).

III. Solitariis seminibus. Semine in fructibus unico (e.g.
Valeriana, Daphne, Urtica, Cyperus, Gramineae).

IV. Solitariis pericarpiis. Seminibus in fructu pluribus,
quibus est conceptaculum carnosum, bacca aut pomum (e.g.
Cucurbitaceae, Solaneae, Asparagus, Ruscus, Arum).

V. Solitariis vasculis. Seminibus in fructu pluribus quibus

Chap. II.] fwiu Ccsalpvio to Liuiiacus. 57

est conceptaculuni e sicca materia (e.g. various Leguminosae,
Caryophylleae, Gentianeae, etc.).

VI. Binis seminibus. Semina sub singulo flosculo invicem
conjuncta, ut unicum videantur ante maturitatem ; cor in parte
superiore, qua flos insidet. Flores in umbella (Umbelliferae).

VII. Binis conceptaculis (e.g. Mercurialis, Poterium, Galium,
Orobanche, Hyoscyamus, Nicotiana, Cruciferae).

VIII. Triplici principio (ovary) non bulbosae. Semina
trifariam distributa ; corde infra sito, radi.x non bulbosa (e.g.
Thalictrum, Euphorbia, Convolvulus, Viola).

IX. Triplici principio bulbosae. Semina trifariam distributa;
corde infra sito, radix bulbosa (Large-flowered Monocotyledons).

X. Quaternis seminibus. Semina quatuor nuda in communi
sede (Boragineae and Labiatae).

XI. Pluribus seminibus, a.nthemides. Semina nuda plurima,
cor seminis interius vergens ; flos communis distributus per
partes in apicibus singuli seminis (Compositae only).

XII. Pluribus seminibus, cichoraceae aut acanaceae. Semi-
na nuda plurima, cor seminis inferius vergens, flos communis
distributus per partes in apicibus singuli seminis (Compositae,
Eryngium, and Scabiosa).

XIII. Pluribus seminibus, flore communi. Semina solitaria
plurima, corde interius ; flos communis, non distributus, infe-
rius circa fructum (e.g. Ranunculus, Alisnia,Sanicula, Geranium,
Linum).

XIV. Pluribus folliculis. Semina plura in singulo folliculo
(e.g. Oxalis, Gossypium, Aristolochia, Capparis, Nymphaea,
Veratrum, etc.).

XV. Flore fructuque carentes (Filices, Equiseta, Musci
including Corals, Fungi).

The examples appended by me to the diagnoses show that
with the exception of the sixth, tenth, and fifteenth classes, no
one perfectly represents a natural group of the vegetable king-
dom. Most of them are a collection of heterogeneous objects,
and the distinction of Dicotyledons and Monocotyledons, almost

^H Artificial Systems and Terminology of Organs [Book i.

perfectly carried out by de I'Obel and Bauhin, is to a great
extent effaced ; the ninth class certainly contains only Mono-
cotyledons, but not all of them. This result of great efforts on
the part of a mind so well trained as Cesalpino's is highly
unsatisfactory. Not a single new group founded on natural
afifinities is established, which does not appear already in the
herbals of Germany and the Netherlands. It is characteristic
of the natural system to reveal itself to a certain extent more
readily to instinctive perception than to the critical understand-
ing. We have seen that Cesalpino intended as far as possible
to give expression in his system to natural afifinities, and the
final result was a series of highly unnatural groups, almost
every one of which is a collection of the most heterogeneous
forms. The cause of this apparently so remarkable fact is this,
that he believed that he could establish on predetermined
grounds the marks which indicate natural affinities. The
uninterrupted labour of nearly 300 years, starting again
and again from the same principle or practically under its
influence, has given us inductive proof that the path taken
by Cesalpino is the wrong one. And if, while this path was
pursued even into the middle of the i8th century, we see natural
groups emerge with increasing distinctness, it is because the
botanist, though on the wrong track, was still continually
gaining better acquaintance with the ground over which he was
wandering, and attained at length to an anticipation of the truer
way.

Joachim Jung^ was born in Liibeck in the year 1587, and
died after an eventful life in 1657, He was a contemporary of
Kepler, Galileo, Vesal, Bacon, Gassendi, and Descartes. After
having been already a professor in Giessen, he applied himself
to the study of medicine in Rostock, was in Padua in 16 18 and

'■ See his biography by Guhrauer, 'Joachim Jungius und sein Zeitalter,'
Tubingen, 1850 ; on his place in philosophy consult Ueberweg ('Geschichte
der Philosophic,' iii. p. 1 19), who regards him as a forerunner of Leibnitz.

Chap. II.] fvom Ccsttlpiuo to Liiiuaciis. 59

1619, and there, as we may confidently believe, became
acquainted with the botanical doctrines of Cesalpino, who had
died fifteen years before. Returning to Germany, he held
various professorships during the succeeding ten years inLiibeck
and Helmstiidt, and became Rector of the Johanneum in Ham-
burg in 1629. He occupied himself with the philosophy of
the day, in which he appeared as an opponent of scholasticism
and of Aristotle, and also with various branches of science,
mathematics, physics, mineralogy, zoology, and botany. In all
these subjects he displayed high powers as a student and a
teacher, and especially as a critical observer ; in botany at least
he was a successful investigator. He was the first in Germany,
as Cesalpino had been in Italy, who combined a philosophi-
cally educated intellect with exact observation of plants.

His pupils were at first the only persons who profited by his
botanical studies, for with his many occupations and a perpetual
desire to make his investigations more and more complete he
himself published nothing. In 1662 his pupil Martin Fogel
printed the ' Doxoscopiae Physicae Minores,' a work of enor-
mous compass left in manuscript at the master's death, and
another pupil, Johann Vagetius, the ' Isagoge Phytoscopica,' in
1678. Ray however tells us that a copy of notes on botanical
subjects had already reached England in 1660. The ' Doxo-
scopiae ' contains a great number of detached remarks on single
plants and on their distinguishing marks, and propositions con-
cerning the methods and principles of botanical research, — all
in the form of aphorisms which he had from time to time
committed to paper. The number and contents of these
aphorisms show the earnest attention which he bestowed on
the determination of species ; he is displeased that so many
botanists devote more time and labour to the discovery of new
plants, than to referring them carefully and logically to their
true genera by means of their specific differences. He was the
first who objected to the traditional division of plants into
trees and herbs, as not founded on their true nature. But

6o Artificial Systems and Terminology of Organs [Book i.

how firmly this old dogma was established is well shown by
the fact, that Ray at the end of the century still retained this
division, though he founded his botanical theories on the
' Isagoge ' of Jung. Jung was in advance of Cesalpino and
his own contemporaries in repeatedly expressing his doubt of
the existence of spontaneous generation.

The ' Isagoge Phytoscopica,' a system of theoretical botany,
very concisely written and in the form of propositions arranged
in strict logical sequence, was a more important work, and had
more lasting effects upon the history of botany. We must look
more closely into the contents of this volume, because it con-
tains the foundation of the terminology of the parts of plants
subsequently established by Linnaeus. Since the matter of the
' Isagoge ' is produced in Ray's ' Historia Plantarum ' in italics,
with special mention of the source from which it is derived, it
cannot be doubted that Linnaeus had made acquaintance with
the teaching of Jung as a young man, in any case before
1738. It is as important as a matter of history to know that
Linnaeus' terminology is founded on Jung, as it is to learn
that his most general philosophical propositions on botanical
subjects are to be traced to Cesalpino. It will moreover be
fully shown in the account of the doctrine of sexuality that his
knowledge of that subject was derived from Rudolf Jacob
Camerarius.

The first chapter of the ' Isagoge ' discusses the distinction
between plants and animals. A plant is, according to Jung,
a living but not a sentient body ; or it is a body attached to a
fixed spot or a fixed substratum, from which it can obtain
immediate nourishment, grow and propagate itself A plant
feeds when it transforms the nourishment which it takes up
into the substance of its parts, in order to replace what has
been dissipated by its natural heat and interior fire. A plant
grows when it adds more substance than has been dissipated,
and thus becomes larger and forms new parts. The growth of
plants is distinguished from that of animals by the circumstance

Chap. II.] from Ccsalpiiio to Linnaeus. 61

that their parts are not all growing at the same time, for leaves
and shoots cease to grow as soon as they arrive at maturity ;
but then new leaves, shoots, and flowers are produced. A
plant is said to propagate itself when it produces another
specifically like itself; this is the idea in its broader accepta-
tion. We see that here, as in Cesalpino, the idea of the species
is connected with that of propagation. The second chapter,
headed ' Plantae Partitio,' treats of the most important mor-
phological relations in the external differentiation of plants ;
here Jung adheres essentially to Cesalpino's view, that the
whole body in all plants, except the lowest forms, is composed
of two chief parts, the root as the organ which takes up the
food, and the stem above the ground which bears the fructi-
fication. Jung, too, draws attention to the meeting-point of
the two parts, Cesalpino's ' cor,' but under the name of ' fundus
plantae.'

The upper part, or a portion of the plant, is either a stem, a
leaf, a flower, a fruit, or a structure of secondary importance,
such as hairs and thorns. His definition of the stalk and the
leaf is noteworthy ; the stalk, he says, is that upper part which
stretches upwards in such a manner, that a back and front,
a right and left side, are not distinguished in it. A leaf is that
which is extended from its point of origin in height, or in
length and breadth, in such a manner, that the bounding
surfaces of the third dimension are different from one another,
and therefore the outer and inner surfaces of the leaf are
differently organised. The inner side of the leaf, which is
also called the upper, is that which looks towards the stem, and
is therefore concave or less convex than the other side. One
conclusion he draws, which is a striking one for that time, that
the compound leaf is taken for a branch by inexperienced or
negligent observers, but that it may easily be determined by
having an inner and an outer surface, like the simple leaf, and
by falling off as a whole in autumn. He calls a plant ' diffor-
miter foliata,' whose lower leaves are strikingly different from

62 Artificial Systems and Terminology of Organs [Book i.

the upper, an idea which Goethe, in the fragment in Guhrauer,
seems to have altogether misunderstood.

In connection with these general definitions, the different
forms of the stem and of the ramification, and the varieties of
leaves are pointed out and supplied with distinctive names,
which are for the most part still in use. The fourth chapter
treats of the division of the stem into internodes ; if the stem
or branch, says Jung, is regarded as a prismatic body, the
articulations, that is, the spots where a branch or a leaf-stalk
arises, are to be conceived of as cross-sections parallel to the
base of the prism. These spots when they are protuberant are
called knees or nodes, and that which lies between such spots
is an internode.

It is not possible to quote all the many excellent details
which follow these definitions ; but some notice must be taken
of Jung's theory of the flower, which he gives at some length
from the 13th to the 27th chapters. It suffers, as in Cesalpino,
from his entire ignorance of the difference of sexes in plants,
which is sufficient to render any satisfactory definition of the
idea of a flower impossible. Like Cesalpino too he distin-
guishes the pistil from the flower, instead of making it a part of
the flower. He regards the flower as a more delicate part of
the plant, distinguished by colour or form, or by both, and con-
nected with the young pistil. Like all botanists up to the end
of the 1 8th century, he follows Cesalpino in including under the
term fruit both the dry indehiscent fruits which were supposed
to be naked seeds, and any seed-vessel. He differs from him in
calling the stamens 'stamina,' and the style 'stilus,' but like
Cesalpino he uses the word 'folium' for the corolla. He calls a
flower perfect only when it has all these three parts. He
afterwards describes the relations of form and number in the
parts of the flower, and among other things he enunciates the
first correct view of the nature of the capitulum in the Com-
positae, which Cesalpino quite misunderstood ; and he examined
inflorescences and superior and inferior flowers, which Cesalpino

Chap. II.] froui Ccsalpiuo to LiunacHS. 63

had already distinguished, with more care than they had pre-
viously received. In his theory of the seed he follows
Cesalpino, and adds nothing to him.

There is nothing which more essentially distinguishes the
theoretical botany of Jung, and marks the advance which
he made upon Cesalpino's views, than the way in which he
discusses morphology in as entire independence as was possible
of all physiological questions, and therefore abstains from
teleological explanations. His eye is fixed on relations of
form only, while his mode of treating them is essentially com-
parative, and embraces the whole of the vegetable kingdom
that was known to him. -Jung certainly learnt much from
Cesalpino ; but in rejecting at least the grosser aberrations of
the Aristotelian philosophy and of scholasticism, he freed him-
self from the prepossessions of his master, and succeeded in
arriving at more correct conceptions of the morphology of
plants. That his mathematical gifts assisted him in this respect
is easy to be gathered from his definitions as given above,
which bring into relief the symmetry apparent in the forms of
stems and leaves. No more profound or apt definitions were
supplied till Schleiden and Nageli introduced the history of
development into the study of morphology.

While Cesalpino, Kaspar Bauhin, and Jung stand as soli-
tary forms each in his own generation, the last thirty years of
the 17th century are marked by the stirring activity of a
number of contemporary botanists. While during this period
physics were making rapid advances in the hands of Newton,
philosophy in those of Locke and Leibnitz, and the anatomy
and physiology of plants by the labours of ^Lalpighi and Grew,
systematic botany was also being developed, though by no means
to the same extent or with equally profound results, by Morison,
Ray, Bachmann (Rivinus), and Tournefort. The works of these
men and of their less gifted adherents, following rapidly upon
or partly synchronous with each other, led to an exchange of
opinions and sometimes to polemical discussion, such as had

64 Artificial Systems and Terminology of Organs [book i.

not before arisen on botanical subjects ; this abundance of
literature, with the increased animation of its style, excited a
more permanent interest, which spread beyond the narrow
circle of the professional adepts. The systematists above-
named endeavoured to perfect the morphology and the termin-
ology of the parts of plants, and they found ready to their
hands in the works of their predecessors a considerable store
of observations and ideas, upon which they set themselves
to work. A very great number of descriptions of individual
plants had been accumulated since the time of Fuchs and
Bock, and the fact of natural aflSnity had been recognised in
the ' Pinax ' of Kaspar Bauhin as the foundation of a natural
system ; Cesalpino had pointed to the organs of fructification
as the most important for such a system, and Jung had
supplied the first steps to a comparative morphology in place
of a mere explanation of names. The botanists of the last
thirty years of the 17th century could not fail to perceive that
the series of affinities as arranged by de I'Obel and Bauhin
could not be defined by predetermined marks in the way
pursued by Cesalpino, nor fashioned in this way into a well-
articulated system. Nevertheless they held fast in principle to
Cesalpino's mode of proceeding, though they endeavoured to
amend it by obtaining their grounds of division, not as he had
done, chiefly from the organisation of the seed and fruit, but
from other parts of the flower ; variations in the corolla, the
calyx, and the general habit were employed to found systems,
which were intended to exhibit natural affinities. And while
the true means were thus missed, the end itself was not clearly
and decidedly adhered to ; a system was desired for the pur-
pose of facilitating the acquisition of a knowledge of the
greatest possible number of individual forms ; the weight of
the burden caused by the foolish demand that every botanist
should know all described plants, was continually increasing,
and naturally led to seeking some alleviation in systematic
arrangement. Excessive devotion to the describing of plants

Chap. II.] from Ccsalpiuo to Linnaeus. 6^

stood in the way of such a profound study of the principles of
systematic botany as might have led to enduring results, and
even destroyed the very capacity for those difficult intellectual
operations, which were absolutely necessary to build up a truly
natural system on scientific foundations ; the wood could not
be seen for the trees. Above all the morphology founded by
Jung, though acknowledged and employed, was not suffi-
ciently developed by the labours of others to form the
foundation of the system in its grander features, — a reproach
which must be made against the systematists of the succeeding
hundred years with few exceptions. How could the botanists
of the 1 7th century succeed in acquiring a true conception of
the larger groups indicated by natural affinity, when they still
held to the old division into trees and herbs, which Jung
had already set aside and which is opposed to all consistent
morphology, and when they paid so little attention to the
structure of the seed and the fruit, that they commonly treated
dry indehiscent fruits as naked seeds, and were guilty of other
and similar mistakes ? But if nothing new and good in prin-
ciple found its way into systematic botany, much service was
rendered to it in matters of detail. The working out of various
systems helped to show what marks are not admissible in
fixing the limits of the natural groups ; the contradiction
between the method and aim of the systematists became in
this empirical way continually more apparent, till at length
Linnaeus was able to recognise it distinctly ; and this was
beyond doubt a great gain.

To attempt to give an account of all the systematists of
England, France, Italy, Germany, and the Netherlands during
this period would serve only to obscure the subject ; all that is
historically important will be brought out more clearly by
mentioning those only who have really enriched systematic
botany. Whoever wishes for a more complete knowledge of
all the systems which made their appearance before Linnaeus
will find a masterly account of them in his ' Classes Plantarum,'

F

66 Artificial Systems and Terminology of Organs [Book i.

and another worth consulting in Michel Adanson's ' Histoire de
la Botanique ' (Paris, 1864). It is sufficient for our present
purpose to consider more particularly the labours of the four
men whose names have recently been mentioned.

Robert Morison\ who was born in Aberdeen in 1620 and
died in London in 1683, was the first after Cesalpino and
Bauhin who devoted himself to systematic botany, that is, to
founding and perfecting the classification of plants. He was
reproached by his contemporaries and successors with havin^^
borrowed without acknowledgment from Cesalpino ; this was
an exaggeration. Morison commenced his efforts as a syste-
matist with a careful examination of Kaspar Bauhin's ' Pinax ' ;
there he obtained his conceptions of natural relationship in
plants ; and if he afterwards founded his own system more
peculiarly on the forms of the fruit, it was in a very different
way from that adopted by Cesalpino. Linnaeus answers the
reproach above-mentioned by the pertinent remark, that
Morison departs as far from Cesalpino in this point as he is
inferior to him in the purity of his method. In the year 1669
appeared a work with the characteristic title, ' Hallucinationes
Kaspari Bauhini in Pinace tum in digerendis quam denomi-
nandis plantis,' which Haller justly calls an ' invidiosum opus ' ;
for as there are writers at all times who ungratefully accept all
that is good and weighty in their predecessors as self-evident,
while they point with malicious pleasure to every little mistake
which the originator of a great idea may commit, so Morison
has no word of recognition for the great and obvious merits of
the ' Pinax,' though such a recognition was specially due from
one whose design was to point out the numerous mistakes in
that work on the subject of affinities. Kurt Sprengel in his

^ Morison served in the royal army against Cromwell, and after the
defeat of his party retired to Paris, where he studied botany under Robin.
He was made physician to Charles II and Professor of Botany in 1660, and
Professor of the same faculty in Oxford ten years later. See Sprengel, ' Ge-
schichte der Botanik,' ii. p. 30.

Chap. II.] froYU Ccsalphw to Linuaeus. 67

' Geschichte,' ii. p. 30, also suspects with reason that Jung's
manuscript, which was communicated by Hartheb to Ray in
1 66 1, was not unknown to Morison, and in this paper he
might certainly have found much that suited his purposes.
Sprengel says well, that the ' Hallucinationes ' are a well-
grounded criticism of the arrangement of plants, which tlie
Bauhins had chosen ; that the writer goes through the ' Pinax '
page by page, and shows what plants occupy a false position,
and that it is certain that Morison laid the first foundation of a
better arrangement and a more correct discrimination of genera
and species.

His 'Plantarum umbelliferarum distributio nova,' Oxford,
1672, shows considerable advance; it is the first monograph
which was intended to carry out systematic principles strictly
within the limits of a single large family. The very complex
arrangement is founded exclusively on the external form of the
fruit, which he naturally terms the seed. It is the first work in
which the system is no longer veiled by the old arrangement in
books and chapters, perspicuity being provided for by typo-
graphical management, — an improvement which de I'Obel, it is
true, made a feeble attempt to introduce a hundred years
before. Morison also endeavours to give a clear idea of the
systematic relations within the family by the aid of linear
arrangement, to some extent the first hint of what we now call
a genealogical tree, and a proof at any rate of the lively concep-
tion which he had formed of affinity, not drawn indeed only ' ex
libro naturae,' as the title of his book states, but in principle
from Bauhin. Morison's inability to appreciate the merits
of his' predecessors, and to believe that when he made a step
in advance the way had ever been trodden before, may be seen
in this work also. One of its merits is, that it contains for the
first time careful representations of separate parts of plants,
executed in copper plate \ In 1680 appeared the first volumes

' The wood-engraving of the i6th century had fallen into decay, and

F 2

68 Artificial Systems and Tenninology of Organs [Book i.

of his ' Historia plantarum universalis Oxoniensis,' the third
portion of which was pubhshed after his death by Bobart in 1699,
— a collection of most of the plants then known and a large
number of new ones with descriptions ; the systematic arrange-
ment in this work is to be seen in Linnaeus' 'Classes
Plantarum.' If Morison in his criticism of Bauhin displayed
considerable acuteness within narrow circles of affinity, his
universal system on the contrary shows extremely small feeling
for affinities on the large scale ; the most different forms are
brought together even in the smaller divisions ; the last class
of his Bacciferae, for example, contains genera like Solanum,
Paris, Podophyllum, Sambucus, Convallaria, Cyclamen, a result
which is the more surprising as Morison does not, like
Cesalpino, confine himself to single fixed marks, but has
regard also to the habit. On the whole his arrangement as
an expression of natural affinities must be ranked after those
of de rObel and Bauhin.

Morison's merit lay in truth less in the quality of what he
did, than in the fact that he was the first to renew the culti-
vation of systematic botany on a comprehensive scale. The
number of his adherents was always small ; in Germany Paul
Ammann, Professor in Leipsic, adopted Morison's views in his
'Character Plantarum Naturalis ' (1685), and Paul Hermann,
Professor in Leyden from 1679 to 1695, after collecting plants
in Ceylon for eight years, proposed a system founded on that
of Morison, but which can scarcely be called an improvement
upon it.

In contrast to Morison, John Ray^ (1628 to 1705) not only

engraving on copper-plate had taken its place. A thick volume of figures
of plants in the largest folio size engraved on copper, the ' Hortus Eistad-
tensis,' appeared in the beginning of the 17th century.

^ John Ray, born at Black Notley in Essex, was also a zoologist of emi-
nence. He studied theology and travelled in England and on the continent,
and afterwards devoted himself entirely to science, being supported by
a pension from Willoughby. See Carus, ' Geschichte der Zoologie,' p. 428.

Chap. 11] froui Cesalphto to Linnaeus. 69

knew how to adopt all that was good and true in the works of
his predecessors, and to criticise and complete them from his
own observations, but could also joyfully acknowledge the
ser\-ices of others, and combine their results and his own into a
harmonious whole. He wrote many botanical works ; but
none display his character as a man and a naturalist better
than his comprehensive ' Historia Plantarum,' published in
three large folio volumes without plates in the period from
1686 to 1704. This work contains a series of descriptions of
all plants then known ; but the first volume commences with a
general account of the science in fifty-eight pages, which, printed
in ordinary size, would itself make a small volume, and which
treats of the whole of theoretic botany in the style of a modern
text-book. If morphology, anatomy, and physiology, in which
latter subject he relies on the authority of Malpighi and Grew,
are not kept strictly apart in his exposition, yet it is easy to
separate the morphological part, and his theory of systematic
botany is in fact given separately. Jung's definitions of the
subject-matter of each of the chapters on morphology are first
given, and Ray then adds his own remarks, in which he
criticises, expands, and supplements those of his predecessor.
Omitting all that is not his own, and the anatomical and
physiological portions, we will describe some of the more
important results of his studies on system. First and foremost
Ray adopted the idea which Grew had conceived, but in a very
clumsy form, that difference of sex prevails in the vegetable
kingdom, and hence the flower had a different meaning and
importance for him from what it had had for his predecessors,
though his views on the subject were still indistinct. Ray
perceived more clearly than Cesalpino that many seeds contain
not only an embryo but also a substance, which he calls ' pulpa '
or ' medulla,' and which is now known as the endosperm, and
that the embryo has not always two cotyledons, but sometimes
only one or none ; and though he was not quite clear as regards
the distinction, which we now express by the words dicotyle-

70 Artificial Systems and Terminology of Organs [BookI.

donous and monocotyledonous embryo, yet he may claim the
great merit of having founded the natural system in part upon
this difference in the formation of the embryo. He displays
more conspicuously than any systematist before Jussieu the
power of perceiving the larger groups of relationship in the
vegetable kingdom, and of defining them by certain marks ;
these marks moreover he determines not on a priori grounds,
but from acknowledged affinities ; but it is only in the great
divisions of his system that he is thus true to the right course ;
in the details he commits many and grievous offences against
his own method, as we shall see below when we come to an
enumeration of his classes. Modern writers have often
attributed to Ray the merit of having first taught the trans-
mutation of species, and of being thus one of the founders
of the theory of descent. Let us see how much truth there is
in this assertion. Though plants, says Ray, which spring from
the same seed and produce their species again through seed,
belong to the same species, yet cases may occur in which the
specific character is not perpetual and infallible. Seeds may
sometimes degenerate and produce plants specifically distinct
from the mother-plant, though this may not often happen, and
so there would be a transmutation of species, as experience
teaches. It is true that he considered the statements of various
writers, that Triticum may change into Lolium, Sisymbrium
into Mentha, Zea into Triticum, etc., to be very doubtful, yet
there were, he thought, other cases which were well ascertained ;
it was in evidence in a court of law that a gardener in London
had sold cauliflower seed which had produced only common
cabbage. It is to be observed, he says, that such transmu-
tations only occur between nearly allied species and such as
belong to the same genus, and some perhaps would not allow
that such plants are specifically distinct. These words,
especially when judged by Ray's general views, appear only
to express the opinion that certain inconsiderable variations
are possible within a narrow circle of affinity, especially in

Chap. II.] from Ccsalpino to Linnaeus. 71

cultivated plants. Ray docs not speak of the appearance
of new forms, but says that a known form changes into another
already existing and known form, which is the reverse of that
which the theory of descent requires.

In his development of the principles of his system, among
other errors we encounter one that leads to very important conse-
quences in his application of the dictum, 'natura non facit saltus,'
which he interprets as though all affinities must present them-
selves in a series that would be represented by a straight line,
— an error which has misled systematists even in recent times,
and was first recognised as an error by Pyrame de CandoUe.
Ray overlooked the fact that the dictum holds good even when
the affinities arrange themselves in the form of branching series,
that is, after the manner of a genealogical tree. Much more sound
is his remark, that the framing of the true system had previously
been impossible, because the differences and agreements of
forms were not sufficiently known; and another saying of his, that
nature refuses to be forced into the fetters of a precise system,
shows the dawn of the knowledge which afterwards led in
Linnaeus to a strict separation of the natural and artificial
systems.

It excites no small astonishment after all Ray's judicious and
clear-sighted utterances on the nature and method of the
natural system to find him adopting the division into woody
plants and herbs ; nor is the matter improved by his making
the distinctive mark of trees and shrubs to be the forming of
buds, that is, distinct winter buds, which is a mistake into the
bargain. Yet we feel ourselves in some degree compensated for
this serious error by his dividing trees and herbs into those
with a two-leaved and those with a one-leaved or leafless
embryo, in modern language into Dicotyledons and Mono-
cotyledons. Ray's system is undoubtedly the one which in the
time preceding Linnaeus does most justice to natural affinities.
The following synopsis of his Classes will serve to show the
progress made since Cesalpino. The names in brackets are

72 Artificial Systems and Terminology of Organs [Book i.

the Linnaean names for some of the genera in particular
classes.

A. Plantae gemmis carentes (herbae).

(a) Imperfectae.

I. Plantae submarinae (chiefly Polypes, Fucus).

II. Fungi.

III. Musci (Confervae, Mosses, Lycopods).

IV. Capillares (Ferns, Lemna, Equisetum).

(b) Perfedae.

Dicotyledones (binis cotyledonibus).

V. Apetalae.

VI. Planipetalae lactescentes.

VII. Discoideae semine papposo.

VIII. Corymbiferae.

IX. Capitalae (vi-ix are Compositae).

X. Semine nudo solitario (Valerianeae, Mirabilis, Thesium,

etc.),

XI. Umbelliferae.

XII. Stellatae.

XIII. Asperifoliae.

XIV. Verticillatae (Labiatae).

XV. Semine nudo polyspermo (Ranunculus, Rosa, Alisma !).

XVI. Pomiferae (Cucurbitaceae).

XVII. Bacciferae (Rubus, Smilax, Bryonia, Solanum, Meny-

anthes).
XVIIL Multisiliquae (Sedum, Helleboreae, Butomus,
Asclepias).

XIX. Vasculiferae monopetalae (various).

XX. Vasculiferae dipetalae (various).

XXI. Tetrapetalae siliquosae (Cruciferae, Ruta, Monotropa).

XXII. Leguminosae.

XXIII. Pentapetalae vasculiferae enangiospermae (various).

Chap. II.] fvom Ccsttlpiuo to Liunacus. 73

Monocotyledones (singulis aut nullis
cotyledonibus).

XXIV. Graminifoliae floriferae vasculo tricapsulari (Lili-

aceae, Orchideae, Zingiberaceae).

XXV. Stamineae (Grasses).

XXVI. Anomalae incertae sedis.

B. Plantae gemmiferae (arbores).

(a) Monocotyledones.

XXVII. Arbores arundinaceae (Palms, Dracaena).

(b) Dicoty/edones.

XXVIII. Arbores fructu a flore remoto seu apetalae (Coni-

ferae and various others).

XXIX. Arbores fructu umbilicato (various).

XXX. Arbores fructu non umbilicato (various).

XXXI. Arbores fructu sicco (various).

XXXII. Arbores siliquosae (woody Papilionaceae).

XXXIII. Arbores anomalae (Ficus).

Of these classes only the Fungi, Capillares, Stellatae,
Labiatae, Pomiferae, Tetrapetalae, Siliquosae, Leguminosae,
Floriferae, and Stamineae can pass as wholly or approximately
natural groups, and there are mistakes even in these ; more-
over the majority of them had long been recognised. The
examples annexed in brackets show how open the others are to
objection. If it must be allowed on the one side that Ray,
like Jung, doubts whether the Cryptogams are propagated
without seeds, it is on the other side obvious that he makes as
little objection as his predecessors, contemporaries, and imme-
diate successors to the idea that Polypes and Sponges are
vegetables. But worse than this is the extremely faulty sub-
ordination and coordination in his system ; while the class of
Mosses contains the Confervae, Lichens, Liverworts, Mosses,
and Clubmosses, and therefore objects as distinct from one
another as Infusoria, Worms, Crabs, and Mollusks, we find
on the contrary the one family of Compositae split up into

74 Artificial Systems and Terminology of Orgatts [BookI.

four classes founded on quite petty and unimportant differ-
ences. Finally, if Ray recognised the general importance to
the system of the leaf-formation in the embryo, he was still far
from strictly separating all Monocotyledons and Dicotyledons.

Ray's chief merit is that he to some extent recognised
natural afifinities in their broader features ; the systematic
separation of the smaller groups was but little advanced by
him. He too, like Morison, found two adherents in Germany
in the persons of Christopher Knaut (i 638-1 694), who pub-
lished a flora of Halle in 1687 arranged after Ray's method,
and Christian Schellhammer (1649-17 16), professor at Helm-
stadt and afterwards at Jena.

Augustus Quirinus Bachmann (Rivinus)^ (1652-1725)
was for Germany what Morison and Ray were for England, and
Tournefort for France. From the year 1691 he was Professor of
botany, physiology, materia medica, and chemistry in Leipsic ;
he applied himself with such ardour to astronomy that he injured
his eyesight by observing spots in the sun. With such a variety
of occupations it is not surprising that his special knowledge of
plants was inconsiderable when compared with that of the three
just named; but he was better able than they to appreciate
the principles of morphology laid down by Jung, and to use
them for deciding questions of systematic botany. He did
most service by his severe strictures on the more prominent
errors which botanists up to his time had persisted in, his own
positive contributions, at least as far as the recognition of affinities
is concerned, being inconsiderable. His ' Introductio univer-
salis in rem herbariam,' which appeared in 1690, and contains
39 pages of the largest size, is the most interesting for us ; in

* A. Q. Bachmann (Rivinus) was the third son of Andreas Bachmann, a
physician and philologist of Halle. He is said to have spent 80,000
florins on the publication of his works and the providing them with
the 500 copper-plates with which they were illustrated. A life of him
and just estimate of his work, by Du Petit-Thouars, is to be found in
the ' Biographic universelle ancienne et modeme.'

Chap. II.] from Ccsalpifio to Linnaeus. 75

it he declines the great quantity of unnecessary work witli wiiich
botanists occupied themselves, and declares the scientific study
of plants to be the only end and aim of botany. He first
treats of naming, and lays down with respect to generic and
specific names the principles which Linnaeus afterwards con-
sistently applied, whereas Bachmann himself did not follow his
own precepts, but injured his reputation as a botanist by a
tasteless nomenclature. Nevertheless he declared distinctly
that the best plan is to designate each plant by two words, one
of which should be the name of the genus, the other that of the
species, and he ingeniously pointed out the great convenience
of this binary nomenclature in dealing with medicinal plants,
and in the writing of prescriptions. He refused to regard
cultivated varieties as species, though Tournefort and others
continued to do so.

In his system he rejected the division into trees, shrubs, and
herbs, showing by good examples that there is no real distinc-
tion of the kind in nature. From many of his remarks in his
critical dissertations we might infer that he possessed a very
fine feeling for natural relationship, but at the same time
expressions occur which seem to show that he did not at all
appreciate its importance in the system ; we notice this in
Tournefort also. Because flowers come before the fruit he
jumps with curious logic to the conclusion that the main divi-
sions in the system should be derived from the flower, and in
following this rule he makes use of exactly that mark in the
corolla which has the least value for classification, namely,
regularity or irregularity of form. It is strange, moreover,
that Bachmann, who spent a considerable fortune on the pro-
duction of copper-plate figures of plants without any special
object, though he founded his system on the form of the
flower, should yet have devoted only a superficial study to its
construction ; his account of it is very inferior to that of any
one before or since his time. His classification thus founded
cannot be said to be an advance in systematic botany ; never-

76 Artificial Systems and Terminology of Organs [Book i.

theless, he had no lack of adherents, and among them in
Germany, Heucher, Knaut, Ruppius, Hebenstreit, and Ludwig;
in England, Hill and others, who made alterations here and
there in his system, but any real development of it was from its
nature an impossibility ; he endeavoured to defend it against
the assaults of Ray and Dillen ; Rudbeck also declared against
him.

Joseph Pitton de Tournefort^ (1656-1708) founded his
system also on the form of the corolla, but his views are to
some extent opposed to those of Bachmann. While the latter
was pre-eminently critical and deficient in knowledge of species,
Tournefort was more inclined to dogmatise, and atoned in the
eyes of his contemporaries for want of morphological insight by
his extensive acquaintance with individual plants. He is
commonly regarded as the founder of genera in the vegetable
kingdom ; but it has been already shown that the conceptions
of genera and species had been framed as early as the i6th
century from the describing of plants, and that Kaspar Bauhin
also, in naming his plants, consistently distinguished genera
and species ; moreover Bachmann in 1690 had supported the
claims of the binary nomenclature as the most suitable for the
designation of plants, though he did not himself adopt it ;
Tournefort did adopt it, but in an entirely different way from
that of Bauhin. Bauhin gave only the name of the genus, and
supplied the species with characters ; Tournefort, on the other
hand, provided his genera with names and characters, and
added the species and varieties without special description.
Tournefort therefore was not the first who established genera ;

* Totimefort was bom at Aix in Provence, and received his early educa-
tion in a Jesuit college. He was intended for the Church, but after his
father's death, in 1677, he was able to devote himself entirely to botany.
After travelling in PVance and Spain, he became Professor at the Jardin des
Plantes in 1683 ; but while thus engaged he made various journeys in
Europe, and in 1 700 visited Greece, Asia, and Africa — everywhere diligently
collecting the plants which he afterwards described.

Chap. II.] froui Ccsalpiiio to Linnaeus. 77

he merely transferred the centre of gravity, so to speak, in
descriptive botany to the definition of the genera; but in doing
so he committed the great fault of treating specific differences
within the genus as a matter of secondary importance. How
little depth there was in his botanical ideas may be seen not
only from his very poor theory of the flower, the imperfections
in which, as in the case of Bachmann, are the more remarkable,
since he founded his system on the outward form of the flower,
but still more from the expression which he uses at the end of
his history of botany, a work otherwise of considerable merit ;
he says there that the science of botany has been so far
advanced since the age of Hippocrates, that hardly anything is
still wanting except an exact establishing of genera. His
general propositions on the subject of systematic botany,
together with much that is good, but which is generally not new
and is better expressed in the works of Morison, Ray, and
Bachmann, contain strange misconceptions ; for instance, he
classes plants which have no flower and fruit with those in
which these parts are to be seen only with the microscope, that
is, the smallness of the organs is equivalent to their absence. It
may seem strange that his theory of the flower should be so
imperfect, when the excellent investigations of Malpighi and
Grew into the structure of flowers, fruit, and seed were already
before the world (1700), and Rudolph Jacob Camerarius had
made known his discovery of sexuality in the vegetable king-
dom. This doctrine, however, Tournefort expressly refused to
admit. But the reproach of neglecting the labours of Malpighi
and Grew is equally applicable to Bachmann and the systematists
up to A. L. de Jussieu ; we have here only the first example of
the fact since so often confirmed, that professed systematists
shrank with a certain timidity from the results of more delicate
morphological research, and rested their classifications as far as
possible on obvious external features in plants, — a proceeding
which more than anything else delayed the construction of the
natural system.

78 Artificial Systems and Terminology of Organs [Book i.

Tournefort's system is thoroughly artificial, if possible, more
artificial than that of Bachmann, and certainly inferior to Ray's.
If we meet with single groups that are really natural, it is simply
because in some families the genera so agree together in all
their marks, that they necessarily remain united, whatever mark
we select for the systematic purpose. We do not find in Tour-
nefort the distinction between Phanerogams and Cryptogams
already established by Ray, nor the division of woody plants
and herbs into Monocotyledons and Dicotyledons ; if his chief
work, to which we confine ourselves here, the ' Institutiones rei
herbariae,' did not bear the date of 1700, we might conclude
that it was written before the ' Historia Plantarum ' of Ray, and
the chief work of Bachmann. Yet it has one merit of a purely
formal kind ; it is pervaded by a rigorous spirit of system ;
every class is divided into sections, these into genera, and these
again into species ; figures of the leaves and of the parts of the
flcrvver, very beautifully engraved on copper-plate and filling a
whole volume, are perspicuously arranged ; the whole work
therefore is easy to consult and understand. But to form an
idea of the confusion as regards natural affinities that reigns in
his system, we need only examine the first three sections of his
first class, when we shall find Atropa and Mandragora together
in the first section, Polygonatum and Ruscus in the second,
Cerinthe, Gentiana, Soldanella, Euphorbia, and Oxalis in
the third. The handiness of the book, the httle interest taken
by most of the botanists of the time in the question of natural
relationship, and the continually increasing eagerness for a
knowledge of individual plants, are evidently the reasons why
Tournefort gained over to his side most of the botanists not
only of France, but also of England, Italy, and Germany \ and
why later attempts in systematic botany during the first thirty
or forty years of the i8th century were almost exclusively
founded on his system, as they were afterwards on the sexual
system of Linnaeus. Boerhaave, among others, proposed a
system in 17 10, which may be regarded as a combination of

Chap. II.] froyu Ccsalphto to Linnaeus. 79

those of Ray, Hermann, and Tournefort, but it met with no
support on any other grounds.

We here take our leave of the systematists of the 17th cen-
tur}', and, passing over the mere plant-collectors of the first
thirty years of the i8th, turn at once to Linnaeus.

Carl Linnaeus', called Carl von Linne after 1757, was born
in 1707 at Rashult in Sweden, where his father was preacher.
He began the study of theology, but was soon drawn away
from it by his preference for botany, and in this pursuit he was
encouraged by Dr. Rothmann, who sent him to the works of
Tournefort. In Lund, where he now studied medicine, he
became acquainted with Vaillant's treatise, ' De se.\-u plantarum,'
and had his attention drawn by it to the sexual organs. In
1730, when he was only twenty-three years old, the aged
Professor Rudbeck gave up to him his botanical lectures and
the management of the botanic gardens, and here Linnaeus
began the composition of the ' Bibliotheca Botanica,' the
' Classes Plantarum,' and the ' Genera Plantarum.' In the year
1732 he made a botanical journey to Lapland, and in 1734 to
Dalecarlia ; in 1735 ^^ went to Holland, where he obtained a
degree ; in that country he remained three years, and printed
the works above-named, together with the ' Systema Naturae,'
the 'Fundamenta Botanica,' and other treatises. From Holland
he visited England and France. In the year 1738 he returned
to Stockholm and was compelled to gain a livelihood as a
physician, till in 1741 he became Professor of Botany in
Upsala, where he died in the year 1778.

Linnaeus is commonly regarded as the reformer of the

• In addition to the Autobiography of Linnaens, various accounts of his
life have been written, some of which are mentioned in Pritzel's ' Thesaurus
Lit. Bot.' A strange revelation of his character and sentiments is to be
found in his treatise on the ' Nemesis divina,' which he bequeathed to his son.
Of this work Professor Fries has unfortunately published an ejiitome only,
which is noticed in the Rcgensburg F"lora, No. 44 (1851). On Linnaeus'
services to zoology, see Carus, 'Geschichte der Zoologie,' Miinchen, 1872.

8o Artificial Systems and Terminology of Organs [Book r.

natural sciences which are distinguished by the term descriptive,
and it is usual to say that a new epoch in the history of our
science begins with him, as a new astronomy began with
Copernicus, and new physics with Galileo. This conception
of Linnaeus' historical position, as far at least as his chief
subject, botany, is concerned, can only be entertained by one
who is not acquainted with the works of Cesalpino, Jung, Ray,
and Bachmann, or who disregards the numerous quotations
from them in Linnaeus' theoretical writings. On the contrary,
Linnaeus is pre-eminently the last link in the chain of develop-
ment represented by the above-named writers ; the field of
view and the ideas of Linnaeus are substantially the same as
theirs ; he shares with them in the fundamental errors of the
time, and indeed essentially contributed to transmit them to
the 19th century. But to maintain that Linnaeus marks not
the beginning of a new epoch, but the conclusion of an old
one, does not at all imply that his labours had no influence
upon the time that followed him. Linnaeus stands in the same
relation to the systematists of the period we are considering
that Kaspar Bauhin does to the botanists of the i6th century;
as Bauhin gathered up all that was serviceable in his predeces-
sors, Cesalpino only excepted, while the botanists of our second
period drew again from him, though they set out from other
points of view than his ; so Linnaeus adopted all that the
systematists of the 17th century had built upon the foundation
of Cesalpino's ideas, gave it unity and fashioned it into a system
without introducing into it anything that was fundamentally
and essentially new ; all that had been developed in systematic
botany from Cesalpino to Tournefort culminated in him, and
the results, which he put together in a very original form and
with the power of a master, were no more unfruitful for the
further development of botany than the contents of Kaspar
Bauhin's works for the successors of Cesalpino.

Whoever carefully compares the works of Cesalpino, Jung,
Morison, Ray, Bachmann, and Tournefort with Linnaeus,

Chap. II.] Orgaus from Cesalpino to Lwnaeus. 8 1

'Fundamenta Botanica' (i 736), his ' Classes Plantarum ' (1738),
and his ' Philosophia Botanica' (1751), must be thoroughly
convinced that the ideas on which his theories are based are
to be found scattered up and down in the works of his prede-
cessors ; further, whoever has traced the history of the sexual
theory from the time of Camerarius (1694), must allow that
Linnaeus added nothing new to it, though he contributed
essentially to its recognition, and that even after Koelreuter's
labours he continued to entertain some highly obscure and
even mystical notions on the subject.

But that which gave Linnaeus so overwhelming an import-
ance for his own time was the skilful way in which he gathered
up all that had been done before him ; this fusmg together of
the scattered acquisitions of the past is the great and charac-
teristic merit of Linnaeus.

Cesalpino was the first who introduced Aristotelian modes
of thought into botany ; his system was intended to be a
natural one, but it was in reality extremely unnatural ; Lin-
naeus, in whose works the profound impression which he had
received from Cesalpino is everywhere to be traced, retained all
that was important in his predecessor's views, but perceived at
the same time what no one before him had perceived, that the
method pursued by Cesalpino, Morison, Ray, Tournefort, and
Bachmann could never do justice to those natural affinities
which it was their object to discover, and that in this way only an
artificial though ver)' serviceable arrangement could be attained,
while the exhibition of natural affinities must be sought by
other means.

As regards the terminology of the parts of plants, which was
all that the morphology of the day attempted, Linnaeus simply
adopted all that was contained in the Isagoge of Jung, but
gave it a more perspicuous form, and advanced the theory of the
flower by accepting without hesitation the sexual importance
of the stamens, which was still but little attended to ; he thus
arrived at a better general conception of the flower, and this

G

82 Artificial Systems and Terminology of [BookI.

bore fruit again in a terminology which is as clear as it is con-
venient ; the terms monoecious, dioecious, triandrous, mono-
gynous, etc., still used in the science, and the later-invented
expressions dichogamous, protandrous, protogynous, etc., owe
their origin to this correct conception of the sexual relations in
plants. But there was one great misconception in the matter,
which has not a little contributed to increase Linnaeus' reputa-
tion. He called his artificial system, founded on the number,
union, and grouping of the stamens and carpels, the sexual
system of plants, because he rested its supposed superiority on
the fact, that it was founded upon organs the function of which
lays claim to the very highest importance. But it is obvious that
the sexual system of Linnaeus would have the same value for
the purposes of classification, if the stamens had nothing what-
ever to do with propagation, or if their sexual significance were
quite unknown. For it is exactly those characters of the sta-
mens which Linnaeus employs for purposes of classification,
their number and mode of union, which are matter of entire
indifference as regards the sexual function.

But though the notion that this artificial system has any im-
portant connection with the doctrine of the sexuality of plants
is evidently due to a confusion of idea.s, yet the progress of the
science has shown, that Linnaeus' sexual system did often and
necessarily lead to the establishing of natural groups for the
very reason, that the characters of the stamens which he
employed are entirely independent of their function ; for we
must regard it as an important result of the labours of systema-
tists, that those characters of organisms are shown to be of the
greatest value for classification, which are entirely or in a very
great measure independent of the functions of the organs. The
error, which led Cesalpino to make the functional importance
of the parts of fructification the principle of his division, re-
appears therefore in Linnaeus in another form ; to find a
principle of division, he turns to those organs, whose function
appears to him the most important, but he takes his characters

Chap. II.] Organs from Ccsalpino to Linnaeus. 83

not from differences of function, but from the number and mode
of union, which are of no importance for the sexual function.
We meet with this error in Leibnitz and Burckhard, who are
mentioned here merely to defend Linnaeus from the charge
repeatedly brought against him by his contemporaries that he
was indebted to these two writers for the idea of his sexual
system. They erroneously found in the great physiological
importance of the sexual organs a reason for deriving from their
differences the principles of division that were to found a
system ; this error in theory Linnaeus shared with them, but
they did not correct it in practice, as Linnaeus did, by confining
himself to purely morphological features in working out his
system. What the renowned philosopher' incidentally uttered
in the year 1701 on the matter in question is moreover so un-
important and so indistinct, that Linnaeus could not gain much
from it; what Burckhard' says on the subject in his often-
quoted letter to Leibnitz (1702) is indeed much better, and
comes near to Linnaeus' idea ; but it is a very long way from
the hints there given to th» completion of the well-articulated
and highly practical system which Linnaeus constructed.

The botanists of the i6th century, and in the main even
Morison and Ray, had in one-sided fashion devoted their
chief attention to distinguishing species, Bachmann and
Tournefort to the establishment of generic characters, while
they neglected species ; Linnaeus, on the contrary, applied
equal care and much greater skill to describing both genera and
species. He reduced to practical shape the suggestion which
Bachmann had left to his successors, and so must be regarded,
if not as the inventor, at least as the real founder of the binary
nomenclature of organisms.

It is only fulfilling the duty of a historian to state the sources

' Printed in Jessen's ' Botanik der Gegenwart und Vorzeit,' p. 287.
' •Epi>tola ad Godofredum Gulielmum Leibnitzium etc. cum Laurentii
Heisteri praefatione,' Helmstadii, 1750.

G 2

84 Artificial Systems and Terminology of [BookI.

from which linnaeus drew, but it would be a misapprehension
to see in this any depreciation of a great man ; it were to be
desired that all naturalists would, like Linnaeus, adopt all that is
good in the contributions of their predecessors, and improve or
adapt it as he did. Linnaeus himself has repeatedly quoted
the sources of his knowledge as far as they were known to
him, and has in many cases estimated the services of his
predecessors with a candour which never betrays a trace of
jealousy, but often displays a warm respect, as may be seen
especially in the short introductions to the several systems
given in the * Classes Plantarum.' Linnaeus could not only
recognise what was good in his predecessors and occasionally
make use of it, but he imparted life and fruitfulness to the
thoughts of others by applying them as he applied his own
thoughts, and bringing out whatever theoretical value they pos-
sessed. It was evidently this freshness of life that often misled
his successors into believing that Linnaeus thought out and
discovered everything for himself. We learn to appreciate the
contributions of Cesalpino and his successors in the 17th
century, and even of Kaspar Bauhin for the first time in the
works of Linnaeus ; we are astonished to see the long-known
thoughts of these writers, which in their own place look unim-
portant and incomplete, fashioned by Linnaeus into a living
whole ; thus he was at once and in the best sense both recep-
tive and productive, and he might perhaps have done more for
the theory of the science if he had not been entangled in one
grave error, which was more sharply pronounced in him than
in his predecessors and contemporaries, that, namely, of sup-
posing that the highest and only worthy task of a botanist is to
know all species of the vegetable kingdom exactly by name.
Linnaeus distinctly declared that this was his view, and his
school in Germany and England adhered to it so firmly that
it established itself with the general public, who to the present
day consider it as a self-evident proposition that a botanist
exists essentially for the purpose of at once designating any

Chap. II,] Orgaiis from Cesalpino to Linnaeus. 8,5

and every plant by a name. Like his predecessors, Linnaeus
regarded morphology and general theoretical botany only as
means to be used for discovering the principles of terminology
and definition, with a view to the improvement of the art of
describing plants.

We have hitherto spoken chiefly of the manner in which
Linnaeus dealt with his subject in matters of detail ; in his
inner nature he was a schoolman, and that in a higher degree
than even Cesalpino himself, who should rather be called an
Aristotelian in the strict sense of the word. But to say that
Linnaeus' mode of thought is thoroughly scholastic is virtually
saying that he was not an investigator of nature in the modern
meaning of the word ; we might point to the tact that Linnaeus
never made a single important discovery throwing light on the
nature of the vegetable world ; but that would still not prove
that he was a schoolman.

True investigation of nature consists not only in deducing
rules from exact and comparative observation of the phe-
nomena of nature, but in discovering the genetic forces from
which the causal connexion, cause and effect may be derived.
In the pursuit of these objects, it is compelled to be constantly
correcting existing conceptions and theories, producing new
conceptions and new theories, and thus adjusting our own
ideas more and more to the nature of things. The under-
standing does not prescribe to the objects, but the objects to
the understanding. The Aristotelian philosophy and its
medieval form, scholasticism, proceeds in exactly the con-
trary way ; it is not properly concerned with acquiring new
conceptions and new theories by means of investigation, for
conceptions and theories have been once for all established ;
experience must conform itself to the ready-made system
of thought ; whatever does not so conform must be dialecti-
cally twisted and explained till it apparently fits in with the
whole. From this point of view the intellectual task consists
essentially in this twisting and turning of facts, for the general

86 Artificial Systems and Terminology of [BookI.

idea of the whole is already made and needs not to be altered.
Experience in the higher sense of investigation of nature is
rendered impossible by the fact, that we are supposed to know
all the ultimate principles of things ; but these ultimate principles
of scholasticism are at bottom only words with extremely inde-
finite meaning, abstractions obtained by a series of jumps from
every-day experience, which has not been tried and refined in
the crucible of science, and is therefore worthless ; and the
higher the abstraction is raised, the farther it withdraws from
the guiding hand of experience, the more venerable and more
important do these 'abstracta' appear, and we can finally come
to a mutual understanding about them, though again only
through figures and metaphors \ Science, according to the
scholastic method, is a playing with abstract conceptions ; the
best player is he who can so combine them together, that the
real contradictions are skilfully concealed. On the contrary,
the object of true investigation, whether in philosophy or in
natural science, is to make unsparing discovery of existing
contradictions and to question the facts until our conceptions
are cleared up, and if necessary the whole theory and general
view is replaced by a better. In the Aristotelian philosophy
and in scholasticism facts are merely examples for the illustra-
tion of fixed abstract conceptions, but in the real investigation of
nature they are the fruitful soil from which new conceptions,
new combinations of thought, new theories, and general views
spring and grow. The most pernicious feature in scholasticism
and the Aristotelian philosophy is the confounding of mere
conceptions and words with the objective reality of the things
denoted by them ; men took a special pleasure in deducing the
nature of things from the original meaning of the words, and
even the question of the existence or non-existence of a thing

^ See the excellent account of the Platonic and Aristotelian philosophies
and of scholasticism in Albert Lange's ' Geschichte des Materialismus,'
second edition, 1874.

Chap, II.] Organs froiii Ccsalpino to Linnaeus. 87

was answered from the idea of it. This way of thinking is
found everywhere in Linnaeus, not only where he is busy as
systematist and describer, but where he wishes to give infor-
mation on the nature of plants and the phenomena of their life, as
in his ' Fundamenta,' his ' Philosophia Botanica,'and especially
in his 'Amoenitates Academicae.' From among many in-
stances we may select his mode of proving sexuality in plants.
Linnaeus knew and lauded the services rendered to botany by
Rudolph Jacob Camerarius, who as a genuine investigator of
nature had demonstrated the sexuality of plants in the only
possible way, namely, that of experiment. But Linnaeus cares
little for this experimental proof; he just notices it in passing,
and expends all his art on a genuine scholastic demonstration
intended to prove the existence of sexuality as arising neces-
sarily from the nature of the plant. He connects his demon-
stration with the dictum ' omne vivum ex ovo,' which Harvey
had founded on an imperfect induction, and which he evidently
takes for an a priori principle, and concludes from it that plants
also must proceed from an 'ovum,' overlooking the fact that in
' omne vivum ex ovo ' plants already form a half of the ' omne
vivum ' ; then he continues, ' reason and experience teach us
that plants proceed from an 'ovum,' and the cotyledons confirm
it'; reason, experience, and cotyledons ! Surely a remarkable
assemblage of proofs. In the next sentence he confines himself
at first to the cotyledons, which according to him spring in
animals from the yolk of the egg, in which the life- point is found;
consequently, he says, the seed-leaves of plants, which envelope
the 'corculum,' are the same thing; but that the progeny is
formed not simply from the ' ovum,' nor from the fertilising
matter in the male organs, but from the two combined, is
shown by animals, hybrids, reason, and anatomy. By reason
in this and the previous sentence he understands the necessity,
concluded from the nature, that is, the conception of the thing,
that it must be so ; animals supply him with the analogy, and
anatomy can prove nothing, as long as it is not known wliat is

88 Artificial Systems and Terminology of [Book i.

the design of the anatomical arrangements. But the weakest
side of this proof Hes in the hybrids, for Linnaeus, when he
wrote the ' Fundamenta,' knew of none except the mule ;
hybrids in plants were first described by Koelreuter in 1761,
and these Linnaeus nowhere mentions ; and what amount of
proof can be drawn from the vegetable hybrids, which
Linnaeus afterwards supposed himself to have observed,
but which were no hybrids, we shall see in the history
of the sexual theory ; here we need only remark that he
arrives at the existence of these hybrids from the idea of
sexuality exactly as he arrived at that of sexuality from the
idea of hybridisation. Then he goes on with his demon-
stration ; ' that an egg germinates without fecundation is
denied by experience, and this must hold good therefore
of the eggs^ of plants — every plant is provided with flower
and fruit, even where these are not visible to the eye'; with
Linnaeus, of course, this is logically concluded from the
conception of the plant or of the ' ovum ' ; he alleges indeed
certain observations as well, but they are incorrect. He con-
tinues, ' The fructification consists of the sexual organs of the
flowers ; that the anthers are the male organs, the pollen the
fertilising matter, is proved by their nature, further by the fact
that the flower precedes the fruit, as also by their position, the
time, the loculaments (anthers), by castration, and by the
structure of the pollen.' Here too the main point with
Linnaeus is the nature of the male organs, and that we may
know what this nature is he refers to a former paragraph,
where we learn that the essence of the flower is in the anthers
and stigma. Almost all his demonstrations consist of such
reasonings in a circle and in arguing from the thing to be proved.
And while the passages quoted show how much he did for the

' The comparison of the vegetable seed with the egg in animals, which is
in itself incorrect, comes, as Aristotle tells us, from Empedocles, and was a
favourite one with the systematists.

Chap, II.] Orgaus from Ccsalpino to Linnaeus. 89

doctrine of sexuality, we find this sophistical style of reasoning
still more copiously displayed in the essay entitled ' Sponsalia
Plantarum ' in the ' Amoenitates' (i. p. 77), and in a worse
form still in the essay, ' Plantae Hybridae ' (Amoen. iii. p. 29).
That Linnaeus had not the remotest conception of the way in
which the truth of a hypothetical fact is proved on the prin-
ciples of strict inductive investigation is shown by these and
many other examples, and by his enquiry into the seeds of
mosses (Amoen. ii. p. 266), upon which he prided himself not
a little, but which is really inconceivably bad even for that time
(1750). It was not Linnaeus' habit to occupy himself with
what we should call an enquiry ; whatever escaped the first
critical glance he left quietly alone ; it did not occur to him to
examine into the causes of the phenomena that interested him ;
he classified them and had done with them ; as for instance
in his * Somnus Plantarum,' as he called the periodical move-
ments of plants. We cannot read much of the ' Philosophia
Botanica ' or the ' Amoenitates ' without feeling that we are
transported into the literature of the middle ages by the kind
of scholastic sophistry which is all that his argumentation
amounts to ; and yet these works of Linnaeus date from the
middle of the last century, from a time when Malpighi, Grew,
Camerarius, and Hales had already carried out their model
investigations, and his contemporaries Duhamel, Koelreuter,
and others were experimenting in true scientific manner. This
peculiarity in Linnaeus explains why men like Buffon, Albert
Haller, and Koelreuter treated him with a certain contempt ;
and also why his strict adherents in Germany, who lived on his
writings and were unable to separate what was really good in
him from his mode of reasoning, came to make their own
botany like anything rather than a science of nature. Linnaeus
was in fact a dangerous guide for weak minds, for his curious
logic, among the worst to be met with in the scholastic
writers, was combined with the most brilliant powers of
description ; the enormous extent of his knowledge of par-

90 Artificial Systems and Terminology of [BookI.

ticulars, and above all the pre-eminent firmness and certainty
which distinguished his mode of deahng with systematic
botany, could not fail to make the profoundest impression
on those who judged of the powers of an investigator of
nature by these qualities alone. One of his greatest gifts was
without doubt the power which he possessed of framing pre-
cise and striking descriptions of species and genera in the animal
and vegetable kingdoms by means of a few marks contained
in the smallest possible number of words ; in this point he was
a model of unrivalled excellence to all succeeding botanists.

On the whole the superiority of Linnaeus lay in his natural
gift for discriminating and classifying the objects which engaged
his attention ; he might almost be said to have been a classi-
fying, co-ordinating, and subordinating machine. He dealt
with everything about which he wrote in the way in which he
dealt with objects of natural history. The systematic botanists
whom he mentions in the ' Classes Plantarum ' are classified
then and there as fructists, coroUists, and calycists. All who
occupy themselves in any way with botany are divided into two
great classes, the true botanists and mere botanophils, and it is
very characteristic of his way of thinking that he places
anatomists, gardeners, and physicians in the latter class. True
botanists again are either mere collectors or systematists. To
the collectors belong all who add to the number of known
plants, also authors of monographs and floras, and the
botanical explorers of foreign countries, whom we should
now more courteously call systematists. By systematists
Linnaeus understands those who occupy themselves with the
classification and naming of plants, and he divides them into
philosophers, systematists proper, and nomenclators ; the
philosophers are those who study the theory of the science
on principles founded on reason and observation, and are
subdivided into orators, institutors, erystics, and physiologists ;
the latter are those who discovered the mystery of sexuality in
plants, and hence Malpighi, Hales, and such men are not

Chap. II.] Orgaus fioui Ccsalpiiio to Linnaeus. 91

physiologists in Linnaeus' sense. The second class of system-
atists, the systematists proper, he distinguishes into orthodox
and heterodox, the former taking the grounds of division
exclusively from the organs of fructification, while the latter
use other marks as well. In this manner Linnaeus treats
every subject of which he has to speak, and w^herever he can
in short, numbered sentences, which look like descriptions of
genera and species. His mind and character were fully formed
in 1736 when he wrote his * Fundamenta,' and he preserved his
peculiarities of style from that time forward ; we find the same
modes of expression in the ' Nemesis Divina,' a treatise on
religion and morals addressed as a legacy to his son. Where
these peculiarities of manner and expression are suitable they
make a favourable impression on the reader, as for instance in
the short accounts he gives of the various systems in the
' Classes Plantarum,' a work in which Linnaeus was quite in
his element ; there he traces with a fine instinct the guiding
principles of each system, pronounces upon its merits and
defects, and sets it before the reader in numbered sentences
of epigrammatic brevity. This manner is strictly adhered to
in the ' Philosophia ' also, and it has certainly helped not
a little to withdraw the attention of his reader from his many
fallacies in argument, especially his oft-recurring reasonings in
a circle.

This remarkable combination of an unscientific philosophy
with mastery over the classification of things and conceptions,
this mixture of consistency in carrymg out his scholastic prin-
ciples with gross inaccuracies of thought, impart to his style an
originality, which is rendered still more striking by the native
freshness and directness, and not unfrequently by the poetic
feeling, which animate his periods.

In any attempt to estimate the advance which the science
owes to the labours of Linnaeus, the chief prominence must be
assigned to two points; first to his success in carrying out
the binary nomenclature in connection with the careful and

92 Artificial Systems and Terminology of [Booki.

methodical study which he bestowed on the distinguishing of
genera and species ; this system of nomenclature he endea-
voured to extend to the whole of the then known vegetable
world, and thus descriptive botany in its narrower sense
assumed through his instrumentality an entirely new form,
which, serving as a model for the naming and defining of
the larger groups, could be applied without modification to the
founding and completing the natural system. When at a later
time Jussieu and De Candolle marked out their families and
groups of families, their mode of proceeding was in the main
that of Linnaeus when distinguishing his genera by abstraction
of specific differences. This merit has been always assigned
to Linnaeus without reserve. The second merit has been less
recognised, and yet it is at least of equal importance ; it is that
of having first perceived that the attempt made by Cesalpino
and his successors to found a system, that shall do justice
to natural affinities, on predetermined marks can never
succeed. Linnaeus framed his artificial sexual system, but he
exhibited a fragment of a natural system by its side, while he
repeatedly declared that the chief task of botanists is to dis-
cover the natural system. Thus he cleared the ground for
systematic botany. He made use of his own system, because
it was extremely convenient for describing individual plants,
but he ascribed all true scientific value exclusively to the
natural system ; and with what success he laboured to advance
it may be gathered from the fact, that Bernard de Jussieu
founded his improved series of famihes on the fragment of
Linnaeus, and that his nephew, A. L. de Jussieu, by simply
adopting Linnaeus' conception of the principle which lies at
the foundation of the natural system, succeeded in carrying it
on to a further stage of development.

The main features of Linnaeus' theoretical botany can best
be learned from the ' Philosophia Botanica,' which may be
regarded as a text-book of that which Linnaeus called botany,
and which far surpasses all earlier compositions of the kind in

Chap. II.] Organs from Cesalpino to Linnaeus. 93

perspicuity and precision, and in copiousness of material ; and
indeed it would be difficult to find in the ninety years after
1 781 a text-book of botany which treats what was known on
the subject at each period with equal clearness and complete-
ness. In giving the reader some idea of the way in which
Linnaeus deals with his subject, it will be well to pass over the
first two chapters, which discuss the literature and the various
systems which had been proposed, and turn to the third,
which under the heading ' Plantae ' treats of the general nature
of plants, and specially of the organs of vegetation. The
vegetable world, says Linnaeus, comprises seven families,
Fungi, Algae, IMosses, Ferns, Grasses, Palms, and Plants. All
are composed of three kinds of vessels, sap-vessels which
convey the fluids, tubes which store up the sap in their
cavities, and tracheae which take in air ; these statements
Linnaeus adopts from Malpighi and Grew. He gives no
characteristic marks for the Fungi ; of the Algae he says that
in them root, leaf, and stem are all fused together ; to the
Mosses he ascribes an anther without a filament, and separate
from the female flower which has no pistil ; the seeds of the
Mosses have no integument or cotyledons ; this characteristic
of the Mosses is explained in his paper entitled * Semina
Muscorum ' in the ' Amoenitates Academicae,' ii. The Ferns
are marked by the fructification on the under side of the
fronds, which are therefore not conceived of as leaves. The
very simple leaves, the jointed stalk, the 'calyx glumosus,' and
the single seed mark the Grasses. The simple stem, the rosette
of leaves at the summit, and the spathe of the inflorescence
are characteristic of the Palms. All vegetable forms which
do not belong to any of the previous families he names Plants.
He rejects the customary division into herbs, shrubs, and trees
as unscientific. This arrangement of the vegetable kingdom
must not be confounded with Linnaeus' fragment of a natural
system, in which he adopts sixty-seven families (orders), the
Fungi, Algae, Mosses, and Ferns forming each a family. He

94 Artificial Systems and Terminology of [BookI.

evidently introduces the divisions in the ' Philosophia,' in order
that it may be seen how far the statements that follow are
applicable to all the Vegetabilia or only to certain sections of
them. The parts in the individual plant which the beginner
must distinguish are three ; the root, the herb\ and the parts
of fructification, in which enumeration Linnaeus departs from
his predecessors, by whom the fructification and the herb
together are opposed to the root. In the central part
of the plant is the pith, enclosed by the wood which is
formed from the bast ; the bast is distinct from the rind,
which again is covered by the epidermis ; these anatomical
facts are from Malpighi ; the statement that the pith grows by
extending itself and its envelopes is borrowed from Mariotte.
Cesalpino's view on the formation of the bud is expressed by
Linnaeus in the statement, that the end of a thread of the pith
passing through the rind is resolved into a bud, etc. The bud
is a compressed stem, capable of unlimited extension till
fructification puts a term to vegetation. The fructification is
formed by the leaves uniting into a calyx, from which the apex
of a branch issues as a flower about one year in advance, while
the fruit arising from the substance of the pith cannot begin
a new life till the woody substance of the stamens has been
absorbed by the fluids of the pistil. In this way Linnaeus
corrected Cesalpino's theory of the flower, that he might take
into account the sexual importance of the stamens discovered
by Camerarius, He concludes by saying that there is no new
creation but only a continuous generation, for which he gives
the remarkable and thoroughly Cesalpinian reason, ' cum cor-
culum seminis constat parte radicis medullari.'

The root, which takes up the food, and produces the stem
and the fructification, consists of pith, wood, bast, and rind,
and is divided into the two parts, 'caudex' and 'radicula.'

' Linnaeus uses the word ' herba ' for the older word ' gennen,' which with
him means the ovary.

Chap. II.] Organs from Ccsalpino to Linnaeus. 95

The * caudex ' answers pretty nearly to our primary root
and rhizomes, the ' radicula ' to what we now call secondary
roots.

The herb springs from the root, and is terminated by
the fructification ; it consists of the stem, leaves, leaf-supports
('fulcrum'), and the organs of hibernation (' hibernaculum ').
Then follow the further distinctions of stem and leaves ;
the terminology, still partly in use and resting essentially
on the definitions of Jung, is here set forth in great detail.
Linnaeus however does not mention the remarkable dis-
tinction between stem and leaf which Jung founded on
relations of symmetry, and in general he shows less depth
of conception than Jung, confining himself more to the
direct impression on the senses, and so distinguishing some-
times where there is no real difference. Examples of this
are furnished by the paragraph devoted to ' fulcra.' By this
term he designates the subsidiary organs of plants, among
which he reckons stipules, bracts, spines, thorns, tendrils,
glands, and hairs. It appears from this, that Linnaeus did not
extend the idea of the leaf ('folium') to stipules and bracts, and
the examples he gives of tendrils show at the same time that
he was ignorant of the different morphological character of the
organ in Vitis and Pisum. The putting the seven organs
above-named together under the idea of ' fulcrum ' shows plainly
enough that Linnaeus, in framing his terminology, aimed only
at distinguishing what was different to the sense by fixed
words, in order to obtain means for short diagnoses of species
and genera. He had no thought of arriving at more general
propositions from a comparison of forms in plants, in order to
attain to a deeper insight into their nature. The same thing
appears from his notion of 'hibernaculum,' by which he under-
stands a part of the plant which envelopes the stem in its
embryonal state and protects it from harm from without ; he
here distinguishes bulbs from the winter buds of woody plants.
In this course of mixing up morphological and biological

96 Artificial Systems and Terminology of [Booki.

relations of organs he was followed by botanists till late into
our own century.

Linnaeus goes far beyond his predecessors in distinguishing
and naming the organs of fructification, the subject of the
fourth chapter of the 'Philosophia Botanica.' The fructi-
fication, he says, is a temporary part in plants devoted to
propagation, terminating the old and beginning the new. He
distinguishes the following seven parts : (i) the calyx, which
represents the rind, including in this term the involucre of
the Umbelliferae, the spathe, the calyptra of Mosses, and even
the volva of certain Fungi, — another instance of the way in
which Linnaeus was guided by external appearance in his
terminology of the parts of plants ; (2) the corolla, which
represents the inner rind (bast) of the plant ; (3) the stamen,
which produces the pollen ; (4) the pistil, which is attached to
the fruit and receives the pollen ; here for the first time the
ovary, style, and stigma are clearly distinguished. But nexi
comes as a special organ (5) the pericarp, the ovary which
contains the seed. As bulbs and buds were treated not simply
as young shoots, but as separate organs, so here too the ripe
fruit is regarded not merely as the developed ovary, but as
a special organ. Nevertheless, Linnaeus distinguishes the
different forms of fruit much better than his predecessors had
done. (6) The seed is a part of the plant that falls off from it,
the rudiment of a new plant, and it is excited to active life by
the pollen. The treatment of the seed and its parts is the
feeblest of all Linnaeus' efforts ; he follows Cesalpino, but his
account of the parts of the seed is much more imperfect than
that of Cesalpino and his successors. The embryo is called
the ' corculum,' and two parts are distinguished in it, the ' plu-
mula' and the ' rostellum' (radicle). The cotyledon is co-ordi-
nated with the ' corculum,' and is regarded therefore not as part
of the embryo but as a distinct organ of the seed ; it is defined
as ' corpus laterale seminis bibulum caducum.' Nothing could
be worse, and it seems almost incredible that so bad a defini-

Chap. II.] Orgaus froni Cesalpino to Linnaeus. 97

tion and distinction could be given in 1751, and again in 1770,
by the first botanist of his time, when Malpighi and Grew,
nearly a hundred years earlier, had illustrated the parts of the
seed and even the history of its development and its ger-
mination by numerous figures. He does not mention the
endosperm, evidently confounding it with the cotyledon, though
Ray had already distinguished it clearly from the other parts
of the seed. Linnaeus' terminology of the seed supplies more
than sufficient corroboration of our previous remark, that he
shows incapacity for the careful investigation of any object
at all difficult to observe, and it will now seem a small matter
that he, like most of the earlier botanists, treats one-seeded
indehiscent fruits as seeds, and hence makes the pappus a part
of the seed. (7) By the word ' receptaculum ' he understands
ever>'thing by which the parts of the fructification are con-
nected together, both the 'receptaculum proprium,' which
unites the parts of the single flower, and the ' receptaculum
commune,' under which term he comprises the most diverse
forms of inflorescence (umbel, cyme, spadi.x).

He concludes with the remark that the essence of the flower
consists in the anther and the stigma, that of the fruit in the seed,
that of the fructification in the flower and the fruit, and that of
all vegetable forms in the fructification, and he adds a long
list of distinctions between the organs of fructification with
their names ; among these organs appear the nectaries, which
he was the first to distinguish.

In the fifth chapter he discu.sses the question of difference of
sex in plants. His views on this subject have been already
mentioned in order to show that they were entirely founded on
worthless scholastic deductions ; here we may quote a few of the
propositions which were famous in after times. We assume, he
says, that two individuals of different sexes were created in the
beginning of things in every kind of living creatures. Plants,
though they are without sensation, yet live as do animals, for
they have a beginning and an advance in age (aetas), and are

H

98 Artificial Systems and Terminology of [Book i.

liable to disease and death ; they have also a power of move-
ment, a natural appetency (propulsio), an anatomy, and an
organic structure (organismus). Simple explanations are given
of these words, but they prove nothing about the matter. He
then expounds the whole theory of sexuality, which is made to
rest entirely on scholastic arguments, and in doing this he spins
out to excessive length the parallel which he draws between
the conditions of sexuality in animals and plants. It is mani-
festly this chapter of the ' Philosophia Botanica,' together with
the treatise ' Sponsalia Plantarum,' which led the adherents of
Linnaeus, who were ignorant of the older literature of the
subject and were much impressed by his scholastic dexterity, to
celebrate him as the founder of the sexual theory of plants ;
whereas a more careful study of history shows incontrovertibly
that Linnaeus helped in this way to disseminate the doctrine,
but did absolutely nothing to establish it.

The writings of Linnaeus which we have hitherto examined
are occupied with the nature of plants, and of this he knew
nothing more than he gathered from the investigations and
reflections of his predecessors ; and it is here especially that
his peculiar scholasticism is exhibited in contrast with the facts
obtained by induction which he communicated to his readers.
But the strong side of his intellect appears with splendid effect in
the succeeding chapters of the ' Philosophia,' which treat of the
principles of systematic botany ; here, where he has no longer
to establish facts, but to arrange ideas, to dispose and sum-
marise, we find Linnaeus thoroughly in his element.

The groundwork of botanical science, he begins, is twofold,
classification and naming. The constituting of classes, orders,
and genera he calls theoretical classification ; the constituting
of species and varieties is practical classification. The work of
classification carried out by Cesalpino, Morison, Tournefort,
and others leads to the establishing of a system ; the mere
practice of describing species may be carried on by those who
know nothing of systematic botany. These expressions of

Chap, ii] Orgaus from Cesalpino to Linnaeus.. 99

Linnaeus are interesting, because like other remarks of his they
show that he placed the establishment and arrangement of the
larger groups above the mere distinguishing of individual forms ;
his disciples to a great extent forgot their master's teaching,
and fancied that the collecting and distinguishing of species was
systematic botany. He opposes the system itself, which deals
with the relative conceptions of classes, orders, genera, species,
and varieties, to a mere synoptical view, serving with its
dichotomy only to practical ends. Then comes the often-
quoted sentence, 'We reckon so many species as there were
distinct forms created " in principio." ' In a former place he had
said 'ab initio' instead of 'in principio'; instead therefore of
a beginning in time he here posits an ideal, theoretical begin-
ning, which is more in accordance with his philosophical views.
That new species can arise is, he continues, disproved by
continuous generation and propagation, and by daily observa-
tion, and by the cotyledons. It is hard to understand how the
Linnaean school till far into our own centurj' could have
remained firm in a doctrine resting on such arguments as
these. Linnaeus' definition of varieties shows that he understood
by the word species fundamentally distinct forms ; there are,
he says, as many varieties as there are different plants growing
from the seed of the same species ; and he adds that a variety
owes its origin to an accidental cause, such as climate, soil,
warmth, the wind ; but this is evidently mere arbitrar)' assump-
tion. Judging by all he says, his view is that species differ in
their inner nature, varieties only in outward form. Here,
where we find the dogma of the constancy of species for the
first time expressed in precise terms, — a dogma generally
accepted till the appearance of the theory of descent, we
should be justified in demanding proof; but since dogmas
as a rule do not admit of proof, Linnaeus simply states his
view', unless we are to take the sentence, 'negat generatio

' It would not be difficult to prove that the doctrine of the constancy of

H 2

100 Artificial Systems and Terminology of [Book i.

continuata, propagatio, observationes quotidianae, cotyledones,'
as proving the assertion that new species never appear. We
shall see further on to what surprising conclusions Linnaeus
was himself led by his dogma, when he had to take into
account the relations of affinity in genera and larger groups.
The species and the genus, he continues, are always the work
of nature, the variety is often that of cultivation ; the class and
the order depend both on nature and on art, which must mean
that the larger groups of the vegetable kingdom have not the
same objective reality as the species and the genus, but rest
partly on opinion. That Linnaeus estimated the labours of
the systematists after Cesalpino and the contributions of the
German fathers of botany up to Bauhin, as they have been
judged of in the present work, is shown by paragraph 163,
where he explains the word habit, and adds that Kaspar
Bauhin and the older writers had excellently divined (divina-
runt) the affinities of plants from their habit, and even real
systematists had often erred, where the habit pointed out to
them the right way. But he says that the natural arrange-
ment, which is the ultimate aim of botany, is founded, as the
moderns have discovered, on the fructification, though even
this will not determine all the classes. It is interesting there-
fore to observe how Linnaeus further on (paragraph 168)
directs, that in forming genera, though they must rest on the
fructification, yet it is needful to attend to the habit also, lest
an incorrect genus should be established on some insignificant
mark (levi de causa) : but this attention to the habit must be
managed with reserve, so as not to disturb the scientific
diagnosis.

species is properly a conclasion from scholasticism, and nltimately from the
Platonic doctrine of ideas, and was therefore assumed as self-evident before the
time of Linnaeus, who only gave it a more distinct and conscious expression ;
his arguments from experience are without force. The strength of the dogma
lies in its relation to the platonico-scholastic philosophy, which the syste-
matists followed, more or less consciously, up to quite recent times.

Chap. II.] Organs froui Ccsalpino to Linnaeus. loi

Linnaeus next lays down with great detail each several rule,
which must be observed in establishing species, genera, orders,
and classes, and it is here that he displays his unrivalled skill
as a systematist. These rules were strictly observed by him-
self in his numerous descriptive works, and thus a spirit of
order and clearness was introduced into the art of describing
plants, which gave it at once a different appearance from
that which it had received at the hands of his predecessors.
Whoever therefore compares the 'Genera Plantarum,' the
' Systema Naturae,' and other descriptive works of Linnaeus
with those of Morison, Ray, Bachmann, or Tournefort, finds so
great a revolution effected by them, that he is impressed with
the persuasion that botany first became a science in the hands of
Linnaeus ; all former efforts seem to be so unskilful and with-
out order in comparison with his method. Without doubt the
greatest and most lasting service which Linnaeus rendered both
to botany and to zoology lies in the certainty and precision
which he introduced into the art of describing. But if a refor-
mation was thus effected in botany, as Linnaeus himself took
pleasure in saying, it must not be overlooked that the know-
ledge of the nature of plants was rather hindered than advanced
by him. Ray, Bachmann, and in part also Morison and Tourne-
fort, had already liberated themselves to a great extent from
the influence of scholasticism, and they still give us the
impression of having been genuine investigators of nature ;
but Linnaeus fell back again into the scholastic modes of
thought, and these were so intimately combined with his
brilliant performances in systematic botany, that his successors
were unable to separate the one from the other.

The feeling for order and perspicuity, which made Linnaeus
a reformer of the art of describing, combined with his scholas-
ticism, was evidently the cause of his not bestowing more
energetic labour on the natural system. It has been repeatedly
mentioned that it was he who first established sixty-five truly
natural groups in his fragment of the early date of 1738 ; and

102 Artificial Systems and Terminology of [Book i.

a certain feeling for natural affinity is shown in the establish-
ment of his seven families, Fungi, Algae, Mosses, Ferns,
Grasses, Palms, and Plants properly so-called. Moreover in
paragraph 163 of the 'Philosophia Botanica,' he carries out
the division of the whole vegetable kingdom into Acotyledons,
Monocotyledons, and Polycotyledons with their subdivisions
very admirably; and thus we see him continually impelled
towards a natural arrangement, but never bestowing upon it
the necessary labour and thought.

And so two different conceptions of a system of plants
continued to subsist side by side with each other in the mind
of Linnaeus ; one more superficial, and adapted for practical
use, expressed in his artificial sexual system, and one more
profound and scientifically valuable, embodied in his fragment
and in the natural groups above-mentioned.

The same may be said also of Linnaeus' morphological
views ; here, too, a more superficial pursued its way along
with a more profound conception. He formed his terminology
of the parts of plants for practical use in describing them,
and convenient as it is, it seems nevertheless shallow or
superficial, because its foundations are not more deeply laid
in the comparative study of forms. But we discover from
very various passages in his writings that he felt the need of
a more profound conception of plant-form, and what he was
able to say on the subject he put together under the head
of ' metamorphosis plantarum.' His doctrine of metamor-
phosis is entirely based on the views of Cesalpino, with
which we have already become acquainted, though he did
not adopt them in their original form, but endeavoured to
develop them in true Cesalpinian fashion; for on the one
hand he derived leaves and parts of flowers from the tissues
of the stem, and on the other conceived of the parts of the
flower as only altered leaves. This doctrine of metamorphosis
appears in somewhat confused form in the last page of his
' Philosophia Botanica.' There he says that the whole of the

Chap. II.] Organs from Ccsalpino to Linnaeus. 103

herb is a continuation of the medullary substance of the root ;
the principle of the flowers and leaves is the same, because both
spring from the tissue-layers surrounding the pith, as Cesalpino
had taught. The statement which follows, that the principle of
the bud and the leaves is identical, would be a departure from
Cesalpino, and in any case inconsistent, without the explana-
tion that the bud consists of rudimentary leaves ; but this again
puts the axial portion of the bud out of sight. The perianth,
he says, comes from concrescent rudiments of leaves. How
closely Linnaeus adhered to Cesalpino in his later years
appears in his explanation of the catkin, which comes next
and which is taken entirely from Cesalpino's theory. That
a more superficial and a more profound conception pursue
their way together unadjusted in Linnaeus' speculations on form
is specially shown by the fact, that in the text of the ' Philosophia
Botanica,' paragraph 84, he places the 'stipulae' under the idea
of 'fulcra' and not under that of 'folia,' while on the contrary at
the end of the same work, where he brings together the
different paragraphs respecting metamorphosis, he speaks of
the ' stipulae ' as appendages of the leaves.

The idea of Cesalpino, that the parts of the flower which
surround the fruit arise like the ordinary leaves from the tissues
that enclose the pith, is further developed by Linnaeus in his
' Metamorphosis Plantarum,' in the fourth volume of the
' Amoenitates Academicae' (1759), in a very strange manner.
He compares the formation of the flower with the metamor-
phosis of animals, and especially of insects, and after describing
the changes that take place in animals, he says at page 370
that plants are subject to similar change. The metamorphosis
of insects consists in the putting off different skins, so that
they finally come forth naked in their true and perfect form.
This metamorphosis we also find in most plants, for they
consist, at least in the truly living part of the root, of rind, bast,
wood, and pith. The rind is to the plant what the skin is to
the larva of an insect, and after putting this skin ofi" there

I04 Artificial Systems and Terminology of [Book i,

remains a naked insect. When the flower is produced in the plant
the rind opens and forms the calyx (exactly Cesalpino's view),
and from out of this the inner parts of the plant issue to form
the flower, so that the bast, the wood, and the pith issue forth
naked in the form of corolla, stamens, and stigma. So long as
the plant lies concealed within the rind and clothed only with
leaves, it appears to us as unrecognisable and obscure as a
butterfly, which in its larva-condition is covered with skin and
spines.

In this doctrine of metamorphosis, which Linnaeus founded
on Cesalpino, the chief point to observe is, that the ordinary
leaves are identical with the exterior parts of the flower, because
both originate in the outer tissues of the stem. The pertinent
fact, which may easily be observed without a microscope, that
the concentric arrangement of outer and inner rind, wood, and
pith occurs only in some flowering plants, that the case is quite
different with Monocotyledons, and that Cesalpino's theory of
the flower cannot properly be applied to them, — these are
things which we must not expect to find Linnaeus with his
peculiar modes of thought taking into consideration.

The want of firm standing-ground in experience is shown
also by the fact, that with his own and Cesalpino's theory of
the flower he combined another view of its nature, which under
the name of 'prolepsis plantarum ' was set forth in two disserta-
tions in 1760 and 1763, but the two theories are scarcely com-
patible with one another. While the last paragraph in the
* Philosophia Botanica ' says, 'Flos ex gemma annuo spatio foliis
praecocior est,' the dissertations contain the doctrine^, that the
flower is nothing but the synchronous appearance of leaves,
which properly belong to the bud-formations of six consecutive
years, in such a way that the leaves of the bud destined to be
unfolded in the second year of the plants become bracts, the

' The authority for the contents of these dissertations is Wigand's ' Kritik
und Geschichte der Metamorphose' (1846}.

Chap. II.] Ovgaus fi'om Ccsalphio to Linnaeus. 105

leaves of the third year the calyx, those of the fourth the corolla,
those of the fifth the stamens, those of the sixth the pistil.
Here we see once more how Linnaeus moves in the sphere of
arbitrary assumptions with no thought of exact observation, for
this whole theory of prolepsis rests on nothing that can be
called a well-ascertained fact.

Yet a third time we find in Linnaeus the juxtaposition of a
superficial view resting on every-day perception, and a more
profound and to some extent a philosophical view ; this is the
case where he is concerned on the one hand with the dogma
of the constancy of species, and on the other hand has to
explain the fact of natural relationship and its gradations.
Apart from some insignificant verbal explanations, Linnaeus
adduced nothing in support of the dogma but the every-day
perception of the unchangeableness of species, and to this he
held fast to the end of his life ; but it was important to find an
explanation of the fact, to which he himself repeatedly drew
attention, that genera, orders, and classes do not merely rest on
opinion but indicate really existing affinities. His mode of solv-
ing the difficulty was a very remarkable one ; not only does the
scholastic manner of thought appear here again quite unalloyed
by modern science, but he grounds his explanation once more
on the old a priori notion that the pith is the vital principle in
the plant, and also on his own assumption, that in the sexual
act the woody substance of the anthers combines with the pith-
substance of the pistil. Hugo Mohl has given a clear account
of the matter in No. 46 of the ' Botanische Zeitung' for 1870,
although neither he nor Wigand nor most of Linnaeus' biogra-
phers seem to know, that his theories are all to be traced to
Cesalpino. Linnaeus' theory of natural affinities, as he gave it
in 1762 in the ' Fundamentum Fructificationis,' and in 1764 in
the sixth edition of the ' Genera Plantarum,' is as follows : At
the creation of plants (in ipsa creatione) one species was made
as the representative of each natural order, and these plants so
corresponding to the natural orders were distinct from one

To6 Artificial Systems and Terminology of [Book I.

another in habit and fructification, that is, absolutely distinct. In
the communication of 1764 the following words occur : —

1. Creator T.O. in primordio vestiit vegetabile medullare
principiis constitutivis diversi corticalis, unde tot difformia indi-
vidua, quot ordines naturales, prognata.

2. Classicas has plantas Omnipotens miscuit inter se, unde
tot genera ordinum, quot inde plantae.

3. Genericas has miscuit natura, unde tot species congeneres,
quot hodie existunt.

4. Species has miscuit casus, unde totidem quot passim occur-
runt varietates.

Hugo Mohl was right in rejecting Heufler's assumption that
a view resembling the modern theory of descent was contained
in these paragraphs. It must be plain to any one who knows
the ideas of Aristotle, Theophrastus, and Cesalpino, within the
sphere of which Linnaeus is here moving, what he understands
by his 'vegetabile medullare' and 'corticale'; that he does not
for a moment mean a plant of simplest organisation, but that both
expressions indicate only the original elements of vegetation
which the Creator, according to L,innaeus, united to one another
at the first. He assumed that plants of the highest and of the
lowest grades of organisation were originally created at the same
time and alongside of one another ; no new class-plants were
afterwards created, but from the mingling together of the exist-
ing ones by the act of the Creator generically distinct forms
were produced, and the natural mingling of these gave birth to
species, while varieties were mere chance deviations from
species. But it is to be noticed that in these minglings or
hybridisations the woody substance of the one form which
supplies the pollen is united with the pith-substance of the
other form, whose pistil is thus fertilised ; and so in these
supposed crossings it is always the two original elements of the
plant, the medullary and the cortical, which are mingled
together.

Chap. II.] Organs from Ccsalpino to Linnaeus. 107

No further proof is wanting that this theory of Linnaeus is
no precursor of our theory of descent, but is most distinctly
opposed to it ; it is utterly and entirely the fruit of scholasti-
cism, while the essential feature in Darwin's theory of descent
is that scholasticism finds no place in it.

CHAPTER III.

Development of the Natural System under the
Influence of the Dogma of the Constancy of Species.

1759-1850.

From the year 1750 Linnaeus' terminology of the organs of
plants and his binary method of naming species came into
general use ; the opposition which his doctrines had till then
encountered by degrees died away, and if all that he taught
was not universally accepted, his treatment of the art of
describing plants soon became the common property of all
botanists.

But in course of time two very different tendencies were
developed ; most of the German, English, and Swedish
botanists adhered strictly to Linnaeus' dictum, that the merit
of a botanist was to be judged by the number of species with
which he was acquainted ; they accepted Linnaeus' sexual
system as one that completed the science in every respect ;
they thought that botany had reached its culminating point in
Linnaeus, and that any improvement or addition could only
be made in details, by continuing to smooth over some uneven-
nesses in the system, to collect new species and describe them^
The inevitable result was that botany ceased to be a science ;
even the describing of plants which Linnaeus had raised to an
art became once more loose and negligent in the hands of such
successors ; in place of the morphological examination of the
parts of plants there was an endless accumulating of technical
terms devoid of depth of scientific meaning, till at length a

Development of the Natural System. 109

text-book of botany came to look more like a Latin dictionary
than a scientific treatise. In proof of this we may appeal to
Bernhardi's 'Handbuch der Botanik,' published at Erfurt in 1804,
and Bernhardi was one of the best representatives of German
botany of the time. How botany, especially in Germany,
gradually degenerated under the influence of Linnaeus' authority
into an easy-going insipid dilettantism may very well be seen
from the botanical periodical, entitled ' Flora,' the first volumes
of which cover the greater part of the first fifty years of the
19th century; it is scarcely conceivable how men of some culti-
vation could occupy themselves with such worthless matter.
It would be quite lost labour to give any detailed account of
this kind of scientific life, if it can be so called, this dull occu-
pation of plant-collectors, who called themselves systematists, in
entire contravention of the meaning of the word. It is true
indeed that these adherents of Linnaeus did some service to
botany by searching the floras of Europe and of other quarters
of the globe, but they left it to others to turn to scientific
account the material which they collected.

But before this evil had spread very widely, a new direction
to the study of systematic botany and morphology was given in
France, where the sexual system had never met with great accept-
ance. Bernard de Jussieu and his nephew, Antoine Laurent de
Jussieu, taking up Linnaeus' profounder and properly scientific
eff"orts, made the working out of the natural system, in Lin-
naeus' own opinion the highest aim of botany, the task of their
lives. Here more was needed than a perpetual repetition of
descriptions of single plants after a fixed pattern ; more exact
inquiries into the organisation of plants, and especially of the
parts of the fructification, must supply the foundation of larger
natural groups. It was a question therefore of new inductive
investigation, of real physical science, of penetrating into the
secrets of organic form, whereas the botanists who confined
themselves to Linnaeus' art of description made no new dis-
coveries respecting the nature of plants. And if these men

110 Development of the Natural System under [book i.

held to the dictum just quoted from Linnaeus, and therefore
regarded themselves as his genuine disciples, the founders of
the natural system had as good a right to the title, not because
they followed his nomenclature and method of diagnosis, but
because they strove after exactly that object which he had
placed first in the science, the construction of the natural
system ; they were really the men whom he had meant when
he spoke of 'methodici'and 'systematici.' The German, English,
and Swedish collectors of plants adhered to the less profound,
every-day, practical precepts of their master ; the founders of
the natural system followed the deeper traces of his knowledge.
This direction proved to be the only one endowed with living
power, the true possessor of the future.

The efforts of Jussieu, Joseph Gartner, De Candolle, Robert
Brown, and their successors up to Endlicher and Lindley, are
not marked only by the fact that they did truly seek to exhibit
the gradations of natural affinities by means of the natural
system ; equally characteristic of these men is their firm belief
in the dogma of the constancy of species as defined by Lin-
naeus. Here at once was a hindrance to their efforts ; the
idea of natural relationship, on which the natural system
exclusively rests, necessarily remained a mystery to all who
believed in the constancy of species ; no scientific meaning
could be connected with this mysterious conception ; and yet
the farther the inquiry into affinities proceeded, the more
clearly were all the relations brought out, which connect
together species, genera, and families. Pyrame de Candolle
developed with great clearness a long series of such afifinities as
revealed to us by comparative morphology, but how were these
to be understood, so long as the dogma of the constancy of
species severed every real objective connection between two
related organisms? Little indeed could be made of these
acknowledged affinities ; still, in order to be able to speak of
them and describe them, recourse was had to indefinite
expressions, to which arbitrary and figurative meanings could

Chap. Ill] thc Dogma of Coiistancy of Species. 1 1 1

be assigned. Where Linnaeus had spoken of a class-plant or
generic plant, the expression ' plan of symmetry ' or ' type ' was
used, meaning an ideal original form, from which numerous
related forms might be derived. It was left undecided, whether
this ideal form ever really existed, or whether it was merely the
result of intellectual abstraction; and thus the forms of thought
of the old philosophy soon began to reappear. The Platonic
ideas, though mere abstractions and therefore only products of
the understanding, had been regarded not only by the school
of Plato, but also by the so-called Realists among the school-
men, as really existing things. The systematists obtained the
idea of a type by abstraction, and the next step was easy, to
ascribe with the Platonists an objective existence to this crea-
ture of thought, and to conceive of the type in the sense of a
Platonic idea. This was the only view that was possible in
combination with the dogma of the constancy of species, and
so Elias Fries, in his 'Corpus Florarum,' 1835, in speaking of
the natural system, could consistently say, ' est quoddam supra-
naturale,' and maintain that each division of it 'ideam quandam
exponit.' So long as the constancy of species is maintained,
there is no escaping from the conclusion drawn by Fries, but
it is equally certain that systematic botany at the same time
ceases to be a scientific account of nature. Systematists,
adopting this conclusion as necessarily following from the
dogma, might consider themselves as seeking to express in the
natural system the plan of creation, the thought of the Creator
himself; but in this way systematic botany became mixed up
with theological notions, and it is easy to understand why the
first feeble attempts at a theory of descent encountered such
obstinate, nay, fanatical opposition from professed systematists,
who looked upon the system as something above nature, a
component part of their religion. And if we look back we
find that these views are based on the dogma of the constancy
of species, while Linnaeus' ' Philosophia Botanica ' teaches us
on what grounds this dogma rests, where it says, ' Novas species

112 Development of the Natural System under [book i.

dari in vegetabilibus negat generatio continuata, propagatio,
observationes quotidianae, cotyledones.'

In spite of all this one important advance was made by the
successors of Jussieu ; the larger groups of genera, the families,
were defined with the certainty and precision, with which
Linnaeus had fixed the boundaries of species and genera, and
were supplied with characteristic marks. They succeeded also
in clearly distinguishing various still larger groups founded on
natural affinity, such as the Monocotyledons and Dicotyledons ;
the distinction between Cryptogams and Phanerogams was by
degrees better appreciated, though this point could not be
finally settled, so long as it was attempted to reduce the Cryp-
togams entirely to the scheme of the Phanerogams. The chief
hindrance however to the advance of systematic botany, at
least at the beginning of this period, lay in the defective mor-
phology enshrined in Linnaeus' terminology and in his doctrine
of metamorphosis. A great improvement certainly was effected
in the early part of the 19th century by De Candolle's doctrine
of the symmetry of plants, — a doctrine which has been much
undervalued, and that merely on account of its name ; it is
really a comparative morphology, and the first serious attempt of
the kind since the time of Jung that has produced any great
results ; a series of the most important morphological truths,
with which every botanist is now conversant, were taught for
the first time in De Candolle's doctrine of symmetry in 1813.
But one thing was wanting not only in Jussieu and De CandoUe,
but in all the systematists of this period, with the single excep-
tion of Robert Brown, and this was the history of development.
The history of the morphology and systematic botany of this
period shows indeed, that the comparison of mature forms
leads to the recognition of many and highly important morpho-
logical facts ; but as long as matured organisms only are
compared, the morphological consideration of them is always
disturbed by the circumstance that the organs to be compared
are already adapted to definite physiological functions, and

Chap. II I. J tlic Dogiua of CoHstancy of species. 113

thus their true morphological character is often entirely
obscured ; on the other hand, the younger the organs are, the
less is this difficulty experienced, and this is the real reason
why the history of development is of so great service to mor-
phology. It was then one of the characteristic features of the
period we are describing, that its morphology was formed upon
the study of matured forms ; the history of development, or at
all events of very early stages of development, could not be
turned to account till after 1840, for skill in the use of the
microscope, here indispensable, was not sufficiently advanced
before that time to make it possible to follow the growth of
organs from their first beginnings.

The establishment of natural affinities combined with the
assumption of the constancy of species, the growth of compara-
tive morphology without the history of development, lastly, the
ver}' subordinate attention still paid to the Cryptogams, — these
are the special characteristics of the period which has now to
be described at greater length.

Here we must once more call attention to the fact, that
Linnaeus was the first to perceive that a system which was to
be the expression of natural affinities could not be attained in
the way pursued by Cesalpino and his immediate successors.
All who have attentively studied the writings of Linnaeus which
appeared after the ' Classes Plantarum ' (1738) must have seen
the difference between that way and the one recommended by
him — a difference which is the more obvious because Linnaeus
himself, like his predecessors, constructed an artificial system
on predetermined principles of classification, and always em-
ployed it for practical purposes, while he published at the same
time in the above-named work his fragment of a natural system,
and in the preface set forth the peculiar features of the natural
and artificial systems in striking contrast with one another. The
first thing and the last, he says in his prefatory remarks to his

I

114 Development of the Natural System under [Booki.

fragment, which is demanded in systematic botany, is the
natural method, which slighted by less learned botanists has
always been highly regarded by the more sagacious, and has
not yet been discovered. If, he continues, we collect the
natural orders from all existing systems (up to 1738), we shall
get but a small list of really allied plants, though so many
systems have claimed to be natural. He had himself long
laboured to discover the natural method and had found out
some things that were new ; but though he had not succeeded
in carrying it through to a perfect work, he would continue his
efforts as long as his life lasted. He makes the very important
remark, that a key, that is, a priori principles of classification,
cannot be given for the natural method, till all plants have been
reduced to orders ; that for this no a priori rule is of value,
neither this nor that part of the fructification, but the simple
symmetry alone (simplex symmetria) of all the parts, which is
often indicated by special marks. He suggests to those who
are bent on trying to find a key to the natural system, that
nothing has more general value than relative position, especi-
ally in the seed, and in the seed especially the 'punctum
vegetans,' — a distinct reference to Cesalpino. He says that he
establishes no classes himself, but only orders ; if these are
once obtained, it will be easy to discover the classes. The
essence of the natural system could not have been more clearly
expounded in Linnaeus' time, than it is in these sentences. He
established as early as 1738 sixty-five natural orders, which he
at first simply numbered ; but in the first edition of the
' Philosophia Botanica ' in 1751, where the list is increased to
sixty-seven, he gave a special name to each group 5 and he
showed his judgment by either taking his names from really
characteristic marks, or what was still better, by selecting a
genus and so modifying its name as to make it serve as a
general term for a whole group. Many of these designations
are still in use, though the extent and content of the groups
have been greatly changed. This mode of naming is an import-

Chap. III.] the Dognia of Constancy of Species. 115

ant point, because it expresses the idea, that the different
genera of such a group are to some extent regarded as forms
derived from the one selected to supply the name. Many of
Linnaeus' orders do in fact indicate cycles of natural affinity,
though single genera are not unfrequently found to occupy a
false position ; at all events, Linnaeus' fragment is much
the most natural system proposed up to 1738, or even to 1751.
It is distinguished from Kaspar Bauhin's enumeration in this,
that its groups do not run into one another, but are defined by
strict boundaries and fixed by names.

The Linnaean list is distinctly marked by the endeavour to
make first the Monocotyledons, then the Dicotyledons, and
finally the Cryptogams follow one another ; that the old division
into trees and herbs already rejected by Jung and Bachmann,
but still maintained by Tournefort and Ray, disappears in
Linnaeus' natural system will be taken for granted after what
has been already said of it, and from this time forward this
ancient mistake is banished for ever.

In Bernard de Jussieu's^ arrangement of 1759 we find
some improvements in the naming, the grouping, and the succes-
sion, but at the same time some striking offences against natural
affinity. He published no theoretical remarks on the system,
but gave expression to his views on relations of affinity in the
vegetable kingdom in laying out the plants in the royal garden
of Trianon, and in the garden-catalogue. His nephew pub-
lished his uncle's enumeration in the year 1789 in his 'Genera
Plantarum,' affixing the date of 1759 given above. The differ-
ence between it and the Linnaean fragment does not seem

' Bernard dejussieu, born at Lyons in 1699, ^"^ «i* fi""^*^ ^ practising
physician there, was by Vaillant's intervention called to Paris, and after
Vaillant's death became Professor and Demonstrator at the Royal Garden.
He and Peissonei were among the first who declared against the vegetable
nature of the Corals. It is expressly stated in his filoge (' Histoire de
TAcademie Royale des Sciences,' Paris, 1777) that he founded his natural
families on the Linnaean fragment. He died in 1777.

I 2

ii6 Development of the Natural System under [BookI.

sufficiently marked to make it necessary to reproduce it here.
It should be noticed however that Jussieu begins with the
Cryptogams, passes through the Monocotyledons to the Dico-
tyledons, and ends with the Conifers. Adanson's claims of
priority over Bernard de Jussieu (see the ' Histoire de la
Botanique' de Michel Adanson, Paris, 1864, p. 36) may be
passed over as unimportant. The natural system was not
advanced by Adanson to any noticeable extent ; how little he
saw into its real nature and into the true method of research
in this department of botany is sufficiently shown by the fact,
that he framed no less than sixty-five different artificial systems
founded on single marks, supposing that natural affinities would
come out of themselves as an ultimate product, — an effort all
the more superfluous, because a consideration of the systems
proposed since Cesalpino's time would have been enough to
show the uselessness of such a proceeding.

The first great advance in the natural system is due to
Antoine Laurent de Jussieu^ (1748-1836). After all that
has been said no further proof is needed that he was no more
the discoverer or founder of the natural system than his uncle
before him. His real merit consists in this, that he was the
first who assigned characters to the smaller groups, which we
should now call families, but which he called orders. It is not
uninteresting to note here how Bauhin first provided the species
with characters, and named the genera but did not characterise
them, how Tournefort next defined the limits of the genera,
how Linnaeus grouped the genera together, and simply named
these groups without assigning to them characteristic marks,
and how finally Antoine Laurent de Jussieu supplied characters

^ A. L. de Jussieu, born at Lyons, came to Paris to his uncle Bernard in
1765. In 1790 he was a member of the Municipality, and till 1792 Superin-
tendent of Hospitals. When the Annales du Museum were founded in
1802, he resumed his botanical pursuits. In 1826 his son Adrien took his
place at the Museum. See his life by Brougniart in the ' Annales des
Sciences Naturelles,' vii (1837).

Chap, in.] ihc DoguiG of Coustancy of Species. 117

to the families which were now fairly recognised. Thus
botanists learnt by degrees to abstract the common marks
from like forms ; the groups thus constituted were being con-
stantly enlarged, and an inductive process was thus completed
which proceeded from the individual to the more general.

It might appear that the merit of Antoine de Jussieu is
rated too low, when we praise him chiefly and simply for
providing the families with characters ; but this praise will not
seem small to those who know the difficulty of such a task ;
very careful and long-continued researches were necessary to
discover what marks are the common property of a natural
group. Jussieu's numerous monographs show with what
earnestness he addressed himself to the task ; and it must be
added, that he was not content simply to adopt the families
established by Linnaeus and by his uncle and the limits which
they had assigned to them, but that he corrected their boun-
daries and in so doing established many new families, and was
the first who attempted to distribute these into larger groups,
which he named classes. But in this he was not successful.
His attempt to exhibit the whole vegetable kingdom in all its
main divisions, to unite the classes themselves into higher
groups, was also unsuccessful, for these larger divisions
remained evidently artificial. The three largest groups on the
contrary, into which he first divides the world of plants, the
Acotyledons, Monocotyledons, and Dicotyledons are natural ;
but they had been already partly marked out by Ray, after-
wards by Linnaeus, and finally in Bernard de Jussieu's
enumerations. Still it is the younger Jussieu's great and
abiding merit, to have first attempted to substitute a real divi-
sion of the whole vegetable kingdom into larger and gradually
subordinate groups for mere enumerations of smaller co-ordin-
ated groups, — an undertaking which Linnaeus expressly declared
to be beyond his powers. If then Jussieu's system was far
from giving a satisfactory insight into the affinities of the
great divisions of the vegetable kingdom, yet it opened out

1 1 8 Development of the Natural System tinder [Book i.

many important points of view, from which they could after-
wards be discovered, and it certainly became the foundation
for all further advance in the natural method of classification ;
for this reason it is necessary to give a view of it in the follow-
ing table : —

A. L. de Jussieu's System of 1789.

Acotyledones
Monocotyledones

Apetalae
r5 I Monopetalae

Stamina hypogyna
perigyna
epigyna

Stamina epigyna
perigyna
hypogyna
'Corolla hypogyna
perigyna

epigyna

antheris connatis
distinctis

CLASS.

I.

II.

III.

IV.

V.

VI.

VII.

VIII.

IX.

X.

XI.

XII.

XIII.

XIV.

XV.

! Stamina epigyna
hypogyna
perigyna
\ Diclines irregulares

This table shows that Jussieu did not oppose the Crypto-
gams, which he calls Acotyledones, to the whole body of
Phanerogams, as Ray did under the name of Imperfectae ; he
rather regards the Acotyledones as a class co-ordinate with
the Monocot}'ledones and Dicotyledones ; but this mistake or
similar mistaken views run through all systematic botany up to
1840 ; the morphology founded by Nageli and by Hofmeister's
embryological investigations first showed that the Cryptogams
separate into several divisions, which co-ordinate with the
Monocotyledons and Dicotyledons. At the same time the use
of the word Acotyledones for Linnaeus' Cryptogams shows that
Jussieu overrated the systematic value of the cotyledons,
because, as is seen from the introduction to his ' Genera
Plantarum,' he was quite in the dark on the subject of the great
difference between the spores of Cryptogamic plants and the
seeds of Phanerogams. His conception of the organs of

Chap. III.] thc Doguia of Cofistancy of Species. 119

generation was essentially that of Linnaeus ; hence he judged
of the Crj'ptogams according to the scheme of the Phanero-
gams, and, not perceiving their peculiarities, he virtually
characterised them by negative marks.

If we notice in the above table how the Phanerogams are
separated into classes, it strikes us that the triple division into
hypogynous, perigynous, and epigynous is repeated no less
than four times; this shows that Jussieu had mistaken ideas of
the value of these marks for classification, whereas the recur-
rence of them so often should of itself have suggested a doubt
on this point. To judge of his system more exactly we must
here give his series of the families, which he had already raised
to the number of a hundred.

Class L

1. Fungi.

2. Algae.

3. Hepaticae.

4. Musci.

5. Filices.

6. Naiades.

Class IL

7. Aroideae.

8. Typhae.

9. Cyperoideac.

10. Gramineae.

Class IIL

11. Palmae.

12. Asparagi.

13. JuncL

1 4. Lilia.

15. Bromeliae.

16. AsphodelL

17. NarcissL

18. Irides.

Class IV.

19. Musae.

20. Cannae.

21. Orchides.

22. Hydrocharides.

Class V.

44.

Polemonia.

23-

Aristolochiae.

45-

Bignoniae.

Class VI.

46.

Gentianeae.

24.

Elaeagni.

47.

Apocyneae.

25-

Thymeleae.

48.

Sapotae.

26.

Proteae.

Class IX.

27.

Lauri.

49.

Guajacanae.

28.

Polygoneae.

50-

Rhododendra.

29.

Atriplices.

51.

Ericae.

Class VII.

52.

Campanulaceae.

30.

Amaranthi.

Class X.

31-

Plantagines.

53.

Cichoraceae.

32-

Xyctagines.

54-

Cinarocephalae.

33-

Plumbagines.

55-

Corymbiferae.

Class VIII.

Class XI.

34-

Lysimachiae.

56.

Dipsaceae.

3.'>-

Pediculares.

57-

Rubiaceae.

36.

Acanthi.

58.

Caprifolia.

37-

Jasmineae.

Class XII.

38.

Vitices.

59-

Araliae.

39-

Labiatae.

60.

Umbelliferae.

40.

Scrophulariae.

41.

Solancae.

Class XIII.

42.

IJorragineae.

61.

Ranunculaceae.

43.

Convolvuli.

62.

Papaveraceae.

120 Development of the Natural System under [Booki.

63. Cruciferae.

64. Capparides.

65. Sapindi.

66. Accra.

67. Malpighiae.

68. Hyperica.

69. Guttiferae.

70. Aurantia.

71. Meliae.

72. Vites.

73. G crania.

74. Malvaceae.

75. Magnoliae.

76. Anonae.

77. Menisperma.

78. Berberides.
7y. Tiliaceae.

80. Cisti.

81. Rutaceae.

82. Caryophylleae.

Class XIV.

83. Sempervivae.

84. Saxifragae.

85. Cacti.

86. Portulaceae.

87. Ficoideae.

88. Onagrae.

89. Myrti.

90. Melastomae.

91. Salicariae.

92. Rosaceae.

93. Leguminosae.

94. Terebinthaceae.

95. Rhamni.

Class XV.

96. Euphorbiae.

97. Cucurbitaceae.

98. Urticae.

99. Amentaceae.
100. Coniferae.

Jussieu's division of the Cryptogams and Monocotyledons
offers much that is satisfactory, if we put the position of the
Naiades out of sight. The grouping of the Dicotyledons on the
contrary is to a great extent unsuccessful, chiefly owing to the
too great importance which he attached to the insertion of the
parts of the flowers, that is, to the hypogynous, perigynous, and
epigynous arrangement. It is in this grouping of families into
classes that the weak side of the system lies ; it is utterly
artificial, and the task of his successors has been to arrange the
families of the Phanerogams, which were most of them well-
established, and especially those of the Dicotyledons, in larger
natural groups. But this could not be effected, till morphology
opened new points of view for systematic botany ; Jussieu, as
has been already remarked, accepted Linnaeus' views of the
morphology of the organs of fructification in Phanerogams,
though he introduced many improvements in details. He laid
greater stress on the number and relative positions of the
different parts of the flower ; attention to their insertion on the
flowering axis, which he designated as hypogynous, perigynous,
and epigynous, would have been a great step in advance, if he
had not overrated its systematic value. The morphology of
the fruit is very superficial in Jussieu ; even the designation of
dry indehiscent fruits as naked seeds recurs in his definitions,

Chap. III.] thc Dogma of Constancy of Species. 121

though as it happens this misconception does not cause any
great disturbance. How inexact was his investigation of the
organs of fructification, when they were somewhat small and
obscure, is best shown by the fact that the Naiades, which are
made to include Hippuris, Chara, and Callitriche, appear among
the Acotyledons, and that Lemna and the Cycads are placed
with the Ferns.

Jussieu explained the dictum, ' Natura non facit saltus,' to
mean that the whole body of plants in its natural arrangement
must exhibit a lineal series ascending from the most imperfect
to the highest forms ; but he does not say whether Linnaeus'
comparison of the natural system to a geographical map, the
countries in which answer to orders and classes, is also admis-
sible.

His theoretical observations on the value to be given to
certain marks in a systematic point of view are not attractive,
and for the most part not very correct ; he speaks as though
some marks must have a more extensive, others a less exten-
sive value ; the perception of the fact, so far as it is true, rests
entirely upon induction ; that is, after the natural affinities have
been already recognised to a certain extent, it becomes appa-
rent that certain marks remain constant in larger or smaller
groups ; the systematist can now go on to try whether such
constant marks occur in other plants also, which he had
hitherto assigned to other groups, and thus put it to the test
whether those marks may not be accompanied by others, which
would serve to establish the affinities ; that Jussieu did so pro-
ceed in defining his families admits of no doubt, but he was
not himself thoroughly conscious of the fact ; at all events, he
did not extend this mode of proceeding, the seeking after
leading marks, to the establishing of larger groups or classes,
for these he founded on predetermined principles.

Jussieu's labours as a systematist were not confined to the
publication of his 'Genera Plantarum'; on the contrary, his
most fruitful researches began after 1802, and were continued

122 Development of the Natural System under [Booki.

to the year 1820, and their results appeared in a long series of
monographs on different families in the Memoires du Museum.
He felt with De Candolle, Robert Brown, and later systematists,
that the perfecting of the natural system depended mainly on
the careful establishing and defining of famihes. His efforts
received a new impulse from the work of a German writer,
whose first volume had appeared in 1788, a year therefore
before the 'Genera Plantarum,' a second following it in 1791,
and a supplementary volume in 1805.

This work was Joseph Gartner's^ 'De fructibus et semini-
bus plantarum,' in which the fruits and seeds of more than a
thousand species are described and carefully figured. But
almost more important than these numerous descriptions,
though they offered rich material to the professed systematists,
were the introductions to the first two volumes, and especially to
those of 1788. They contain valuable reflections on sexuality
in plants, — a subject which had remained in the condition in
which it was left by Camerarius (1694) till it was greatly deve-
loped by Koelreuter after 1761, and had since then been little
studied, — and an account of the morphology of fruits and seeds,
the knowledge of which had gone back rather than advanced
since the days of Malpighi and Grew. Gartner was well quali-
fied for this work by his unparalleled knowledge of the forms of
fruits, and still more by the character of his mind. Free from

^ Joseph Gartner was born at Calw in Wiirtenaberg in 1732, and died in
1791. He commenced his studies in Gottingen in 1751, where he was a pupil
of Haller. He travelled into Italy, France, Holland, and England in order
to make the acquaintance of famous naturalists, and worked also at physics
and zoology. In 1760 he was Professor of Anatomy in Tiibingen, and
in 1 76S became Professor of Botany at St. Petersburg ; but finding himself
unable to bear the climate, he returned to Calw in 1770, and gave himself
up entirely to his book, ' De fructibus et seminibus plantarum,' which he had
already commenced. Banks and Thunberg, one of whom had returned from
a voyage round the world, the other from Japan, handed over to him the
collections of fruits which they had made. His persistent study, partly
with the microscope, brought him near to blindness. There is an interest-
ing life of Gartner by Chaumeton in the ' Biographie Universelle.*

Chap, ih.] the DogDia of Constancy of Species. 123

Linnaeus' scholastic bias, he addressed himself to the examin-
ation of the most difficult organs of plants with as great freedom
from prepossessions as exact acquaintance with the writings of
others ; he gives us the impression of a modern man of science
more than any other botanist of the i8th century, with the
exception of Koelreuter. He knew how to communicate with
clearness of language and perspicuity^ of arrangement whatever
he gathered of general importance from each investigation.
Though it is easy to see that the founding of the natural
system was ever before his mind as the final object of his
protracted labours, he was in no eager haste to reach it ; he
contented himself with arranging his fruits, saying expressly
that the natural system would never be founded by these
means alone, though the exact knowledge of fruits and seeds
supplied the most important means for decision. Thus
his great work was at once an inexhaustible mine of single
well-ascertained facts, and a guide to the morphology of the
organs of fructification and to its application to systematic
botany. The imperfections, which are to be found even in
this work, are due to the circumstances of the time ; in spite
of Schmiedel's and Hedwig's researches into the Mosses there
was still the old obscurity with regard to the organs of jiro-
pagation in the Cryptogams, and this rendered a right defini-
tion of the ideas, seed and fruit, extremely difficult. But
Gartner made one great step in advance on this very point
when he showed that the spores of the Cryptogams were
essentially different from the seeds of Phanerogams, with
which they had been hitherto compared, because they contain
no embryo ; he called them therefore not seeds, but gemmae.
The second great hindrance to a true conception of certain
characters in fruits and seeds on the part of Gartner was the
entire ignorance of the history of development which then
reigned ; yet even here we see an advance, if only a small one,
made by him in his repeatedly going back to the young state
for a more correct idea of the organs.

1 24 Development of the Natural System tinder [Book i.

Above all, Gartner put an end to the blunder of regarding
dry indehiscent fruits as naked seeds, by rightly defining the
pericarp as in all cases the ripened wall of the ovary, and by
considering its strong or weak construction, its dry or pulpy
condition, as a secondary matter. It is obvious that the whole
theory of the flower was thus placed upon a better basis, since
dry indehiscent fruits may come from inferior or superior ovaries.
But Gartner's theory of the seed is one of his most valuable
contributions to the science. After careful consideration of
the seed-envelopes, he submitted the inner portion (nucleus)
enclosed by them to a searching comparative examination ;
he correctly distinguished the endosperm from the cotyledons,
and described the variations in its form and position. This
was the more needful, since Linnaeus had denied the existence
of an ' albumen ' in plants, which Grew had already recognised
and so named ; to Linnaeus it appeared to be of no use to the
seed. Though Gartner speaks of the cotyledons as uniting
with the embryo to form the nucleus of the seed, yet his
account shows that he regarded them as outgrowths of the
embryo itself. The uncertainty which still existed in the inter-
pretation of the parts of the seed is shown even in Gartner by
his curious notion of a ' vitellus,' which in fact takes in every-
thing that he was unable to explain aright inside the seed ;
for instance, he makes the scutellum in grasses, and even the
cotyledonary bodies of Zamia a vitellus, and applies the same
name to the whole contents of the spores of Seaweeds, Mosses,
and Ferns. In spite of the striking defects connected with
this mistaken notion in his theory of the seed, his views far
surpass in clearness and consistency all that had hitherto been
taught on the subject. His giving the term embryo to that
part of the seed which is capable of development was also an
advance in respect of logic and morphology, in spite of his
mistake in not admitting the cotyledons which are attached to
the embryo into the conception ; this, however, could easily
be corrected at a later time. What Gartner now named the

Ciup. III.] ihc Dogma of Constancy of Species. 125

embryo, had been up to his time called the 'corculum seminis,'
especially by Linnaeus and Jussieu ; it was evidently thought
that Cesalpino's phraseology was thus retained ; but he, as we
have seen, understood by the words * cor seminis ' the spot where
the cotyledons spring from the germ, which spot he wrongly
took for the meeting-point of root and stem and the seat of the
soul of the plant. And so at last after two hundred years the
word disappeared from use, which might have reminded the
botanist of Cesalpino's views respecting the soul of plants.

A work such as Gartner's could scarcely find a fruitful soil
in CJermany, where some thirty years before even Koelreuter's
brilliant investigations had met with little sympathy, and Conrad
Sprengel's remarkable enquiries into the relations of the struc-
ture of the flower to the insect-world in 1793 failed to be
understood ; Gartner complains in the second part, published
in 1 791, that not two hundred copies of the first volume were
sold in three years. But the work, which forms an epoch in
the histor)' of botany, was better received in France, where the
Academy placed it as second in the list of the productions
which in later times had been most profitable to science ; there
lived the man who was able to measure the whole value of such
a work — Antoine Laurent de Jussieu. But even in Germany,
where plant-describing was comfortably flourishing, there were
not altogether wanting men who knew how to estimate both the
services of Gartner and the importance of the natural system.
First among these was August Johann Georg Karl Batsch,
Professor in Jena from 1 761 to 1802, who published in the latter
year a 'Tabula affinitatum regni vegetabilis,' with characters
of the groups and families. Kurt Sprengel, who was born in
1766, and died as Professor of Botany in Halle in 1833, con-
tributed still more to the spread of clearer views respecting the
real character of the natural system and the task of scientific
botany generally by numerous works, and especially by his
'Geschichte der Botanik,' which appeared in 1817 and 1818.
But even this highly gifted and accomplished man agreed with

1 %6 Development of the Natural System under [Book i.

the Linnaean botanists in attributing an excessive value to
the describing of plants, as is shown in his history, where to
exalt the merits of the old botanists he gives figures of the
plants first described by them.

Meanwhile the meritorious efforts of these men were not in
themselves capable of directly advancing the natural system,
or of greatly increasing the number of its adherents in
Germany, nor did it find general acceptance in that country
till it had made considerable progress in the hands of the
two foremost botanists of the time, De Candolle and Robert
Brown.

AuGUSTiN Pyrame DE Candolle^ (1778-1841) belongs to
the number of those distinguished investigators of nature, who
at the end of the last and the beginning of our own century made
their native city Geneva a brilliant centre of natural science.
De Candolle was the contemporary and fellow-countryman of
Vaucher, Theodore de Saussure, and Senebier. Physics and
physiology especially were being successfully cultivated at that

^ Augustin Pyrame de Candolle sprang from a Proven9al family, which had
fled from religious persecution to Geneva, where it was and is still held in
great estimation. He associated as a boy with Vaucher, and on his first visit
to Paris in 1796 with Desfontaines and Dolomieu, and after his return to
Geneva was a friend of Senebier. The elder Saussure, and afterwards
Biot, whom he assisted in an investigation in physics, endeavoured to attach
him to that study. He spent the years from 1798 to 1808 in Paris, where
he lived in close intercourse with the naturalists of that city. Numerous
smaller monographs, and the publication of his work on succulent plants
and of a new edition of De Lamarck's ' Flore Fran9aise,' occupied this earlier
period of his life. From 1808 to 18 16 he was Professor of Botany at Mont-
pellier. During this time he made many botanical journeys in all parts of
France and the neighbouring countries, and wrote many monographs, his
essays on the geography of plants, and his most important work, the
' Theorie elementaire.' From 1816 till his death in 1841 he resided once
more in Geneva, which had freed itself in 1813 from the enforced connection
with France established in 1798. Here De Candolle found time to take
part in political and social questions, in addition to an almost incredible
amount of botanical labour. (Notice sur la vie et les ouvrages de A. P. De
Candolle par De la Rive, Geneve, 1845.)

Chap. III.] flic Dognia of CoHstaficy of species. 1 27

time in Geneva, and Pyrame de Candolle was attracted to
these studies ; among his youthful efforts are some important
investigations into the effect of h'ght on vegetation, and the
contributions which he made to vegetable physiology in his
great work on that subject will be noticed in a later portion of
this history. De Candolle turned his attention to all parts of
theoretical and applied botany, but his importance for the
history of the science lies chiefly in the direction of morphology
and systematic botany, and it is this which we will now proceed
to describe.

The amount and compass of De Candolle's labours as a
systematic and descriptive botanist exceed those of any writer
before or after him. He wrote a series of comprehensive
monographs of large families of plants, and published a new
edition of De Lamarck's large ' Flore Fran^aise ' substantially
altered and enlarged ; and in addition to these and many
similar works and treatises on the geographical distribution
of plants, he set on foot the grandest work of descriptive
botany that is as yet in existence, the ' Prodromus Systematis
Naturalis,' in which all known plants were to be arranged
according to his natural system and described at length, —
a work not yet fully completed, and in which many other
descriptive botanists of the last century participated, but none
to so large an extent as De Candolle, who alone completed
more than a hundred families. It is not possible to give
an account in few words of the service rendered to botany by
such labours as these ; they form the real empirical basis of
general botany, and the better and more carefully this is laid,
the greater the security obtained for the foundations of the
whole science.

But a still higher merit perhaps can be claimed for De
Candolle, inasmuch as he not only like Jussieu elaborated the
system and its fundamental principles in his descriptive works,
but developed the theory, the laws of natural classification,
with a clearness and depth such as no one before him had

128 Development of the Natural System under [booki.

displayed. To this purpose he apphed morphological re-
searches, which in profundity and wealth of thought and
in the fruitfulness of their results for the whole domain of
systematic botany far surpassed all that Linnaeus and Jussieu
had accomplished, and show us that while engaged in his
splendid labours in descriptive botany he had caught during
his ten years' residence in Paris the true spirit of modern
investigation of nature, as it had been developed by the
French naturalists of the end of the previous century. Scarcely
a trace is to be found in De Candolle of the scholasticism
of Cesalpino and Linnaeus, which occasionally makes its
appearance even in Jussieu. For instance, he dealt with
morphology as essentially the doctrine of the symmetry of
form in plants, that is, he found the basis of morphological
examination in the relative position and numbers of the
organs, disregarding their physico-physiological properties as
of no account from the morphological point of view. He was
therefore the first who recognised the remarkable discordance
between the morphological characters of organs, which are
of value for systematic purposes, and their physiological
adaptations to the conditions of life, though it must at the
same time be acknowledged, that he did not consistently carry
out this principle, but committed grave offences against it
in laying down his own system. It is a point of the highest
interest in De CandoUe's morphological speculations, that
he was the first who endeavoured to refer certain relations
of number and form to definite causes, and thus to distinguish
what is primary and important in the symmetry of plants from
merely secondary variations, as is seen in his doctrine of the
abortion and adherence of organs. In these distinctions
De Candolle laid the foundation of morphological views,
which, though now modified to some extent, do still contain
the chief elements of morphology and the natural system ;
but his morphological speculations were confined to the
domain of the Phanerogams, and chiefly advanced the theory

Chap. III.] tJic Dogma of Constajicy of Spcctes. 129

of the flower ; a morphology of the Cryptogams was as little
to be thought of in the condition of microscopy before 1820,
as the application of the history of development to the
establishment of morphological theories.

De CandoUe published his morphology or doctrine of
symmetry and his theory of classification together in a book
which appeared first in 181 3, with the title, 'Theorie Elemen-
taire de la botanique ou exposition des principes de la classifi-
cation naturelle et de I'art de decrire et d'etudier les veg^taux,'
and again in 1819 in an improved and enlarged edition.
The second edition will be the one referred to in the further
account of his views. The second chapter of the second book
concerns us most at present. After alluding to the fact, that
anatomy and physiology are concerned with the structure of
the individual organ only so far as the power to fulfil its
proper function depends on the structure, he points out that
the physiological point of view is no longer sufficient when
we are engaged in comparing the organs of different plants.
Though it is true that the function of the organs is the most
important for the life and permanence of the individual, yet
we find these functions modified in the case of homologous
organs in different plants ; for the natural classification we
must take into consideration only the entire system of organi-
sation, that is, the symmetry of the organs. All organisms of
a kingdom, he continues, have the same functions with slight
modifications ; the immense amount of variation in syste-
matically different species depends therefore only on the
way in which the general symmetry of structure varies. This
symmetry of the parts, the discovery of which is the great
object in the investigation of nature, is nothing more than
the sum total (I'ensemble) of the positional relations of the
parts. Whenever these relations (disposition) are regulated
according to the same plan, the organisms exhibit a certain
general resemblance to one another, independently of the
form of the organs in detail ; when this general resemblance

K

130 Development of the Natural System under [Booki.

is perceived, without any attempt to give any account of it
in the detail, we have what has been called habitual relation-
ship ; but it is the task of the doctrine of symmetry to resolve
this likeness of habit into its elements, and to explain its
causes. Without this study of symmetry it may easily happen
that two different kinds of symmetry may be supposed to
be alike, because they seem outwardly alike to our senses,
just as forms of crystals of different systems may be con-
founded together for want of careful examination ; the chief
thing is to know the plan of symmetry in every class of plants,
and the study of this is the foundation of every theory of
natural affinities. But success in this study depends on the
certainty with which organs are distinguished, and the dis-
tinguishing them must be independent of changes of form,
size, and function. He then shows that the difficulties in
the morphological comparison of organs, or, as we should
now say, in the estabHshing the homology, are due to three
causes ; abortion, degeneration, and adherence (adherence).
These three causes, by which the original symmetry of a class
is changed and may even be utterly obscured, are then fully
illustrated by examples.

In respect to abortion he distinguishes that which is pro-
duced by internal causes from that which is due to accidental
and external ones ; he refers especially to the abortion of two
loculaments in the fruit of the horse-chestnut and the oak, to
the suppression of the terminal bud in some shrubs by the
adjoining axillary buds, and to the fact that all organs of
plants may become abortive in a similar manner ; for instance,
the sexual organs disappear entirely in the disk-flowers of
Viburnum Opulus, and one of the two sexes in the flower
of Lychnis dioica. He goes on to answer the question, how
it is possible to discover the symmetry in such cases ; one
method he finds supplied by monstrosities, among which
there are even some that may be regarded as a return to
the original symmetry, the cases known as peloria. Analogy

Chap. III.] tJw Dogma of Cojistancy of Species. 131

or ' induction ' is, he says, less certain, but of much more
extensive apphcation ; this is founded exclusively on the
knowledge of the relative position of organs. Armed with
this, we find that the flower of Albuca, which corresponds
to a flower of Liliaceae in everything except in having only
three stamens, is to be considered one of the Liliaceae,
because it has three filaments placed between the three
stamens exactly in the position of the three other stamens
in the Liliaceae ; it must be concluded therefore that they are
abortive stamens. Similar conclusions from analogy must be
carried from species to species, from organ to organ, and the
great systematists have in fact done so. In certain cases
abortion is produced by defect, in others by excess of nourish-
ment, of which he gives examples. An important sentence
occurs in this place ; everything in nature, he says, leads us to
believe that all organisms in their inner nature are regular,
and that different forms of abortion differently combined are
the cause of all irregularity ; from this point of view the
smallest irregularities are important, because they lead us to
expect greater ones in nearly allied plants ; and wherever in
a given system of organisation there are inequalities between
organs of the same name, the inequality will possibly reach
a maximum, that is, end by annihilating the smallest part.
Thus in the Labiatae with two stamens, it is the two which in
other cases also are the smaller, which are here completely
aborted. When in Crassulaceae there are twice as many
stamens as petals, those that alternate with the petals are
larger and earlier developed, and we may therefore expect
that those which are opposite the petals may become abortive ;
and therefore we may place a genus like Sedum, in which the
latter are sometimes wanting, with Crassulaceae ; but we could
not do so, if we found only the stamens that are superposed
upon the petals. It occurs sometimes, he continues, that an
organ is prevented from fulfilling its function by partial
abortion. In this case it may assume another function, as

K 2

133 Development of the Natural System under [Booki.

the abortive leaves of the vetch and the abortive inflorescences
of the vine are employed as tendrils. In other cases the
abortive organ appears to be quite useless, as for instance
many rudimentary leaves. All such useless organs, says De
Candolle, exist only in consequence of the primitive symmetry
of all organs. Finally the abortion may be so complete that
no trace of the organ remains, of which case there are
however two kinds, one where the organ is at first perceptible
and afterwards quite disappears, as in the abortive loculaments
in the fruit of the oak ; in other instances no trace is to be
seen from the first of the abortive organs, as happens with the
fifth stamen of Antirrhinum.

All that has here been said might be alleged word for word
in proof of the theory of descent, but our author is an adherent
of the dogma of the constancy of species ; what from his point
of view he really means by abortion is difficult to say, for the
object which is aborted is wanting. If species are constant,
and therefore of absolutely distinct origin, we must not speak
of abortion ; we can only say that an organ which is present
or large in one species is small or wanting in another. In
introducing the idea of abortion De Candolle at once goes
beyond the dogma of the constancy of species, without being
clear in his own mind with regard to this important step. His
proceeding shows that facts lead even a defender of constancy
against his will to theories which run counter to that dogma.
This is confirmed by his perception of the correlation of
growth, which is connected with abortion ; he points to the
fact that owing to the disappearance of sexual organs in the
disk-flowers of Viburnum Opulus the corollas become larger,
as do the bracts of the abortive flowers of Salvia Horminum ;
similarly he regards the disappearance of the seeds in Ananas,
Banana, and the Bread-fruit tree as the cause of the enlarge-
ment of the pericarps ; it does not escape him, that the fertile
flowerstalks in Rhus Cotinus remain naked, while an elegant
pubescence forms on the barren ones ; the leaf-like expansion

Chap. III.] tJic Doguitt of Coustaucy of Spectcs. 133

of the leaf-stalks of Acacia heterophylla, which do not develop
their laminae, he refers also to this correlation of growth. He
finds the most remarkable example of the kind in the doubling
of flowers, where according to his view the disappearance of
the anthers is a condition of the corolline expansion of the
filaments ; in the same way sometimes the carpel is changed
into a petal through the disappearance of the stigma. Though
in many of these cases it is quite possible to conceive of
the relations of cause and effect in the reverse way, yet
De Candolle's principle of correlation will be equally ap-
plicable.

The second cause by which the symmetry may be obliter-
ated, namely degeneration, asserts itself in the formation of
thorns, of threadlike prolongations of membranous expansions,
and in the production of fleshy parts,, or of parts with dry
membranes.

The third kind of departure from the symmetrical plan is
the adherence of parts, the theory of which he grounds first
and chiefly on the i)henomena of grafting, and then passes
to more difficult cases. The close packing of the ovaries in
some species of honeysuckle, is, he says, the primary cause of
their adherence. This therefore does not depend on the plan
of symmetry, but upon an accident, which however is constant
in its appearance, owing to the specific constitution of such
plants. In connection with the phenomena of adherence he
next considers the question whether a structure composed of
several parts, as for instance a compound ovar}', should be
considered as originally simple and afterwards divided into
parts, or whether the converse is the true account, and he
says that we must examine each particular case and decide
which is the correct conception. Thus it may be shown that
the perfoliate leaves of honeysuckles, as well as the involucres
of many Umbelliferae, and monosepalous calyces and mono-
petalous corollas are due to adherence, and he proceeds to
prove that ovaries with several loculaments and several parts

134 Development of the Natural System under [BookI.

have in like manner been formed by adherence of two or more
carpellary leaves, and concludes by pointing out the systematic
importance of such considerations. Further on he takes
occasion to speak of the significance of the relative number
of the parts of the flower, on which head he says much that is
good, but does not thoroughly investigate the matter ; it was
not till a later time that Schimper's doctrine of phyllotaxis
made it possible to express these relations of number and
position more precisely.

He concludes his rules for the application of his morphology
to the determination of relations of affinity with the declaration,
that the whole art of natural classification consists in dis-
cerning the plan of symmetry, and in making abstraction of all
the deviations from it which he has described, — much in the
same way as the mineralogist seeks to discover the funda-
mental forms of crystals from the many derivative forms. It is
obvious that all this teaching was a great step in advance upon
the right path, that De Candolle has here given utterance for
the first time to an important principle of morphology and
systematic botany ; nevertheless he did not succeed in always
consistently carrying out his own principle; he was true to
himself only in the determination of small groups of relation-
ship ; in framing the largest divisions of the vegetable kingdom
he entirely lost sight of the rule which he had himself laid
down, that the morphological character of organs and the
extent to which it can be turned to account for systematic
purposes is entirely independent of their physiological character,
and that the most important physiological characters are just
those which are of quite subordinate importance in the determi-
nation of affinities. In spite of this strange inconsistency, to
De Candolle belongs the merit of being the first to point
emphatically to the distinction between morphological and
physiological marks, and to bring clearly to light the dis-
cordance between morphological affinity and physiological
habit; but in this discordance lurks a problem, which could

Chap. III.] the Dogma of CoHstaucy of Species. 135

only be solved forty years later by Darwin's theory of selection.
A genuine inductive process alone could reveal these re-
markable relations between the morphological and physio-
logical characters of organs. But it is at the same time true
that L)e Candolle could not have made this discovery, if his
predecessors had not already established a large number of
affinities. It was while he was engaged in an exact comparison
of forms already recognised as undoubtedly related to one
another, that that which he called the plan of symmetry, and
which was afterwards named a type, revealed itself to him; and as
he examined it more closely, and compared it with peculiarities
of habit in different plants formed on the same plan, he
discovered certain causes, by means of which the deviations
were to be explained ; these w-ere abortion, degeneration, and
adherence. By attending to these he succeeded in discovering
affinities that had been hitherto doubtful or unknown ; this
was at all events the true inductive way of advancing the
system, and whatever the earlier systematists had effected that
was really valuable had been effected virtually in the same
way, only they never arrived at a clear understanding of their
own mode of proceeding ; they had followed unconsciously the
method which De Candolle clearly understood and consciously
pursued.

The majority of De CandoUe's successors were far from
fully appreciating the entire significance of his theory, its
importance as a matter of method and principle ; on the
contrary in the search for affinities they continued to surrender
themselves to a blind feeling rather than to a clearly recognised
method, and the same must be said unhappily of De Candolle
himself, when he was dealing with the establishment of the
large divisions of the vegetable kingdom. With equal surprise
we find him in the book before us, in which he has developed
the true method in systematic botany, expressing the opinion
that the most important physiological characters must be
employed for the primary divisions of the system, and this

136 Development of the Natural System under [book i.

idea is not improved by the fact that he ascribes to the organs
physiological characters which they do not really possess ; thus
he regards the vessels as the most important organs of nutri-
tion, which they are not in fact, and upon this double error
he builds his primary division of the whole vegetable kingdom
into vascular and cellular plants, and then by a third mistake
believes that this division coincides with the division of plants
into those which have and those which have not cotyledons.
The already established division into Monocotyledons and
Dicotyledons, which rests upon a leading and purely morpho-
logical mark, is spoilt by De CandoUe through his following
Desfontaines in ascribing to the Dicotyledons a different mode
of growth in thickness from that of the Monocotyledons, and
characterising the one as exogenous, the other as endogenous.
But this notion is utterly incorrect, as von Mohl showed twelve
years later ; and if it were correct, it would still be unimportant
in a systematic point of view, because it appeals to a mark
which is morphologically of quite subordinate importance.
The worst consequence of these mistakes was, that the
Vascular Cryptogams were introduced into the same class
with the Monocotyledons, — a decided step backwards, if we
compare De Candolle's system with that of Jussieu. In spite
of these grave defects in the primary divisions of the whole
vegetable kingdom De Candolle's system deserved the fame
which it acquired and long maintained ; it had this advantage
over Jussieu's system that in the class of Dicotyledons, the
largest division of the whole kingdom, larger sub-divisions
appeared, and these served to unite families that were in
many points essentially related ; the Dicotyledons were in
fact divided first of all into two artificial groups according to
the presence of two floral envelopes or one; the first and
much the larger of these was again broken up into a series of
subordinate groups, which pointed in many ways to natural
affinities. That these groups, which have only quite recently
been materially altered, did to a very considerable extent take

Chap. III.] tkc Dogum of Coustaucy of Specics. 137

account of natural affinities, is due to the fact that De Candolle
in framing them really followed his own rules, whereas the
superior divisions, which are artificial, owe their existence to
his disregard of them.

De Candolle declared emphatically against the old notion,
that the vegetable system answers to a linear series, — a notion
which sprang from a misunderstanding of the saying, ' Natura
non facit saltus,' — and demonstrated its impossibility by ex-
amples; but he allowed himself to be too much influenced
by the idea which had been thrown out by Linnaeus, and taken
up by Giseke, Batsch, Bernardin de St. Pierre, L'Heritier, Du
Petit-Thouars and others, that the vegetable kingdom might
be compared as respects its grouping to a geographical map,
in which the quarters of the globe answer to the classes, the
kingdoms to the families, and so on. If the theory of descent
is to a certain degree compatible with the idea of a linear
sequence from the most imperfect to the highest forms of
plants, it is quite incompatible with the above comparison ;
and systematic investigation, led astray from the right path,
is in danger of ascribing the importance of real affinities to
mere resemblances of habit, incidental analogies, by which a
group of plants appears to be connected with five or six others.
In exhibiting his system on paper De Candolle allowed the
use of the linear sequence as a convenience, for here it was
not, he said, a matter of any importance, since the true task
of the science is to study the relations of symmetry in each
family and the mutual relations of families to one another ;
yet in a linear presentation of the system for didactic purposes
the sequence ought not to begin with the most simple plants,
for these are the least known, but with the most highly de-
veloped. Thus De Candolle was the means of removing from
the system the last trace of anything which harmonised with
an ascending and uninterrupted development of forms. Resting
on the doctrine of the constancy of species, and assuming that
every group of relationship is founded on a plan of symmetry

138 Development of the Natural System under [BookI.

round which individual forms are grouped as crystals round
their parent form, De Candolle was quite consistent in his
views. The mode of representation came to prevail in the
vegetable kingdom which De CandoUe's contemporary, Cuvier,
an equally sturdy defender of the dogma of constancy, had
introduced in the animal kingdom as the type-theory. Thus
the most splendid results obtained by induction were united
in the case of De Candolle with the barren dogma of the
constancy of species, which, as Lange wittily remarks, comes
direct from Noah's ark, to form an intimate mixture of truth
and error ; nor did De CandoUe's many adherents succeed in
unravelling the coil, though they removed the chief errors from
his system and introduced many improvements.

To these remarks may be appended a table of the main
divisions of De CandoUe's system of 18 19, which so far as it is
presented in linear arrangement he calls expressly an artificial
system.

I. Vascular plants or plants with cotyledons.

1. Exogens or Dicotyledons.

A. With calyx and corolla :
Thalamiflorals (polypetalous hypogynous),
Calyciflorals (polypetalous perigynous),
Corolliflorals (gamopetalous).

B. Monochlamydeous plants (with a single floral envelope).

2. Endogens or Monocotyledons.

A. Phanerogams (true Monocotyledons),

B. Cryptogams (vascular Cryptogams including Naiadeae).

II. Cellular plants or Acotyledons.

A. With leaves (Muscineae),

B. Without leaves (Thallophytes).

The number of families, with Linnaeus 67, with A. L. de
Jussieu 100, was increased by De Candolle to 161.

Chap. III.] tlic Dogma of Coustaucy of Spccies. 139

If the principles of comparative morphology laid down by
De Candolle were at first prevented from being rapidly dis-
seminated in Germany by the philosophical tendencies then
reigning among its botanists, and especially by the obscurities
of Goethe's doctrine of metamorphosis, yet these principles and
his views also on the natural system won their way by degrees
to acknowledgment and acceptance; and after the year 1830
the study of the system was prosecuted by the botanists of
Germany, as well as by those of England and France, as the
proper object of the science. We may even say that the
impulse given by De Candolle worked more powerfully from
that time forward in Germany than in France. It may be said
too of De Candolle's contemporary, the Englishman Robert
Brown^ (1773-1858), whose chief labours fall in the period
between 1820 and 1840, that he, like De Candolle, was better

^ Robert Brown was the son of a Protestant minister of Montrose, and
studied medicine first at Aberdeen and afterwards in Edinburgh ; he then
became a surgeon in the army, and was at first stationed in the north
of Ireland. ^Vhen the Admiralty despatched a scientific expedition to
Australia under Captain Flinders in 1801, he was appointed naturalist
to the expedition on the recommendation of Sir Joseph Banks, F. Bauer
being associated with him as botanical draughtsman. Good as gardener,
Westall as landscape-painter ; one of the midshipmen of the vessel was
John Fianklin. In consequence of the unseaworthiness of the ship
Flinders left Australia, intending to return with a better one, but was ship-
wrecked on the voyage and detained by the French at Port Louis as
a prisoner of war till 1810. The naturalists of the expedition remained
in Australia till 1805, when Brown returned to England with 4000 for
the mcst part new species of plants. Sir J. Banks appointed him his
librarian and keeper of his collections in 1810 ; he was also Librarian to the
Linnaean Society of London. In 1823 he received the bequest of Banks'
library and collections, which were to be transferred after his death to
the British Museum ; but by his own wish they were deposited there
at once, and he himself received the appointment of Custodian of the
Museum and remained in that position till his death. At Humboldt's
suggestion Sir Robert Peel's Ministry granted him a yearly pension of
£200. His merits were universally acknowledged, and Humboldt even
named him ' botanicorum facile princeps.'

140 Development of the Natural System under [BookI.

appreciated during that time in Germany than in any other
country. Robert Brown, who spent the five years from 1801
to 1805 in Australia, studied the flora of that quarter of the
world, and discussed in numerous essays the botanical results
of various journeys made by other naturalists in polar regions
and in the tropics. In this way he found opportunity to leaven
the ideas, which through Humboldt's influence had become
predominant respecting the geography of plants, with the spirit
of the natural system ; he also made the morphology and
systematic position of a number of families the subject of
critical investigation.

Robert Brown's literary efforts were limited to these mono-
graphs ; he nowhere attempted to give a connected account of
the principles which he follows in them, an exposition of his
morphology or a theory of classification, nor did he frame a new
system. The results of his studies which were really fruitful
and served to advance the science are to be found in the more
general remarks, which he managed to insert quite incidentally
in his monographs. In this way he succeeded in clearing up
the morphology of the flower and with it the systematic position
of some difficult families of plants, such as the Grasses, Orchids,
Asclepiads, the newly-discovered Rafflesiaceae and others, and to
throw new light at the same time on wider portions of the system ;
in his considerations on the structure and affinities of the most
remarkable plants, which had been collected in Africa by
different travellers in the years immediately following 1820, he
discussed difficult and remarkable morphological relations in
the structure of the flower. He referred especially in this essay
(1826) to the relations between the numbers of the stamens and
carpels, and those of the floral envelopes in the Monocotyledons
and Dicotyledons, and showed how these typical, or as he calls
them in De CandoUe's phraseology, symmetrical relations were
changed by abortion, while he entered at the same time into a
more exact determination of the position of the aborted and of
the perfect organs, in order to discover new relations of affinity.

Chap. III.] thc Dogma of Constancy of Species. 141

His most valuable work in this direction is a paper on a genus
Kingia, discovered in New Holland in 1825; the structure of
the seeds in this genus led him to seek more accurate knowledge
of the unfertilised ovule in the Phanerogams generally, and
especially in the Cycads and Conifers. In spite of the labours
of Gartner and the later researches of Treviranus, there was still
considerable obscurity attaching to the theory of the seed, for
no one had yet succeeded in referring the position of the embryo
in the ripe seed to a general law. For this it was necessary to
submit the ovule before fertilisation to careful examination, and
Robert Brown carried out this first step to a history of develop-
ment with great success ; he was the first to distinguish the
integuments and the nucleus in the ovule, and the embryo-sac
in the nucleus, parts which Malpighi and Grew had indeed
observed but had not brought out with perfect clearness. The
micropyle and the hilum of the seed had not yet been properly
distinguished, but had been to some extent even confounded
with one another. Robert Brown showed that the hilum
answers to the point of attachment of the ovule, while the
micropyle is a canal formed by the integuments of the ovule
and leading to the summit of the nucleus ; that in anatropous
ovules the micropyle lies beside the hilum, in orthotropous
ovules opposite to it ; that the embryo in the embryo-sac
(amnion) is always formed at the spot which lies nearest the
micropyle, and that the radicle of the embryo is always turned
towards the micropyle, — facts which at once established the
general rule by which to determine the position of the embryo
in the seed and in the fruit. He also gave the first correct
explanation of the endosperm as a nourishing substance formed
inside the embryo-sac after fertilisation, and more than this, he
was the first to distinguish the perisperm as a substance formed
outside the embryo-sac in the tissue of the nucleus.

In this way Robert Brown established morphological rela-
tions in the organisation of the seed of the Monocotyledons
and Dicotyledons, which count among the most important

142 Development of the Natural System under [Booki.

principles of classification in these classes ; he was still more
happy in being the first to detect the peculiar structure of the
flower of Conifers and Cycads, as compared with that of other
flowering plants ; it was he who perceived that what had been
hitherto called a female flower in these plants was really a naked
ovule, a view which Trew of Nuremberg had, it is true, sug-
gested in the year 1767. He also called attention to the
agreement in structure of the male and female organs in these
families. Thus one of the most remarkable facts in vegetation,
the gymnospermy of the Conifers and Cycads, was for the first
time estabhshed, and this led afterwards through Hofmeister's
investigations to the important result, that the Gymnosperms,
which had been up to that time classed with Dicotyledons, are
to be regarded as co-ordinate with Dicotyledons and Monoco-
tyledons, forming a third class through which remarkable
homologies were brought to light in the propagation of the
higher Cryptogams and the formation of seeds in Phanerogams.
No more important discovery was ever made in the domain of
comparative morphology and systematic botany. The first steps
towards this result, which was clearly brought out by Hof-
meister twenty-five years later, were secured by Robert Brown's
researches, and he was incidentally led to these researches
by some difficulties in the construction of the seed of an
Australian genus. He discussed in a similar manner, if not
always with such important results, a great variety of questions
in morphology and systematic botany ; even purely physiologi-
cal problems were raised by him in this peculiar way, and
especially the question how the fertilising matter of the pollen-
grains is conveyed to the ovule ; he had already concluded
from the position of the embryo that it is conveyed through
the micropyle and not through the raphe and the hilum, as was
then supposed, and he was the first also to follow the passage
of the pollen-tubes in the ovary of Orchids up to the ovules ;
but this is a point which will be more properly considered in
the history of the sexual theory.

Chap. III.] thc Dogma of Coustaucy of Spccics. 143

The peculiar character of the natural system as compared
with every artificial arrangement is brought out into higher
relief by Robert Brown than by Jussieu and De Candolle, and
he succeeded better than any of his predecessors in separating
purely morphological and systematically valuable relations of
organisation from the physiological adaptations of organs.
While the majority of systematists surrendered themselves to
the guidance of a blind feeling in the discovery of affinities,
their correct determinations being the accidental result of
instinct and unconscious operations of the understanding,
Brown endeavoured to give an account to himself in every case
of the reasons why he took this or that view of the relationships
which he determined ; from what was already established and
indubitable he gathered the value of certain marks, in order to
obtain rules for the determination of unknown relationships.
In this way he discovered also, that marks, which are of great
value for classification within the limits of certain groups of
affinity, may possibly prove to be valueless in other divisions.
Thus Robert Brown in his numerous monographs supplied the
model, by which others might be guided in further applying
and completing the method of the natural system ; and in this
respect he was met by the botanists of Germany in the spirit
of the best good-will and most profound appreciation, as is
shown by the fact that a collection of his botanical works,
translated by different German botanists, was edited in five
volumes by Nees von Esenbeck as early as the period between
1825 and 1834. The natural system established itself in
Germany through the labours of Brown and De Candolle ; and
the more correct appreciation of it as compared with the
sexual system of Linnaeus was promoted by a work of Carl
Fuhlrott which appeared in 1829, in which the systems of
Jussieu and De Candolle are compared with those of Agardh,
Batsch, and Linnaeus, and the superiority of the natural system
is clearly set forth. A still greater effect in this direction was
produced by the appearance in 1830 of the 'Ordines naturales

144 Development of the Natural System under [BookI.

plantarum' of Bartling, an independent contribution to this
department of botany, and a distinct advance upon what had
hitherto been effected. The contemporary monographs of
Roeper on the Euphorbiaceae and Balsamineae and his treatise
'De organis plantarum' (1828), are an able, independent, and
logical application of the principles of the morphology of the
flower laid down by De Candolle and Brown to the elucidation
of morphological and systematic conceptions. But the new
methods of investigation introduced by De Candolle and
Robert Brown had to encounter in Germany, and to some
extent in France also, not only the antiquated views of Lin-
naeus, but, what was still worse, the erroneous notions of the
nature-philosophy founded by Schelling. The misty tenets of
this philosophy could scarcely find a more fruitful soil than the
natural system with its mysterious affinities, and Goethe's
doctrine of metamorphosis contributed not a little to
increase the confusion. These historical phenomena will be
further considered in the following chapter ; at present we are
more concerned to show how the professed systematists pursued
the path opened by De Candolle and Brown. And here it must
be noticed that from about the year 1830, in Germany especi-
ally, morphological enquiry became separated as a special
subject from systematic botany ; it became more and more the
fashion to treat the latter as independent of morphology, and
thus to forsake the source of deeper insight which comparative
and genetic morphology alone can open to the systematist;
morphology on the other hand took a new flight, and as it
thus developed itself apart from pure systematic botany, its
progress must be described by itself in a later portion of this
history.

If advance in systematic botany depended on the number of
systems that were proposed from 1825 to 1845, that period
must be looked upon as its golden age ; no less than twenty-
four systems made their appearance during these twenty years,
without counting those which were inspired by the views of the

Chap. III.] the Dognitt of Coustancy of Species. 145

nature-philosophy. There was great and spreading growth,
but no corresponding depth ; no really new points of view
were opened for classification, and as regards the true prin-
ciples of the natural system there were symptoms of evident
decline rather than of advance, as will be shown below. Im-
provements were effected certainly in the details of the system,
since botanists generally adhered to the principles laid down
by Ue Candolle, Jussieu, and Brown. Families were cleared
up and better defined, and groups of families were proposed
which assumed more and more the appearance of natural
cycles of relationship. The class more especially treated was
the extensive one of the Dicotyledons, in which the families,
continually growing more and more numerous, were in Jussieu's
arrangement a chaos, but had been united into larger groups
in a somewhat artificial manner by De Candolle. Here we see
once more how the formation of the system rises step by step
from the particular to the more general ; at an earlier period
genera were constructed out of species, and families out of
genera, and during the years from 1820 to 1845 the families
were united into more comprehensive groups ; but these orders
or classes were not yet grouped together in such a manner as
to ensure the separation of the largest divisions of the vegetable
kingdom in a natural manner. The great class of Dicotyledons
is not even yet so arranged that the smaller aggregates of
families connect satisfactorily one with another. Nevertheless
a considerable advance was made by the establishment of a
large number of smaller groups of families, and Bartling and
Endlicher were especially successful in founding such groups
and supplying them with names and characters.

If on the other hand we turn to the primary divisions of the
vegetable kingdom, we find that certain large and natural
groups came to be most generally recognised and placed in
the front rank in every scheme ; such were the groups of the
Thallophytes, Muscineac, Vascular Cryptogams, Gymnospcrms,
Dicotyledons and Monocotyledons. But the co-ordination of

L

146 Development of the Natural System under [Book i.

these great divisions of the whole vegetable kingdom was
far from being rightly understood. It was usage rather
than anything else, which gradually put them forward as
primary types ; in the systems themselves some received too
great, others too little prominence, or other groups of doubtful
character were admitted alongside of them. Bartling, for
instance, whose system up to 1850 or even longer may rank as
one of the most natural, adheres to De Candolle's division of
the vegetable kingdom into cellular and vascular plants, and
rightly divides the former into two main groups, Thallophytes
and Muscineae (Homonemeae and Heteronemeae), while he
separates the latter into Vascular Cryptogams and Phanero-
gams ; but the Phanerogams are divided into Monocotyledons
and Dicotyledons, which again are distributed into four groups,
one of these being characterised by the presence of a vitellus,
that is, of an endosperm surrounded by a perisperm, — a
thoroughly artificial division. The three other divisions are
named apetalous, monopetalous, and polypetalous, but the
Coniferae and Cycadeae are placed in the apetalous division.
Less satisfactory is the primary division into Thallophytes and
Cormophytes proposed by Endlicher ', the latter separating
into the divisions Acrobrya (Muscineae, Vascular Cryptogams,

' Stephen Ladislaus Endlicher was bom at Pressburg in 1805, and
abandoning the study of theology became Scriptor in the Imperial Library
at Vienna in 1828, and in 1836 Custos of the botanical department of the
Imperial Collection of Natural History. Having graduated at the Univer-
sity in 1840, he became Professor of Botany and Director of the Botanic
Garden. His library and herbarium, valued at 24,000 thalers, he pre-
sented to the State, and with his private means founded the Annalen des
Wiener-Museums, purchased botanical collections and expensive botanical
books, and published his own works and works of other writers. His official
salary was small, and having exhausted his resources in these various
expenses, he put an end to his own life in March 1849. Endlicher was not
only one of the most eminent systematists of his day, but a philologist also,
and a good linguist. He wrote among other things a Chinese grammar.
See 'Linnaea,' vol. xxxiii (1864 and 1865), p. 583.

Chap. III.] the Dogtua of Constancy of Species. 147

and Cycads), Amphibrya (Monocotyledons), and Acramphibrya
(Dicotyledons and Conifers); the names of the three latter
groups, the first of which is utterly unnatural, are founded on
erroneous assumptions respecting growth in length and thick-
ness, which Endlicher borrowed from Unger. While End-
licher's great work has continued down to our own time to
be indispensable to the botanist as a book of reference on
account of the fulness of its descriptions of families and
genera, the system projected by Brongniart in 1843 has
acquired a sort of official authority in France. The whole
vegetable kingdom is here distributed into two divisions,
Cryptogams and Phanerogams, and the former are incorrectly
characterised as asexual, the latter as having distinction of
sex. The Phanerogams, divided into Monocotyledons and
Dicotyledons, are distributed into groups in a manner that
is not satisfactory ; but the system has one merit, that it keeps
the Gymnosperms together in one body; and if they are
incorrectly classed with the Dicotyledons, it was still- a sign
of progress, that Robert Brown's discovery of gymnospermy
was to some extent practically recognised. The system de-
vised by John Lindley ^ attained to about the same importance
in England as attached to those of Bartling and Endlicher in
Germany, and that of Brongniart in France. After various
earlier attempts he proposed a system in 1845, in which, as in
Brongniart's arrangement, the Cryptogams are characterised as
asexual or flowerless plants, the Phanerogams as sexual or
flowering plants ; the former are divided into Thallogens and
Acrogens, the Phanerogams into five classes; (x) Rhizogens
(Rafflesiaceae, Cytineae, Balanophorae) ; (2) Endogens (pa-
rallel-nerved Monocotyledons); (3) Dictyogens (net-veined
Monocotyledons) ; (4) Gymnogens (Gymnosperms) ; (5) Exo-
gens (Dicotyledons). This classification is one of the most un-
fortunate that were ever attempted; the systematic value of the

' John Lindley, Professor of Botany in the University of London, was
bora at Chatton near Norwich in 1799, and died in London in 1865.

L 2

148 Development of the Natural System under [Book i.

Rhizogens is much overrated on account of their striking
habit ; the Monocotyledons are separated into two classes on
the strength of an unimportant mark. The characters assigned
to all these groups are on the whole thoroughly faulty.

These systems have been selected for notice from among
many others, because they attained an extended notoriety and
importance from the circumstance that their authors, Brong-
niart excepted, made them the occasions of comprehensive
descriptions of the whole vegetable kingdom, and again be-
cause it would be superfluous for our present purpose to
bestow a closer consideration on the systems of less eminent
men. Whoever desires further information on the matter will
find it in the introduction to Lindley's ' Vegetable Kingdom '
of 1853.

If we consider the principles and points of view adopted
in these systems, one thing especially strikes us, that, except
in the case of Bartling, physiologico-anatomical marks were
employed along with morphological ones to characterise the
primary divisions ; their authors fell into the mistake committed
by De CandoUe, and unfortunately these very marks rested in
part or wholly on misapprehensions, as in Endlicher's division
into Acrobrya, etc., and Lindley's classes of Rhizogens and
Dictyogens. It was still more unfortunate that individual sys-
tematists obstinately refused to accept well authenticated facts,
which it is true had not been discovered by systematists, but
were nevertheless of the highest value for the system. It is
scarcely credible that Lindley in 1845, ^"^ again in 1853,
maintained the distinction between endogenous and exogenous
growth in stems, though Hugo von Mohl had in 1831 produced
decisive proof that this distinction laid down by Desfontaines
and adopted by De Candolle had no real existence. The
same was the case with the characters of the Cryptogams, in
which the mark of having no sexual organs was repeatedly
adopted as running through the whole class, although various
instances of sexuahty in Cryptogams were known before 1 845 ;

Chap, III.] the Dogma of Constancy of Species. 149

Schmidel had described the sexual organs of the Liverworts
about the middle of the previous century, Hedwig those of the
Mosses in 1782, and Vaucher in 1803 had suggested that the
conjugation of Spirogyra among the Algae should be regarded
as a sexual act ; the systematists in fact did not know what to
make of these intimations.

It was again a misfortune that the systematists in their
labours often neglected to distinguish between the search
for marks and the use to be made of them ; the examination
of all possible marks should lead to the establishing the sys-
tematic importance of certain fixed marks or their value for
classification. When research has done its work, then it is
sufficient in exhibiting the system to put forward only the
prominent marks ; and frequently a single one suffices to
unite a natural group. Such a leading mark is like the
standard of a regiment ; its significance is not great in itself,
but it serves the great practical purpose of indicating a whole
group of marks which are connected with it. It was a still
greater misfortune that scarcely any systematist after De Can-
dolle endeavoured to form a clear conception in his own mind
of the principles on which the natural system must be ela-
borated, and to set them forth in a connected form as the
theory of the system. The student had to accept the arrange-
ment offered him as a fact simply without understanding it,
and the systematists themselves usually followed only a blind
feeling in the framing of their groups, and never unfolded the
grounds of their proceeding with logical distinctness. In this
respect John Lindley forms an honourable exception, inas-
much as he did, on several occasions after 1830, give full
expositions of his views on the principles of natural classi-
fication, and like De Candolle endeavoured to develop a
theory of the system*. But he deserves credit only for the

' Auguste de Saint Hilaire was born at Orleans in 1779, and died there
in 1853 ; he was Professor at Paris, and in 1840 published his ' Lemons de
Bolauique comprenant principalement la Morphologic Vegctale," etc. This

150 Development of the Natural System under [Book 1.

endeavour, for the principles themselves which he laid down
are not only to a great extent incorrect, but they are opposed
to his own and to every other natural system. We find this
opposition between theory and practice much more strongly
marked in Lindley than in De CandoUe ; the cases only are so
far different, that De Candolle laid down correct principles for
the determination of affinities, but in some cases did not follow
them, whereas Lindley deduced quite incorrect rules of system
from existing and long-established natural affinities. The con-
sideration of all the systems framed up to the year 1853 shows
clearly that the characters of truly natural groups are to be
found only in morphological marks ; yet Lindley enunciates
the principle that a mark, or, as he incorrectly says, an organ,
is more important for classification in proportion as it pos-
sesses a higher physiological value for the preservation and
propagation of the individual. If this were true, nothing would
be easier than to frame a natural system of plants ; it would
suffice to divide plants first of all into those without and those
with chlorophyll, for the presence of chlorophyll is more essen-
tial than that of any other substance to the nourishment of
plants, and its physiological importance is therefore pre-
eminent ; in that case of course such Orchideae as have
no chlorophyll, the Orobancheae, Cuscuta, Rafflesia, etc.,
would form one class with the Fungi, and all other plants the
other. It is very important for the existence of a plant whether
its organisation is adapted to its growing in water, or on dry
land, or underground, and if we took Lindley at his word, he

work contains a somewhat diffuse account of P. de CandoUe's doctrine of
symmetry, together with Goethe's theory of metamorphosis and Schimper's
doctrine of phyllotaxis, and his own views also on classification founded on
the comparative morphology of the day. It is marked by fewer errors
than will be found in Lindley's theoretical writings, but it is less profound,
and touches only incidentally on fundamental questions ; at the same time it
possesses historical interest as giving a lucid description of the state of
morphology before 1840.

Chap. III.] the Doguia of Constaucy of Species. 151

would be obliged to bring the Algae, Rhizocarps, Vallisnerias,
water Ranunculuses, Lemna, etc., into one group. It is very
important for the existence of a plant whether it grows upright
of itself, or climbs upwards by the aid ol tendrils or of a twining
stem or otherwise, and accordingly we might on Lindley's prin-
ciple collect certain ferns, the vine, the passion-flower, many
of the pea kind, etc., into one order. It is obvious that Lind-
ley's main axiom of systematic botany appears in this way
utterly unreasonable ; yet by this principle he judges of the
systematic value of anatomical characters, those of the embryo
and endosperm, of the corolla and the stamens, everywhere
laying stress on their physiological importance, which in these
parts has really little systematic value. This mode of pro-
ceeding on the part of Lindley, compared with his own system,
which with all its grave faults is still always a morphologically
natural system, proves that like many other systematists, he did
not literally and habitually follow the rules he himself laid
down, for if he had, something very different from a natural
system must have been the result. The success which was
really obtained in the determination of affinities was due chiefly
to a correctness of feeling, formed and continually being per-
fected by constant consideration of the forms of plants. It
was still therefore virtually the same association of ideas as in
de rObel and Bauhin, operating to a great extent unconsciously,
by which natural affinities were by degrees brought to light ;
and men like Lindley, of pre-eminent importance as .system-
atists, were, as the above examples show, never clear about
the very rules by which they worked. And yet in this way
the natural system was greatly advanced in the space of fifty
years. The number of affinities actually recognised increased
with wonderful rapidity, as appears from a comparison of the
systems of Kartling, Endlicher, Brongniart, and Lindley, with
those of De CandoUe and Jussieu. Nothing shows the value
of the systems thus produced before 1850 as classifications of
the vegetable kingdom more forcibly than the fact that a clear

153 Development of the Natural System under [Book i.

and methodical thinker like Darwin was able to draw from
them the chief supports of the theory of descent. For it is
quite certain that Darwin has not framed his theory in opposi-
tion to morphology and system, and drawn it from any hitherto
unknown principles ; on the contrary, he has deduced his most
important and most incontestable propositions directly from
the facts of morphology and of the natural system, as it had
been developed up to his time. He is always pointing ex-
pressly to the fact that the natural system in the form in which
it has come to him, which he accepts in the main as the true
one, is not built upon the physiological, but upon the morpho-
logical value of organs ; it may, he says, be laid down as
a rule, that the less any portion of the organisation is bound
up with special habits of life, the more important it is for
classification. Like Robert Brown and De Candolle, he insists
upon the high importance for purposes of classification of
aborted and physiologically useless organs ; he points to cases
in which very distant affinities are brought to light by numerous
transition-forms or intermediate stages, of which the class of
the Crustaceae offers a specially striking example in the animal
kingdom, while certain series of forms of Thallophytes, the
Muscineae, the Aroideae and others, may be adduced as in-
stances of the same kind in the vegetable world ; in such
cases the most distant members of a series of affinities have
sometimes no one common mark, which they do not share
with all other plants of a much larger division. From these
and other similar statements of Darwin we see plainly, that he
actually did gather from existing natural systems of plants and
animals the rules by which systematists had worked, but which
they themselves observed only more or less unconsciously, and
never with a full and clear recognition of them. He says quite
rightly, when the investigators of nature are practically engaged
with their task, they do not trouble themselves about the
physiological value of the characters which they employ for
the limiting a group or the establishment of a single species.

Chap. III.] the Dogma of Constancy of Species. 153

Darwin clearly perceived and consistently kept in view the
discordance between the systematic affinity of organisms and
their adaptation to the conditions of life, which De Candolle
had already but imperfectly recognised. The clear perception
of this discordance was in fact the one thing needed to mark the
true character of the natural system, and to make the theory of
descent appear as the only possible explanation of it. The
fact which morphologists and systematists had painfully
brought to light, but had not sufficiently recognised in its
full importance, that two entirely different principles are united
in the nature of every individual organism, that on the one
hand the number, the arrangement, and the history of the
development of the organs of a species point to corresponding
relations in many other species, while on the other hand the
manner of life and the consequent adaptation of the same
organs may be quite different in these allied species. This
fact admits of no explanation but the one given by the theory
of descent ; it is therefore the historical cause and the strongest
logical support of that theory, and the theory itself is directly
deduced from the results which the efforts of the systematists
have established. That the majority of systematists did at
first distinctly declare against the theory of descent can sur-
prise no one who observes that they were so little able to give
an account of their own mode of procedure, as appears in so
striking a manner from Lindley's theoretical speculations.

One consequence of this want of clearness in combination
with the dogma of the constancy of species has been already
mentioned in the introduction ; namely, the notion professedly
adopted by Lindley, Elias Fries, and others, that an idea lies
at the foundation of every group of affinities, that the natural
system is a representation of the plan of creation. But the
question, how such a plan of creation could explain the strange
fact that the physiological adaptations of organs to the con-
ditions of life have nothing at all to do with their systematic
connection, was quietly disregarded ; and in fact the notion,

154 Development of the Natural System.

founded on Platonic and Aristotelian philosophy, of a plan of
creation and of ideal forms underlying systematic groups,
could not explain this discordance between morphological and
physiological characters. It would be easy to maintain the
view of the systematists, that the natural system represents
a plan of creation, if physiological and morphological charac-
ters went always truly hand in hand, if the adaptation of the
organs to the conditions of life in the species were perfect ; but
facts show that the adaptation is in the best of cases compara-
tively imperfect, and that it is in all cases brought about by the
accommodation to new requirements of organs which originally
served to other functions.

CHAPTER IV.

Morphology under the Influence of the Doctrine of
Metamorphosis and of the Spiral Theory.

1 790-1850.

The efforts of Jussieu, De Candolle, and Robert Brown were
directed to the discovery of the relationship between different
species of plants by comparing them together ; the doctrine of
metamorphosis founded by Goethe set itself from the first to
bring to light the hidden relationship between the different
organs of one and the same plant. As De Candolle's doctrine
of symmetry derived the different species of plants from an
ideal plan of symmetry or type, so the doctrine of metamor-
phosis assumed an ideal fundamental organ, from which the
different leaf-forms in a plant could be derived. The stem
came into consideration only as carrying the leaves, the
root was almost entirely disregarded. As the resemblance of
nearly allied species of plants suggests itself naturally and
unsought to the mind of the unbiassed observer, so also does
the connection between different organs of a leafy nature in
one and the same plant. Cesalpino called the corolla simply
a 'folium' (leaf); he and Malpighi regarded the cotyledons also
as leaves ; Jung called attention to the variety of the leaf-
forms, which are found in many plants at different heights on
the same stem ; Caspar Friedrich Wolff, the first who bestowed
systematic consideration on the subject, declared in 1 766, that

156 Morphology under the Doctrine of [Book i

he saw nothing ultimately in the plant but leaves and stem,
including the root in the stem\

Long before Goethe's time speculation had busied itself with
attempts to explain these observations ; we saw how Cesalpino
and Linnaeus, starting from the old view that the pith is the
seat of the soul in plants, regarded the seeds as metamorphosed
pith, the floral envelopes with the stamens and the true leaves
as metamorphosed layers of the rind and wood of the stem.
The word metamorphosis from their point of view had a very
plain meaning ; it was really the cylindrical pith whose upper
end changed into seeds, it was the actual substance of the
cortex which produced both the ordinary leaves and the parts
of the flower. Wolff on the other hand from a point of view
of his own gave an apparently intelligible physical explanation
of the proposition, that all appendages of the stem are leaves,
but the explanation had the fault of not being true ; he
attributed the metamorphosis of leaves to altered nourishment,
the flowers especially to his ' vegetatio languescens.'

Goethe's conception of the matter was from the first much
less clear, and chiefly because he was never able to bring the
abnormal into its true connection with the normal or ascending
metamorphosis. In the first sentence of his ' Doctrine of meta-
morphosis ' (1790) he says, 'that it is open to observation that
certain exterior parts of plants sometimes change and pass into
the form of adjacent parts, either wholly or in a greater or less
degree.' In the cases of which Goethe is here thinking a distinct
meaning can be affixed to the word metamorphosis ; if, for
example, the seeds of a plant with normal flowers produce a plant
which has petals in place of stamens, or in which the ovaries are
resolved into green expanded leaves, it is actually the case that
a plant of a known form has given rise to another plant of a
different form, in other words, a change or metamorphosis has

^ See Wigand, 'Geschichte und Kritik der Metamorphose,' Leipzig, 1846,
p. 3S.

Chap. IV.] Mctamorphosts and of the Spiral Theory. 157

really taken place. But we cannot reason in this way in the case
of that which Goethe calls normal or ascending metamorphosis.
When in a given species, which has remained constant with
all its marks for countless generations, the cotyledons, the
leaves, the bracts, and the parts of the flower are called leaves,
this must be merely the result of abstraction, which has led to
the generalising of the idea of a leaf ; if we make abstraction
of the physiological characters of the carpels, stamens, floral
envelopes, and cotyledons, and regard only the way in which
they originate on the stem, we are justified in including them
in one general idea with ordinary leaves, and to this idea we
quite arbitrarily give the name leaf. But this does not justify
us in speaking of a change of these organs, so long as we
consider the whole plant in question as a hereditary and
constant form. For the plant therefore taken as constant the
idea of metamorphosis has only a figurative meaning; the
abstraction performed by the mind is transferred to the object
itself, if we ascribe to it a metamorphosis which has really taken
place only in our conception. The case would be different, if
here as well as in the abnormal instances above-mentioned we
could assume that the stamens and other organs of the plants
lying before us were ordinary leaves in their progenitors. So
long as this assumption of an actual change is not even hypo-
thetically made, the expression change or metamorphosis is
purely figurative, the metamorphosis is a mere ' idea.' This
distinction Goethe has not made ; he did not clearly see that
his normal ascending metamorphosis can only have the mean-
ing of a scientific fact, if a real change is assumed to take place
in the course of propagation in this case, as in that of abnormal
metamorphosis or misformation. A comparison of his various
expressions shows that he took the word metamorphosis some-
times in its literal, sometimes in its ideal and figurative sense ;
for instance, he says expressly, ' We may say that a stamen is
a folded petal, just as we may say that a petal is a stamen in a
state of expansion.' This sentence shows that Goethe did not

158 Morphology under the Doctrine of [Book i-

regard a particular leaf-form as first in time, and that others
proceeded from it by change ; he uses the word metamor-
phosis in a purely ideal sense. At other times his remarks
may be interpreted as though he really considered the normal
ascending metamorphosis to be a real change in the organs,
arising from a transmutation of the species. With this con-
fusion of notion and thing, idea and reality, subjective
conception and objective existence, Goethe took up exactly
the position of the so-called nature-philosophy.

Goethe's doctrine could only make its way to logical con-
sistency and clearness of thought by deciding for the one or
the other way ; he must either assume that the different leaf-
forms, which were regarded as alike only in the idea, were
really produced by change of a previous form, — a conception
that at once presupposes a change of species in time ; or he
must entirely adopt the position of the idealistic philosophy, in
which idea and reality coincide. In this case the assumption
of a change in time was not necessary ; the metamorphosis
remained an ideal one, a mere mode of view ; the word leaf
then signifies only an ideal fundamental form from which the
different forms of leaves actually observed may be derived, as
De CandoUe's constant species from an ideal type.

If now we read Goethe's further remarks on the doctrine of
metamorphosis attentively ^ we perceive that he really arrived
at neither of these conclusions, but perpetually vacillated
between the two ; a number of his sayings might be collected,
which might be taken for precursors of a theory of descent, as
they have been taken by some modern writers ; but it is quite
as easy to make a selection which would carry us back to the
position of the ideal philosophy and the constancy of species.
In the later years of his life the idea of a physical metamor-
phosis accomplished in time, and involving a change of
species, does appear more distinctly in Goethe's writings. This

^ See Goethe's collected works in forty volumes, Cotta, 1858, vol. xxxvi.

Chap. IV.] Metamorphosts and of the Spiral Theory. 159

explains the lively, nay passionate, interest which he took in
the dispute between Cuvier and Geoffrey de St. Hilaire in
1830 \ We gather from it that Goethe, in spite of all his
wanderings in the mists of the nature-philosophy of the time,
felt a growing need for some clearer insight into the nature of
metamorphosis, both in plants and animals, without ever being
able to make his way into the clear light.

But these better motions remained without importance for
the history of botany ; the adherents of his doctrine of meta-
morphosis all apprehended it in the sense of the nature-
philosophy, and Goethe himself did not remonstrate against
the frightful way in which it was distorted by them. Its
further development therefore was in accordance with the
principles of that philosophy, which was accustomed to apply
the results of purely idealistic views in an uncritical way to
imperfectly observed facts. Above all the difficulty remained
unsolved, how the dogma of the constancy of species was to
be brought into logical connection with the idea of the meta-
morphosis of organs. The supranatural, which Elias Fries
found in the natural system, subsisted still in the doctrine of
metamorphosis in comparing the organs of a plant.

Still more obscure and entirely the product of the nature-philo-
sophy is Goethe's view of the spiral tendency in vegetation.
At p. 194 of his essay entitled ' Spiraltendenz der Vegetation '
( 1 831) he says : 'Having fully grasped the idea of metamorphosis
we next turn our attention to the vertical tendency, in order to
gain a nearer acquaintance with the development of the plant.
This tendency must be looked upon as an immaterial staff,
which supports the existence .... This principle of
life (!) manifests itself in the longitudinal fibres which we
use as flexible threads for many purposes ; it is this which
forms the wood in trees, which keeps annual and biennial plants
erect, and even produces the extension from node to node

' See Haeckel, ' Natiirliche Schopfungsgeschichte,' ed. 4, 1S73, p. 80.

t6o Morphology under the Doctrine oj [Book i.

in climbing and creeping plants. Next we have to observe the
spiral direction which winds round the other.' This spiral
direction which passes at once with Goethe into a 'spiral
tendency,' is seen in various phenomena of vegetation, as in
spiral vessels, in twining stems, and sometimes in the position
of leaves. The closing remarks of this short essay, in which
he explains the vertical tendency as the male, the spiral as the
female principle in the plant, show how far Goethe lost himself
in the profundities of the nature-philosophy. Thus he intro-
duced his readers into the deepest depths of mysticism.

It would be as useless as it would be wearisome to follow
out in detail to its extremest point of absurdity the pro-
gressive transformation which the doctrine of metamorphosis
underwent in the hands of the botanists of the nature-philo-
sophy school, and to see how its catchwords, polarity, con-
traction and expansion, the stem-like and the fistular,
anaphytosis and life-nodes, and others, were compounded
with the results of the most every-day observation into mean-
ingless conglomerates; rough obscure impressions of the
sense, as well as incidental fancies, were regarded as ideas
and principles. A full account of these inconceivable aberra-
tions is to be found in Wigand's 'Geschichte und Kritik
der Metamorphose.' Our own countrymen certainly, Voigt,
Kieser, Nees von Esenbeck, C. H. Schulz, and Ernst Meyer
(the historian of botany) bear off the palm of absurdity, but
there were others also, among them the Swedish botanist
Agardh, and many Frenchmen, Turpin, for instance, and Du
Petit-Thouars ', who were not altogether free from this weak-

* Robert du Petit-Thonars was bom in Anjou in 1758 and collected plants
during many years in the Mauritius, Madagascar, and Bourbon. He
was afterwards Director of the Botanic Garden at Roule, and became
Member of the Academy in 1820. He died in 1831. His articles in the
'Biographie Universelle' prove him to have been a writer of ability. Pre-
conceived opinions interfered with the success of his own investigations,
especially into the increase in thickness of woody stenjs, and obstinate

CiiAP. IV.] Metamorphosis and of the Spiral Theory. i6i

ness. Even the best German botanists of the time, such as
Ludolph Treviranus, Link, G. W. Bischoff, and others, managed
to escape the influence of this philosophy of nature, only where
they confined themselves to the most barren empiricism.
Strange phenomenon ! that as soon as gifted and understand-
ing men began to talk of the metamorphosis of plants, they
fell into senseless phrase-mongering ; Ernst Meyer, for instance,
was it is true no great botanist, but he shows in his ' Geschichte
der Botanik' that he possessed a clever and cultivated intellect.
The painful impression, which the treatment of the doctrine of
metamorphosis by these writers makes upon us, is due partly
to the fact that the deeper meaning of the idealistic philosophy
never attained to logical expression in their hands, and still
more to their indulgence in an unmeaning play of phrases,
combining the highest abstractions with the most negligent
and rudest empiricism, and sometimes with utterly incorrect
observations. Oken can claim the merit of more correct
observation and greater philosophical consistency, and if we
reject his views, yet his mode of presenting them has at least
the pleasing appearance of more consequential reasoning. We
perceive for the first time the full greatness of the debt which
modern botany owes to men like Pyrame de Candolle, Robert
Brown, von Mohl, Schleiden, Niigeli, and Unger, the latter of
whom only slowly worked his way out of the trammels of the
nature-philosophy, when we compare the literature of the
doctrine of metamorphosis before the year 1840 with the
present condition of our science, for which they paved the way.
In spite of the real and apparent differences between
Goethe's doctrine of metamorphosis and De Candolle's doc-
trine of a plan of symmetry, these writers agreed in this, that
they set out alike from the doctrine of the constancy of
species, and led up equally to the result, that alongside of

adherence to such notions prevented an unbiassed interpretation of what he
saw. See Flora, 1845, p. 439.

M

i6'Z Morphology under the Doctrine of [Book r.

manifold physiological differences in the organs of plants
certain points of formal agreement can be discovered, which
are expressed chiefly in the order of their succession and in
their relative positions. In this distinction lay the good kernel
of the doctrine of metamorphosis in Goethe, and Wolff, and
even in Linnaeus and Cesalpino : it was only necessary to set
this free from the dross with which the nature-philosophy had
surrounded it, and to make the relations of position in organs
the subject of earnest investigation, in order to secure im-
portant results in this branch of morphology. The first step
in this direction was taken by Carl Friedrich Schimper, who
was followed by Alexander Braun ; both adopted the main
idea of the doctrine of metamorphosis in the form in which it
can be reconciled with the doctrine of constancy, that is, in
a purely idealistic sense. Both liberated themselves from the
gross errors of the nature-philosophers, and thus gave a more
logical expression to the purely idealistic morphological con-
sideration of form in plants.

Karl Friedrich Schimper^ founded before the year 1830
the theory of the arrangement of leaves which is named after
him, and which he expounded to the naturalists assembled at
Stuttgart in 1834 as a complete and perfected system. Alex-
ander Braun, in a review of Schimper's exposition in ' Flora '
of 1835, gave a clear and simple account of the theory, having
already himself published an excellent and comprehensive
treatise on the same subject. The doctrine of phyllotaxis

^ K. F. Schimper, born in Mannheim in 1803, was at first a student
of theology in Heidelberg, but having afterwards travelled as a paid col-
lector of plants in the south of France, he applied himself to the study
of medicine. From 1828 to 1842 he was employed as a teacher in the
University of Munich, though occasionally engaged in exploring the Alps,
Pyrenees, and other districts, in the service of the King of Bavaria. It was
during this period of his life that he composed his most important works on
phyllotaxis, and essays on the former extension of glaciers, and on the glacial
period. He returned to the Palatinate in 1842, and died at Schwetzingen in
1867 in the enjoyment of a pension from the Grand duke of Baden.

Chap. IV.] Mctamovphosis mid of the Spiral Theory. 163

appeared in these publications with a formal completeness
which could not fail to attract the attention of the botanical
world and indeed of a larger audience ; and justly so, for, as
unfortunately so very seldom happens in botanical subjects,
a scientific idea was in this case not merely incidentally sug-
gested, but was worked out in all its consequences as a complete
structure, and this structure gained in external splendour from
the circumstance that its propositions, dealing with geometrical
constructions, could be expressed in numbers and formulae, —
a thing hitherto unknown in botanical science.

That the leaves are arranged on the stems that produce
them according to fixed geometrical rules had been noticed by
Cesalpino and by Bonnet in the middle of the eighteenth
centur}' ; but nothing more resulted than weak attempts at
mere description of different cases. Schimper's theory is marked
by that which is at once its greatest merit and its fundamental
error, the referring of all relations of position to a single prin-
ciple. This principle lies in the idea that growth in a stem
has an upward direction in a spiral line, and that the formation
of leaves is a local exaggeration of this spiral growth. The
direction of the spiral line may change in the same species, or
in the same axis, and may even change from leaf to leaf.
The important variations in the arrangement of leaves are not
shown in their longitudinal distances, but in the measure of
their lateral deviations on the stem. The characteristic point
in this theory is the mode of considering these lateral de-
viations or divergences of the leaves as they follow one another
on an axis, the referring them to a more general law of posi-
tion. Means were at the same time skilfully supplied for
discovering the true conditions of arrangement, the genetic
spiral, in cases where the genetic succession of the leaves, and
consequently their divergence, could not be immediately re-
cognised. After innumerable observations, it appeared that there
is a wonderful variety in the disposition of leaves, but that at
the same time a comparatively small number of these variations

M 2

164 Morphology under the Doctrine of [Book i.

commonly occur, and that these ordinary divergences \, f , f ,
tV> Wi stc. have this remarkable relation to one another, that
both the numerator and denominator of each successive
fraction are obtained by adding together the numerators and de-
nominators of the two preceding fractions, or the individual
fractions named are the successive convergents of a continuous
fraction : —

1 + I

By change of single cyphers in this, the simplest of all con-
tinuous fractions, the expressions were also obtained for all
measures of position that deviate from the usual main series.
The common occurrence of so-called leaf- whorls seemed at
once to be opposed to the principle of special growth and to
the doctrine of position founded upon it, especially in the
cases in which it was supposed that all the leaves of a whorl
arise simultaneously. But the founders of the doctrine, relying
on their geometrical constructions, declared that every theory
is incorrect, which sets out from the whorl as a simultaneous
formation. But the way in which the different leaf-whorls of a
stem are arranged among themselves, and are connected with
continuous spiral positions, required new geometrical con-
structions ; it was necessary to assume a supplementary rela-
tion (prosenthesis), which the measure of the phyllotaxis
adopts in the transition from the last leaf of one cycle to the
first of the next. Artificial as this construction appears, it has
the advantage of saving the spiral principle, and the prosen-
thetic relation Itself admits of being again expressed in highly
simple fractions, — a great advantage for the formal consideration
of the relative positions of the parts of the flower, and their
relation to the preceding positions of the leaves. The great
skill shown by the founders of the doctrine in the morpho-
logical consideration of the whole plant-form appears equally
in the establishment of the rules, according to which the

Chap. IV.] Mctamovphosis and of the Spiral Theory. 165

relations of position of the leaves of a side-shoot connect with
those of the mother-axis, and which made it possible to repre-
sent the nature of inflorescences especially w'ith extreme
clearness by means of geometrical figures. An expressive and
elegant terminology not only made the whole theory attractive,
but fitted it in a high degree to supply a suitable, plain, and
precise phraseology for describing the most varied forms of
plants. That the theory possesses such advantages as these
may be gathered from the fact, that since 1835 the morpho-
logical examination and comparison not only of flowers and
inflorescences, but also of vegetative shoots and their ramifica-
tion, has reached great formal completeness. A thorough
acquaintance with the principle of this doctrine has made it
possible to explain to reader or hearer the most intricate forms
of plants so clearly, that they may be said to reveal the law of
their formation themselves, and to grow before the eye of the
observer, while at the same time the most recondite relations
of the organs of the same or of different plants were brought
out distinctly and in elegant phraseology. When this mode of
description was combined with De Candolle's views on abor-
tion, degeneration, and adherence, and at the same time took
into consideration the chief physiological forms of leaf-structures,
according as these were developed as scales, foliage-leaves,
bracts, floral envelopes, staminal and carpellary leaves, it
was possible to give such an artistic account of every form of
plant, as made it visible to sense in its entirety, and at the
same time brought out the morphological law of its con-
struction. Whoever reads the writings of Alexander Braun
and Wydler, and especially of Thilo Irmisch (after 1873), who
knew how to combine his descriptions in a variety of ways
with remarks on the biological relations of plants, cannot fail
to admire the extraordinary skill displayed by these men in
describing plants. Compared with the dry diagnoses of the
systematists, their descriptions attain to the dignity of an art,
and present the commonest forms to the reader in a new

i66 Morphology under the Doctrine of [Book i.

and attractive light. But the theory had a further advantage ;
it seemed not only to present the form of the plant in its
matured state, but to treat it genetically; and in fact it did
possess an element of historical development, inasmuch as it
made the genetic succession of the leaves and of their axillary
shoots, which is at the same time the succession from the base
to the summit, the foundation of all consideration of the plant-
form. But it is also true that in this lay one of the weak sides
of the theory ; as long as it was a question only of continuous
spirals, the succession of matured leaves does also represent the
succession of their formation in time ; but this was not actually
proved in the case of leaf-whorls, and here, to save the theory,
genetic relations had to be pre-supposed for which no further
proof was forthcoming, while fresh researches have repeatedly
shown that a strict application of Schimper's theory is found
frequently to contradict the facts of development as directly
observed ^ Moreover, regard was had only to those measure-
ments of divergence on the continuous genetic spiral which
were taken on the matured stem, while there was always the
possibility that the divergences might have been different at
the first, and been afterwards modified, as Nageli subsequently
suggested ^. And again, the theory had a dangerous adversary
to encounter in the frequent occurrence of leaves that are
strictly alternate or crossed in pairs, and to conceive of this as
a spiral arrangement must at once appear to be an arbitrary
proceeding both from the mathematical point of view and from
that of historical development ; the assumption of a return of
the genetic spiral from leaf to leaf, as for instance in the
Grasses, like the prosenthesis in the change of divergence,
afforded, it is true, a construction which was geometrically
correct, but which could hardly be made to agree with the

^ See Hofmeister, 'Allgemeine Morphologic' (1868), pp. 471, 479, and
Sachs, ' Lehrbuch der Botanik,' ed. 4 (1874), p. 195.

^ See Nageli, ' Beitrage zur Wissenschaftlichen Botanik ' (1858), I, pp. 40,
49.

Chap. IV.] Mctamorphosis mid of tkc Spiral Thcory. 167

history of development and the mechanical forces concerned.
Again, it was a great and essential defect in the theory, that in
assuming the spiral arrangement it entirely neglected the
relations of symmetry of the plant-form, which are in many
cases clearly expressed, and their connection with the outer
world, on which Hugo von Mohl had already published some
excellent remarks in 1836, — a defect, which unhappily is not
yet sufficiently appreciated. A due consideration of these
objections, and of the cases in which the history of develop-
ment is opposed to the constructions of the theory, must have
led to the conviction that the idea of a spiral tendency in the
growth of plants is at least not borne out in all cases, and
more profound reflexion would show, that a scientific prin-
ciple, really explaining the phenomena, is no more to be
found in the assumption of such a general tendency, than in
a like assumption with regard to the heavenly bodies, that
they have a tendency to elliptic movement because they com-
monly move in ellipses. Hence Hofmeister, the latest investi-
gator of the doctrine of phyllotaxis on the basis of the history
of development, comes to the conclusion that the notion of
a screw-shaped or spiral course of evolution of lateral members
of plants is not merely an unsuitable hypothesis, but an error.
Its unreserved abandonment is, he considers, the first con-
dition for attaining an insight into the proximate causes of the
varieties of relative position in the vegetable kingdom. But
this judgment, correct as it is, was pronounced thirty years
after the appearance of Schimper's theory ; history, which
speaks from another point of view, and not only enquires into
the correctness of a theory but has to appraise its historical
importance, speaks in a less unfavourable manner. The chief
point here is not whether the theory was right, but how far it
contributed to the advance of the science. It was distinctly
fruitful in results, for it brought the important question of the
relative positions of organs for the first time into the front
rank in the study of morphology ; we may even say that a

1 68 Morphology under the Doctrine of [Book i.

large part of the results of the study of the history of develop-
ment were first brought into the true light by the consistent
application of the theory, or in the effort to disprove it. With
all its fundamental errors, Schimper's theory remains one of
the most interesting phenomena in the history of morpho-
logy, because it was carried out with thorough logical consist-
ency. We should as little wish to omit it from our litera-
ture, as modern astronomy would wish to see the old theory
of epicycles disappear from its history. Both theories
served to connect together the facts that were known in their
time.

The fundamental error of the theory lies much deeper than
appears at first sight. Here too we have the idealistic con-
ception of nature, which refuses to know anything of the
causal nexus, because it takes organic forms for the ever-
recurring copies of eternal ideas, and in accordance with this
platonic sphere of thought confounds the abstractions of the
mind with the objective existence of things. This confusion
shows itself in Schimper's doctrine, inasmuch as he takes the
geometrical constructions, which he transfers to his plants and
which, though they may be highly suitable from his point of
view, are nevertheless purely arbitrary, for actual characters of
the plants themselves, in other words, takes the subjective
connection of the leaves by a spiral line for a tendency
inherent in the nature of the plant. Schimper in making his
constructions overlooked the fact that, because a circle can be
described by turning a radius round one of its extremities, it does
not follow that circular surfaces in nature must really have been
formed in this way; in other words, he did not see that the
geometrical consideration of arrangements in space, useful as it
may otherwise be, gives no account of the causes to which they
are due. But this was not properly an oversight in Schimper's
case, for he would have scarcely admitted efficient causes in
the true scientific sense into his explanations of the form of
plants. How far Schimper was from regarding plants as some-

Chap. IV.] Mctamovpliosis and of the Spiral Thcory. 169

thing coming into being in time and according to natural laws,
how profoundly he despised the principles of modern natural
science is shown in his judgment of Darwin's theory of descent
and of the modern atomic theory, the coarseness of which is
the more surprising, because Schimper was a man of refined and
even poetic feeling. ' Darwin's doctrine of breeding,' he says,
'is, as I discovered at once and could not help perceiving
more and more after repeated and careful perusal, the most
shortsighted possible, most stupidly mean and brutal, much
more paltry even than that of the tesselated atoms with which
a modern buffoon and hired forger has tried to entertain us.'
Here is the old platonic view of nature flying at modern
science ; the sternest ' opposites ' that culture has ever
produced.

The theory of Schimper, which should rather be called
the theory of Schimper and Braun, considering the active part
which Braun took from the first in framing and applying it,
was capable of further development only in the mathematical
and formal direction, as was shown especially in Naumann's
essay, * Ueber den Quincunx als Grundgesetz der Blattstellung
vieler Pflanzen' (1845). The defects above described, but not
the merits of the theory were shared by the doctrine of phyl-
lotaxis laid down about ten years later by the brothers Louis
and Auguste Bravais. Their theory makes use of mathematical
formulae to even a greater extent than that of Schimper with-
out paying any attention to genetic conditions, and yet it is
less consistent with itself, for it assumes two thoroughly different
kinds of phyllotaxis, the positions in which are arranged in a
straight and in a curved line; for the latter without any
apparent reason a purely ideal original divergence is assumed
which stands in irrational relation to the circumference of the
stem, and from it all other divergences should be derivable ;
and this ultimately degenerates into mere playing with figures
which in this form afford no deeper insight into the causes
of the relations of position. As regards serviceableness in the

1 70 Morphology under the Doctrine of [Book i,

methodic description of plants the theory of the brothers
Bravais is much inferior to that of Schimper \

The genetic morphology founded about the year 1840 had
to make the best terms it could with the doctrine of phyllotaxis,
which was constructed on a totally different principle ; the two
went their way on the whole side by side without disturbance
from one another till the year 1868, when Hofmeister in his
general morphology attacked the principle of Schimper's theory,
and endeavoured to substitute a genetic and mechanical ex-
planation of the relative positions for the purely formal account
of them ; this attempt however, which from the nature of the
case has not yet led to a finished theory but nevertheless
contains the germ of a further development of this important
doctrine, does not come within the scope of this history.

The doctrine of phyllotaxis of Schimper and Braun, as it
appeared after 1830, had clearly presented only one side of the
theory of metamorphosis ; what other elements there were in it
capable of being turned to speculative account were further culti-
vated by Alexander Braun between the years 1840 and i860.
In this period fresh points of view were asserting themselves in
botanical research ; the founding of the doctrine of cells, the
study of the more delicate anatomy of plants and of the history
of development, and increased methodical knowledge of the
Cryptogams were enlarging the repertory of botanical facts,
while the physico-mechanical method of investigation was
being more and more adopted. Braun, who took an active
part by his own researches in this revolution in morphological
botany, remained true nevertheless to idealistic views ; and in
his frequent and comprehensive discussions of the general
results of the new investigations in accordance with these
views he has shown how far the idealistic platonising con-

1 A comparison of the two theories and a refutation of Schleiden's asser-
tion, that that of the brothers Bravais expresses better 'the simplicity of the
law,' will be found in ' Flora,' 1847, No. 13, from the pen of Sendtner,
and in Braun's ' Verjiingung,' p. 126.

Chap. IV.] Mdamorphosis and of the Spiral Thcovy. 171

templation of nature is in a condition to do justice to the
results of exact inductive enquiry. The opposition between
his point of view and that of the most eminent representatives
of the inductive method became more and more pronounced
as years went on, and must be treated here as a historical fact.
But if the new tendency in botany pursued especially by von
Mohl, Schleiden, Nageli, Unger, and Hofmeister may be called
inductive in the absence of a better term, and be contrasted with
the idealistic tendency represented by Braun and his school, it
must not be supposed that the latter did not equally contribute
in matters of detail to the enriching of the science by the
method of induction ; on the contrary, Braun himself was the
author of a series of important works conceived in this spirit.
When the new method is here called inductive, it should be
understood that the word is used in a higher than the usual
sense, and some explanation of this point will not be super-
fluous in this place. Idealistic views of nature of all times,
whether they present themselves as Platonism, Aristotelian
logic. Scholasticism or modern Idealism, have all of them this
in common, that they regard the highest knowledge attainable
by man as something already won and established ; the highest
axioms, the most comprehensive truths are supposed to be
already known, and the task of inductive enquiry is essentially
that of verifying them ; the results of observation serve to
elucidate already received views, to illustrate already known
truths ; inductive enquiry has only to establish individual facts.
But in the sense in which inductive enquiry was understood
by Bacon, Locke, Hume, Kant, and Lange, its task is one
that goes essentially farther than this ; it must not be content
with establishing individual facts, but it must employ them in
the critical examination of the most general notions that have
come down to us, and do its best to deduce new and com-
prehensive theories from them, even where these may be
entirely opposed to traditional views. But it is part of the very
nature of this method of investigation, that its general results

172 Morphology under the Doctrine of [bookI.

are subject to constant modification and improvement ; each
more general truth has only a temporary value, and endures as
long as no new facts militate against it. The distinction there-
fore between idealism and the inductive method in the domain
of natural science comes to this, that the former fits new facts
into a scheme of old conceptions, the latter deduces new
conceptions from new facts ; the one is in its nature dogmatic
and intolerant, the other eminently critical ; the one is con-
servative, the other always pressing forwards ; the one inclines
to philosophic contemplation, the other to vigorous and
productive investigation. To this must be added one point
of great importance ; the idealistic view of nature, rejecting
causality, explains nature from notions of design, and is
teleological ; ethical and even theological elements are thus
introduced into natural science.

It is in this form that the distinction between the idealistic
view represented by Braun and the modern inductive mor-
phology presents itself to us. If it were the task of this history
only to record the discovery of new facts, it would be super-
fluous to allude to these differences here ; but then it would
also be impossible to estimate rightly that portion of Braun's
long scientific labours which is at once the most original and
the most interesting from the historical point of view, and
which is to be found not so much in his many descriptive and
monographic works, as in his philosophic efforts in the domain
of morphology; these moreover deserve our consideration,
because they carry out Goethe's half-explained conceptions to
their remotest consequences, and express in purer form the ideal-
ism which lies at the foundation of the older nature-philosophy.
No botanist since Cesalpino has so thoroughly endeavoured to
leaven the entire results of inductive investigation with the prin-
ciples of an idealistic philosophy, and to explain them in its light.

Braun's philosophical views not only accompany his know-
ledge of facts, but everywhere permeate and colour it ; in his
writings, contributions, and monographs on the most various

Chap. IV.] MetamoKpliosis and of the Spiral Theory. 173

subjects, facts are regarded from the point of view of his
philosophy. He has given a general view of his philosophical
principles and illustrated them by a vast variety of facts in his
famous book, ' Betrachtungen iiber die Erscheinung der
Verjiingung in der Natur, insbesondere in der Lcbens- und
Bildungsgeschichte der Pflanze ' (1849-50). He himself directs
attention to the opposition between his own stand-point and
the modern induction in the tenth page of the preface, where
he replies to the obvious objection, that his ideas may be
regarded as antiquated, in the words, ' A more living contem-
plation of nature, such as is here attempted, which seeks in
natural bodies not merely the operation of dead forces, but the
expression of a living fact, does not lead, as is supposed, to
airy structures of fancy, for it does not pretend to gain a
knowledge of life in nature in any other way than as it is
revealed in phenomena,' etc. This thought is still more
distinctly uttered in page 13 of the text; 'As external nature
without mankind presents to us only the spectacle of a laby-
rinth without a guide, so too scientific contemplation, which
denies the inner spiritual principle in nature and the intimate
connection of nature with the informing spirit^, leads to a chaos
of substances and forces, which are unknown because divorced
from spirit, or, to speak more precisely, to a chaos of nothing
but unknown causes, which work together in an inexplicable
manner.' In a note to this passage he points expressly to * the
comfortless character of such an unreal mode of viewing nature,
which must necessarily endeavour to root out everything in the
conceptions and language of science which appears from its
own point of view to be anthropopathic,' and he requires a
tender, ethical element as essential to botanical investiga-
tion. The chief object of the volume is to prove that every-
thing in organic life may be resolved into rejuvenescence, of

' This is not at all true of modern inductive science, which merely forms
a different idea of the connection, and has regard to the relation between the
percipient subject and the phenomena.

174 Morphology under the Doctrine of [Book i.

which idea no definition is actually given, though the whole
contents of the book are a search after a definition. We
may regard the idea of rejuvenescence, as presented by
Braun, as an extension of the idea of metamorphosis, in which
extended form it is adapted to take in even the results
of the cell-theory, of the history of development, and of the
modern knowledge of the Cryptogams from the idealistic
point of view. One peculiarity of his mode of expounding his
views is observed here, as on other occasions, namely, that he
gives no precise and arbitrary definition to a word, for instance,
like rejuvenescence in the present place, and in a later work to
the word individual, but looks behind the word for a profound
or even mysterious meaning, which is to be perceived and
brought to light by contemplation of the phenomena. In
page 5 he says, ' Thus we see youth and age appear alternately
in one and the same history of development ; we see youth
burst through age, and by growth or transformation step into
the middle of the development. This is the phenomenon of
rejuvenescence, which is repeated in endless multiplicity in
every province of life, but nowhere appears more clearly
expressed or more accessible to investigation than in the
vegetable kingdom. Without rejuvenescence there is no
history of development.' — ' If then we ask for the causes of
the phenomena of rejuvenescence (page 7), we shall indeed
allow that nature, into which special life enters in its various
manifestations, excites, awakes, and works by the influences
which the years and even the days bring with them ; but the
true and inner cause can only be found in the desire after
perfection which belongs to every being in its kind, and urges
it to bring the outer world, which is strange to it, more and
more into complete subjection to itself, and to fashion itself in
it as independently as its specific nature admits.' Further
on he says (page 1 7), ' The impulse or tendency to develop-
ment in each creature is likewise no direction of activity
impressed from without, but one given from within and

Chap. IV.] M ctamorpkosis and of the Spiral Theory. 175

working as an inner determination and force from the depth
of the inner nature.' A passage also from page 1 1 1 of his
treatise on polyembryony, [)ubh'shed in i860, may be quoted
here ; 'Though the organism, in the process of reaUsing itself,
is subject to physical conditions, yet the proper causes of its
morphological and biological characteristics do not lie in these
conditions ; its laws belong to a higher stage of development
of its being, to a sphere in which the faculty of self-deter-
mination is distinctly manifested. If this is so, the laws of an
organic being appear as tasks imposed, the fulfilling of which
is not absolutely necessary but only in relation to the attain-
ment of a definite end, as precepts, to which strict obedience
may possibly not be paid.' To return once more to the idea
of rejuvenescence, we find at page 18 the words, 'As regards
the idea of rejuvenescence, from the foregoing considerations
we draw the conclusion, that the surrender of growths already
accomplished and the going back to new beginnings, the com-
mencement of rejuvenescence, indicate only the outer side of
the proceeding, while the essential part of it is an inner gather-
ing up of forces, a new creating, as it were, out of the indi-
vidual principle of life, a fresh reflecting upon the specific task
or the gaining renewed hold upon the type which is to be
presented in the outer organism. By this means rejuven-
escence maintains its fixed relation to development, which can
and ought to present in gradually attained perfection that only
which lies in the nature of the creature, and is most intimately
its own.' And at the conclusion of the work (page 347) he
says, 'The way in which the inner spiritual nature of life is
specially manifested in the phenomenon of rejuvenescence may
be defined as reminiscence in the true sense of the word, as the
power of grasping anew in the phenomenon the inner destination
of life as contrasted with its daily alienation and decay, and apply-
ing it with renewed strength towards that which is without,' etc.
This conception of rejuvenescence is, then, applied to all the
phenomena of life in plants ; not only the metamorphosis of

176 Morphology under the Doctrine oj [Book i.

leaves, the formation of shoots and their ramification, and the
different modes of cell-formation, but even palaeontological
facts are manifestations of rejuvenescence, which in the sequel
puts off the form of an abstract idea, and becomes personified
into an active personality, as is seen in page 8 in the expression,
' activity of rejuvenescence.'

The relation of Braun's views to the question of the con-
stancy of species may to some extent appear doubtful ; some
utterances of his may be interpreted to admit a transmutation
of species accomplished in the course of ages, while others are
opposed to this, and it is the latter which appear to be consis-
tent with the idealistic position. We read, for instance, at
page 9, ' The appearance, as though the like was always repeat-
ing itself in nature, is suggested when we glance back from our
station in time upon the succession of former epochs. Here
we find the real first beginnings of species and genera, and
even of orders and classes in the vegetable and animal king-
doms ; we see at the same time that more or less thorough
transformations are connected with the appearance of the
higher grades in the organic kingdom, so that genera and
species of the old world disappear, and new ones step into
their place. All this change expresses not the mere accident
of convulsions, which, while they destroy, at the same time
prepare new ground for the prosperity of organic nature, but
rather definite laws whose action pervades all the individual
detail of the development of organic life.' On the other hand we
find at the conclusion of the treatise on polyembryony, written
a short time before the appearance of Darwin's memorable
work, a sentence which makes the assumption of a transmuta-
tion of species appear very doubtful; it says (page 257), 'If
we are justified in assuming a general organic connection in
the history of development in plant-forms, can we imagine
that the type of the Mosses and of the Ferns has come from
the Algae, or vice versa, that the Alga-form owes its origin to
the Mosses and Ferns ? '

Chap. IV.] McfamorpJiosis and of tJic Spiral Tlicory. I'j'j

The sentences here quoted to show Braun's philosophical
position still give no idea of the way in which the principles
embodied in them influence the whole manner of presenting
the facts in the arrangement of his empirical material, but to
give a clear idea of this is impossible in so brief a notice as the
present. His conception of his subject is shown still more
distinctly in a treatise which appeared three years later, entitled
' Das Individuum der Pflanze in seinem Verhiiltniss zur Species,
Generationsfolge, Generationswechsel und Generationstheilung
der Pflanze' (1852-3V The definition of the word individual
is here sought, as that of rejuvenescence was in the previous
work, — a really difficult task, if we consider how many
meanings have been assigned to this word in the course of
time ; in the individuals or atoms of Epicurus, the individuals
or monads of Leibnitz, the atoms of modern chemistry, the
speculations of the schoolmen on the ' principium individua-
tionis' as opposed to the reality which they assigned to universal
conceptions, and in the customary application of the word in
every-day language, in which a man or a single tree is called
an individual, we have the general views of various centuries,
showing how the sense and meaning of old words become
changed, not unfrequently into their exact opposites. From
the nominalist position of modern natural science this is
of little importance, because this treats words and ideas as
mere instruments for mutual understanding, and seeks no
meaning in either which has not been previously and purposely
assigned to them. Braun's mode of proceeding is quite differ-
ent ; by comparison of very various phenomena of vegetation,
and by examining former views on the subject of the individual
plant, he seeks to demonstrate a deeper meaning which must
be connected with the word.

Moreover, he makes the enquiry into the individual only a
thread on which to string his own reflections, in the course of
which he once more explains the principles of the teleological
nature-philosophy, and points out its opposition to modern

N

178 Morphology under the Doctrine of [BookI.

science, the latter being grievously misrepresented as material-
istic, its atoms qualified as dead, its forces as blind. It would
scarcely be guessed from Braun's account that the history of
philosophy could point to Bacon, Locke, and Kant, as well as
to Aristotle, that even the question of the individual had
been already handled by the schoolmen. A consideration of
the other point of view would have been all the more profitable,
since the author in the beginning of his treatise expresses the
opinion that the doctrine of the individual belongs to the
elements of botany ; it might certainly be maintained that it is
altogether superfluous.

His train of thought in search of that which must be called
an individual in the vegetable kingdom is briefly as follows :
In forming a conception of the plant-individual as the unity of
a cycle of formation or a morphological whole, our chief
difficulty lies in the division into parts and the divisibility
(Getheiltheit und Theilbarkeit) which are present in the very
different stages of the organic structure of plants. It is requisite
therefore to find the middle way between the morphological
consideration of the individual plant which breaks up the
whole from above downwards, and the physiological which
extends it in the upward direction beyond all hmits. Neither
the leaf-bearing shoots, though they are capable of developing
into independent plants, nor the parts of them, which have the
same power, neither the single cells, nor the granules they
contain, and least of all the atoms of dead matter which are
the sport of blind forces, would answer to the idea of the indi-
vidual in plants. We have therefore to decide which member
of this many-graded series of potences in the cycle of develop-
ment subordinated to the species deserves by preference the
name of individual (p. 48). A compromise is then made ; it
is sufficient to find a part of the plant which answers above all
others to the idea of the individual, for in this idea there must
be two genetic forces, multiplicity and unity. He then decides
for the shoot or bud. ' In contemplating the plant-stem which

Chap. IV.] Metauiorphosis ttud of the Spiral Thcovy. 179

is usually branched, especially a tree with its many branches,
mere instinctive feeling awakens the suspicion that it is not
a single being, a single life, to be classed with the individual
animal or individual man, but that it is a world of united
individuals which spring from one another in a succession of
generations,' etc. He proceeds to show that this conception,
arising as it does from a sound, natural feeling, is also con-
firmed by scientific examination. It appears, however, that
many phenomena in the growth of plants will not fall in well
with this instinctive feeling, and so he says at page 69, 'We
cut the Gordian knot in this way, that if we have other and
sufficient grounds for regarding branches as individuals, we
come to the determination to let every branch pass for an indi-
vidual, however strongly the appearance may be against it.'
The shoot is therefore the morphological individual in the
plant, and is analogous to the individual animal. It may
certainly be objected, that we may cut the knot in another way
and maintain with Schleiden that the cells are the individuals
in the vegetable kingdom, if we do not actually arrive by the
same path at calling each atom, or at the other end of the
scale the whole self-nourishing plant, an individual, for about
equally strong reasons might be adduced for both one and the
other of these views. It all depends on the point of view we
adopt in such speculations, and on the weight we allow to
instinctive feeling in establishing scientific ideas. Braun
declares very decidedly in page 39 against the notion that the
invisible ' individua ' or atoms of dead matter can be introduced
into the consideration of the plant-individual, as though the
plant were a mere concrete of mutually attracting and repelling
atoms. If, he says, we will understand by the term individual
something absolutely indivisible, this is certainly the last resort,
but then we shall have no plant-individual. Moreover, no eye
has ever seen these atoms ; their assumption is a mere hypo-
thesis, which we may confront with the other hypothesis of the
continuity and permeability of matter. The question therefore,

N 2

i8o Morphology under the Doctrine of [Booki.

he says, at page 39, is whether we can speak of individuals in
plants at all, and this coincides with the other question,
whether the plant is a mere product of the activity of matter,
and so an unsubstantial appearance in the general circulation
of nature, the offspring of blind agencies, or whether it possesses
a peculiar and independent existence. The views of the phy-
siologists, who reject the vital force and explain the phenomena
of life by physical and chemical laws, have robbed life of its
mysterious and most directly operative principle, and pulled
down the strong wall of separation between organic and in-
organic nature. * Because physical forces appear to be every-
where confined to matter and show in their operation a strict
subjection to law, men have ventured to regard the sum total of
natural phenomena as the result of original matter working in
conjunction with definite powers according to the laws of
blind necessity, as a natural mechanism moving in endless
circulation.' But he objects that the eternally necessary can
only be conceived of as accomplished from all eternity, and
thus this physical view would make all eventuality inconceiv-
able. Further, the purpose of the movement of nature must
remain an insoluble enigma in this scheme of blind necessity.
' The inadequateness of the so-called physical view of nature as
compared with the teleological is therefore most felt in the
domain of organic nature, where special purpose in the
phenomena of life appears everywhere in greatest distinctness.'
The last remark is indisputable so long as we maintain either
the constancy of species or a merely internal law of develop-
ment ; the solution of the enigma was discovered a few years
later in Darwin's hypothesis, that all adaptations of organisms
are to be explained by the maintenance or suppression of
varieties, according as they are well or ill provided with the
means of sustaining the struggle for existence. No other
refutation or rather explanation of teleology in the science of
organic life has hitherto been attempted. It has been already
pointed out that systematic botany, by establishing the fact of

Chap. IV.] Mctamorphosis and of the Spiral Tkcovy. i8i

affinity, saw itself compelled at last to give up the constancy of
specific forms in order to make this fact intelligible, and
here we see how the idea of the adaptation of organisms is
found to conflict with causality, unless we assume that the
forms which arise through variation only maintain themselves,
if they are sufficiently adapted to the surrounding conditions.

The movement which began with Goethe and the nature-
philosophy assumed a clearer form, found its purest expression,
and revealed its most hidden treasures in the writings of
Schimper and Alexander Braun ; it would be superfluous to
submit to a detailed review the numerous works of less impor-
tant representatives of these views.

We turn from this realm of idealistic philosophy and imagin-
ation, from rejuvenescence, the wave-pulse of metamorphosis,
the spiral tendency of growth, and the individuality of plants, to
the last chapter of our history of systematic botany and mor-
phology, where there is less dogmatism and less poetry, but a
firmer ground on which will spring an unexpected wealth of
new discoveries and of deeper insight into the nature of the
vegetable world.

CHAPTER V.

Morphology and Systematic Botany under the

Influence of the History of Development and the

Knowledge of the Cryptogams.

I 840-1 860.

In the years immediately before and after 1840 a new life
began to stir in all parts of botanical research, in anatomy,
physiology, and morphology. Morphology was now specially
connected with renewed investigations into the sexuality of
plants and into embryology, and attention was no longer con-
fined to the Phanerogams but was extended to the higher and
later on to the lower Cryptogams. These researches into the
history of development first became possible, when von Mohl
had restored the study of anatomy, and Nageli had founded and
elaborated the theory of cell-formation about the year 1845.
The success of both these enquirers was due to the previous
development of the art of microscopy ; it was the microscope
which revealed the facts on which the foundations of the new
researclj were laid, while its promoters at the same time
started from other philosophical principles than those which
had hitherto prevailed among botanists. Investigation by
means of the microscope enforces on the observer the very
highest strain of attention and its concentration on a definite
object, while at the same time a definite question to be
decided by the observation has always to be kept before the
mind ; there are sources of error on all sides to be avoided,
and possible deceptions to be taken into consideration ; the

Morphology and Systematic Botany. 183

securing of the facts demands all the powers which specially
display the individual character of the observer. Thus serious
attention to microscopy was one of the causes which intro-
duced the best observers to the practice of inductive enquiry,
and gave them an insight into its nature ; and in a few years'
time when the actual results of these investigations began
to appear, and when a wholly new world disclosed itself to
botanists, especially in the Cryptogams, then questions arose
on which the dogmatic philosophy had not essayed its ancient
strength ; the facts and the questions were new and untouched,
and presented themselves to unprejudiced observation in a
purer form than those, which during the first three centuries
had been so mixed up with the old philosopliy and with the
principles of scholasticism. Von Mohl, who only occasionally
occupied himself with morphological subjects, was a firm
adherent of the inductive method, and was bent on the
establishment of individual facts rather than of general
principles ; but the founders also of the new morpholog}-,
Schleiden and Nageli, started from philosophical points of
view, which, different as they were in the two men, had yet
two things in common, a demand for severely inductive
investigation as the foundation of all science, and the rejection
of all teleological modes of explaining phenomena, in which
latter point their opposition to the idealistic nature-philosophy
school was most distinctly manifested. They had indeed one
very important point of contact with this school, the belief in
the constancy of organic forms ; but this belief, not being
connected with the Platonic doctrine of ideas, was with them
only a recognition of every-day observations, and was therefore
of less fundamental importance, being felt merely as an
inconvenient element in the science. Treating the question
in this way, and influenced by the results of the new researches,
they either inclined to entertain the idea of descent before the
appearance of Darwin's great work, or gave a ready assent to
the principle of the new doctrine, though they expressed some

1 84 Morphology and Systematic Botany under [Book i.

doubts respecting matters of detail. Hofmeister's researches
in morphology and embryology (' Vergleichende Untersuch-
ungen,' 1851) threw an entirely new light on the relations of
affinity between the great groups in the vegetable kingdom,
and were leading more and more to the view, that there must
be some special peculiarity in the question of the constancy
of organic forms. But the idea of evolution in the vegetable
kingdom was brought more distinctly home to men's minds by
palaeontological researches; Sternberg (1820-1838), Brong-
niart (1828-1837), Goeppert (1837-1845), and Corda (1845)
made the flora of former ages the subject of careful study,
and compared fossil plants with living allied forms. Unger
especially, while advancing the knowledge of the structure
of cells and of vegetable anatomy and physiology, and generally
taking a prominent part in the development of the new botany,
applied the results of its investigations to the examination
of primeval vegetation, and showed the morphological and
systematic relations between past and existing floras. After
twenty years of preliminary study he declared distinctly in
1852, that the immutability of species is an illusion, that the
new species which have made their appearance in geological
periods are organically connected, the younger having arisen
from the elder ^ It was shown in the former chapter, how
about the same time the leading representative of idealistic
views, Alexander Braun, was driven to the hypothesis, though
in a more indefinite form, of an evolution of the vegetable
kingdom : and in the year that Darwin's book on the origin
of species appeared, Nageli (' Beitrage,' ii. p. 34) wrote : —
' External reasons, supplied by the comparison of the floras of
successive geological periods, and internal reasons given in
physiological and morphological laws of development and
in the variability of the species, leave scarcely a doubt that
species have proceeded one from another.'

^ See A. Bayer, ' Leben und Wirken F. Unger's,' Gratz (1872), p. 52.

Chap, v.] the Influence of the Histovy of Development. 185

Though these words might not contain a theory of descent
capable at once of scientific appHcation, yet they show that
the latest researches and candid appreciation of facts were
compelling the most eminent representatives of the botany
of the day to give up the constancy of forms. At the same
time in the genetic morphology which had developed itself
mainly under Nageli's guidance since 1844, and still more in
embr)'ology, which in Hofmeister's hands was leading to results
of the greatest systematic importance, there lay a fruitful
element destined to correct and enrich Darwin's doctrine of
descent in one essential point. That doctrine in its original
form sought to show that selection, the result of the struggle
for existence, combined with perpetual variation was the sole
cause of progressive improvement in organic forms ^ ; but
Nageli, relying on the results of German morphology, was able
as early as 1865 to point out that this explanation was not
satisfactory, because it leaves unnoticed certain morphological
relations, especially between the large divisions of the vege-
table kingdom, which scarcely seem explainable by mere
selection in breeding. While Nageli allowed that Darwin's
principle of selection was well adapted to explain fully the
adaptation of organisms to their environment and the
suitableness and physiological peculiarities of their structure,
he pointed out that in the nature of plants themselves there
are intimations of laws of variation, which lead to a perfecting
of organic forms and to their progressive differentiation, in-
dependently of the struggle for existence and of natural
selection ; the importance of this result of morphological
research has since been recognised by Darwin. Thus Nageli
supplied what was wanting in the theory of descent and gave
it the form, in which it is adequate to explain the problem
already recognised by the systematists of the old persuasion,

' See Darwin's repudiation of this statement on p. 421 of Ed. 6 of the
' Origin of Species.'

1 86 Morphology and Systematic Botany under [Book i,

namely, how it is possible for the morphological affinity of
species in the system to be in so high a degree independent of
their physiological adaptation to their environment.

The modern teaching on vegetable cells, modern anatomy,
and morphology, and the improved form of the theory of
selection are the product of inductive enquiry since 1840,
a product, the full importance of which will be described
in the following portions of our history. At present we have
to deal only with morphological and systematic results, and
therefore with a part only of the abundant labours of the
botanists who will be noticed in this chapter ; the remainder
will be reserved for succeeding books, which contain the
history of the anatomy and physiology of plants.

It is one of the characteristic features of this period of
botany, that morphology enters into the closest connection
with the doctrine of the cell, with anatomy and embryology,
and that researches, especially into the process of fecundation
and the formation of the embryo, form to some extent the
central point of morphological and systematic investigations.
A strict separation of these various enquiries, which are all
ultimately applicable to the purposes of systematic botany, can
therefore scarcely be maintained, and least of all in dealing
with the lower Cryptogams.

The condition of botanical literature about the year 1840
was highly unsatisfactory ; it is true that eminent service was
rendered in the several domains of systematic botany, mor-
phology, anatomy, and physiology, and a number of von Mohl's
best works were produced in this period ; Meyen also,
Dutrochet, Ludolph Treviranus and others were cultivating
vegetable anatomy and physiology, and it has been already
stated that good and noticeable work was done in the previous
years in morphology and systematic botany. But there was
no one to put together, to criticise and apply the knowledge

Chap, v.] tJic Infliiciicc of tJic History of Dcvelopmcjif. 187

which had been accumulated in all parts of the science ;
no one really knew what a wealth there was at that time
of important facts ; least of all was it possible to form a
judgment on the matter from the text-books of the period,
which were deficient in ideas and facts, and crammed with
a superfluous terminology; their mode of treating their subject
was trivial and tasteless, and whatever was specially worth
knowing and important to the student they did not contain.
Those who undertook really scientific enquiries separated
themselves from those who dealt with botany after the old
schematism of the Linnaean school ; but botanical instruction,
the propagation of knowledge, was almost everywhere in the
hands of this school, though it was the one least fitted for the
task ; and thus a mass of lifeless phrases was the instruction
offered to the majority of students under the name of botany,
with the inevitable effect of repelling the more gifted natures
from the study. This was the evil result of the old and
foolish notion, that the sole or chief business of every botanist
is to trifle away time in plant-collecting in wood and meadow
and in rummaging in herbaria, — proceedings which could do
no good to systematic botany even as understood by the
Linnaean school. Even the better sort lost the sense for
higher knowledge while occupying themselves in this way with
the vegetable world ; the powers of the mind could not fail
after a time to deteriorate, and every text-book of the period
on every page supplies proof of this deterioration.

But such a condition of things is dangerous for every
science ; of what profit is it, that single men of superior merit
advance this or that part of the science when a connected
view of the whole is wanting, and the beginner has no opjjor-
tunity of studying the best things in their mutual relations.
However, the right man was found at the right moment to
rouse easy indolence from its torpor, and to show his con-
temporaries, not in Germany only but in all countries where
botany was studied, that no progress was possible in this

i88 Morphology and Systematic Botany under [BookI.

way. This man was Matthias Jacob Schleiden, born
at Hamburg in 1804, and for many years Professor in Jena.
Endowed with somewhat too great love of combat, and
armed with a pen regardless of the wounds it inflicted, ready
to strike at any moment, and very prone to exaggeration,
Schleiden was just the man needed in the state in which
botany then was. His first appearance on the scene was greeted
with joy by the most eminent among those who afterwards
contributed to the real advance of the science, though their
paths it is true diverged considerably at a later period, when
the time of reconstruction was come. If we were to estimate
Schleiden's merit only by the facts which he discovered, we
should scarcely place him above the level of ordinarily good
botanists ; we should have to reckon up a list of good mono-
graphs, numerous refutations of ancient errors and the like ;
the most important of the theories which he proposed, and
over which vigorous war was waged among botanists during
many years, have long since been set aside. His true his-
torical importance has been already intimated ; his great merit
as a botanist is due not to what he did as an original inves-
tigator, but to the impulse he gave to investigation, to the aim
and object which he set up for himself and others, and opposed
in its greatness to the petty character of the text-books. He
smoothed the way for those who could and would do really
great service ; he created, so to speak, for the first time an
audience for scientific botany capable of distinguishing scien-
tific work from frivolous dilettanteism. Whoever wished from
this time forward to take part in the discussion of botanical
subjects must address all his powers to the task, for he would
be judged by another standard than had hitherto prevailed.

Schleiden, who had commenced his botanical labours with
some important researches in anatomy and the history of
development, the most valuable of which in matter and form
was an enquiry into the development of the ovule before
fertilisation (1837), composed also a comprehensive text-book

Chap, v.] the Itijliicncc of the History of Development, 189

of general botany, which appeared first in 1842-3, and in much
improved editions in 1845 and 1846, and in two subsequent
years. The difference between this and all previous text-books
is the difference between day and night ; in the one, an
indolent carelessness and an absence of ideas ; in the other,
a fulness of life and thought, calculated to influence young
minds all the more, because it was in many respects incom-
plete and still in a state of fermentation. On every page of
this remarkable work, by the side of facts really worth know-
ing, the student found interesting reflections, a lively and
generally coarse polemic, and praise and blame of others. It
was not a book to be studied quietly and comfortably, but one
that excited the reader everywhere to take a side for or against,
and to seek for further instruction.

The work is generally quoted as ' Grundziige der wissenschaft-
lichen Botanik,' but its chief title is ' Die Botanik als inductive
Wissenschaft,' which indicates the point on which Schleiden
laid most stress. His great object was to place the study,
which had been so disfigured in the text-books as scarcely
to wear the semblance of a natural science, on the same foot-
ing with physics and chemistry, in which the spirit of genuine
inductive enquiry into nature had already asserted itself in
opposition to the nature-philosophy of the immediately pre-
ceding years. It may seem strange to us now to see a
text-book of botany introduced by a formal essay, 131
pages long, on the inductive method of investigation as
opposed to dogmatic philosophy, and to find the principles
of induction set forth again and again in connection with
a great variety of subjects in the book itself Many objec-
tions may be raised to the contents of this introduction ; it
may be said that many philosophical dicta are misunderstood in
it ; that Schleiden himself has frequently offended against the
rules there laid down, for instance, when he substitutes a
formative impulse (nisus formativus) for the vital force which
he rejects, which is only introducing vital force again under

190 Morphology and Systematic Botany under [Book l

another name ; that it is superfluous to present the history of
development as a ' maxim ' in Kant's use of the word, instead
of showing that the history of development enters naturally and
of itself into inductive investigation, and so on. All this will
not lessen the historical importance of this philosophic intro-
duction ; the traditional way in which descriptive botany was
at that time presented to the student was so thoroughly dog-
matic and scholastic, trivial and uncritical, that it was necessary
to impress upon him in many words, that this is not the
method of true investigation of nature.

Passing on to the more special problems of botanical en-
quiry, Schleiden next dwells on the history of development as
the foundation of all insight into morphology, though he over-
shot the mark when he rejected as unfruitful the simple com-
parative method, which had produced considerable results in
the hands of De Candolle, and was virtually the fruitful ele-
ment in the doctrine of phyllotaxis of Schimper and Braun.
Still he took an active part himself in the study of development
in plants, and gave special prominence to embryology ; he also
discussed the doctrine of metamorphosis from the point of
view of the history of development, and pointed to Caspar
Friedrich Wolff's treatment of that subject as much clearer
than that which had been introduced by Goethe. Finally,
Schleiden's mode of dealing with the natural system must be
reckoned among the good services which he rendered to
method ; not because his classification of the vegetable king-
dom presents any specially interesting features or brought to
light any new affinities, but because we see an attempt made
for the first time to give detailed characters drawn from mor-
phology and the history of development to the primary divi-
sions, and because by this means the positive and distinct
nature of the Cryptogams was from the first clearly brought
out. The old way of treating morphology, as though there
were only Phanerogams in the world, and then having recourse
to unmeaning negatives in dealing with the Cryptogams, was

Chap, v.] tJic I)ijlitcucc of tlic Histo)y of Development. 191

thus set aside, much to the \)Xo^\\. of the immediate future,
which directed its attention specially to the Cryptogams.

Schleiden however did not succeed in securing firm ground
for the morphology of the Cryptogams as founded on the history
of their development. His investigations into the morphology
of the Phanerogams were more successful. His theory of the
flower and fruit is an admirable performance for the time, even
though we abandon his view of the stalk nature of placentas
and some other notions, as we obviously must. As Robert
Brown founded the history of the development of the ovule, so
Schleiden founded that of the flower, and his example influ-
enced other botanists. Soon investigations into the genesis
of the flower was one of the chief occupations of morpho-
logists, and the results of enquiry into development proved to
be of great value for the systematic arrangement of the Pha-
nerogams, especially when more exact attention was paid to
the sequence of development in the organs of an inflorescence,
to abortion, doubling and branching of the stamens, and to the
like matters. Duchartre, Wigand, Gelesnoff and many others,
were soon working in the same direction with great success.
Paver deserves special mention for his enormous perseverance
in examining the development of the flower in all the more
important families in his 'Organogenic de la fleur,' 1857, and
thus producing a standard work, distinguished alike for the
certainty of the observations, the simple unbiassed interpreta-
tion of the things observed, and the beauty and abundance of
the figures — a work which became more important every year
for the morphology of the flower.

Schleiden's text-book was the first of its kind that supplied
the student with really good figures based on careful ob-
servations. With all its many and obvious defects it had one
merit which cannot be rated too highly; its appearance at
once put botany on the footing of a natural science in the
modern sense of the word, and placed it upon a higher plat-
form, extending its horizon by raising its point of view.

192 Morphology and Systematic Botany under [BookI.

Botany appeared all at once as a science rich in subject-
matter; Schleiden had not only himself made many inves-
tigations and broached new theories, but he everywhere drew
attention to what was already before the world and was im-
portant; for it is not sufficient as regards the literature of
a science that there should be good investigators; it is as
necessary that the scientific public, and especially the rising
generation of professed students, should be well and sufficiently
instructed in the art of distinguishing important from unim-
portant contributions. It must be distinctly affirmed in this
place, that if Schleiden's theory of cell-formation, his strange
notion about the embryology of Phanerogams and the like
were very quickly shown to be untenable, this does not in the
least affect the great historical importance which his writings
possess in the sense here indicated.

That others besides Schleiden in the period following 1840
felt strongly, that botany must thenceforward give up its com-
placent resting in the old ideas, was shown among other things
by the addition at this time of new periodicals to the old journal
' Flora.' The ' Botanische Zeitung ' was founded by von Mohl
and Schlechtendal in 1843, and the 'Zeitschrift fiir wissenschaft-
liche Botanik ' by Schleiden and Nageli. The latter, however,
only lived three years, from 1844 to 1846, and was filled almost
entirely with Nageli's contributions. Both pubhcations expressly
set themselves the task of representing the new aims in the
science. The immediate consequence was that ' Flora '
braced up its energies, and endeavoured to do more justice
to the modern spirit ; excellent notices of botanical works now
appeared in it under the exclusive management of Fiirnrohr.

Schleiden's productivity in the higher sense of the word
expended itself in his labours on the elements of scientific
botany. His later somewhat discursive writings exerted no
great influence on the further development of the science.
The ideal which he had set up for scientific botany and had
sketched in its larger outlines, could only be realised by the

Chap.v,] the Influence of the Knowledge of Cryptogams. 1 93

most persevering labour not of one man only, but of whole
generations of observers and thinkers, nor did he apply him-
self with painful unremitting industry to the attainment of this
exalted aim.

Soon after Schleiden's ' Grundziige ' first stirred the scientific
world, a man of a verj' different character of mind began to
address himself to the great task. This was Carl Nageli,
whose researches from this time onwards laid the foundations
of knowledge in every department of botany. He showed what
points were the most immediately attainable, and aided in
perfecting the inductive method of enquiry and in advancing
the study of the history of development. He did not make
discoveries here and there by desultory efforts, but worked
with earnest endurance at every question which he took up till
he had arrived at a positive result ; and this was almost always
an enlargement of previous knowledge, and a new foundation on
which others might build, and a copious literature be developed.

Nageli like others felt the necessity of first determining his
position with respect to the philosophical principles of the
investigation of nature, but he did not proceed to give a
general exposition of the inductive method as opposed to the
dogmatism of the idealistic school. He went straight to the
application of the laws of induction to the most general
problems of organic nature, and specially of vegetation. It
is easy to say that the task of natural science is simply to
deduce conceptions and laws from the facts of experience by
aid of exact observation. Many considerations present them-
selves as soon as the attempt is made to satisfy this demand ;
for it is not enough merely to accumulate individual facts, the
point to which the inductive enquir}' is to lead must be kept
constantly and clearly before the mind. Nageli insisted that
it is only in this way that facts and observations have any
scientific value ; that the one important thing is to make every
single conception obtained by induction find its place in the
scheme of all the rest of our knowledge. With greater con-

o

1 94 Morphology and Systematic Botany under [Book i.

sistency of reasoning than Schleiden, and in entire accordance
with the nominahst view of genuine investigation of nature in
its sternest opposition to the ideahstic school, NageU's first
principle is not only to deduce conceptions from the observation
of phenomena, to classify them and establish their subordin-
ation, but to treat these conceptions as mere subjective pro-
ducts of the understanding and employ them as instruments
of thought and communication, and to be always ready to
modify them as soon as inductive enquiry renders such modi-
fication necessary. Till this happens, the conception once laid
down and connected with a word is to be strictly adhered to,
and every arbitrary change or confusion with another concep-
tion is strictly forbidden. Since in nature everything is in
movement, and every phenomenon is transitory, presenting
itself to us in organic life especially as the history of develop-
ment, all due regard must be paid to this condition of con-
stant motility in forming scientific conceptions. The history
of development is not merely to be treated generally as one
of various means of investigation, but as identical with inves-
tigation into organic nature. These views are expressed in
Nageli's detailed observations on method in the first and
second volume of the journal which he brought out in con-
junction with Schleiden in 1844 and 1855, where the chief
hindrance to his carrying them out fully and consistently is
also to be found; for, like all his contemporaries, Nageli be-
lieved at that time in the constancy of species, and consistently
with this view he looked upon the natural system as a frame-
work of conceptions, though these do not take the form of
Platonic ideas with him as with the systematists of the idealistic
school. It is equally consistent with his philosophical posi-
tion, which refused to regard a change in our conceptions as
a change in things themselves, that 'the idea of metamor-
phosis' in the sense of Goethe and Alexander Braun disap-
pears in Nageli from the field of scientific observation. It has
been shown in the previous chapter that what Goethe called

Chap, v.] fjic Injlueucc oftlic Kuoidcdgc of Cryptogams. 1 95

the normal or ascending metamorphosis has no scientific
meaning unless species are supposed to be variable. It ap-
peared moreover that if the Cryptogams are made the chief
subjects of investigation, as Niigeli made them, the so-called
metamorphosis of the leaves is a phenomenon of secondary
importance, and only attains to its full importance in the
Phanerogams. If Schleiden, illogically from his point of view,
conceived of metamorphosis as the principle of development,
Nageli on the contrary scarcely employed the word. He
regarded the history of development as the law of growth of
the organs, and, in accordance with the theory of the constancy
of species, the law of growth of every species and every organ
was invariable in the same sense in which we apply the term
to natural laws in physics and chemistry. In a word, Nageli's
considerations on the ' present task of natural history ' in the
work above cited, are not only logically and entirely consistent
on the principles of the inductive method, but they are also
consistent where others have been misled by the theory of the
constancy of species into illogical conclusions.

Nageli set himself in earnest to meet the demands of induc-
tive enquiry, such as he had himself described them. It will
be shown more in detail in the history of phytotomy, how he
satisfied these demands in his refutation of Schleiden's doctrine
of the cell, and in the establishment of his own, and at a later
time in the framing of his theory of molecular structure and of
the growth of organised bodies, and how he made these inves-
tigations true models of genuine inductive enquiry. Here we
are concerned only with what he effected in this way for mor-
phology and systematic botany. In this field of research he
introduced two innovations of the profoundest importance,
which affected both the aim and method of enquiry for some
years. He connected his own morphological investigations, as
far as possible, with the lower Cryptogams, extending them
afterwards to the higher Cr)ptogams and to the Phanerogams ;
that is, he proceeded from simple and plain facts to the more

O 2

1^6 Morphology and Systematic Botany under [booki.

difficult, thus not only introducing the Cryptogams into the
field of systematic investigation, but making them its starting-
point. In this way morphology not only secured a foundation
in exact historical development, but it assumed a different aspect,
inasmuch as the morphological ideas hitherto drawn from the
Phanerogams were now examined by the light of the history of
development in the Cryptogams. This was one innovation;
the second, closely connected with it, was the way in which
Nageli made the new doctrine of the cell the starting-point of
morphology. Both the first commencement of organs and their
further growth were carried back to the formation of the separ-
ate cells ; and the remarkable result was to show, that in the
Cryptogams especially, whose growth is intimately connected
with cell-division, precise conformity to law obtains in the suc-
cession and direction of the dividing walls, and that the origin
and further growth of every organ is effected by cells of an
absolutely fixed derivation. The most remarkable thing was,
that every stem and branch, every leaf or other organ has a
single cell at its apex, and that all succeeding cells are formed
by division of this one cell according to fixed laws, so that the
origin of all cell-tissue can be traced back to an apical cell ;
and as early as the years 1845 and 1846 Nageli described in
the ' Zeitschrift fiir wissenschaftliche Botanik ' the three main
forms, according to which the segmentation of an apical cell
proceeds, namely, in one, two, and three rows (Delesseria,
Echinomitrium, Phascum, Jungermannia, Moss-leaves). In
this way the separate points in the history of growth in the
Cryptogams were brought out with unusual clearness and
decision ; but on the other hand, Nageli showed in 1844 in the
case of a genus of Algae (Caulerpa) that the growth of a plant
may show the usual morphological differentiation into axis,
leaf, and root, when the propagative cell undergoes no cell-
divisions in the process of development and further growth,
and similar conditions were for the first time demonstrated in
1847 in Valonia, Udotea, and Acetabularia. Beside other

Chap. v.] tlic lujlitcucc oftlw Kiiowlcdge of Cryptogams. 197

results it was established by these facts, that morphological
differentiation during growth must not be regarded as an effect
of cell-divisions, and from such cases as these the conception
of the cell experienced a notable expansion.

Moreover, Nageli was not satisfied with seeking instructive
examples for general morphological axioms in the lower Cryp-
togams ; he devoted special study to the Algae for systematic
and descriptive purposes ; and his * Neuen Algensysteme,'
which appeared in 1847, and ' Gattungen einzelliger Algen,'
of 1849, were the first successful attempts to substitute serious
investigation for the mere zeal of the collector in this part of
the vegetable kingdom, which had not indeed been hitherto
neglected, but had not been systematically worked since the
time of Vaucher. In the same spirit Alexander Braun also in
his 'Verjiingung' contributed a rich material of new obser-
vations on the mode of life of the Algae and the morphological
conditions connected with it, and his labours were followed in
the succeeding years by the important researches of Thuret,
Pringsheim, De Bary, and others, to which we shall recur in a
later portion of this history.

But before the examination of the Algae, and soon after of
the Fungi also, led to such great results, the systematic botany
of the higher plants underwent important changes through the
methodical study of the embryology of the Muscineae and Vas-
cular Cryptogams. These groups had been frequently and
carefully examined by good observers since the last century,
and the systematists, without penetrating deeply into the
peculiarities of their organisation, had brought the species and
genera, the families and even the higher divisions into tolerable
order. Comprehensive and methodically arranged catalogues
of these plants had been formed, and attempts had been made
to explain their morphology by that of the Phanerogams;
SchmideH published valuable observations on the Liverworts

* Casimir Christoph Schmidel was born in 1 718 and died in 1792 ; he was

igS Morphology and Systematic Botany under [Booki.

in the year 1750, Hedwig especially on the Mosses in 1782 ;
these works were followed by Mirbel's thorough examina-
tion of Marchantia in 1835, by Bischoff's of Marchantieae
and Riccieae, by Schimper's study of the Mosses in 1850,
and by Lantzius Beninga's^ contributions to the knowledge
of the structure of the moss-capsule in 1847. The organ-
isation, and to some extent the germination, of the Vascular
Cryptogams had become better known since 1828 through
Bischoff's '^ researches; Unger had as early as 1837 described
the spermatozoids in the antheridia of various Mosses, Nageli
had discovered them on an organ of the Ferns which had up
to that time been taken for the cotyledonary leaf of these
plants, and on the same part of the plant Suminski in 1848
observed the female sexual organs and the entrance of the
spermatozoids into them. The history of the germination of
the Rhizocarps, from which Schleiden thought that he had
proved his erroneous theory of fertilisation with more than
usual certainty, had been examined some years before by
Nageli, and also by Mettenius, in great detail ; here too
Nageli detected the spermatozoids. Thus important fragments
of the life and organisation of these plants had been described
up to the year 1848, but until they were more fully understood
and connected together they had but little scientific value, the
one fact perhaps excepted, that fertilisation in the Cryptogams

Professor of Medicine in Erlangen, and was the first who described the sexual
organs in various Liverworts.

1 Lantzius Beninga, born in East Friesland in 1815, was a professor in Got-
tingen, and died in 1871.

^ Gottlieb Wilhelm Bischoff was bom at Diirkheim on the Hardt in 1 797,
and died as Professor of Botany at Heidelberg in 1854. He wrote various
manuals and text-books which are careful and industrious compilations, but
being entirely conceived in the spirit of the times preceding Schleiden they
are now obsolete ; his investigations however into the Hepaticae, Chara-
ceae, and Vascular Cryptogams, illustrated by very beautiful drawings
from his own hand, are still of value ; and the same may be said of his
' Handbuch der botanischen Terminologie und Systemkunde' on account
of its numerous figures.

Chap, v.] the Influence of the Knoivledge of Cryptogams. 1 99

as in animals was effected by spermatozoids. A perfect insight
into the embrj-ological conditions in question could only be
obtained when the embryology of the Phanerogams especially
had been cleared up, for according to Schleiden's theory, which
made the pollen-tube enter the embr)'o-sac in the ovule and
develop into the embryo, the ovule was no longer to be
regarded as a female sexual organ, but only as a place of incu-
bation for the embryo, which was thus really produced asexually.
This important question was set at rest by Wilhelm Hokmeis-
ter's work, ' Die Entstehung des Embryos der Phanerogamen,'
which appeared in 1849. ^'^ this work, and in a series of sub-
sequent treatises, he showed that the egg-cell is formed
in the embryo-sac before fertilisation, and that it is this which
is excited to further development by the appearance of the
pollen-tube, and produces the embryo. Hofmeister had
observed the organisation of the ovule, the nature of the
embryo-sac and of the pollen-grain, and the formation of the
embryo from the fertilised egg-cell step by step and cell by cell,
and his account of these processes was aided by the light which
Niigeli's theor}' of the cell, and his reference of all processes of
development to the processes of cell-formation, had thrown
upon the history of development. He went on to apply the
same method to the study of the embrj'ology of the Muscineae
and the Vascular Cryptogams, and followed the development
of the sexual organs cell by cell in a large number of species ; he
observed the origination of the egg-cell which was to be subse-
quently fertiHsed,and the formation of spermatozoids, and above
all he showed the divisions which take place in the fertilised
egg-cell, and the relation of its segments to the further growth of
the sexual product in course of formation. The whole course
of development in the Muscineae and Vascular Cryptogams
displayed a return twice repeated to the single cell as the
starting-point in each case of a new phase of development ; the
true relation between the asexually produced spore and its
germ-product on the one side, and the sexually generated

200 Morphology and Systematic Botany under [Book i,

embryo on the other, and their significance in the history of
development, were brought out clearly by Hofmeister's investi-
gation, while the exactness of his method rendered lengthy
discussions on the subject unnecessary. With these embryo-
logical processes, especially those of the Rhizocarps and
Selaginellae, in which the presence of two kinds of spores was
now for the first time correctly interpreted, Hofmeister com-
pared the embryology of the Conifers, and by their aid that
of the Angiosperms also.

The results of the investigations published in the ' Verglei-
chende Untersuchungen ' in 1849 and 1851 were magnificent
beyond all that has been achieved before or since in the domain
of descriptive botany ; the merit of the many valuable particu-
lars, shedding new light on the most diverse problems of the
cell-theory and of morphology, was lost in the splendour of the
total result, which the perspicuity of each separate description
revealed to the reader before he came to the conclusion of the
work, and there a few words in plain and simple style gave a
summary of the whole. Brieflly to describe this result in all its
importance for botanical science is a difficult task ; the idea of
what is meant by the development of a plant was suddenly and
completely changed; the intimate connection between such
different organisms as the Liverworts, the Mosses, the Ferns,
the Equisetaceae, the Rhizocarps, the Selaginellae, the Coni-
fers, the Monocotyledons, and Dicotyledons could now be
surveyed in all its relations with a distinctness never before
attained. Alternation of generations, lately shown to exist
though in quite different forms in the animal kingdom, was
proved to be the highest law of development, and to reign
according to a simple scheme throughout the whole long series
of these extremely different plants. It appeared most clearly
in the Ferns and Mosses, though at the same time with a
certain difference in each ; in the Ferns and allied Cryptogams
a small inconspicuous body grows out of the asexually produced
spore, and immediately produces the sexual organs ; from the

Ciup.v.] the Influence of the Knowledge of Cryptogams. 201

fertilisation of these organs proceeds the root-bearing and leafy
stem of the Fern, which in its turn again produces only asexual
spores. In the Muscineae, on the other hand, a much differ-
entiated and usually long-lived plant is developed from the
spore, and this plant proceeds again after some time to form
sexual organs, the product of which is the so-called Moss-plant.
The first generation that arose from the spore, the sexual, is in
the Muscineae the vegetative plant, while in the Ferns and their
allies the whole fulness of vital activity and of morphological
differentiation is unfolded in the second generation which is
asexually produced. Here all was at once clear and obvious ;
but Hofmeister's researches also showed that the same scheme
of development holds good in the Rhizocarps and Selaginellae
where two kinds of spores are formed ; and it appeared plainly
from their case that the recognition of the true relation between
the production of spores and sexual organs is the guide to the
morphological interpretation. When the processes in the large
female spore of the most perfect of the Cryptogams was known,
the formation of the seeds in the Conifers was at once under-
stood ; the embryo-sac in these answered to this large spore,
while the endosperm represented the prothallium,and the pollen-
grain the microspore ; the last trace of alternation of genera-
tions, so obvious in the Ferns and Mosses, was seen in the
formation of the seed in the Phanerogams. The changes,
which the alternation of generations passes through from the
Muscineae upwards to the Phanerogams, were, if possible, still
more surprising than the alternation of generations itself.

The reader of Hofmeister's ' Vergleichende Untersuchun-
gen ' was presented with a picture of genetic affinity between
Cryptogams and Phanerogams, which could not be recon-
ciled with the then reigning belief in the constancy of species.
He was invited to recognise a connection of development
which made the most different things appear to be closely
united together, the simplest Moss with Palms, Conifers, and
angiospermous trees, and which was incompatible with the

202 Morphology and Systematic Botany under [book i.

theory of original types. The assumption that every natural
group represents an idea was here quite out of place ; the
notion entertained up to that time of what was really meant by
the natural system had to be entirely altered ; it could as little
pass for a body of Platonic ideas as for a mere framework of
conceptions. But the effect of the work was great in respect
to the system also ; the Cryptogams were now the most
important objects in the study of morphology ; the Muscineae
were the standard by which the lower Cryptogams must be
tried, the Ferns were the measure for the Phanerogams.
Embryology was the thread which guided the observer through
the labyrinth of comparative and genetic morphology; meta-
morphosis now received its true meaning, when every organ
could be referred back to its parent-form, the staminal and
carpellary leaves of the Phanerogams, for example, to the
spore-bearing leaves of the Vascular Cryptogams. That
which Hackel, after the appearance of Darwin's book, called
the phylogenetic method, Hofmeister had long before actually
carried out, and with magnificent success. When Darwin's
theory was given to the world eight years after Hofmeister's
investigations, the relations of affinity between the great divi-
sions of the vegetable kingdom were so well established and so
patent, that the theory of descent had only to accept what
genetic morphology had actually brought to view.

So gorgeous a picture as Hofmeister had designed of the
genetic connection of the vegetable kingdom, except the
Thallophytes, could not possibly be completely perfect and
correct in all its separate features ; there were still many gaps
to fill up and particular observations to correct. Hofmeister
himself continued his labours ; the remarkable genera
Isoetes and Botrychium were in the following years more
carefully studied by himself, the fertilisation and embryology
of the Equisetaceae by himself and Milde, and those of
Ophioglossum by Mettenius, and all were fitted into their place
in the system. To the present day it is always a profitable

Chap, v.] the Influence of the Knoivledge of Cryptogams. 203

task to submit the different forms of the Muscineae, the
Vascular Cryptogams, and the Gymnosperms to exact inves-
tigation in order to ascertain all the details in the process
of development in these plants, the formation of the embryo,
the succession of cells at the apex, the first appearance and
further growth of the lateral organs ; and the more careful the
observation, the more clearly even to its farthest results does
the correctness of the alternation of generations asserted by
Hofmeister everywhere appear. It does not fall within the
limit of this history to pursue the subject further, and to show
how the doctrine of alternation of generations and the know-
ledge of the morphology of the Cryptogams were further
advanced by later and distinguished researches, such as those
of Cramer on the Equisetaceae, of Pringsheim on Salvinia
(1862), of Niigeli and Leitgeb on the formation of roots in the
Cryptogams, of Hanstein on the germination of the Rhizo-
carps, and of others.

Thallophvtes.

The method of investigation which starts from the first steps
towards the formation of the embryo before and after fertilisa-
tion, and follows the advancing segmentation and growth through
all the stages of development up to the final completion of the
embryo-plant, has led since 1850 in the case of the Muscineae,
Vascular Cryptogams, and Phanerogams to great certainty in
the morphological explanation of the organs, while the deter-
mination of affinities has ceased to be arbitrary and insecure ;
the way was now known which would lead to the desired end,
whenever it was sought to establish the affinities of a genus of
Cryptogams or of the larger groups of Phanerogams ; the day
of ingenious guessing and trying was over ; the only plan was
patient investigation, and this always yielded a result of lasting
value.

The case was quite different with the Thallophytes still in

304 Morphology and Systematic Botany under [Booki.

1850 ; what was certainly known about them only showed how
uncertain the rest was ; the Algae, Fungi, and Lichens pre-
sented a chaotic mass of obscure forms in contrast with the
well-ordered knowledge of the Muscineae and Vascular plants.
In the Mosses and Ferns the series of developments within the
limits of the species was so set forth in its several stages, that
all the important points in the advancing growth were clearly
ascertained, while the alternation of generations at once sharply
distinguished and connected together the chief sections in the
development ; on the other hand the development of the Algae
and Fungi seemed to break up into a disorderly and motley
throng of forms that appeared and disappeared, and it seemed
scarcely possible to discover their regular genetic connection.
Here the important point was to determine which of the known
forms belonged to one and the same cycle of development, for
these plants go back at the most various stages of development
to the segregation of single cells, which are the beginning of a
new development either repeating or carrying on the old one.
The beginnings of the most different species of Algae lay mixed
up together in the same drop of water, those of quite different
Fungi grew together and even upon one another on the same
substratum ; in the Lichens, Fungus and Alga were united
together. Such was the case with the small and microscopic
species; the large Seaweeds, the Mushrooms, and the large
Lichens were easier to distinguish specifically, but less if
possible was known of their developriient than of that of the
microscopic Thallophytes.

Nevertheless the knowledge of individual forms in these
organisms had been considerably extended before 1850.
Collectors and amateurs, intent only on determining what is
immediately presented to the eye and making little enquiry
into origin and affinities, were indefatigable in adding to their
collections, and made catalogues and proposed various systems
founded on external marks taken at pleasure. The names of
species were counted by thousands, their characters filled thick

chap.v.] the Influence of the Knowledge of Cryptogams. 205

volumes and the figures large folios ; the abundance of forms
in the Thallophytes proved to be so great that many botanists
devoted their whole attention to them, many collected and
described only the Algae, others only the Fungi and Lichens.
It is true that a deeper insight into the connection of these
forms of life with one another and with other plants was not to
be obtained in this way; still an empirical basis was formed
for a knowledge of the Cr)-pt ogams, such as had been estab-
lished for the Phanerogams by the herbals of the 17th century.
All forms open to observation were named and arranged in one
way or another : and there was no difficulty in understanding
what form was meant, when names, or tables and figures, were
cited from the various books. Of such works, those of
Agardh\ Harvey, and Kiitzing on the Algae, those of Nees
von Esenbeck", Elias Fries, Leveille, and Berkeley on the
Fungi, and especially Corda's elaborate work on the latter
plants are the most valuable.

^ Karl Adolf Agardh (1785-1859) was until 1835 Professor in Lund,
afterwards Bishop of Wermland and Dalsland. Jacob Georg Agardh, bom
in 1813, was Professor in Lund. William Henry Harvey (1811-1866) was
Professor of Botany in Dublin. Friedrich Traugott Kiitzing, bom in 1807,
was Professor in the Polytechnic School of Nordhausen.

' C. G. Nees von Esenbeck published his ' System der Pilze und
Schwamme ' in 1S16; Th. F. L. Nees von Esenbeck, in conjunction with
A. Henty, a ' System der Pilze' in 1837. The first (1776-1858) was for a
long time President of the Leopoldina, Professor of Botany in Breslau, and
one of the chief representatives of the nature-philosophy. Elias Fries, bom
in 1794, became Professor of Botany in Upsala in 1835 ; he died in 1878.
Leveille (i 796-1 870) was a physician in Paris. August Joseph Corda was
bom at Reichenberg in Bohemia in 1809, and became custodian of the
National Museum in Prague in 1835 ; he undertook a journey to Texas in
1848, from which he never returned, having probably perished by shipwreck
in 1849. Weitenweber, in the ' Abhandlungen der Bohmischen Gesell-
schaft der Wissenschaft, ' Bd. 7, Prag, 1852, gives a full account of this
eminent mycologist. Corda was the first who thoroughly applied the micro-
scope to copying and describing every form of Fungus that was known to him,
and especially the minuter ones. His'IconesFungorumhucusque cognitoram'
(1837-1854) are still an indispensable manual in the study of the subject.

3o6 Morphology and Systematic Botany under [Book i.

The views entertained on the subject of the development and
propagation of the lower Cryptogams down to the year 1850
were very uncertain and fluctuating. In some Algae, Fungi,
and Lichens certain organs of multiplication and propagation
were known, in others they were quite unknown ; some forms
appeared in places and under circumstances which seemed to
necessitate the assumption of spontaneous generation ; in 1827
Meyen declared that the small Algae, known as ' Priestley's
matter,' which are formed in stagnant water and even in closed
vessels, are produced by free generation, and Kiitzing endea-
voured to show this by experiment in 1833 ; some Fungi were
regarded as diseased growths from other organisms, many were
supposed to spring up spontaneously, though they might be
capable at the same time of propagating themselves by spores ;
this view was shared by even the best botanists with regard to
the most simple Fungi up to 1850. But the systematic inves-
tigation of the Algae and Fungi was as little hindered by
the notion of spontaneous generation after 1850 as that of
Phanerogams had been in the 17th century by the same
notion ; it was however at first affected by the view put forth
by Hornschuch in 1821 and by Kiitzing in 1833, that the
simplest of all Alga-ceils (Protococcus and Palmella), once
produced spontaneously, could develop according to circum-
stances into a variety of Algae, and even of Lichens and
Mosses; as some observers even now consider PeniciUium
and Micrococcus to be the starting-points of very different
Fungi. There was a difficulty also in drawing the boundary-
line between the lower animals and plants ; the difficulty was
solved by classing all objects capable of independent move-
ment with animals ; thus whole families of Algae (the
Volvocineae, Bacillariaceae, and others) were claimed by the
zoologists, and when the swarmspores of a genuine Alga were
seen for the first time in the act of escaping, the phenomenon
was described as the changing of the plant into an animal.
Trentepohl in 1807, and Unger in 1830, explained in this way

Chap. v.] thc Injliicuce of the Knowledge of Cryptogams. 207

the escape of the zoospores of Vaucheria. The remarkable
thing is, not that such views were entertained, but that the
majority of botanists combined with them a belief in the
constancy of species. But this dogma rendered good service
to the science in this instance, for the botanists, who at a later
time applied themselves to the systematic examination of the
Algae and Fungi, confided in the constancy of the processes of
development in each species, which they expected would assert
itself in these forms as in the Mosses and higher plants.

With much that was obscure and doubtful, the result of
occasional observation accompanied by uncritical interpreta-
tion, the literature of the subject had contained for some time
a certain number of single well-established facts of real import-
ance, which were well adapted to serve as starting-points for
earnest and exact investigation. Among the Algae the genera
Spirogyra and Vaucheria especially had supplied remark-
able phenomena ; Joseph Gartner observed the formation
of zygospores in Spirogyra in 1788, Hedwig saw in the mode
of their production at least a suggestion of sexuality (1798), and
Vaucher', in his ' Histoire de Conferves d'eau douce,' which
appeared in 1803 and was far in advance of its time, called
conjugation distinctly a sexual process ; the optical means at
his disposal did not enable him to observe the fertilisation in
Vaucheria (Ectosperma), which was named after him, though
he described the sexual organs accurately ; the movement also
of the zoospores in this genus esoiped him, and Trentepohl
first observed their escape and swarming in 1807 -'. Vaucher
had also observed the formation of new nets in the old cells
of Hydrodictyon, and Areschoug repeated the observation in
1842, when he saw the swarming of young cells in the old
ones. Bischoff, as early as 1828, saw the spermatozoids of

* Jean Pierre Etienne Vancher, the instructor and friend of P. de Candolle,
was a minister and professor in Geneva.

* Trentepohl's communication is to be found in the ' Botanische Bermer-
kungen und Perichtigiuigen ' of A. W. Roth, Leipsic, 1807.

2o8 Morphology and Systematic Botany under [Book i.

Chara, though without understanding them. Observations on
conjugating Algae were multiphed ; Ehrenberg in 1834 saw
corresponding phenomena in Closterium, and Morren described
them more exactly in 1836. The formation of swarmspores in
fresh-water and salt-water Algae was frequently observed
between 1820 and 1830, and in his ' Neues System,' iii, which
appeared in 1839, Meyen gave a summary of all that was
known up to that time of the propagation of the Algae. But
a new aspect was given to the knowledge of the Algae by those
researches of Nageli between the years 1844 and 1849, which
have been already mentioned, and which are the first since
Vaucher's time that can be regarded as systematic. Nageli
studied especially the laws of cell-division in sexual multiplica-
tion and growth, but he considered the Florideae to be the
only Algae that were sexually differentiated, and distinguished
the rest as being without sexuality. Braun in his ' Verjiingung'
(1850) made numerous contributions to the biology of the
fresh-water Algae, affording many and most interesting glimpses
into a connection still little understood between these forms ;
and in 1852 he gave an account of the history of growth in the
Characeae, a work conceived in Nageli's spirit and a model of
scientific research, in which the mode of derivation of every
cell from the apical cell of the stem was shown, the sexual
organs were minutely examined, and the relation established
between the direction of the ' streaming ' of the cell-contents
and the morphology of the organs. Gustav Thuret had already
made the zoospores of the Algae the subject of detailed exam-
ination.

Such was the condition of affairs with respect to the Algae
about the year 1850, when Hofmeister made the formation of
the embryo in the Phanerogams, the Vascular Cryptogams,
and the Muscineae the central point of investigation in
morphology and systematic botany. He made it clear that
a perfect insight into the whole cycle of development in the
plant and into its affinities can only be obtained, if we succeed

Chap. V,] the Influence of the Knowledge of Cryptogams. 209

in making its sexual propagation, the first commencement
of the embryo, the starting-point of the investigation. It
was natural to expect as happy results from the embryology
of the Algae, as had been obtained in the case of the
higher plants ; it was important therefore, that the observer
should no longer rest satisfied with a knowledge of the sexual
multiplication of the Algae ; he must enquire into their asexual
propagation, and by its aid discover the complete history of
their development. Former observations suggested the pro-
bability that here too sexual propagation is the prevailing
rule ; but it was easy to foresee that it would be a task of
great labour to make out a connected historj' of develop-
ment, a task of which the collectors who liked to call them-
selves systematists had never formed a conception ; but
Nageli's and Hofmeister's researches had made botanists
familiar with the highest demands of this kind, and the men
who were to gain new conquests for genuine science were
already engaged in the work in 1850. A splendid result
appeared in 1853, in Thuret's account of the fertilisation of
the genus Fucus ; this was a simple process as a matter of
embryology ; but the sexual act was so clear, and even open
to experimental treatment, that it threw light at once upon
other cases more difficult to observe. Then followed dis-
coveries of sexual processes in rapid succession ; Pringsheim
solved the old enigma in Vaucheria in 1855, and between
1856 and 1858 in the Oedogonieae, Saprolegnieae and
Coleochaetae ; in 1855 Cohn observed the sexual formation
of spores in Sphaeroplea. Pringsheim however was not
content with carefully observing the sexual act ; he gave
detailed descriptions of growth in the same families in its pro-
gress cell by cell, of the formation of the sexual organs, and the
development of the sexual product. The asexual proj^agations
which are intercalated into the vegetation and embr}'ology were
shown in their true connection. Processes were recognised
which often recalled the alternation of generations in the Mus-

p

2IO Morphology and Systematic Botany under [Book i.

cineae ; it was shown that very different forms of sexuahty and of
general development occur in the Algae, and these led to the
formation of systematic groups, quite different from those
founded on the superficial observation of collectors. It soon
appeared in the Algae, and later in the Fungi and Lichens,
that special investigation must lay new foundations for the
system. From the confused mass of forms not before under-
stood, Pringsheim brought out a series of characteristic groups,
which, thoroughly examined and skilfully described in words
and by figures, stood out as islands in the chaotic sea of still
unexamined forms, and threw light in many ways on all
around them. In like manner the morphology of the Con-
jugatae was thoroughly examined by De Bary before i860;
fragments of the history of development in the Algae were
added by Thuret, and he and Bornet cleared up the remark-
able embryology of the Florideae in 1867, while Pringsheim
established the pairing of the swarm-spores in the Volvocineae
in 1869. The Algae offer at present a greater variety in the
processes of development than any other class of plants ;
sexual and asexual propagation and growth work one into the
other in a way which opens entirely new glimpses into the
nature of the vegetable world.

The old conceptions of the nature of plants had been
greatly modified by Hofmeister's discovery of the alternation
of generations, and the reduction to it of the formation of the
seed in Phanerogams ; in like manner the first beginnings
of plant-life, the simplest forms of Algae, exhibit phenomena,
which compel us to revise our fundamental conceptions of
morphology, if we are ever to be able to give a systematic view
of the whole vegetable kingdom.

The methodical examination of the Fungi after 1850 led to
similar but still more comprehensive results. From earliest
times the Fungi had been objects of wonder and superstition ;
what Hieronymus Bock said of them has been told in the
first chapter ; this was repeated by Kaspar Bauhin, and similar

Chap, v.] the Itiflitcucc oftJte Kttowlcdgc of Cryptogam s. 21 \

notions existed till late into our own century ; about the
middle of the 17th century Otto Von Munchausen thought
that mushrooms were the habitations of Polypes, and Linnaeus
assented to that view. What the nature-philosophers, as Nees
von Esenbeck for instance, had to say on the nature of Fungi,
need not be reproduced here.

Still some useful observations had been accumulating for
some time on this subject; as early as 1729 Micheli^ had
collected the spores of numerous Fungi, had sown them and
obtained not only mycelia but also sporophores (fructifications),
and Gleditsch confirmed these observations in 1753; Jacob
Christian Schaeffer'^ about the year 1762 published ver)' good
figures of all the Fungi of Bavaria and the Palatinate, and
collected the spores of many species. Yet Rudolphi and Link
at the beginning of the present century ventured to deny the
germination of the spores of Fungi; Persoon in 18 18 thought
that some Fungi grow from spores, others from spontaneous
generation. A decided improvement appears after 1820 in
the views of botanists with respect to Fungi, and to this
Ehrenberg's elaborate essay, ' De Mycetogenesi,' published
in that year in the Leopoldina, contributed greatly. In that
work he collected together all that was then known on the
nature and propagation of the Fungi, and communicated
observations of his own on spores and their germination ;
he gave figures also, of the course of the hyphae in large
sporophores and in other parts, but his most important
service was a description of the first observed case of

' Pier' Antonio Micheli, bom at Florence in 1679, was Director of the
Botanic Garden there, and died in 1737. Johann Jacob Dillen l^Dillenius),
bom in Darmstadt in 1687, ^^^ Professor of Botany in Oxford, and died in
1747. These two botanists were the first who submitted the Mosses and the
lower Cryptogams to scientific examination, and endeavoured to prove the
presence of sexual organs in these plants.

* Jacob Christian Schaefi'er, bom in 1718, was Superintendent in Regens-
bnrg ; he died in 1790.

P 2

21 a Morphology and Systematic Botany under [Book l

sexuality in a Mould, namely, the conjugation of the branches
of Syzygites. In the same year Nees von Esenbeck sowed
Mucor stolonifer on bread, and obtained ripe sporangia
in three days (Flora, 1820, p. 528); Dutrochet proved in 1834
(Mem. ii. p. 173) that the larger Fungi are only the sporo-
phores of a filiform branching plant, which spreads usually
under ground or in the interstices of organic substances, and
had been till that time regarded as a peculiar form of Fungus
under the name of Byssus. Soon after, Trog (Flora, 1837,
p. 609) carried these observations further; he distinguished
the mycelium from the sporophore, and pointed out that
the former is often perennial and is the first product of the
gierminating spores. He made an attempt to examine the
morphology of the larger sporophores, and showed that it was
possible to collect the spores of mushrooms on paper, and
that those of Peziza and Helvella are forcibly ejected
in little clouds of dust ; he also produced ' new proofs of
Gleditsch's statement, that the spores of Fungi are dis-
seminated everywhere by the air. Schmitz published in ' Lin-
naea,' between the years 1842 and 1845 excellent observations
on the growth and mode of life of several of the larger Fungi.
It was not unnecessary at that time to make it clearly
understood that the spores of Fungi reproduce their species
exactly.

But the lower, the small and simple Fungi, those especially
which are parasitic on plants and animals, were the most
attractive objects in the whole field of mycology. Here were
difficulties in abundance, here were the darkest enigmas with
which botany has ever had to deal, here was new ground to be
slowly won by extreme scientific circumspection and foresight.
In these forms, as in the Algae, the first thing to be done was
to make out the complete history of development in a few
species ; but it was much more difficult in the Fungi than in
the Algae to discover what properly belonged to one cycle of
development, and to separate it from casual phases of develop-

Chap. V.] the Injliicucc oftJw Knowledge of Cryptogams. 2 1 3

merit of other associated Fungi. The merit of first breaking
ground in this direction belongs to the brothers Tulasne, who
pubHshed before 1850 the first more exact researches into the
Smuts and Rusts ; these were followed by a long series of
excellent works on different forms of Fungi, especially the
subterranean, whose mode of life and anatomy were described
and illustrated by splendid figures ; but their account of the
development of Ergot of rye (1853), their further investigations
into the formation of the spores and the germination of Cysto-
pus, Puccinia, Tilletia, and Ustilago, and their discovery of
the sexual organs in Peronospora before 1861, were of greater
theoretical importance. The ' Selecta Fungorum Carpologia,'
which appeared in three volumes from 1861 to 1865 with fine
figures, some of which represented the process of development,
contributed greatly to the reformation of mycology. Mean-
while, Cessati had published investigations into the Muscardine-
fungus of the silkworm-caterpillar, and Cohn into a remarkable
Mould, the Pilobolus.

But mycology owes its present form to none more than to
Anton de Bary, whose writings, the fruit of twenty years'
labour, it would take too much space to enumerate one by one.
With a correct understanding of the only means which can lead
to sure results in this difficult branch of study, De Bary made it
his first endeavour to perfect the methods of observation, and
not only sought for the stages of development of the lower
Fungi in their natural places of growth, but cultivated them
himself with all possible precautions, and thus obtained com-
plete and uninterrupted series of developments. By these
means he succeeded in proving that parasitic Fungi make their
way into the inside of healthy plants and animals, and that
this is the explanation of the remarkable fact, that Fungi live
in the apparently uninjured tissue of other organisms, a fact
which formerly had led to the supposition that such Fungi owe
their origin to spontaneous generation, or to the living contents
of the cells of their entertainers. Pringsheim had already

214 Morphology and Systematic Botany under [Book i.

observed these occurrences in 1858 in the case of an unusually
simple water-fungus (Pythium). De Bary showed that the
intrusive parasite vegetates inside the plant or animal which is
its host, and afterwards sends out its organs of propagation
into the open air, and that at a given time the organism
attacked by the fungus sickens or dies. These investigations
were not only of high scientific interest to the biologist, but
they produced a series of results of the greatest importance to
agriculture and forestry, and even to medicine.

With the Fungi, even more than with the Algae, the chief
difficulty in making out a complete series of developments in
the history of each species arose from the frequent intercalation
of the asexual mode of multiplication into the course of its
development, and in the further peculiarity, that the several
stages of development in some cases could only be completed
on different substrata. One of the most important tasks was
to find the sexual organs, the existence of which was rendered
probable by various analogies, and after De Bary had observed
the sexual organs in the Peronosporeae in 1861, he succeeded
in 1863 in proving for the first time that the whole fruit-body
of an Ascomycete is itself the product of a sexual act, which
takes place on the threads of the mycelium.

The literature of mycology based on De Bary's methods of
observation and its actual results has been enriched by others
also in various directions since i860 ; in the case of the Fungi,
as in that of the Algae, it is not possible yet to see to what
results investigation will ultimately lead ; but it is one of the
fairest fruits of strictly inductive method, that it has succeeded
in smoothing this thorny and indeed perilous route, where the
enquirer is constantly in danger of being misled, and in satisfy-
ing the severest demands of science. Conclusions have been
already reached that are important for morphology and syste-
matic botany, and among these the establishment of the nature
of the large sporophores, and of processes similar to the
alternation of generations in the higher Cryptogams should be

Chap, v.] the Influence of the Knowledge of Cryptogams. 215

especially mentioned. But the most important result remains
to be told ; it is, that the two classes of Algae and P'ungi,
hitherto kept strictly separate, must obviously be now united,
and an entirely new classification adopted, in which Algae and
Fungi recur as forms differing only in habit in various divisions
founded on their morphology ^

A few words must be given here to the Lichens. They are
the division of the Thallophytes, whose true nature was last
recognised, and that only in modern times; till after 1850
scarcely more was known of their organisation than Wallroth
had discovered in 1825 -, namely, that green cells, known as
gonidia are scattered through the fungus-like hyphal tissue of
the thallus. After Mohl's investigations in T833, it was known
that free spores Avere formed in the tubes of the fructifications
(apothecia), and that a dust collected from the thallus and
consisting of a mixture of gonidia and hyphae was in a
condition to propagate the species. The genetic relation
between the chlorophyll-containing gonidia and the fungus-like
hyphae long continued to be obscure, till at last, after 1868, it
was shown that the gonidia are true Algae, and the hyphal
tissue a genuine Fungus, and that therefore the Lichens are not
a class co-ordinating with the Algae and Fungi, but a division
of Ascomycetes, which have this peculiarity, that they spin
their threads round the plants on which they feed, and take
them up into their tissue. De Bary suggested this explanation,
but it was Schwendener who adopted it without reserve and
openly declared it, as much to the surprise as the annoyance
of Lichenologists. It may be foreseen that their opposition
will yield to the weight of facts, which already leave no doubt
in the minds of the unprejudiced.

Thus researches in the domain of the Thallophytes have led

' See Sachs, 'Lehrbuch der Botanik,' ed. 4 (1874), p. 245.
"^ Fr. Wilh. Wallroth, bora in the Ilarz in 1792, was district physician at
Nordhausen. He died in 1857. See ' Flora ' for 1857, p. 336.

ai6 Morphology and Systematic Botany.

during the last twenty years to a complete revolution in the
views entertained with respect to the nature of these organisms,
and enriched botany with a series of surprising achievements ;
and the movement there is still far from having come to an end.
But we must regard it as one of the great results for the whole
science that through the examination of the lower and higher
Cryptogams, morphology and systematic botany have been
rescued from many ancient prejudices, that the survey has
become freer, the methods of investigation surer, the questions
more clearly seen and put in more definite form.

SECOND BOOK

HISTORY OF VEGETABLE ANATOMY

(1671-1860)

INTRODUCTION.

That the substance of the more perfect plants consists of
layers of different constitution was a fact that could not escape
the most untutored observation in primitive times ; ancient
languages had still words to designate the most obvious ana-
tomical components of plants, rind, wood and pith. It was
also easy to perceive that the pith consists of an apparently
homogeneous succulent mass, the wood of a fibrous substance,
while the rind of woody plants is composed partly of mem-
branous layers, partly of fibrous and pith-like tissue. The
obtaining of threads for spinning from the rind of the flax-
plant, for instance, must have suggested some idea, if only
a vague one, in the earliest ages of the way, in which the
fibrous could be separated from the pulpy part of the bark by
decay and mechanical treatment. Neither Aristotle nor
Theophrastus failed to compare these components of veget-
able substance with corresponding ones in animal bodies, and
it has been already shown in the first book how Cesalpino,
following his masters, took the pith for the truly living part of
the plant and the seat of the vegetable soul, and applied this
idea in his morphology and physiology. He remarked that the
root generally has no pith, and that the part of the root which
answers to the wood of the stem is often soft and fleshy ; the
composition of the leaves from a green and succulent substance
and strands of fibres at once suggested a certain resemblance to
the green rind of the stem ; and it was evidently this which led
him to consider that not only the leaves, but also the leaf-
forms of the flower-envelopes had their origin in the rind of the

220 Introduction. [Book II.

stem, while the soft, pulpy, succulent condition of the unripe
seeds and seed-vessels seemed to point to their identity with
the pith. That not only are juices contained in plants, but
that they must move in them, could not escape the simplest
reflection ; and further, the bleeding of the vine, the flow of
gum from resiniferous trees, the gushing of a milky juice from
the wounds of certain plants, exhibited so striking a resem-
blance to the bleeding of a wound in the body of an animal,
that the idea of canals inside the plant, which, like the veins in
animals, contain those juices and set them in motion, ap-
peared quite natural, as we see plainly from Cesalpino's reflec-
tions on these structural conditions. If we add that it was
known that the seeds are enclosed in the fruits, and that the
embryo, together with a pulpy mass (cotyledons and endo-
sperm), are in their turn enclosed in the seed, we have pretty
well the whole inventory of phytotomic knowledge up to about
the middle of the seventeenth century.

With careful preparation and skilful dissection of suitable
parts of plants, and attentive consideration of the changes pro-
duced by decay and corruption, anatomical knowledge might
have been considerably enlarged at an earlier time ; but seeing
is an art that must be learnt and cultivated; a definite aim
and end must stimulate the observer into willingness to see
exactly, and to distinguish and connect together correctly what
he sees. But this art of seeing was not far advanced in
the middle of the 17th century. All that was achieved in
this direction did not go beyond the distinguishing the outer
organs of leaf-forms and stem-forms, and we have seen in the
first book how unsuccessful was the attempt to distinguish the
minuter parts of the flower and fruit.

The invention of the microscope made small things seem
large, and revealed to sight what was too small to be seen
without it ; but the use of magnifying glasses brought an ad-
vantage with it of a different kind — it taught those who used
them to see scientifically and exactly. In arming the eye with

Chap, I.] Introduction. 221

these increased powers the attention was concentrated on defi-
nite points in the object ; what was seen was to some extent
indistinct, and always only a small part of the whole object ;
perception by means of the optic nerve had to be accom-
panied by conscious and intense reflection, in order to make
the object, which is observed in part only with the magnifying
glass, clear to the mental eye in all the relations of the parts to
one another and to the whole. Thus the eye armed with the
microscope became itself a scientific instrument, which no
longer hurried lightly over the object, but was subjected to
severe discipline by the mind of the observer and kept to
methodical work. The philosopher Christian Wolff observed
very truly in 1721, that an object once seen with the micro-
scope can often be distinguished afterwards with the naked
eye ; and this, which is the experience of ever)' microscopist, is
suflScient evidence of the effect of the instrument in educating
and training the eye. This remarkable fact appears also in
another way. ^^'e saw in the history of morphology and sys-
tematic botany that botanists for a hundred years scarcely
attempted to make themselves masters in a scientific sense of
the external and obvious relations of form in plants, and to
consider them from more general points of view. Jung was
the first who applied systematic reflection to the morphological
relations of plants which lay open before his eyes, and it was
not till late in our own century that this part of botany was
again handled in a scientific and methodical manner. This
extremely slow progress in obtaining a mental mastery over
external form in plants on the part of those who are continually
occupied with them appears to be due chiefly to the fact, that
the unassisted eye glances too impatiently over the form of the
object, and the attention of the observer is disturbed by its
hasty movements. In direct contrast to this customary want
of thoughtfulness in contemplating the external form of plants,
we find the first observers with the microscope, Robert Hooke,
Malpighi, Grew, and Leeuwenhoek in the latter half of the

222 Introduction. [Book II.

seventeenth century, endeavouring by earnest reflection to
apply the powers of the mind to the objects seen with the
assisted eye, to clear up the true nature of microscopic objects,
and to explain the secrets of their constitution. If we compare
the works of these men with the utterances of the systematists
of the same period on the relations of form in plants, we can-
not fail to see how superior the matter of the former is in
intellectual value. This appears most strikingly when we put
what Malpighi and Grew tell us of the construction of the
flower and fruit side by side with the knowledge of Tournefort,
Bachmann, and Linnaeus on the same subject.

This enhancement of the mental capacity of the observer by
the microscope is however the result of long practice; the
best microscope in unpractised hands is apt soon to become
a tiresome toy. It would be a great mistake to suppose that
progress in the study of the anatomy of plants has simply
depended on the perfecting of the microscope. It is obvious
that the perception of anatomical objects must grow more dis-
tinct as the magnifying power of the instrument is increased,
and the field of sight is made brighter and clearer, but these
things by themselves would not add much to real knowledge.
In examining the structure of plants, as in every science, it is
necessary to work with the mind upon the object seen with the
eye of sense, to separate the important from the unimportant,
to discover the logical connection between the several percep-
tions, and to have a special aim in the examination ; but the
aim of the phytotomist can only be to obtain so clear an idea
of the whole inner structure of the plant in all its connections,
that it can be reproduced by the imagination at any moment
in full detail with the perfect distinctness of sense-perception.
It is not easy to attain this end because the more the micro-
scope magnifies, the smaller is the part of the whole object
which it shows ; skilful and well-considered preparation is
required, careful combination of different objects and long
practice. The history of phytotomy shows how difficult a task

Chap. 1.] Introduction. 223

it is to combine the separate observations and to fashion what
has been seen bit by bit into a clear and connected repre-
sentation.

It appears then that progressive improvement of the micro-
scope was not in itself sufificient to ensure the advance of phy-
totomy. It would not indeed be too much to say, that the
progress which microscopic anatomy made step by step with
the aid of imperfect instruments repeatedly gave the impulse
to energetic efforts to improve them. Only practical micro-
scopists could tell where the real defects of existing instruments
lay ; it was their anxiety to make them more manageable, their
constant complaints of the poor performance of the optical
part — complaints loudly expressed, especially at the end of the
previous and the beginning of the present century, which urged
the opticians to turn their attention to the microscope and to
endeavour to make it more perfect. Moreover, essential im-
provements in the instrument were made by microscopists
themselves. Thus Robert Hooke was the first who in 1760
gave the compound microscope a form convenient for scien-
tific observation, and Leeuwenhoek developed the powers of
the simple microscope to their highest point. The modern
microscope is greatly indebted for its perfectness to Amici ; nor
ought the name of von Mohl to be omitted here, who invented
improved methods for microscopic measurement, and in his
work ' Mikrographie ' (1846) on the construction of the micro-
scope gave many practical hints to the opticians.

We shall not then make the most important advances in
the anatomy of plants depend as a matter of course and quite
passively on the history of the microscope ; they were deter-
mined here as in other parts of botany by a logical necessity of
their own ; here as elsewhere we have to fix our eye on the
objects pursued by successive enquirers. If for this purpose
we cast a glance over the history of the subject, it will appear
that its founders in the latter half of the seventeenth century,
Malpighi and Grew, were chiefly bent on determining the con-

324 Introduction. [Book II.

nection between the cellular and fibrous elements in the struc-
ture of plants. Two fundamental forms of tissue were assumed
from the first, the succulent cellular tissue composed of cham-
bers or tubes, and, in contrast to this, the elongated usually
fibrous or tubular elementary organs, the distinction of which
into open canals or vessels and fibres with closed ends continued
to be doubtful. The characteristic feature of this period is, that
the investigation of the more delicate structure is everywhere
closely interwoven with reflections on the function of the ele-
mentary organs, and that thus anatomy and physiology support
each other, but not without mutual injury through the imper-
fections of both. But the physiological interest far outweighed
the anatomical with the first phytotomists, who used anato-
mical research for the purposes of physiology.

The imperfectness of the microscope during the whole of the
eighteenth century produced a certain disinclination to ana-
tomical studies, which were after all only regarded as auxiliary
to physiology. The latter had made very important progress
without the help of anatomy in the hands of Hales, and later
on towards the end of the i8th century in those of Ingen-
Houss and Senebier, and thus the interest in phytotomy was
almost extinguished. Not only was very little addition
made to the contributions of Malpighi and Grew during the
1 8th century, but they had to some extent ceased to be
understood.

However towards the end of that time the microscope came
again into fashion ; in the compound form it had become
somewhat more convenient and manageable ; Hedwig showed
how it revealed the organisation of the smallest plants, and
especially of the Mosses, and he examined also the con-
struction of cell-tissue and vascular bundles in the higher
plants. But with the beginning of the present century the
interest in phytotomy suddenly rose high again ; Mirbel in
France, Kurt Sprengel in Germany made the microscopic
structure of plants once more the subject of serious investi-

Book II.] Introduction. 225

gation. The performances of both men were at first extremely
weak and contradicted one another; a Hvely dispute on the
nature of cells, fibres, and vessels grew up during the succeed-
ing years, and many German botanists soon took part in it ;
life was once more infused into the whole subject, especially
when the academy of Gottingen in 1804 offered a prize for the
best essay on the disputed points, for which Link, Rudolphi
and Treviranus contended, while Bernhardi occupied himself
with private researches into the nature of vessels in plants. It
was not much that was attained in this way ; men began once
more from the beginning, and after 130 years Malpighi and
Grew were still the authorities to whom everybody appealed.
Yet the questions now discussed were in the main different
from the old ones ; Malpighi, Grew and Leeuwenhoek had
chiefly set themselves the task of studying the different
tissues in their mutual connection ; the moderns were chiefly
concerned to get a clearer understanding of the more delicate
construction of the various tissues themselves, to know what
was the true account of cell-structure in parenchymatous tissue,
and the real nature of vessels and fibres. That very slow
progress was made at first in this direction was due partly
to the imperfectness of the microscope, and still more to very
unskilful preparations, to the influence of various prejudices,
and to too slight exertion of the mind. But a comprehensive
work by the younger Moldenhawer in 181 2 was a considerable
step in advance. It is marked by careful and suitable
preparation of the objects, and by critical examination of what
was observed by the writer himself and of what had been
written by others ; in fact it is a fresh commencement of a
strict scientific treatment of phytotomy. Hugo von Mohl con-
tinued Moldenhawer's work after 1828, and Meyen was a con-
temporary and a zealous student of phytotomy ; but the period
in the study of vegetable anatomy which reaches to 1840 may
be said to have been brought to a conclusion chiefly by von
Mohl's contributions. Weak as the beginnings were at the

226 Introduction. [BookII.

commencement of this period (i 800-1 840), and important as
was the advance made by von Mohl towards the end of it,
yet we may include all that was done during that time in one
view, since the questions examined were essentially the same ;
like Mirbel and Treviranus, Moldenhawer and Meyen, von
Mohl was chiefly occupied up to the year 1840 in deciding
the questions, what is the nature of the solid framework
of cellulose in the plant in its matured state, whether a
single or double wall of membrane lies between two cell-
spaces, what is the true account of pits and pores, and of the
various forms of fibres and vessels ; one great result of these
efforts must be mentioned, namely, the establishment of the
fact that all the elementary organs of plants may be referred to
one fundamental form, the closed cell ; that the fibres are
only elongated cells, but that true vessels are formed by cells
which are arranged in rows, and have entered into free
communication with one another.

Phytotomists before 1840, and von Mohl especially, had oc-
casionally paid attention among other things to circumstances
connected with the history of development, and single cases of
the formation of various cells had been described by von Mohl
and Mirbel between 1830 and 1840, but greater interest was
taken in the right understanding of the structure of mature
tissues ; physiological questions also, though no longer of the
first importance in anatomical investigations, were still of
weight, so far as the enquiry was influenced by the relation of
anatomical structure to the functions of elementary organs.
But with Schleiden and Nageli the question of historical de-
velopment and the purely morphological examination of in-
terior structure assumed an exclusive prominence in phyto-
tomy. The first commencement of vegetable cells especially
and their growth were the subjects now discussed. Schleiden
had proposed a theory of cell-formation before 1840, which,
resting on too few and inexact observations, referred all
processes of cell-formation in the vegetable kingdom to a

Book II.] Introduction. 227

single form ; it attracted great attention in the botanical world,
but could not easily be reconciled with what was already
known; and in 1846 it was completely refuted by Niigeli,
who substituted for it the history of the formation of the
various kinds of vegetable cells in their main features, based
on profound and extensive investigations. It was natural that
these researches into the formation of cells should turn the
attention of observers, which had hitherto been almost ex-
clusively devoted to the solid framework of cell-tissue, to the
juicy contents of cells. Robert Brown had already discovered
the cell-nucleus ; Schleiden recognised its more constant pre-
sence, but misunderstood its relation to cell-formation ; Nageli
and von Mohl next demonstrated the peculiar nature of proto-
plasm, the most important component of vegetable cells, and
especially the weighty part which it plays in their origination.
Unger in 1855 called attention to the great resemblance which
exists between the protoplasm of the vegetable cell and the
sarkode of the more simple animals, — a discovery which was
subsequently brought into prominence by observations on the
behaviour of the Myxomycetes, and after i860 finally led
zootomists as well as phytotomists to the conclusion, that proto-
plasm is the foundation of all organic development, vegetable
and animal. But there is yet another direction in which the
study of the history of development by the phytotomist
led to new points of view and to new results ; we have
already pointed in the end of the first book to the way in
which Nageli after 1844 made the sequences of cell-division in
the growth of organs the basis for his morphology,, and how
in this way the Cryptogams especially revealed their inner
structure; we also noticed the splendid results which Hofmeister
achieved by his study of the development of the embryo ;
here we have further to show, how after 1850 the various forms
of tissue, especially the vascular bundles, were examined by
observation of the history of their development, and how
in this way botanical science has succeeded in explaining the

Q 2

23^8 Introduction.

inner histological connection between leaves and axes, shoots
and parent-shoots, primary and secondary roots, and above all
in gaining a correct insight into subsequent growth in thickness
and so learning to understand the true mode of formation of a
woody body and of the secondary rind.

It is then the task of the following chapter to give a more
detailed account of the history of phytotomy, the salient
points in which have now been indicated.

chaptp:r I.

PhYTOTOMY founded by MaLPIGHI and (iREW,

I67I-I682.

The foundation of vegetable anatomy, indeed of all insight
into the structure of the substance of plants, is the knowledge
of their cellular structure. We find the first perception of this
truth in a comprehensive work of Robert Hooke\ which
appeared in London in 1667 under the title of ' Micrographia
or some physiological descriptions of minute bodies made by
magnifying glasses.' The author of this remarkable book was
not a botanist, but an investigator of nature of the kind more
especially to be found in the seventeenth century ; he was
mathematician, chemist, physicist, a great mechanician, and
later an architect, and moreover a philosopher of the new
school then rising. Beside many discoveries in various sub-
jects he succeeded in 1660 in so far improving the compound
microscope, that with considerable increase in magnifying power
it had tolerably clear definition. With this instrument Henshaw
in 1 66 1 is stated to have discovered the vessels in walnut-
wood, a fact not of importance for our history. Hooke himself
was anxious to show the world how much could be seen with his

' Robert Hooke, born in 1635 at Freshwater in the Isle of Wight, was a
man of marvellous industry and varied acquirement in spite of a delicate
constitution. He became a Fellow of the Royal Society in 1662, and was
afterwards its Secretary and Professor of Geometry in Gresham College.
He died in 1703. There is a good account of him by de I'Aulnaye in the
' Biographie Universelle.'

230 Phytotomy founded [Book ii.

improved instrument ; as an adherent of the inductive method
he desired to aid in perfecting the perceptions of sense which
are the foundation of all human knowledge ; with this feeling
he submitted all sorts of objects to his glass, that it might be
known how much the unassisted eye fails to perceive. He
made what he saw texts for discussions on a multiplicity of
questions of the day. The book therefore was not devoted to
phytotomy ; the structure of the substance of plants is noticed
in the same incidental manner, as the discovery of parasitic
fungi on leaves, or other similar matters. And what Hooke
saw of the structure of plants was not much, but it was new,
and on the whole fairly judged. It appears that he discovered
the cellular structure in plants by examining charcoal with his
glass, and that he then tried cork and other tissues. He says
that a thin section of cork on a black ground (by direct light
therefore) looks like honey-comb ; he distinguishes between
the hollow spaces (pores) and the dividing walls, and to the
former he gives the name which they yet bear ; he calls them
cells. The arrangement of the cork-cells in rows misleads
him into taking them for divisions of elongated hollow spaces,
separated by diaphragms. These, he says, are the first micro-
scopic pores, which he or any one else had ever seen, and he
regards the cell-spaces of plants as examples of the porousness
of matter, as do the text books of physics up to modern times.
Hooke employed his discovery especially to explain the
physical qualities of cork ; he estimates the number of pores
in a cubic inch at about twelve hundred millions. He draws
another botanical conclusion ; he gathers from the structure
of the cork that it must be an outgrowth from the bark of a
tree, and appeals to the statements of one Johnston in proof
of this hypothesis. The fact, that cork is the bark of a tree, was
therefore not yet known to all educated people in England.
Hooke afterwards says that this kind of texture is not confined
to cork ; for as he examined the pith of elder and other trees
with his microscope and the pulp of hollow stems, such as

Chap. I.] by Malpighi and Grew. 23 r

those of fennel, teasel and reed, he found a similar kind of
structure with the difference only, that in the latter the pores
(cells) are arranged lengthwise, in cork in transverse rows.
He says that he has never seen any passages for communi-
cation between the cells, but that they must exist, because the
nourishing juice passes from one to another; for he has seen
how in fresh plants the cells are filled with sap, as are the
long pores in the wood ; but these he found empty of sap in
the carbonised wood, and filled with air.

It is plain that it was not much that Hooke saw with his
improved microscope ; thin cross-sections of the stem of
balsam or gourd, two plants that grew at that time in every
garden, would have shown the naked eye as much or even
more of vegetable structure. At the same time there is proof
here of what was said above on the influence of the micro-
scope on the use of the eye ; the pleasure in the performance
of the new instrument must first direct attention to things
which can be seen without it, but were never seen.

About the time of the appearance of Hooke's ' Micrographia '
Malpighi and Grew had already made the structure of the
plant the subject of detailed and systematic investigations, the
results of which they laid before the Royal Society in London
almost at the same time in 167 1. The question to which of
the two the priority belongs has been repeatedly discussed,
though the facts to be considered are undoubted. The first
part of Malpighi's large work, the * Anatomes plantarum idea,'
which appeared at a later time, is dated Bologna, November i,
1671 ; and Grew, who from 1677 was Secretary to the Royal
Society, informs us in the preface to his anatomical work of
1682, that Malpighi laid his work before the Society on
December 7, 167 1, the same day on which Grew presented
his treatise, ' The Anatomy of plantes begun,' in print, having
already tendered it in manuscript on the eleventh of May in
the same year. But it must be observed that these are not the
dates of the larger works of the two men, but only of the

233 Phytotomy founded [Book ii.

preliminary communications, in which they gave a brief sum-
mary of the researches they had then made ; the fuller and
more complete treatises appeared afterwards ; the preliminary
communications formed the first part of the later works and to
some extent the introduction to them. Malpighi's longer
account was laid before the Society in 1674, while Grew pro-
duced a series of essays on different parts of vegetable anatomy
between 1672 and 1682 ; and these appeared together with his
first communication in a large folio volume under the title,
' The anatomic of plantes,' in 1682. Thus Grew had opportunity
to use Malpighi's ideas in his later compositions ; he actually
did so, and the important point as regards the question of
priority is, that where he makes use of Malpighi he distinctly
quotes from him. No more is necessary to remove the serious
imputation which Schleiden has made against Grew in the
'Grundziige' (1845), i. p. 207.

Whoever has not himself read the elaborate works of
Malpighi and Grew, but knows them only from the quotations
in later phytotomists, may easily imagine that these fathers of
phytotomy had found their way to a theory of the cell, such as
we now possess. But it is not so ; their works have very little
resemblance to modern descriptions of vegetable anatomy ; the
difference lies chiefly in this, that modern writers in their
accounts of the structure of plants start with the idea of the
. cell, and afterwards treat of the connection of cells into masses
of tissue. The founders of phytotomy on the contrary, as
might naturally be expected, consider first and foremost the
coarser anatomical circumstances ; they describe the rind,
bast, wood, and pith chiefly of woody dicotyledons, and the
histological distinctions between root, stem, leaf, and fruit in
their broader relations, and examine the detail of the structure
of buds, flowers, fruits, and seeds for the most part only so far as
it can be setn with the naked eye. The more delicate struc-
tural conditions are afterwards discussed as a supplement to
this less minute anatomy and always in close connection with

Chap. I.] by MttlpigJiP and Grew. 2;^^

it. The chief emphasis is laid on the consideration of the way in
which the fibrous tissue connects with the succulent parenchyma,
while such questions as the nature of the cell, the fibre, and the
vessel are only incidentally touched upon or discussed at
greater length in the course of the exposition. The mode of
investigation and exposition is therefore chiefly analytic, while
in modern compendiums of phytotomy it is essentially syn-
thetic. It need scarcely be said that with this mode of
treatment the questions which are now regarded as funda-
mentally important are either treated as of secondary moment,
or are disregarded ; we must not therefore, in judging of the
merit of these men, approach their works with the demands
upon them which our more advanced science would lead us to
make. It would be quite wrong even to think of measuring
the value of their books by the extent to which their contents
agree with the modern cell-theory. Both of them had enough to
do to find their way at all in the new world which the micro-
scope had revealed ; many questions which have become trivial
for us had then to be solved for the first time, and the chief
merit of both lies in this very effort to understand first of all
the coarser relations of the anatomical structure of plants ; in
this respect the study of their works may yet be recommended
to beginners, because modern phytotomical books are generally
very imperfect on these points. And yet we must not under-
value what Malpighi and Grew had to say on the more delicate
anatomy, and especially on the nature of the solid framework of
cell-membrane in the plant ; imperfect and crude as their views
on such points may be, yet they continued for more than a
hundred years to be the foundation of all that was known
about cellular structure ; and when phytotomy took a new
flight at the beginning of the present century, Malpighi's and
Grew's scattered remarks on the union of cells with one
another, and on the structure of fibres and vessels, were
adopted by the later phytotomists and connected with their
own investigations.

234 Phytotomy founded [Book ii.

If the views of Malpighi and Grew agreed in the main on the
points here mentioned, yet the style and manner of the two
were very different. Malpighi kept more closely to that which
could be directly seen ; Grew delighted in tacking on a variety
of theoretical discussions to his observations, and especially
endeavoured to follow the path of speculation beyond the
limits of what was visible with the microscope. Malpighi's
account reads like a masterly sketch, Grew's like an elaborate
production of great and almost pedantic carefulness ; Malpighi
displays a greater formal cultivation, and deals with the ques-
tions with light touches, allusively, and almost in the tone of
conversation. Grew on the other hand is at pains to reduce
the new science to a learned and well-studied system, and to
bring it into connection with chemistry, physics, and above all
with the Cartesian philosophy. Malpighi was one of the most
famous physicians and zootomists of his time, and treated
phytotomy from the points of view already opened in zootomy ;
Grew too occupied himself occasionally with zootomy, but he
was a vegetable anatomist by profession, and gave himself up,
especially after 1688, almost exclusively to the study of the
structure of plants with a devotion hardly to be paralleled till
we come down to Mirbel and von Mohl.

As in medicine in the 17th century human anatomy was
intimately connected with physiology, and the latter was not
yet treated as a distinct study, so the founders of phytotomy
naturally combined the physiological consideration of the
functions of organs with the examination of their structure.
Considerations on the movement of sap and on food appear in
the front of every anatomical enquiry; relations of structure,
which the microscope could not reach, were assumed hypo-
thetically on physiological grounds, although little positive
was known at the time about the functions of the organs of
plants ; hence recourse was had to analogies between vegetable
and animal life, and it is true that vegetable physiology received
its first great impulse by this means, but occasion was given at

Chap. I.] bj> Mttlpiglli Gud GrClV. 235

tlie same time to many errors, which in their turn often misled
the anatomist. At present, when vegetable anatomy has
separated itself more than is desirable from physiology, that is,
from the investigation of the functions of organs, it is difficult,
nay impossible, to give the reader a brief account of the con-
tents of these two books which form an epoch in the science.
I must confine myself to noticing a few chief points, which
are historically connected with the further development of
phytotomy, though some of these are just the questions to
which Malpighi and Grew only gave occasional attention, and
which it is therefore a little unjust to them to bring into
prominent notice. I shall recur to the physiological portion of
their writings in the third book of this history, confining myself
here to that which concerns the structural relations of plants.

The phytotomical work of Marcello Malpighi^ appeared
under the title ' Anatome Plantarum,' and to it was added
a treatise on hens' eggs during the process of incubation
(1675). The phytotomical portion of the book separates into
two main divisions, the first of which, the 'Anatomes Plan-
tarum idea,' was, as was stated above, completed in 167 1, and
contains a general abstract and survey of Malpighi's views on
the structure and functions of vegetable organs in fourteen-and-
a-half folio pages ; the second and much larger portion illus-
trates in detail by numerous examples and with the help of
many copper-plates the views expressed in the first part ;
it will answer our purpose best to turn principally to the
connected expression of the author's views in the first part.

He begins his remarks with the anatomy of the stem, and
as the rind first attracts the eye, he takes it first. The outer

' Marcello Malpighi, bora at Crevalcuore near Bologna in 162S, became
Doctor of Medicine in 1653, and after 1656 was Professor in Bologna, Pisa.
Messina, and a second time in Bologna; in 1691 he was named Physician to
Innocent XII. He died in 1694. On his services to comparative anatomy,
and the anatomy of the human body, see the ' Biographic Universelle ' and
Carus, ' Geschichlc dcr Zoologie,' p. 395.

236 Phytotomy founded [Book ii.

part of it, he says, the cuticle, consists of utricles or little sacs
arranged in horizontal rows ; these die in time and decay, some-
times forming a dry epidermis. On the removal of the epidermis,
layer after layer of woody fibre is disclosed, and these layers,
usually forming reticulations and lying one on another, follow the
longitudinal direction of the stem. These fibrous bundles are
composed of numerous fibres, and each single fibre of tubes
which open into one another (' quaelibet fibra insignis fistulis
invicem hiantibus constat') and so on. The interspaces of the
network are filled with roundish tubes, which usually have a
horizontal direction towards the wood. If the rind is removed
the wood appears, chiefly composed of elongated fibres and
tubes, and consisting of rings or vesicles open towards one
another and arranged in longitudinal rows. The fibres also of
the wood do not run parallel to one another, but allow a net-
work of angular anastomosing spaces to be formed between
them, the larger of which are filled with bundles of tubes, which
run from the rind through these interspaces to the pith, etc., etc.
Between the fibrous and fistulose bundles of the wood lie the
spiral tubes ('spirales fistulae'), smaller in number but of larger
size, so that in cross sections of the stem they appear with open
orifices. They lie in different positions, but the majority in
concentric circles. He says that in the course of ten years'
examination (from 1661 therefore) he found these spiral tubes
in all plants, and it may be added here that Grew in the intro-
duction to his book expressly concedes the priority in this
discovery to Malpighi ; but Malpighi's ideas on the subject of
these tubes are extremely indistinct^, and this gave occasion to

^ We read at p. 3 : ' Componuntur expositae fistulae (spirales") zona
tenui et pellucida, velut argentei coloiis, lamina parum lata, quae spiraliter
locata et extremis lateribus unita tubum interius et exterius aliquantulum
asperum efficit ; quin et avulsa zona capites seu extreme trachearum tum
plantarum tum insectorum non in tot disparatos annulos resolvitur, ut
in perfectorum trachea accidit ; sed unica zona in longum soluta et extensa
extrahitur.'

Chap. I.] by Mttlptghi and Grew. 237

much misinterpretation and to gross errors on the part of later
writers. Malpighi thought he observed a peristaltic movement
in these vessels, a delusion to which many of the nature-
philosophers were particularly fond of surrendering themselves
at the beginning of the present century.

In addition to the bundles of fibres and the tracheae, Mal-
pighi observed a number of tubes in Ficus, Cupressus, and
other plants, which allowed the escape of a milky juice, and
he concludes that similar special tubes might be present also
in the wood of stems from which milk, turpentine, gum, and
the like exude.

Such are the elementary organs of plants, as far as they were
known to Malpighi ; in the subsequent part of his book we
find them applied to a histology of the stem, and here a mistake
at once makes its appearance, which, resting on his authority,
was reproduced by the phytotomists of the i8th and even of
the early part of the 19th century, — the theory, namely, that
the young layers of wood in the stem originate in the periodic
transformation of the innermost layers of bark (secondary
bast-layers) ; Malpighi was led into this mistake, as it appears,
partly by the softness and light colour of the alburnum, partly
by its fibrous character. In this substance the spiral tubes are
gradually formed, and as the mass becomes more solid and
compact, it subsequently forms the true wood.

The pith lies in the centre of the stem, and, according to
Malpighi, consists of numerous rows of spheres (' multiplici
globulorum ordine ') arranged longitudinally one after another,
and composed of membranous tubes, as may be clearly seen
in walnut, elder, and other trees. In this place also he men-
tions the milk-vessels in the pith of the elder. Passing over
many and various matters, it may be mentioned next that
Malpighi recognises the connection of the layers of tissue in
young shoots with those of the parent-stem, and very expressly
notices the same continuity of structure between the leaf and
the axis of the shoot. He then briefly touches on the anato-

238 Phytotomy founded [Book 11.

mical relations of the fruit and the seed, the existence of the
embryo in the seed and its structure, and then goes on to
the roots. ' The roots of trees are a part of the stem, which
divides into branches and ultimately ends in capillary threads
('capillamenta'); so that, in fact, trees are simply fine tubes,
which run separate from one another underground but gradually
collect into bundles; these bundles unite further on with other
and larger bundles, and all together ultimately join to form a
single cylinder, the stem, which then by separation of the tubes
at the opposite extremity stretches out its branches, and by
continued gradual separation of the larger into smaller finally
expands into leaves, and so reaches its furthest limits.' The
conclusion of the whole account is chiefly concerned with the
part played by the various kinds of tissue in the nourishment
of the plant.

In the second part published in 1674, the different kinds of
tissue in the stem are discussed at greater length ; here there
is much that is really good, but at the same time much that is
imperfect to an extent which cannot be attributed solely to the
inferiority of his microscope. Very excellent is the way in
which he endeavours to make out the more obvious anatomical
relations of the rind, the wood, and the pith, and in the
texture of the rind and the wood connects the longitudinal
course of the vessels and woody fibre with the horizontal
course of the medullary rays and the 'silver-grain.' The
magnifying powers which he used must, to judge from his
figures, have been very considerable; how much of what is
imperfect in them is due to the indistinctness of the field of view,
and how much to inaccurate observation, we cannot say. For
instance, he sees the bordered pits in the wood of Coni-
fers without perceiving the central pore, and represents them
as coarse grains lying on the outside of the wood-cells ; it was
unfortunate for Malpighi, as for his successors, that the large
vessels in the wood of dicotyledons, to which they gave most
of their attention, are often filled with secondary tissue (thy-

Chap. I.] by MalpigJii and Grew. 239

losis), which Malpighi figures Tab. vi, fig- 21, but the true nature
of which was not understood till 150 years later. Malpighi,
like succeeding phytotomists till as late as 1830, lays great stress
on the structure of the spiral vessels or tracheae, and mentions
particularly that they are surrounded by a sheath of woody
fibre ; but he did not fall into the strange notions which Grew
and other phytotomists entertained with regard to the nature
of these vessels.

We may at present omit the numerous remarks on assimila-
tion and the movement of the sap; the descriptions and
figures of the parts of buds and of the course of the bundles of
vessels in different parts of plants, and especially the analyses
of the flower and fruit and the examination of the seed and
embr}-o, conducted with a carefulness remarkable for that time,
deserve a fuller notice, but this would detain us too long from
our main subject.

If Malpighi's work reads like a masterly sketch in which the
author is bent only on giving the outlines of the architecture
of plants, the much more comprehensive work of Nehemiah
Grevv^, 'The anatomy of plantes ' (1682), has the appearance
of a text-book of the subject thoroughly worked out in all its
details ; the tasteful elegance of Malpighi is here replaced by
a copiousness of minute detail that is often too diffuse ; while
in Malpighi we only occasionally encounter the philosophical
prejudices of his time, which usually lead him into mistakes,
Grew's treatise is everywhere interwoven with the philosophical
and theological notions of the England of that day ; but we
are compensated for this by the more systematic way in which
he pursues the train of thought, and especially by the constant

* Nehemiah Grew, the son of a clergyman in Coventry, appears to have
been born in 1628, Having taken a Doctor's degree in a foreign University,
he practised as a physician in his native town, and pursued at the same
time his phytotomical researches. He became Secretary to the Royal Society
in 1677, and published his ' Cosmographia Sacra' in 1701. He died in
1 71 1. See the ' Biographic Universelle.'

340 Phytotomy founded [Bookii.

effort to give as clear a representation as possible of what he
sees. Though he too everywhere introduces physiological
considerations into his anatomical investigation, yet he keeps
himself free from many preconceptions which his successors
imported in this way into phytotomy. To mention one point
by anticipation, he avoided the erroneous notion so common
at a later time, and first definitively removed by von Mohl in
1828, that the cell-walls must have visible openings to serve
for the movement of the sap.

Grew's work, as has been said, separates into two main
divisions ; the first, ' The anatomy of plants begun, with a
general account of vegetation founded thereupon,' was printed
in 167 1, and contains a brief and rapid account of the general
anatomy and physiology of plants in forty-nine folio pages.
Then the anatomy of roots, stems, leaves, flowers, fruits and
seeds appeared as separate treatises in the following years up
to 1682. We may pass over the chemical researches embodied
in this work and the enquiries into the colours, taste and smell
of plants, as well as the previously issued treatise, ' An idea of
a philosophical history of plants,' which, as it was first laid
before the Royal Society in 1672, we may imagine to have
been intended as a counterpart to Malpighi's 'Anatomes
plantarum idea,' though it is very different in character and
admits much that is foreign to vegetable anatomy and
physiology.

With Grew as with Malpighi the main point of enquiry is
not the individual cell, but the histology ; after distinguishing,
like Malpighi, between the parenchymatous tissue and the
longitudinally elongated fibrous forms, the true vessels and
the sap-conducting canals, he is chiefly bent on explaining the
combination of these tissues in the different organs of the
plant ; and in this point he is superior to Malpighi both in
carefulness of description and in the beauty of his delineations.
Grew's numerous figures on copper plates, more carefully
executed than Malpighi's, give in fact so clear an idea especially

Chap. I.] bv Mttlpighi aficL Grew. 241

of the structure of the root and stem that a beginner may still
use them with advantage ; such figures as those on plates 36
and 40 and elsewhere show that he knew how to fashion his
observations by aid of much reflection into a clear representa-
tion of the thing seen ; there are, as might be expected, many
errors in the details of the more delicate structure of the
various forms of vessels and cells.

Malpighi had not said, whether he considered the cells of
the parenchyma (the term parenchyma comes from Grew) to
be perfectly closed or porous, nor how they cohere ; Grew
leaves no doubt on this point ; he says distinctly on page 6 1
that the cells or vesicles of the parenchyma are closed, that
their walls are not traversed by any visible pores, so that the
parenchyma may be compared to the foam of beer. He
quotes Malpighi's view respecting the vessels of the wood, and
supplements it by saying that the spiral band is not always
single, but that two or more bands entirely separate from one
another may form the wall of the vessel, and also that the
spiral thread is not flat but roundish like a wire, and its turns
are more or less close together according to the part of the
plant. He also notices that the spiral tubes are never
branched, and that when they run straight, as in Arundo
Donax, they can be seen throughout considerable distances.
The view of the structure of spiral vessels, which began with
Malpighi and was maintained through the whole of the
1 8th centur)'. Grew (p. 117) expresses still more distinctly
than Malpighi ; but it is to be observed that neither of them
clearly distinguished true spiral vessels with separable spiral
threads from vessels of the kind which occurs in secondary
wood, and only shows a spiral structure on being torn.
From the way, says Grew, in which the threads are woven,
it comes to pass that the vessels often unroll into a flat
surface, as we may imagine a narrow ribbon wound in a
spiral about a round staff" so that edge meets edge ; and if the
staff" is drawn out, the ribbon so wound will remain behind

R

342 Phytotomy founded [Book ii.

in the form of a tube, and this would answer to an air-vessel
in the plant. We should notice specially that Grew, better
taught than the phytotomists of the i8th century, considers
the vessels of the wood as air-passages, though they some-
times convey water. But he goes on with his description
of the wall of the vessel ; the flat surface disclosed by the
unwinding of a vessel is, he says, itself composed of many
parallel threads, as in an artiiicial ribbon, and the threads that
are spirally wound answer to the warp in an artificial tissue,
being held together by transverse threads, which correspond
to the woof. To realise to ourselves this very strange idea of
the structure of a spiral vessel as it appeared to Grew, we
ought to know that he thinks that all cell-walls, even those of
the parenchyma, are composed of an extremely fine web ; his
previous comparison of cell-tissue with foam was only intended
to make the more obvious circumstances clear to the reader ;
his real idea is, that the substance of the walls of vessels and
cells consists of an artificial web of the finest threads. He
hints at this on pages 76 and 77, and on page 120 he
returns once more to this conception and dwells upon it
at great length. The most exact comparison, he says, which
we can make of the whole body of a plant is with a piece
of fine lace-tissue, such as women make upon a cushion ;
for the pith, the medullary rays, and the parenchyma of the
rind are an extremely delicate and perfect tissue of thread.
The threads of the pith run horizontally like the threads in a
piece of woven stuff, and form the boundaries of the numerous
vesicles of the pith and the rind, as the threads in a web bound
the interstices in it. But the woody fibres and the air-vessels
are perpendicular to this tissue, and therefore at right angles to
the horizontal threads of the parenchyma, just as the needles
in a piece of lace work that lies on the cushion are per-
pendicular to the threads. To complete the comparison we
ought to suppose the needles to be hollow and the tissue of
thread-lace in a thousand layers one above another. Grew

Chap. I.] by Malpigki and Grew. 243

himself states incidentally, that he lit upon this notion from
looking at shrivelled masses of tissue, when he naturally saw
wrinkles and folds, which he took for threads. Besides he
seems to have used blunt knives, which might easily tear the
cell-walls into threads ; so we might gather from the figure in
Plate 40, where what he supposes to have been a tissue of
thread from the walls of a cell is depicted quite plainly.
Lastly the observation of vessels with reticulated thickening,
and parenchyma-cells with crossed striation may have con-
tributed to his view.

It will hardly be superfluous to remark here, that Grevv's
idea of this very delicate structure of cell-walls has evidently
given rise to the common expression cell-tissue (contextus
cellulosus) when speaking of plants and animals, an expression
which has become naturalised in microscopy, and is still re"
tained though we no longer think of Grew's comparison of
cell-structure with artificial lace. But the word tissue has
often misled later writers, as words are apt to do, and made
them found their conception of vegetable structure on the
resemblance to an artificial tissue of membranes and threads.

Grew, like Malpighi, derives the young layers of wood in the
stem from the innermost layers of the rind. The true wood, he
says on page 114, is entirely composed of old lymph-vessels, that
is of fibres, which lay originally in the inner circumference of the
rind. But by true woody substance he understands the fibrous
components of the wood, excluding the air-vessels ; his lymph-
vessels are the bast-fibres and similar forms ; for, he goes on,
the air-vessels with the medullary rays and the true wood form
what is commonly called the wood of a tree ; he uses the term
air-vessels, not because these forms never contain sap, but
because they only contain a vegetable air during the proper
period of vegetation, when the vessels of the rind are filled
with sap.

The above is certainly a very imperfect account of Grew's
services to phytotomy ; for the points here made prominent

R 2

244 Phytotomy founded [Book ii.

were treated by him as accessories only to the coarser histo-
logical relations with which he chieiiy occupied himself.

These two works of Malpighi and Grew, so important not
only for botany but for the whole range of natural science,
were not followed during the course of the next hundred and
twenty years by a single production, which can claim in any
respect to be of equal rank with them ; that long time was a
period not of progress but of steady retrogression, as we shall
see in the next chapter. But before the beginning of the
1 8th century Anton von Leeuwenhoek^ made some contri-
butions to the knowledge of the details of vegetable anatomy,
if not exactly to the settling of very important points in it;
he communicated his observations on animal and vegetable
anatomy in numerous letters to the Royal Society of London,
and these appeared for the first time in a collected form in
Delft in 1695 under the title of 'Arcana naturae.' It is not
easy to gain a clear idea of Leeuwenhoek's phytotomic
knowledge from his scattered statements. He too discussed
the less minute anatomy of fruits, seeds and embryos, and
among other things he made occasional observations on

• Leeuwenhoek's observations in animal anatomy were perhaps more
important than those which he made in botany. Carus (' Geschichte der
Zoologie,' p. 399) says of him : ' While Malpighi used the microscope with
system and in accordance with the requirements of a series of investigations,
the instrument in the hands of the other famous microscopist of the 17th
century was more or less a means of gratifying the curiosity excited in
susceptible minds by the wonders of a world which had hitherto been
invisible. Still the discoveries, which were the fruit of an assiduous use of
the microscope continued during fifty years, embraced many subjects and
were important and influential. Anton von Leeuwenhoek was bom in Delft
in 1632. Being intended for trade, he had not the advantage of a learned
education and is said even to have been ignorant of Latin ; his favourite
occupation was the preparing superior lenses, with which he incessantly ex-
amined new objects without being guided at any time by a scientific plan.
The Royal Society of London, to whom he communicated his observations,
made him a member of their body. He died in his native town in 1723,
being ninety years of age.

Chap. I.] by Malpiglit and Grew. 245

germination, and many on the structure of different woods.
But all bears the stamp of only occasional study of plants ;
he was led to his observations by questions of the nature-
philosophy then in vogue, and especially by such as were
connected with the theory of evolution, not unfrequently by
mere curiosity and pleasure in things obscure and inaccessible
to ordinary people, but he did not gain from them a general idea
of the structure of plants. In the course of these observations
he did unquestionable service in perfecting simple magnifying
glasses ; he made a large number with his own hands, and
these possessed magnifying powers evidently not at the
command either of Malpighi or Grew. By aid of such
glasses he discovered the vessels of secondary wood which
are not spirally thickened but beset with pits, the true
character of which however he did not investigate. He
was the first moreover who perceived the crj-stals in vegetable
tissue, namely in the rhizome of Iris florentina and in species
of Smilax, and this could only be done with strong magnifying
powers. In other matters he repeats the histological views of
Malpighi and Grew, and on the whole his numerous com-
munications seem painfully fragmentary and unscientific in
presence of Malpighi's elegance and perspicuity, and Grew's
systematic thoroughness. His figures too, which were not
drawn by himself, are with some exceptions inferior to those
of his great contemporaries.

CHAPTER 11.

Phytotomy in the Eighteenth Century.

Malpighi had no successor of note in Italy; in England
the new light was extinguished with Hooke and Grew, and
has so remained, we may almost say, till the present day ; in
Holland also Leeuwenhoek found none to follow him of equal
rank with himself, and the work done in Germany up to the
year 1770 is more wretched than can well be imagined. There
was in fact no original phytotomic research in the first fifty or
sixty years of the last century ; the accounts which were given
of the structure of plants were taken from Malpighi, Grew, and
Leeuwenhoek by persons, who, unable to observe themselves,
did not understand their authors and stated things not to be
found in their writings. The feebler and obscurer notions of
the older writers were preserved with a particular preference,
and thus it was Grew's complicated idea of the web-like
structure of cell-walls that made most impression on those
who reported him. This state of decline must not be ascribed
to imperfect microscopes only ; these certainly were not good,
and still less conveniently fitted up; but no one saw and
described clearly even what can be seen with the naked eye
or with very small magnifying power; the worst part of the
case was that no one tried fully to understand either the little
he saw himself or the observations to be found in older works,
but contented himself from want of reflection with most misty
notions of the inner structure of plants. It is not easy to
discover the causes of this dechne in phytotomy in the first
half of the i8th century; but one of the most important
appears to lie in the circumstance, that botanists, following in

Phyfotomy in the Eighteenth Century. 247

this the example of Malpighi and Grew, did not make the
knowledge of structure the sole aim in their anatomical in-
vestigations, but sought it chiefly for the purpose of explaining
physiological processes. The food and circulation of the sap
of plants were more and more the prominent questions, and
Hales showed how much may be done in this direction even
without the microscope ; the interest therefore of the few, who
like Bonnet and Du Hamel occupied themselves almost entirely
with vegetable physiology, was concentrated on experiment.

Others who knew how to use the microscope, as the Baron
von Gleichen-Russworm and Koelreuter, were drawn away from
the examination of the structure of vegetable organs by their
attention to the processes of fertilisation and especially of
propagation. The real botanists, according to the ideas of the
time, and specially those who belonged to the Linnaean school,
considered physiological and anatomical researches generally
to be of secondary importance, if not mere trifling, with which
an earnest collector had no need to concern himself. That
Linnaeus himself thought little of microscopical phytotomy is
sufficiently shown by what has been said of him in the first
book.

It is not worth while to notice each of the few small treatises
on the subject which appeared towards 1760, for they contain
nothing new; a few examples will show the truth of the
opinion here expressed on the general condition of phytotomy
at this time. *

Wt first of all encounter a writer, whom few would expect
to find among the phytotomists, the well-known philosopher
Christian Baron von Wolff, who in his two works, ' Verniinftige
Gedanken von den Wirkungen der Natur,' Magdeburg (1723)
and 'AUerhand niitzliche Versuche,' Halle (1721) gives here
and there descriptions of microscopes and discusses subjects
connected with phytotomy. This he does more particularly in
the latter work, where he describes a compound microscope
with a focussing lens between the objective and the ocular

248 Phytotomy in the Eighteenth Century. [Book 11.

but without a mirror, an instrument which must have served
therefore for observing with the light from above on an
opaque surface ; the objective was a simple lens. But to
magnify objects more strongly, he says that he used a simple
instead of this compound instrument, as was more the custom
at the time. Like a true amateur Wolff submitted all sorts of
small and delicate objects to his glass, without examining any
of them thoroughly and persistently. His phytotomic gains
were small ; he observed for instance that starch-flour (powder)
consists of grains, but believed from the way in which they
refracted light that they were small vesicles filled with a fluid ;
yet he satisfied himself that these grains are already in the
grains of rye and therefore not produced in the grinding. He
laid thin sections of portions of plants on glass which was too
imperfectly polished to allow of his seeing anything distinctly.
His pupil Thiimmig in his 'Meletemata' (1736) addressed
himself to the subject with still less skill. By the case of
these two men we may see plainly that want of success was
due much less to the imperfectness of the microscope than to
unskilful management and unsuitable preparation. But Wolff
and Thiimmig at least endeavoured to see something for
themselves of the structure of plants ; a famous botanist of
the time, Ludwig, plainly never made a similar attempt, for
in his ' Institutiones regni vegetabihs' (1742) he speaks of the
inner structure of the plant in the following manner ; ' Laminae
or membranous pellicles, so connected together that they form
little cavities or small cells and often reticulated by the inter-
vention of fine threads, form the cell-tissue which we see
pervading all parts of plants. These are what Malpighi and
others call tubes, since they appear in different parts in the
form of rows of connected vesicles ! ' Boehmer's ' Dissertatio
de celluloso contextu' (1785) is still worse; 'White elastic
thicker or thinner fibres and threads woven together of
differing shape and size form cavities or cells or caverns,
and are usually known by the name of cell-tissue.' We see

Chap. II.] Pliytotomy in the Eighieenth Century. 249

what mischief Grew did with his theory of the fibrous structure
of the cell-walls, and how the expression cell-tissue literally
taken led the botanists here named and others into utterly
incorrect ideas. The works of Du Hamel, Comparetti, and
Senebier show that such misconceptions were not confined to
Germany, and Hill, a countryman of Grew, according to von
Mohl's account pictured to himself cells as cups standing one
above another, closed below and open above.

Baron von Gleichen-Russworm (17 17-1783), privy coun-
sellor to the Margrave of Anspach, gave much attention to
the perfecting of the mechanical arrangements of the micro-
scope, but his plates themselves show how strangely un-
suitable these arrangements were. With these instruments
he made many observations, which are recorded in two
voluminous works, 'Das Neueste aus dem Reich der Pflanzen '
(1764) and 'Auserlesene mikroskopische Entdeckungen' (1777-
1781). But these works contain little or nothing about micro-
scopic anatomy or the structure of vegetable cells. His
observations with the microscope are chiefly devoted to
processes of fertilisation and to proving that spermatozoa are
contained in the pollen \ and in connection with these
subjects he gives magnified figures of m.any small flowers,
some of them beautifully executed ; these figures must have
made his works very instructive to many in their time. He
saw the stomata, which Grew had already discovered, on the
leaves of ferns, but took them for the male organs of fertilisation,
which at the same time showed that he was still unacquainted
with the existence of stomata in phanerogams.

Caspar Friedrich Wolff'' in his efforts in phytotomy stands

' This subject will be noticed again in the history of the sexual theory.

' C. F. Wolff was bom at Berlin in 1733. He studied anatomy under
Meckel and botany under Gleditsch, in the Collegium Medico-chinirgicum
in that city. He afterwards resorted to the University of Halle, and there
made acquaintance with the philosophy of Leibnitz and Wolff, which
predominates too much in his dissertation, ' Theoria Generationis ' (1759).

250 Phytotoniy in the Eighteenth Century, [bookii.

a solitary figure among his contemporaries, not only because
he was the first since Malpighi and Grew who devoted labour
and perseverance to the study of the anatomy of plants, but
still more because at a time, when the structure even of
matured vegetable organs was almost a forgotten subject, he
endeavoured to penetrate into the history of the development
of this structure and the formation of cellular tissue. Unfor-
tunately he was not directed to this by an exclusive interest
in phytotomy, but by a more general question which he
endeavoured to set at rest in this manner ; he wished to refute
the prevailing theory of evolution by demonstrating the
development of the organs of plants, and to obtain an
inductive basis for his doctrine of epigenesis. Though he was
often diverted by these means from the pursuit of purely
phytotomic questions, yet his famous work, ' Theoria Genera-
tionis' (1759) is nevertheless important in the history of
phytotomy ; for though it was disregarded by botanists during
the succeeding forty years, or at any rate exercised no notice-
able influence, yet it was Wolff's doctrine of the formation of
cellular structure in plants which was in the main adopted
by Mirbel at the beginning of the present century, and the
opposition which it encountered contributed essentially to
the further advance of phytotomy. This late but lasting
influence of Caspar Friedrich Wolff's work was due not to
the actual correctness but to the thoughtfulness of his obser-
vations, and to the earnest desire which inspired them to

Haller, the representative of the theory of evolution against which
this work was directed, replied to it in a kindly spirit and entered into
a correspondence with its youthful author. After lecturing on medicine in
Breslau, he was admitted to teach physiology and other subjects in the Col-
legium Medico-chirurgicum in Berlin, but was twice passed over in the
appointment to professorships in that institution. He received an appoint-
ment in the Academy of St. Petersburg from the Empress Catherine II in
1766, and died in that city in 1794. See Alf. Kirchhoff, ' Idee der Pflan-
zenmetamorphose,' Berlin, 1867.

Chap. II.] Phytotomy in the Eighteenth Century. 251

search out the true nature of vegetable cell-structure and
to explain it on physical and philosophical grounds. The
observations themselves on this point are highly inexact, and
influenced by preconceived opinions, and his account of them
is rendered obscure and often quite intolerable by his eager-
ness to give an immediate philosophic explanation of objects
which he had only imperfectly examined. His efforts to
follow the course of development in the first beginnings of
the formation of cell-tissue were evidently not seconded by
sufficient knowledge of the structure of matured organs, and,
to judge by his figures and by his theoretical reflections, his
microscope was of insufficient power and its definition imper-
fect. Notwithstanding all these deficiencies, Wolffs treatise is
doubtless the most important work on phytotomy that appeared
in the period between Grew and Mirbel, not, as has been said,
on account of any particular excellence of observation, but
because its author was able to make some use of what he saw,
and to found a theory upon it.

According to that theory all the youngest parts of plants,
the punctum vegetationis in the stem, which Wolff first
distinguished, the youngest leaves and parts of the flower,
consist of a transparent gelatinous substance ; this is saturated
with nutrient sap, which is secreted at first in very small drops
(we might say vacuoles), and these, as they gradually gain in
circumference, expand the intermediate substance and so
present enlarged cell-spaces. The intermediate substance
therefore answers to what we should now call the cell-walls,
only these are at first much thicker, and are constantly becom-
ing thinner with the growth of the cell-spaces. We may
compare young vegetable tissue, formed as Wolff imagines,
with the porosity of fermenting dough, except that the pores
are not filled with gas but with a fluid. It is plain from the
above description that the vesicles or pores, as Wolff names
the cells, are connected together from the first by the inter-
mediate substance, and that one lamina or cell-membrane

252 Phytotomy in the Eighteenth Century, [book ii.

only lies between each of two adjoining cells, a point which
succeeding phytotomists were a long time in determining. As
cells are formed by the secretion of drops of sap in the funda-
mental substance which is at first homogeneous, so vessels,
according to Wolff, are produced by longitudinal extension of a
drop in the mucilage and formation of a canal ; consequently
adjoining vessels must be separated from one another by a
single lamina of the fundamental substance. Though Wolff
expressly mentions the movement of the sap within the firm
mucilaginous substance between the cellular cavities and the
vascular canals, a movement of diffusion as it might now be
termed, he inconsistently enough thinks it necessary to assume
the existence of perforations in the bounding-walls of cells and
vessels to serve for the movement of sap from cell to cell
and vessel to vessel ; yet in the single case in which he
succeeded in obtaining isolated cells, namely in ripe fruits,
he was obliged to allow that the walls were closed.

The growth of the parts of plants, according to Wolff, is
effected by expansion of existing cells and vessels, and by the
formation of new ones between them in the same way as the
first vacuoles were formed in the mucilaginous substance of
very young organs ; that is to say, the sap which saturates the
solid substance between the passages and cavities of the tissue
separates in the form of drops, which increase in size and then
appear as cells and vessels introduced between the older ones.
The substance between the passages and cavities, at first soft
and extensible, becomes firmer and harder with increasing
age, and at the same time a hardening substance may be
deposited on it from the sap which is stagnant in the cell-
cavities and in movement in the vascular passages, and this
substance in many cases appears as their proper membrane.

This is in all essential points Wolffs theory. We may omit
his statements on the subject of the first formation of leaves at
the growing point and of the development of the parts of the
flower, as well as his physiological views on food and sexuality,

Chap, ii.] Phytotomy in the Eighteenth Century. 253

which remained for a long time without influence on the growth
of opinion, and mention only his doctrine of the growth of
thickness of the stem. The stem is originally the prolongation
of all the leaf-stalks united together. As many bundles of
vessels are formed in the developed stem as there are leaves
springing from the vegetative axis ; each leaf has a single
vascular bundle belonging to it in the stem, in modern phrase-
ology an inner leaf-trace. The union of these bundles from
the different leaves forms the rind of the stem ; but if the
leaves are very numerous, their descending bundles form a
closed cylinder, and if the stem is perennial, the fresh production
of leaves every year produces new zones of wood of this kind
every year, which are the yearly rings. This view of Wolff^s on
the growth of the stem in thickness bears an unmistakable
resemblance to the theory afterwards suggested by Du Petit-
Thouars, according to which the roots which descend from the
buds are supposed to effect the thickening of the stem.

The contests between Mirbel and his German antagonists at
the beginning of the present century will bring us back again
to the more important points in Wolff's theory of the cell.
Contemporary botanists paid less attention to the 'Theoria
Generationis ' than they did to Hedwig's' phytotomic views,
not on the formation of cells, but on the structure of mature
tissue. Hedwig had given various figures and descriptions of
phytotomic subjects in his ' Fundamentum Historiae Mus-
corum' (1782) and afterwards in his 'Theoria Generationis'

' Johannes Hedwig, the founder of the scientific knowledge of the Mosses,
was bom at Kronstadt in Siebenbiirgen in 1730. Having completed his
studies at Leipsic, he returned to his native town, but was not permitted to
practice there as a physician because he had not taken a degree in Austria.
He consequently went back to Saxony and settled first at Chemnitz, and in
1781 in Leipsic. Here he was appointed in 1784 to the Military Hospital,
and became Professor extraordinary of Medicine in 1786 and ordinary Pro-
fessor of Botany in 1789. He died 1799. He commenced his botanical studies
as a student at the University, and continued them in Chemnitz under trj'ing
circumstances, till as Professor he was free to devote himself entiiely to them.

354 Phytotomy in the Eighteenth Century. [Book ii.

(1784) ; but he treats these topics at greater length in his
treatise ' De fibrae vegetabilis et animalis ortu,' pubHshed
in 1789, and known to the author of this work only imper-
fectly from quotations in later writers. Hedwig's figures of
histological objects appear to be better than those of any
of his predecessors ; they show that he used strong magnifying
powers, and that his glass had a clear field of sight. His
defect lay in preconceived opinions and hasty interpretation
of what he observed. In order to refute Gleichen's view
of the stomata in ferns, he demonstrated the existence of these
organs in many phanerogams, and observed the opening of the
slits, which he named ' spiracula.' On the epidermis which he
had removed for the purpose of these observations he saw
plainly the double contour lines bounding the epidermis-cells,
and therefore the cell-walls, which are at right angles to the
surface. These he took for a particular form of vessel, and
called them ' vasa reducentia ' or ' lymphatica,' and afterwards
*vasa exhalantia,' and he thought that he had found them again
in the interior of parenchymatous tissue, evidently taking the
places where three wall-surfaces meet for vessels ; such vessels
he also saw in the milk-cells of Asclepias, described in
1779 by the elder Moldenhawer, who seems himself to have
regarded even the intercellular spaces in the pith of the rose as
equivalent to these milk-cells. The word vessel even in the 1 8th
century was used in such an indefinite manner, that the broad
air-tubes of the wood and the finest fibres were called vessels,
Hedwig's idea of the construction of spiral vessels was strange
enough ; he took the spiral band itself for the vessel, and
supposed it to be hollow because it is coloured by absorption
of coloured fluids; in those spiral vessels in which the turns of
the spiral band are distant he saw, it is true, the delicate original
membrane which lies between the turns, but he supposed that
it lay inside the spiral band, which was wound round it on the
outside. On the second plate of the first part of the ' Historia
Muscorum ' he even figures the network of ridges which the

Chap. II.] Phytotomy in the Eighteenth Century. 2.55

adjoining cells have left on the wall of the spiral vessel, but
explains it as wrinkles caused by desiccation.

Hedwig was without doubt a very practised microscopist, and
he constantly recommended the extremest care in the interpre-
tation of all that the instrument reveals ; but if an observer so
careful and practised, who moreover was provided with a glass
of tolerably strong magnifying power, fell into such gross mis-
takes, it cannot surprise us if others, as P. Schrank, Medicus,
Brunn, and Senebier, accomplished still less. These highly
unimportant achievements are all that mark the close of the
1 8th century.

CHAPTER III.

Examination of the Matured Framework of Celi.-
membrane in plants.

1800-184O.

There is no sharp line of division between the i8th and the
19th centuries; the phytotomists who appear on the scene
during the first years of the new century are scarcely more
successful than Hedwig and Wolff; careful and judicious
interpretation of their own and others' observations is still rare,
and they are often misled by preconceived opinions.

In one respect indeed a very great improvement appeared
with the commencement of the 19th century; the number
of phytotomists working contemporaneously, checking and
criticising one another, became all at once much larger.
Hitherto ten or twenty years had intervened between every
two works on phytotomy ; but in the course of the twelve
years after 1800 nearly as many publications followed one
another, and scientific discussion enlivened enquiry. Now
we meet with a Frenchman for the first time in the field
of phytotomy, Brisseau Mirbel, who brought out his 'Traite
d'Anatomie et de Physiologie Vegetale' in 1802, and raised
a series of questions in the discussion of which several German
botanists, Kurt Sprengel (1802), Bernhardi (1805), Treviranus
(1806), Link and Rudolphi (1807), at once took part. It was
a step in advance and one affecting all botanical studies, that
with the exception of Rudolphi all these men, like Hedwig
before them, were botanists by profession ; it was at last felt

Exammation of Cell-membrane in Plants. 257

that the examination of the internal structure of plants, as well
as the describing them according to Linnaean patterns, was a
part of botanical enquiry ; it is at the same time true that the
botanical knowledge of these observers was often of service to
them in their phytotomical investigations, and directed their
work decidedly and from the first towards that which was
worth knowing, and towards the objects which claimed the first
attention. This remark applies to the younger Moldenhawer
even more than to the botanists above-named ; his ' Beitrage,'
published in 181 2, may be taken as closing the first section of
this century, during which time he improved the methods of
observation, compared his own observations and those of
others with great acuteness of judgment, and did all that could
be expected with the microscopes of the time.

The period of sixteen years after Moldenhawer, from 1 8 1 2
to 1828, has nothing of material importance to show in
phytotomy. On the other hand, it produced a series of the
most important improvements that the compound microscope
has undergone since its invention.

As early as 1784 Aepinus had produced objectives of flint
and crown glass, and in 1807 Van Deyl' made similar ones
with two achromatic lenses, and still the phytotomists com-
plained of the condition of their instruments. Their figures show-
that they could not see clearly with them, though the magnify-
ing powers were not high ; Link says expressly in the preface
to his prize-essay of 1807, that he usually observed with a lens
that magnified a hundred and eighty times. Moldenhawer
in 1 81 2 gives the preference over all the microscopes he had
used to one by \N>ight, which was serviceable with a magnifx -
ing power of four hundred times, while the German instruments,
especially those by Weickert, could not be used with higher
powers than from one hundred and seventy to three hundred.

A certain inter\-al elapsed each time between an improvement

' See P. Harting, ' Das Mikroskop,' ^§ 433 and 434.

s

258 Examination of the Matured Framework [Book ii.

in the instrument and the appearance of the advantages which
phytotomy derived from it; thus in 1824, SelHgue exhibited
to the Academy of Paris an excellent microscope with double
lenses, several of which could be screwed on one over the
other, and which could be used with ordinary daylight and a
magnifying power of five hundred times ; in 1827 Amici made
the first achromatic and aplanatic objectives with three double
lenses screwed on one over the other, the flat sides being
turned to the object. And yet still in 1836 a practised phyto-
tomist like Meyen spoke with disapproval of the instruments of
his time, and gave the preference to an old English microscope
by James Man, though he allowed that the newest instruments
by Ploessl were a little better. In his work on phytotomy,
which appeared in 1830, all the figures were magnified two
hundred and twenty times, as were the very beautiful figures in
his prize essay of 1836 ; but in his ' Neues System ' (1837), he
had already adopted powers that magnified to over five hundred
times. How rapid the progress was in the years before and
after 1830 is shown by comparing von Mohl's work on climbing
plants of 1827 and its antiquated illustrations, with his publi-
cations of 1 83 1 and 1833, where the figures have a thoroughly
modern appearance.

The art also of preparing anatomical objects rose by degrees
with the improvement of the microscope. It was not in a very
advanced state at the beginning of the century, if we judge by
the language of writers and by their figures. It was a great step
in advance when the younger Moldenhawer in 181 2 isolated
cells by maceration and decay in water, and was thus enabled to
view cells and vessels on every side and in a perfect condition,
to see their real shape, and to survey the manner of their com-
bination more exactly than had hitherto been done. But even
Moldenhawer still made the mistake of submitting delicate
microscopic objects to observation in a dry state, though
Rudolphi and Link in 1807 had urged the advisability of
keeping every part of the preparations moist, especially the

Chap. III.] of Ccll-memhraue in Plants. 259

surface towards the object-glass, which shows that they did not
then use covering glasses. Nor was sufficient attention shown
to the use of sharp knives of suitable form, such as the razor,
which is now almost exclusively employed, or to practice in
making transverse and longitudinal sections of the utmost
possible delicacy, — two things which, through the example of
Meyen's and von Mohl's practice, were afterwards recognised as
indispensable helps to phytotomy ; even in their time observers
were satisfied with crushing and picking their preparations to
pieces.

Drawing from the microscope kept even pace on the whole
with increasing skill in making preparations, and with the
improvement of the instrument. If we compare together the
drawings of Mirbel and Kurt Sprengel in the beginning of the
century, those of Link and Treviranus in 1807, Moldenhawer's
in 181 2, and Meyen's and von Mohl's from 1827 to 1840, we
shall obtain a rapid and instructive survey of the history of phy-
totomy during this period of forty years. The figures testify at
once to constant increase in the magnifying powers, to the
greater clearness of the field of sight, and still more to the
constant improvement in the arts of preparing and observing
objects. But a curious misconception crept in among the
phytotomists at this time ; they believed that more correct and
trustworthy figures would be obtained, if the observer and
writer did not himself make them, but employed other eyes and
other hands for that purpose ; they imagined that in this way
ever)' kind of prejudice, of preconceived opinion would be elimin-
ated from the drawings. Thus both Mirbel and Moldenhawer
had their figures drawn by a woman, and many later phytotomists
entrusted the execution of their drawings to hired draughtsmen,
as Leeuwenhoek had done before them. A drawing from the
microscope, like every other copy of an object in natural
history, cannot pretend to take the place of the object itself,
but is intended to give an exact and clear rendering of what
the observer has perceived, and by so doing illustrate the

s 2

26o Examination of the Matured Framework [book ii.

verbal description. The drawing will be perfect in proportion
to the practised skill of the eye that observes and of the mind
that interprets the forms. The copy should only show to
another person what has passed through the mind of the
observer, for then only can it serve the purpose of a mutual
understanding. There is also another point to be considered ;
it is exactly in the process of drawing a microscopic object that
the eye is compelled to dwell on the individual lines and points
and to grasp their true connection in all dimensions of space ;
it will often happen that in this process relations will be per-
ceived, which previous careful observation had disregarded,
and which may be decisive of the question under examination
or even open up new ones. As the microscope trains the eye
to scientific sight, so the careful drawing of objects makes the
educated eye become the watchful adviser of the investigating
mind ; but this advantage is lost to the observer who has his
drawings made by another hand. It is not one of the least of
von Mohl's merits, that he practised microscopic drawing under
the influence of the views here indicated, and sought to make
his figures no mere undigested copies of the objects, but an
expression of his own opinions about them.

Enough has been said to show that an important portion of
the history of phytotomy lies between the beginning and the
end of the period under consideration. The distance between
the knowledge of the structure of vegetable tissue which existed
at the beginning of the century, and that of Meyen and von Mohl
on the same subject in 1840, is wonderfully great; in the one
case an uncertain groping about among obscure ideas, in the
other a complete exposition of the inner architecture of the
mature plant. But in spite of this great difference between
beginning and end, it is better to review the efforts of this
period of forty years as a connected process of historical
development, and, notwithstanding the interval between the ap-
pearance of Moldenhawer's contributions in 181 2 and Meyen's
and von Mohl's labours about 1840, to consider the latter as

Chap. III.] of CcU-niembraue in Plants. 261

the settlement of the questions taken up at the commencement
of the century. Moreover after 1840, with the appearance of
Schleiden and NageH on the scene, new points of view were
suddenly disclosed, and new aims were proposed in phytotomic
investigation ; it is no objection to this view of the subject, that
the most productive portion of von Mohl's labours falls in the
succeeding twenty years, and that during this later period his
position is one of equal authority with the new tendency and
of participation in it. Up to 1845 his discoveries were the
culminating point of the older phytotomy ; they put the finish-
ing stroke to the work which Mirbel, Link, Treviranus, and
Moldenhawer had begun. The object almost exclusively pur-
sued during all this period was to frame as true a scheme as
possible of the inner structure of the mature organs of the
plant ; it was requisite to gain a right understanding of the
diversities of cells and forms of tissues, to classify them and
supply them with names, and to secure well-conceived defini-
tions of these names. Hence almost exclusive attention was
paid to the configuration of the solid framework of cell-mem-
brane, and of this chiefly in the matured state, to the form of
the several elementary organs and their combination in the
tissue, to the sculpture of the wall-surfaces, and to the connec-
tion of cell-spaces by pores or their separation by closed walls.
There was much discussion, especially at first, on the contents
of vessels and cells, and on supposed movements of sap in
connection with anatomical research, but there was no
careful connected investigation of the cell-contents ; it was not
yet recognised that the true living body of the vegetable cell is
only a definite part of the contents inclosed by the cell-wall ;
the solid walls, the framework of the whole building, were
regarded as of primary importance in the structure of the cell.
It was not till the following period that in the light of historical
development another view asserted itself, namely, that the
solid framework of vegetable tissue with all its importance is
yet in the genetic sense only a secondary product of the

262 Examination of the Matured Framework [Book ii.

phenomena of vegetative life, that the true cell-body, the cell-
protoplasm is prior in time and in conception, and can claim
the higher position.

Mirbel, to whom we now return, had in 1801 laid down a
theory of cell-formation which agreed in the main with that of
Caspar Friedrich Wolff; he supposed with Wolff that each
cell-space was separated from its neighbour by a single wall,
and relying on fresh observations asserted the existence of
visible pores in the dividing walls of parenchyma and of vessels,
and also maintained some new views on the nature and forma-
tion of vessels. The essential points of this theory found an
opponent in Germany in the person of Kurt Sprengel, the
well-known historian of botany, and one of the most variously
accomplished botanists of his time, who had published in 1802
a work written in diffuse and familiar style under the title of
' Anleitung zur Kenntniss der Gewiichse.' He relied on his
own observations, but these were evidently made with small
magnifying powers, an obscure field of sight, and indifferent
preparations. The cell-tissue, says Sprengel, consists of cavities
of very various shape communicating with one another, the
dividing walls being in some places broken through and in
others wanting. He took the starch-granules which he saw in
the seed-leaves of beans and other plants for vesicles, which
increase in size by absorption of water and so form new tissue ;
but he did not explain how we are to conceive of the growth of
organs with such a mode of cell-formation. His account of the
vessels is extremely obscure, even more obscure than Hedwig's,
though he has the merit of refuting the latter's strange theory
of reconducting vessels in the epidermis ; he also suggested,
though only incidentally, the happy idea that spiral passages and
even vessels might arise from cell-tissue, since the youngest
parts of plants have only the latter ; but he did not attempt to
explain how or where the process takes place. Like Malpighi

Chap. III.] of Cell-tnembraiic in Plants. 263

and Grew he supposed that the spiral vessels had no wall of
their own, but thought that the closely-rolled spiral threads
formed a wall ; the constrictions in broad short-membered
vessels he regarded as real contractions in their substance,
caused by the increased tightening of the spiral threads through
a sort of peristaltic movement, — a mistaken notion often enter-
tained at the beginning of the century, by Goethe among
others, and connected with ideas of vital power prevalent at the
time. In the stomata, to which he gave the name still in use,
Sprengel like Grew, Gleichen, and Hedwig, saw a circular
cushion instead of the two guard-cells ; but he notices the
observation first made by Comparetti, that the orifice closes
and opens alternately, being wide open in the morning and
closed in the evening. But he considered the stomata to be
organs of absorption.

Sprengel in enunciating his own theory of cell-formation
accused Mirbel of mistaking the starch-grains in the cells for the
pores of the cell-walls. On this point, so important in the
doctrine of the cell and in physiology, he was followed by the
three candidates for the Gottingen prize, though Bernhardi
had in 1805 defended Mirbel's view, and had pointed out how
little likely it was, that so skilful an observer as Mirbel should
fall into so gross an error. Bernhardi's short treatise, ' Beo-
bachtungen iiber Pflanzengefasse,' Erfurt (1805 '), was in general
distinguished by a variety of new and correct observations, and
was the work of a simple and straightforward understanding,
which takes things as they are presented to the eye without
allowing itself to be led astray by preconceived opinions. His
observations are certainly the best in the whole period from
Malpighi and Grew to the younger Moldenhawer ; his method
of dealing with questions of phytotomy is much more to the
purpose than that of the three rivals for the Gottingen prize.

' Johann Jakob Bernhardi, bom in 1774, was Professor of Botany in
Eri'urt, and died there in 1850.

264 Examination of the Matured Framework [Book it.

In the work just mentioned Bernhardi treats of other forms of
tissue as well as vessels, and endeavours to distinguish and
classify them more exactly than had hitherto been done. He
contrasts favourably with his contemporaries in the fact, that
he sought to define the histological terms employed as precisely
as possible, — a great step in advance at a time when phytotomic
conceptions were in a very misty condition. He distinguishes
three chief forms of vegetable tissue, pith, bast, and vessels.

By pith he means the tissue which Grew had named paren-
chyma, and which is still so called ; it remained a question
with him whether the cells of the pith are pierced by visible
pores. By the word bast he understood not only the fibrous
elements of the rind, but those of the wood also, and in general
what is now known as prosenchyma ; this agrees very well with
Malpighi's view, which was adopted by Bernhardi and by all his
contemporaries, that the inner layers of the bast are changed
into the exterior layers of wood to make the increase in thick-
ness of the woody stem ; but he did not admit the same origin
in the case of the innermost portion of the wood, for this is
formed from the first in the young shoots, which alone contain
true spiral vessels with threads that may be wound off.

Bernhardi distinguishes vessels into two main groups, air-
vessels and vessels properly so called. He calls the first
group air-vessels for the same reason that led Grew to give
them that name, namely, that they are filled with air during a
part at least of the period of vegetation ; they are found in the
wood, and, where there is no closed woody body, there the
woody bundles are formed both of vessels and also of bast
strands which enclose vascular canals. These latter he next
divides into three chief kinds ; annular vessels, which he was
the first to discover, true spiral vessels with a band which can
be unwound, and scalariform vessels, by which term he under-
stood not only those with broad slits, such as are found
in Ferns, but also the pitted vessels in secondary wood. His
idea of annular and spiral vessels was perfectly correct, and he

Chap. III.] of Ccll-membranc in Plants. 265

mentions Hedwig's notion already described, and shows that
its exact opposite is true, namely, that the spiral band is
surrounded by a membrane on the outside, — a fact which was
afterwards denied by Link, Sprengel, and Moldenhawer. On
the other hand he did not understand the sculpturing on the
scalariform vessels ; he took the pits in the dotted vessels for
thickenings of the wall, such as are seen in the transverse ridges
between the slits in true scalariform vessels, and the slits he
thought were closed. If there was much that was erroneous
in these views, yet Bernhardi contributed essentially to the
clearing up of the subject by his effort to distinguish the
different forms of air-vessels, and especially by pointing atten-
tion to the fact that neither spiral nor annular vessels are found
in secondary wood. The resemblance between different forms
of vessels misled many of his contemporaries into supposing
that they are due to metamorphosis of true spiral vessels.
Bernhardi showed that different forms of wall are found inside
one vascular tube, but that this does not depend on modifica-
tion with age ; observation rather teaches that every kind of
vessel receives its character in its young state, and especially
that the youngest scalariform vessels do not present the form
of spiral vessels.

Under the head of vessels proper he reckoned all tubular
forms filled with a peculiar juice, milk-cells and true milk-vessels,
and also resin-ducts and the like, and he made many good and
still valuable observations on their distribution and sap-contents.
He could not see the differences of structure in these various
fluid-conveying vessels with the low magnifying power of his
glass, and therefore attended chiefly to the structure of the
large resin-ducts, which on the whole he rightly understood.

The question whether there are any other forms of vessels in
the plant beside those already named gave him occasion to
define a vessel better than it had yet been defined, namely as
an uninterrupted tube or canal, and at the same time he found
himself obliged to consider whether his bast-threads are vessels ;

266 Examination of the Matured Framework [BookII.

but he did not give a decided answer to the question. He
declared however distinctly against Hedwig's reconducting
vessels in the epidermis, as Sprengel had done, and it is worthy
of recognition that he understood the true nature of the corners
where three longitudinal walls of the parenchyma meet, while
later observers found difficulties in them.

Before the appearance of Bernhardi's work the Royal scien-
tific Society of Gottingen proposed a subject for a prize in the
year 1804, which shows very plainly what uncertainty was felt
at that time on all points of phytotomy. For this reason it
will be well to give it at length from the preface to Rudolphi's
' Anatomie der Pflanzen ' (1807) : ' Since some modern physiolo-
gists deny the peculiar construction of vessels in plants which
is attributed to them by other and especially the older
observers, it would be well to institute new microscopical
investigations, which shall either confirm the observations of
Malpighi, Grew, Du Hamel, Mustel, and Hedwig, or prove
that plants have a special organisation of their own which is
more simple than that of animals, whether that organisation is
supposed to originate in simple peculiar fibres and threads
(Medicus) or with cellular and tubular tissue (tissu tubulaire
of Mirbel). Attention should also be given to the follow-
ing subordinate questions : i. How many kinds of vessels
may certainly be distinguished from the first period of their
development? The existence of certain forms having been
established ; 2. Are the twisted fibres which are called spiral
vessels (vasa spiralia) themselves hollow, and do they there-
fore form vessels, or do they serve by their convolutions for
the formation of closed cavities, and how? 3. Do fluids as
well as gases move in these cavities ? 4. Do the scalariform
ducts arise from adherence of the twisted threads (Sprengel), or
do the threads owe their origin to the ducts (Mirbel)? Do
alburnum and woody fibres originate in the scalariform ducts,
or in true vessels, or in tubular tissue?'

We see in this case as in many similar ones, that the subject

Chap. III.] of Ccll-mcmbranc in Plants. 267

was proposed by persons who understood little of it, and who
were unable to judge of what had been written about it; how
else could they have placed the opinions of a Mustel and
a Medicus side by side with those of Malpighi and Grew?
Had Bernhardi or Mirbel set the question, it would certainly
have been better conceived. It was in keeping that the three
essays sent in, all inferior to Bernhardi's work already men-
tioned, though they contradicted one another on the most
important points, were nevertheless all accepted ; not less so
that Treviranus' essay obtained only the second place, though
it was decidedly better than the other two, and very much
better than Rudolphi's. The best result of the whole affair
was that it stirred up the phytotomists of the day, and led Mir-
bel to submit the three prize treatises to a searching criticism,
especially that of Treviranus, which Mirbel with professional
acumen recognised as the best. Link's essay appeared in 1807
under the title ' Grundlehren der Anatomic und Physiologic der
Pflanzen,' that of Rudolphi as 'Anatomic der Pflanzen,' also in
1807, each forming a handsome octavo volume. The work of
Treviranus had already appeared in 1806 with the title, ' Vom
inwendigen Bau der Gewachse.'

If we compare the works of Link and Rudolphi \ which
both received a prize, and which had all the appearance of
text-books of general vegetable phytotomy and physiology, we
miss in both any clear exposition of the conceptions connected
with the words used, and the train of thought therefore is
constantly obscure and vacillating. Yet it is easy to see that
they are opposed to one another in all essential points, Link^

^ Karl Asmus Rndolphi, bom at Stockholm in 1771, was Professor of
Anatomy and Physiology in Berlin, and died there in 1832.

^ Heinrich Friedrich Link was born at Hildesheim in 1767, and became
Doctor of Medicine of Gottingen in 1788. In 1792 he became Professor of
Zoology, Botany, and Chemistry in Rostock, Professor of Botany in 181 1
in Breslau, and in 1S15 in Berlin, where he died in 1851. He was a clever
man of very varied accomplishment, but not a very accurate observer of

268 Examination of the Matured Framework [bookII.

generally hitting on the correct, or at least the correcter view.
For instance, Rudolphi denies altogether the vegetable nature
of Fungi and Lichens, because he iinds no resemblance
between their hyphae and vegetable cell-tissue, and he supposes
them to arise by spontaneous generation ; even of the Confervae
he says that the microscope has shown him nothing that agrees
with the structure of plants, — evidently a sign of bad observa-
tion or of incapacity to understand what he saw. Link on the
other hand regards all Thallophytes as plants, and sees that
the filaments of Lichens and Fungi consist of cells, and that
cells occur at least in many Algae. Rudolphi praises in the
same breath the views of Wolff and Sprengel on cell-tissue,
although they are directly opposed to one another, and although
he adopts Sprengel's strange theory of cell-formation without
alteration. Link on the contrary declares against Sprengel's
theory, and on good grounds, and shows that the vesicles
which Sprengel took for young cells are starch-grains ; at the
same time he makes new cells be formed between the old ones.
Rudolphi is of opinion that cells open into one another, as is
plainly shown by the passage of coloured fluids. Link main-
tains that cells are closed bodies, and proves it well by the
occurrence of cells with coloured juice in the middle of colour-
less tissue. Rudolphi represents the orifices of the stomata as
encircled by a roundish rim, which he takes without hesitation
for a closing muscle because the apertures enlarge and diminish.

details, and was held in estimation by many chiefly as a good teacher and
philosophic author of popular works on natural science. He was one of
the few German botanists in the early part of the present century who
aimed at a general knowledge of plants, and combined anatomical and
physiological enquiries with solid researches in systematic botany. Of his
many treatises on all branches of botanical science, zoology, physics,
chemistry, and other subjects, his Gottingen prize essay must be considered
to have contributed most to the advancement of science. Von Martins
somewhat overrates his scientific importance in his • Denkrede auf H. F.
Link ' in the ' Gelehrte Anzeigen,' Miinchen (1851), 58-69.

Chap. III.] of Cell-membrane in Plants. 269

Link is more happy in taking the part that surrounds the
aperture for a cell, or a group of cells. Rudolphi considers the
great cavities in hollow stems and in the tissue of water-plants
as the only air-passages in plants ; Link explains these cavities
as gaps caused by the irregular growth of cellular tissue. With
Rudolphi the word vessel means not only vascular forms in
wood, but milk-vessels and resin-ducts also, and to the
former he even transfers Malpighi's view of the structure
of spiral vessels. Link designates the tubes of the wood
only as vessels, combining the most various forms of them
under the term spiral vessels ; he excludes milk-vessels, resin-
ducts, and the like from the conception of a vessel, and in this
he is somewhat inconsistent, since he assumes with Rudolphi
that a vessel, in plants as in animals, is a canal for the convey-
ance of nutrient sap.

With all these contradictions, the two essays agree in adopt-
ing the old Malpighian view of the growth in thickness of stems,
according to which the new layers of wood are formed from the
inner layers of bast, while between the bast-cells, which are
here taken to be identical with woody fibre, new spiral vessels
arise contemporaneously, and, as Link expressly says, from
juices which pour out between the bast-cells.

It is hard to understand how two treatises, so contradictory
as they have been shown to be, could have both received
a prize at the same time, or how the great difference could
have been overlooked between Link's sensible and well-
arranged account of his subject, and Rudolphi's uncritical
statements, which everywhere rely more on old authority than
on his own observation. It is however certain that Link's
better production is inferior to Bernhardi's treatise, unless we
choose to consider the greater copiousness of detail in Link,
the number of his observations, and his aquaintance with the
literature of the subject, as giving him the advantage. His
figures, as well as Rudolphi's, are not so good as those of
Bernhardi.

270 Examination of the Matured Framework [Book 11.

The work of Treviranus', to which the judges at Got-
tingen awarded the second place, is much less comprehensive
than those of his competitors ; the style is inferior to Link's,
and may even be called clumsy. But the much better figures
show at once that Treviranus was the more accurate observer,
and his work, in spite of the inferiority of its style, is of far
higher value on account of the attention paid in it to the
history of development ; Treviranus laid greater stress on this
method than either Link or Rudolphi, and it led him to form
views on some of the fundamental questions of phytotomy,
in which we see the germs of theories afterwards perfected
by von Mohl. His account of the formation of cell-tissue is
mainly that of Sprengel, and therefore an unfortunate one ;
but nevertheless his observations on the composition of wood
and the nature of vessels were as good and correct as could be
expected from the condition of the microscope at the time.
He made one discovery of considerable value, that of the
intercellular spaces in parenchyma, but he lessened its merit
by filling these passages with sap, and even describing its
movement. Woody fibres are due, he thinks, to strong

^ Ludolf Christian Treviranus, bom at Bremen in 1779, became Doctor of
Medicine of Jena in 1 801 , and practised at first in his native town, where he be-
came a teacher at the Lyceum in 1807. In 181 2 he accepted the professorship
in Rostock vacated by Link, and was again his successor in Breslau. In 1830
he exchanged posts with C. G. Nees von Esenbeck, who was a professor in
Bonn ; he died in that town in 1864. In the first part of his life he occu-
pied himself chiefly with vegetable anatomy and physiology, afterwards with
the determination and correction of species. His first works, which are
noticed in the text, and the treatises on sexuality and the embryology of the
Phanerogams, published between 18 15 and 1828, are the most important in
a historical point of view. His ' Physiologic der Gewachse ' in two volumes
(1835-1838) is still of value for its accurate information on the literature
of the subject ; but it can scarcely be said to have contributed to the advance
of physiology, for its author adhered in it to the old views, and especially to
the notion of the vital force, at a time when new ideas were already asserting
themselves. The * Botanische Zeitung' for 1864, p. 176, contains a notice
of his life.

Chap. TIL] of Cdl-mcmhranc in Plants. 271

longitudinal extension of vesicles. He supported Bernhardi's
view of the nature of vessels, that the separable spiral threads
of spiral vessels are not wound round a membranous tube but
are surrounded by one. He maintains against Bernhardi the
distinctness of punctated vessels or porous woody tubes from
false tracheae or scalariform vessels, while he gave a more
correct description of the latter as they occur in Ferns. He
rejected Mirbel's view that the pits in dotted vessels are
depressions surrounded by a raised glandular edge, and ex-
plained them as grains or little spheres. Against this mistake
we may set off the very important step which he made in
advance, when he not only conjectured that the pitted vessels
of the wood are formed from cells previously divided off from
one another, but proved by observation that the members
composing such vessels are at first actually separated by
oblique cross-walls, which afterwards disappear. But this
correct observation was impaired by the mistaken idea, which
Treviranus shared with his predecessors, that the wood is the
result of transformation of the bast, and consequently that the
vessels of the wood are bast-fibres, which elongate considerably
after they are arranged in a direct chain one after the other ;
the unevennesses caused by the oblique junctions of the tissue
gradually disappear, the boundaries of each member of a vessel
being still for some time indicated by oblique transverse
markings. The dividing walls originally existing at these
points disappear by widening of the cavities, so that the
different parts come to form a continuous canal. To illustrate
the disappearance of a parting wall between two adjoining cells
Treviranus aptly points, somewhat to our surprise, to the
formation of the conjugating tube in Spirogyra. He rejects
with Bernhardi the view represented by Sprengel, Link, and
Rudolphi, that the different kinds of vessels are formed from
true spiral vessels ; he says that he had found the scalariform
ducts in Ferns so formed in their earliest stage and not as
spiral vessels; he thinks it highly probable that the distinct

272 Examination of the Matured Framework [Book ii.

transverse bands on false spiral vessels (scalariform ducts) and
the pits of dotted vessels are formed on the walls of membranous
fibre-tubes ; in like manner he derives true spiral vessels from
long thin-walled cells, on whose inner surface the spiral band
is formed, and well compares the members of young spiral
vessels with the elaters of the Jungermannieae. Here then we
find the first more definite indications of a theory of growth in
thickness of cell-walls, which, like the theory of the origin of
vessels from rows of cells, was afterwards developed by von Mohl
and laid on better foundations. At the close of the essay the
histology of the Cryptogams, Monocotyledons and Dicotyledons
is compared, and the subject is better and more perspicuously
handled than in the corresponding chapters of his competitors.
Though Treviranus' account of vegetable tissues was on the
whole weak as far as concerns the history of development, yet
MiRBEL ^ recognised in him the most dangerous opponent of
his own theory, and addressed a public letter to him and not
to his other German antagonists, Sprengel, Link and Rudolphi,
in defence of the views he had formerly expressed. This
letter is the first part of a larger work which appeared in 1808,

' Charles Fran9ois Mirbel (Brisseau-Mirbel) was bom at Paris in 1776,
and died in 1854. He began life as a painter, but having been introduced
by Desfontaines to the study of botany, he became Member of the Institute
in 1808, and soon after Professor in the University of Paris. From 1816 to
1825 the cares of administration withdrew him from his botanical studies,
but he resumed them and became in 1829 Professeur des cultures in the
Museum of Natural History. Mirbel was the founder of microscopic veget-
able anatomy in France. All that had been accomplished there before his
time was still more unimportant than the work done in Germany. His
writings involved him in many controversies, and he made enemies by
refusing in his capacity of teacher to allow the importance at that time at-
tributed to sj-stematic botany, but directed his pupils to the study of struc-
ture and the phenomena of life in plants. We are told by Milne-Edwards
that he suffered much from the fierce attacks which were made upon him ;
he sank at last into a weak and apathetic state, and was for some time
before his death unable to continue his studies or official duties (' Botanische
Zeitung' for 1855, p. 343).

Chap. III.] of Ccll-mcmhrane in Plants. 273

' Exposition et defense de ma thdorie de I'organisation veg^tale,'
in which Mirbel endeavours to meet the objections of his
opponents with great adroitness of style and with the results
of varied rather than profound observation, and to find new
arguments for his theory of vegetable tissue ; he admits that
his former treatises were in many respects faulty, but demands
that his critics should discuss his system as a whole and not
take offence at single expressions. Mirbel's idea of the inner
structure of plants is essentially the same as that broached by
Caspar Friedrich Wolff. The first and fundamental idea is
that all vegetable organisation is formed from one and the
same tissue differently modified. The cell-cavities are only
hollow spaces of varying form and extension in homogeneous
original matter, and have no need therefore of a system of
filaments, as Grew supposed, to hold them together. The
tracheae only are an exception, which Mirbel, in striking
opposition to the much more correct view of Treviranus,
considers to be narrow spirally wound laminae, inserted into
the tissue and connected with it only at the two ends. If it is
asked how interchange of sap is effected in such a cellular
tissue as this, it becomes necessary to assume that the mem-
branous substance of plants is pierced by countless invisible
pores, through which fluids find their way. But nature has a
speedier and more powerful instrument in the larger pores,
which the microscope reveals. Mirbel does not discuss the
question how the fluids are set in motion, easily disregarding
such mechanical difficulties, as was usual in those days, when
vital power was always in reserve to be the moving agent.
He warmly repels the imputation, which Sprengel had made
against him, of having confounded pores and granules, by
appealing to his figures; he says that he has depicted pro-
minences on the outside of the walls of the dotted vessels, and
an orifice in each of them, which his opponents simply never
saw. The question whether these prominences lie on the
inside or the outside of the walls of the vessel has no meaning,

T

274 Examination of the Matured Framework [Book ii.

if we suppose with Mirbel that the dividing wall is single ; he
is only concerned to enquire whether the perforated projections
lie on the one or on the other side of the wall. He refers
Treviranus, who had denied the presence of the pores, to his
description of scalariform vessels, in which he had himself
seen the slits which correspond to the pores.

In comparison with these fundamental questions Mirbel's
further account of matters of detail does not concern us here.
He gave a connected view of the whole of his doctrine of
tissues in the form of aphorisms, which occupy the second
part of his book. Of all that he says on the five kinds into
which he distinguishes vessels the most interesting is the
statement, that diaphragms pierced like a sieve separate the
different members of his ' beaded ' vessels. We find that the
weakest part of Mirbel's phytotomy, as of that of his opponents,
is his description of the true vessels (vasa propria), with which
he classes the milk-cells of the Euphorbiae and the resin-ducts
of Coniferae, but he saw clearly enough that the latter were
canals inclosed in a layer of tissue of their own. The third
part of the book is devoted to these forms of tissue, and we
learn that he classes not only many kinds of sieve-cell-bundles,
but also true bast-fibres, as those of nettle and hemp, with his
bundles of true vessels. Like his opponents he makes the
growth in thickness in woody stems to be due to transformation
of the inner layer of bast; but he gives a new turn to this
view, which brings it nearer to the modern theory ; during the
period of vegetation a delicate tissue with large vessels is
developed in Dicotyledons on the confines of the wood and
the bark, and these augment the mass of the woody body,
while a loose cellular tissue is formed on the other side,
destined to replace the constant losses of the outer rind. To
later phytotomists, who understood by the word cambium a
thin layer of tissue constantly engaged in producing wood and
rind, Mirbel's otherwise indistinct conception of growth in
thickness must have become more indistinct from his using

Chap. III.] of Ccll-membrane in Plants. 275

the word cambium not for the layer of tissue afterwards so
called, but for a highly ' elaborated and purified sap ' which is
intended for the food of the plant and makes its way through
all membranes ; we see this cambium-sap appear at the spots
where it produces new tubes and cells after the manner of the
Wolffian theory. The cells a])pear at first as minute spheres,
the tubes are very fine lines ; both enlarge and gradually show
pores, clefts, etc. This is essentially Wolffs doctrine, which
Mirbel afterwards endeavoured to confirm against his German
opponents from the germination of the date-palm with the
help of a more powerful microscope.

Mirbel insisted more than the German phytotomists of his
day on the idea, that all forms of vegetable tissue are developed
originally from young cell-tissue, an idea suggested by Sprengel
and following naturally with Mirbel from WolflPs theory. Both
Mirbel and Wolff were hasty in observation and too much
under the influence of theory in giving reasons for what they
observed, and therefore too ready with far-reaching explanations
of phenomena which only long-continued observation could
decide.

Treviranus replied, though after some delay, to Mirbel's
polemics by incorporating into his ' Beitrage zur Pflanzen-
physiologie,' Gottingen ( 1 8 1 1 ), an essay entitled ' Beobachtungen
im Betreff einiger streitigen Puncte der Pflanzenphysiologie,'
in which he again took up the questions in dispute between
himself, Mirbel, Link and others, and supported his own views
by fresh investigations. It cannot be denied that in this short
treatise Treviranus brought some important questions nearer
to a decision ; he added materially to the knowledge of
bordered pits, on which subject his views now approximated
more nearly to those of Mirbel ; he drew attention to the
vesicular nature of vegetable cells, which are often separable
from one another, and to the occurrence of true spiral vessels
in the neighbourhood of the pith in Conifers also, and among
other things discovered the stomata on the capsule of Mosses.

T 2

276 Examination of the Matured Framework [Book 11.

On the subject of the theory of cell-formation which he had
borrowed from Sprengel, he endeavoured to extricate himself
from his difficulty by ingeniously pointing out that though
the starch-grains in the seed-leaves of the bean disappear
without producing new cells in them, they are dissolved and
then serve as fluid material for new cell-formation in other
parts of the germinating plant, which however was giving up
Sprengel's theory ; yet he cited as a direct proof of that theory
the origination of gonidia in the cells of Hydrodictyon, and
their development into new nets.

Mirbel and his German opponents moved for the most part
in a circle of ideas which had been formed by the speculations
of Malpighi, Grew, Hedwig and Wolff, though it must be
allowed that the observations of Treviranus did open new
points of view. But Johann Jakob Paul MoLDENHAVi^ER ^
travelled far beyond these older views as early as 181 2 in his
important work, ' Beitrage zur Anatomic der Pflanzen.' He
took up from the first a more independent position as regards
former opinions than either of the writers hitherto considered.
He relied on very detailed, varied, and systematic observations
evidently made with a better instrument, abided by what he
himself saw, and chose his point of view in accordance with it,
while he criticised the views of his predecessors in detail with an
unmistakable superiority, and in so doing displayed minute
acquaintance with the literature of the subject and varied
phytotomical experience. He fixed his eye firmly on the
points in question, and made each one the subject of earnest
investigation and copious and perspicuous discussion. His
figures prove the carefulness of his examination and the greater
excellence of his instrument ; they are undoubtedly the best
that were produced up to 181 2. His mode of dealing with
his subject and his figures, though they were not executed by

* Johann Jakob Paul Moldenhawer was Professor of Botany in Kiel ; he
was bom at Hamburg in 1766, and died in 1827.

Chap. III.] oj Ccll-memhranc in Plants. 277

himself, remind us in many respects of von Mohl, though it
would be more correct to say that von Mohl's manner reminds
us of Moldenhawer, for from the great respect which von Mohl
displays for him, especially in his earlier writings, it can
scarcely be doubted that he formed himself on Moldenhawer's
' Beitrage,' and first learnt from them the earnestness and care-
fulness demanded by phytotomic work.

It has been already mentioned that the study of vegetable
physiology is indebted to Moldenhawer for one important
practical improvement. He was the first who isolated cells
and vessels by allowing parts of plants to decay in water and
afterwards crushing and dissecting them, a process not much
used in modern times, though it may still be applied with
advantage in conjunction with what is known as Schulze's
solution, especially if it is carried out with Moldenhawer's
carefulness and circumspection. The isolation of the ele-
mentary organs of plants by maceration in water necessarily
brought Moldenhawer into direct antagonism with Mirbel,
who with Wolff assumed that the partition between any two
cells was a single wall ; whereas Moldenhawer found that the
cells and vessels were closed tubes and sacs after isolation,
and must necessarily, as it would seem, so lie one against
another in the living plant, that the wall between every two
cell-spaces is formed of two membranous laminae, and he ex-
pressly says that this is the case even in very thin-walled
parenchyma. This result remained unassailable, so long as no
one was in a position to conclude from the history of the
development of cell-tissue that the partitions are originally
single, or by aid of strong magnifying power to prove the true
structure of the walls and their later separation, and the dif-
ferentiation of the once single wall into two separable laminae.
If the view based on the results of maceration was still not the
true view, yet it was nearer the truth as regards the matured
state of the cell-wall than that of Wolff and Mirbel, and the
important advantage was gained of being able to study the

278 Examination of the Matured Framework [Book 11.

form of elementary organs and the sculpture on their walls
more accurately than before. It is true that Link had occa-
sionally isolated cells by boiling in 1809, and Treviranus had
drawn attention in 181 1 to the fact that it was possible to isolate
parenchyma-cells in their natural condition ; but neither of
them made systematic use of these observations, and to
Moldenhawer belongs the exclusive merit of having first
isolated vessels and woody cells; but as usually happens, he
did not himself obtain all the possible results from his method
of preparation. In his work which indeed embraces the whole
of phytotomy, he is continually recurring to one species, maize.
This supplies the starting-point in every question to be dis-
cussed. The results obtained there are the firm supports on
which he leans in the examination of a great variety of plants,
which he then compares together at length. This mode of
treatment was well chosen both for investigation and instruction
in the existing state of the science ; it was a particularly happy
idea that of choosing the maize-plant for his purpose ; former
phytotomists had generally had recourse to dicotyledonous
stems, and preferred those that had compact wood and com-
plex rind, but the examination of these plants presents diffi-
culties at the present day to a practised observer with a good
microscope. Occasionally observers had taken the stem of
the gourd, where the large cells and vessels suited small
magnifying power, but where many abnormal conditions oc-
curred to interfere with their conclusions. The Monocotyle-
dons, like the Vascular Cryptogams, had hitherto been
comparatively neglected. When then Moldenhawer made a
monocotyledonous and rapidly growing plant, with very large-
celled tissue and comparatively very simple structure, the
chief subject of his investigations, he was sure to succeed
in making out many things more clearly than his predecessors.
It was an important point that he found the fibrous elementary
organs in this plant united with the vessels into bundles, which
are separated by a strict line of demarcation from the large-

Chap. III.] of Cell-membj'aiic in Plants. 279

celled parenchyma that surrounds them. Thus the peculiar
character, the idea, of the vascular bundle was brought promi-
nently into contrast with that of other forms of tissue. This
took the place of the distinction between rind, wood, and pith,
which had served former phytotomists as the basis of their
histological survey, but which is in itself only a secondary
result of the later elaboration of certain parts of the plant.
Moldenhawer, in laying the chief stress from the first on the
contrast between vascular bundles and parenchyma, hit upon
a histological fact of more fundamental importance, the right
appreciation of which has since enabled the phytotomist to
find his way through the histology of the higher plants. For
while the construction of Monocotyledons and Ferns must
seem abnormal and quite peculiar to any one who starts with
examining the rind, wood, and pith of old dicotyledonous
stems, those on the contrary who, with Moldenhawer, have
recognised a special histological system in the vascular bundles
of Monocotyledons, have the way opened to them to seek for
a similar one in the Dicotyledons, and to refer the secondar)'
phenomenon of wood and rind to the primary existence of
vascular bundles. Moldenhawer did in fact open this way,
when he showed how the growth of a dicotyledonous stem
may be understood from the structure and position of the
originally isolated vascular bundles (Beitrage, p. 49, etc.). But
he was thus of necessity led to the rejection of Malpighi's
theory of the growth in thickness of woody stems, which all
vegetable anatomists from Grew to Mirbel had adopted.
Though Bernhardi and Treviranus made weak attempts to
discredit it, Moldenhawer was the first who distinctly rejected
the origin of the external layers of wood from the inner bast,
and proposed the first really practical basis for the later and
correct theory of secondary growth in thickness (p. 35). The
removal of this ancient error is in itself a very important
result, and one which, apart from all other services, must
secure him an honourable place in the history of botany.

28o Examination of the Matured Framework [Book ii.

But the light must have its attendant shadow, and all his
carefulness in observation and cautiousness in judgment
did not protect him from one prejudice and its evil conse-
quences. After Moldenhawer had isolated the elementary
organs by maceration, he had to answer the question how we
are to conceive of their firm coherence in the living plant. He
came to the conclusion, as did von Mohl, Schacht, and others after
him, that there must be some special connecting medium ; but
he did not hit upon their idea of a matrix, in which the cells
are imbedded, or of a cement which holds them together, but
on a much stranger theory, which reminds us at once of Grew's
thread-tissue, and like that rests partly on incorrect observ-
ations. These were too hastily accepted as the basis of a
theory which in its turn interfered with after observations.
He thought that the cells and vessels were surrounded and
held together by an extremely delicate net-work of fine fibres ;
in some cases he really believed that he saw these fibres, and
interpreted in this way the thickened bands in the well-known
cells of Sphagnum, and still more strangely he appears to have
taken the thickened longitudinal and transverse edges of cells
and vessels for such threads. The unfavourable impression
produced by this theory is necessarily heightened by the fact
that he gave the name of cell-tissue, a term long used in a dif-
ferent sense, to his fancy-structure of reticulated threads which
were to hold the cells and vessels together, while he called the
parenchyma itself cellular substance, an expression which for-
tunately no one copied, and which certainly contributed at a
later time to discredit the great services which Moldenhawer
rendered to phytotomy.

His ' Beitrage zur Anatomie der Pflanzen ' are divided into
two portions; the first treats of the parts surrounding the
spiral vessels ; the second of the spiral vessels themselves.

The position and collective form of the component parts of
the vascular bundle in the stem of the maize-plant are well
described in the first section of the work. It is correctly stated

Chap. III.] of Cell-membraHc in Plants. 281

that there is a sheath to the whole bundle composed of strongly
thickened fibrous cells, that each of these cells has its own mem-
brane and is entirely closed, and that they resemble the bast
and the fibrous elements of the wood of Dicotyledons. The
segmented wood-cells and the parenchyma-cells of the wood
arranged in rows are incidentally noticed. Under the name of
fibrous tubes he included the cells of the sclerenchyma-sheath
of many vascular bundles .and the true bast and wood-fibres,
which latter he says are wanting in the Coniferae. He explained
the secondary growth in thickness of rind and bast by the ex-
ample of the shoot of the vine, in which he correctly distinguished
the medullary sheath and the spiral vessels. In herbaceous
Dicotyledons he found the bundles of vessels to consist of a
bast portion and a woody portion, and he attributed the forma-
tion of the compact wood of true woody plants to the blending
together of the woody portions of these separate bundles.

In discussing the parenchymatous cell-tissue he rejects em-
phatically and on good grounds the origin of new cells from
the granular contents of older ones, which had been the view
of Sprengel and Treviranus, as also the theory of Wolff and
Mirbel, while he maintains against Mirbel especially, that the
separation of fibrous tubes is possible even where no dividing
line can be seen between them in the cross section. He con-
siders that both in thin-walled and thick-walled parenchyma the
dividing wall is double and the cell-membrane entirely closed.
' It appears,' he continues on p. 86, 'from these observations that
cellular substance consists of separate closed tubes, which may be
round or oval, or more or less elongated, or almost cylindrical
in shape, and these by mutual pressure assume an angular and
flattened form, which is either regular like the cells of the comb
of bees or more or less irregular. Such an aggregate of sepa-
rate cells (and here he is certainly quite right) has nothing in
common with a tissue, and the word cell-tissue seems there-
fore less suitable than the term cellular substance, composed of
cell-like tubes.' Further on he rejects Mirbel's idea of the

282 Examination of the Matured Framework [book ii.

existence of visible holes in the walls of cells, and points out
that they are not necessary for the movement of sap. The
dispute between Mirbel and his opponents respecting the
porousness of cell-walls was extended at the same time to the
stomata of the epidermis \ the slits in them being supposed to
be apertures in the epidermis regarded as a simple membrane.
Moldenhawer took occasion to examine the anatomy of stomata
more closely, and produced the first accurate descriptions and
figures of these organs, showing especially that the apertures are
not surrounded by a simple border, as most previous observers
believed, but lie between two cells, and that therefore they are
not examples of the existence of pores in cell-walls, as Mirbel
imagined. It may be observed here by the way, that Mirbel
afterwards considered stomata to be short broad hairs ; Amici in
1824, Treviranus in 182 1, demonstrated their true structure by
cross sections, and von Mohl at a later period investigated it
thoroughly. Moldenhawer on the present occasion also enquired
into the faculty attributed to stomata of opening and closing
alternately, which, first observed by Comparetti, was then much
discussed by the German phytotomists, and has been made
the subject of repeated investigation in modern times. The
whole of this discussion was in connection with the question of
the pitting of cell-walls, the true nature of which Moldenhawer
however never clearly understood.

The peculiar vessels, known as *vasa propria,' were a stone of
stumbling to Moldenhawer, as they were to his predecessors
and to many of his successors, because misled by the resem-
blance in their contents he included under this name forms of
very different kinds. A very good description of the soft bast
in the vascular bundle of the maize-plant is followed by a notice
of the milk-tubes of Musa, the milk-cells of Asclepias which
he explains incorrectly, and the milk-vessels of Chelidonium

' On the doubts which were entertained till after 1812 on the subject of
stomata, see Mohl's 'Ranken und Schlingpflanzen ' (1827), p. 9.

Chap. III.] of Cell-memhrmic in Plants. 283

which he understood better. All these ' vasa propria ' he took
for cellular vessels, formed of tubes opening into one another ;
but he clearly distinguished the turpentine-ducts from them,
and has given a correct figure of such a duct from the pine,
though he assumes the existence of a special membrane lying
inside the cell-rows which surround it, and lining the passage.
Finally he passes on to the intercellular spaces, which he con-
siders to be gaps in the cellular substance, and illustrates by
Musa and Nymphaea. He does not notice i)articularly the
narrow interstices which Treviranus had observed traversing
the parenchyma.

In the second portion of his work he includes all the vessels
found in the vascular bundle of the maize-plant under the
term spiral vessels, but he distinguishes the different forms of
them well, and especially points out that rings and spirals
appear on one and the same vascular tube in different parts of
its course, as Bernhardi had already shown. The isolating of
the vessels gave him a better opportunity of seeing how they
are made up of portions of different lengths than his prede-
cessors had enjoyed, and he proves at some length the existence
of a thin closed membrane forming the vessel, but like Hedwig
he places the thickenings on the outside. He as little overcame
the difficulties of bordered pits as did von Mohl and Schlei-
den after him. In this case as in others, it was the history of
development which first taught the true nature of these form-
ations (Schacht, i860).

It was mentioned in the Introduction that Moldenhawer
may be said to close the first portion of the period from 1800
to 1840, not only because the majority of the questions ven-
tilated up to that time were to a certain extent settled by him,
but also because there is no material advance in phytotomy to
be recorded for several years after the publication of his work
in 1 81 2. It is true that Kieser in his 'Grundziige der Ana-
tomie der Pflanzen ' (1815) attempted a connected exi)osition of
the >vhole subject, but his book offers nothing really new,

284 Examination of the Matured Framework [Book 11.

being merely a playing with the unmeaning phrases of the
current nature-philosophy, while it revived gross errors like
Hedwig's doctrine of the presence of lymphatic vessels in the
tissue of the epidermis, and made the Mosses consist of
conferva-threads. Phytotomy was on the contrary really
enriched by the miscellaneous works of Treviranus published
in 182 1, especially in respect to questions connected with the
epidermis, and by Amici's discovery in 1823, that the inter-
cellular spaces in plants contain not sap but air, and that the
vessels too chiefly convey air. We may quietly pass over the
later writings of Mirbel, Schulze, Link, Turpin and others, which
appeared after 181 2 and before 1830, as our business is not so
much with an account of the Hterature of the subject as with
evidence of real advance.

Meyen and von Mohl may be said to have commenced their
labours with 1830, and in the course of the succeeding ten
years they became the chief authorities on phytotomy, though
a highly meritorious work of Mirbel's on Marchantia poly-
morpha and the formation of pollen in Cucurbita falls as late
as 1835. We may even pass over so elaborate a work as the
'Physiologic der Gewachse' of Treviranus (1835-1838), which
embraces also the whole of phytotomy, because though its
treatment of some of the details is good, it presents its subject
virtually from the points of view opened before 181 2. This
work, though it neglects no part of its subject and contains
much useful reference to the works of other observers, was
unfortunately out of date at the time of its appearance, for
owing to von Mohl's labours an entirely new spirit had entered
since 1828 into the treatment of phytotomy.

Though Meyen and von Mohl must be regarded as the chiei
representatives of phytotomy from 1830 to 1840, yet they are
men of very different importance in the science. The essential
difference between them cannot perhaps be better shown than
by pointing to the fact, that Meyen's labours cannot at present
claim more than a historical interest, while von Mohl's earliest

Chap. III.] of Cell-membrane in Plants. 285

investigations between 1828 and 1840, so far from being
obsolete, are the sources of our present knowledge, and from
them every one must still draw who proposes to cultivate any
portion of phytotomy. Meyen's views, in spite of the many
investigations which he made himself, are entirely confined
within the circle of thought represented by the Gottingen
essayists, though in his observations he went beyond them,
and even beyond Moldenhawer; but the phytotomical views
of these men were from the first no law to von Mohl ; he took up
an entirely independent position at once with respect even to
Moldenhawer and Treviranus, though a longer time certainly
elapsed, before he succeeded in freeing himself wholly from
Mirbel's authority. For these reasons, and because Meyen's
work was interrupted by his death so early as 1840, while von
Mohl aided to advance phytotomy for another thirty years, we
will speak first of Meyen's labours in that department.

Meven ^ is remarkable for the extraordinary number of
his written productions. In 1826, at the early age of twenty-
two, he wrote his treatise ' De primis vitae phenomenis in
fluidis '; two years later he published researches anatomical
and physiological into the contents of vegetable cells, and in
1830 appeared his ' Lehrbuch der Phytotomie,' founded on
his own investigations in every branch of the subject, with
many figures on thirteen copper plates very beautifully executed
for the time. His industry as a writer was then interrupted by
a voyage round the world made in the years 1 830-1832, but
was again marvellously productive during the last four years of
his life (1836-1840); it is difficult to conceive how he found

* Franz Julius Ferdinand Meyen was bom at Tilsit in 1804, and died as
Professor in Berlin in 1840. He applied himself at first to pharmacy and
afterwards to medicine, and having taken a degree in 1826 he practised for
some years as a physician. In 1830 he set out on a voyage round the world
under instructions from A. von Humboldt, and returned in 1832 with large
collections. He was made Professor in Berlin in 1834. There is a notice
of his life in ' Flora ' of 1845, p. 618.

286 Examination of the Matured Framework [BookII.

time even for the mechanical part of his work, for in 1836 he
published his treatise on the latest advances in vegetable
anatomy and physiology, a quarto volume of 319 pages with
twenty-two plates, which gained the prize from the Teyler
society in Haarlem; the figures are well drawn, the style is
that of a practised writer, but the matter of the work is some-
what superficially handled. A year later (1837) appeared the
first volume of his ' Neues System der Pflanzenphysiologie,'
and two more volumes by the year 1839, — a work also rich in
new observations and figures. In the course of the same
years (1836-39) he wrote detailed annual reports of the results
of investigations in the field of physiological botany, which fill
a portly volume, and published in 1837 a prize-essay on the
organs of secretion, and in 1836 a sketch of the geography of
plants; in 1840 appeared a treatise on fructification and
polyembryony, and a posthumous work on vegetable patho-
logy in 1 841. The number of works thus given to the world
between the years 1836 and 1840, though partly prepared
before that period, is so unprecedented, that it is impossible
for the composer to have maturely meditated his facts or their
inner connection, and the study of his writings shows that he
was often too hasty in propounding new views, and in reject-
ing or accepting the statements of others. The style is per-
spicuous and flowing, and animated by a genuine scientific
spirit ; but the expressions are often inexact, the ideas not
unfrequently immature, and points of fundamental importance
are sometimes neglected for unimportant and secondary
matters. These faults are the result of hasty production ; we
must set against them conspicuous merits ; Meyen had an eye
open to every question in phytotomy and left nothing un-
noticed, while he made it his constant aim to give clear
general views of his subject as a connected whole, and enable
his reader to see his way in every direction, in order to make
phytotomy and vegetable physiology accessible to wider circles
of scientific men ; the like praise is due to his drawings from

Chap. III.] of Cell-membrane in Plants. 287

the microscope which are beautifully executed ; they present
to the reader not the small fragments of earlier phytotomic
works but whole masses of tissue so connected together, that
it is possible to gain some insight into the disposition of the
different systems of tissue and their mutual relations. The
superiority of Meyen's drawings of 1836 as compared with
those of 1830 is very striking, though he used the same micro-
scope in both cases and the same magnifying power of two
hundred and twenty times.

To learn what were Meyen's independent contributions to
the advance of phytotomy, we must turn to his ' Phytotomie '
of 1830 ; for in his later works and especially in the ' Neues
System der Physiologic' of 1837 he was able to avail himself of
von Mohl'searliestandsearchinginvestigations; these necessarily
influenced his views, though he always assumed the character
of a rival and opponent of von Mohl, and treated not only
Treviranus and Link, but even Kieser and men of his stamp, as
entitled to equal rank with him. And as in his later writings
he was reluctant to acknowledge von Mohl's services to science
and overlooked their fundamental importance, so in his earlier
work in 1830 he often appears as an assailant of Moldenhawer
and tries to set up Link's authority against him ; we find to
our astonishment in the first volume of the ' Neues System ' a
dedication to Link as the ' founder of German vegetable
physiology.' The position of a scientific man in relation to his
science as a whole is certainly most simply and clearly defined
by his judgment on the merits of his contemporaries and
predecessors, and we may conclude from what has now been
said that Meyen moved within the circle of ideas of the
Gottingen prize-essays, and did not clearly see the importance
of the points of view opened by Moldenhawer and von Mohl ;
though it must always be allowed that Meyen working in-
dependently far outstripped Link on his own path.

If it was our purpose to write a biography of Meyen, we
should have to go through his works, and show the steps by

288 Examination of the Matured Framework [Book ii.

which his views arrived at clearness and precision ; it is sufficient
in this history to show what was pecuHar and original in his
general conception of the problems of phytotomy. This
appears most plainly in the 'Phytotomie' of 1830; and we
may base our historical survey on that work because its views
are in the main those of the first volume of the ' Neues System '
which appeared seven years later, and still more because a
detailed examination of the later publication would involve us in
a lengthy discussion on Meyen's scientific relation to von Mohl.
It is less important in this place to give an estimate of Meyen's
character as a man of science than to show, how in the year
1830, when Mohl was beginning to apply himself to phytotomy
but as yet exercised no important influence on opinion, views
on the structure of plants were formed by one who gave
himself up to its study with decided ability and great zeal ; in
this way we shall gain a standard by which to judge of the
advance made chiefly by von Mohl and in part by Mirbel during
the succeeding ten years. In judging of Meyen's book, we
must not forget that it was written when he was only twenty-
five or twenty -six years old, and that it is under any view of it
a remarkable performance for so young a man.

Meyen adopted three fundamental forms of elementary
organs in plants ; cells, spiral tubes, and sap-vessels ; systems,
he says, are formed by union of similar elementary organs ;
hence there is a cell-system, a spiral tube-system, and a system
of sap-vessels (vascular system). We see at once by this
classification how closely he follows the ideas formed before
Moldenhawer. The establishment of these three systems is a
retrograde step, since Moldenhawer had already clearly dis-
tinguished between vascular bundles and cell-tissue. Meyen
then discusses each system at length and shows how they are
grouped together. He lays great stress, as he did also at a
later period, on the difference in the characteristic forms of
cell-tissue, for which he introduced the names merenchyma,
parenchyma, prosenchyma and pleurenchyma. These he calls

Chap. III.] of Cell-membrane in Plants. 289

regular cell-tissue, the shapes of the cells being like geome-
trical bodies, in opposition to the irregular tissue of F'uci,
Lichens and Fungi. It is a decided improvement on former
practice, and one that marks his later works also, that in connec-
tion with the structure of the solid cell-fabric he discusses the
contents of cells in a special chapter, in which first the matter
in solution, then the granular bodies with organized structure
are considered, though with the latter he classes not only starch-
grains, chlorophyll-corpuscles and the like, but also the sperma-
tozoa in pollen-grains and layers of thickening matter projecting
on the inside of cell-walls, such as the spiral bands in the elaters
of Jungermannieae and several similar formations. He describes
the crystals in vegetable cells at some length, and finally
discusses the movement of the cell-contents (* sap '), not
omitting that of rotation in the Characeae as observed by
Corti, and in other water-plants. The chapter on intercellular
spaces also shows considerable advance on the views which
obtained in 181 2; Meyen calls it an account of the spaces
produced in cell-tissue by the union of the cells ; the true
intercellular passages filled with air are here distinguished from
receptacles of secretions, resin-passages, gum-passages, oil-
passages, and secretion-receptacles of the nature of cavities.
The large air-passages and gaps, such as occur in water-plants,
are a third form of intercellular space ; his air-canals in the
wood of oak filled with cell-tissue are obviously vessels filled
with the substance known as thylosis. The form of the cells
in the tissue he thinks is not due to mutual pressure, and he
rejects Kieser's view that the ideal fundamental form of cells
must be a rhombododecahedron ; but he thinks there is a
significant resemblance between the shape of cells and that
of basaltic columns.

In dealing with the spiral tube-system he first di.scusses the
spiral fibre, which appears, he says, either detached between the
cells or inside them as well, — an account of the matter decidedly
inferior to those of Bernhardi and Treviranus. The spiral

u

290 Examination of the Matured Framework [BookIJ,

tubes are, he says on page 225, cylindrical or conical bodies
formed of spiral fibres which are afterwards surrounded by a
delicate membrane. He puts annular, reticulated, and pitted
vessels together as metamorphosed spiral tubes. His ex-
planation of these forms cannot well be understood except by
supposing that he assumed an actual metamorphosis in time
in accordance with the view of Rudolphi and Link ; but he
afterwards in his ' Neues System,' i. p. 140 declares this to be
a misunderstanding, though his real meaning is still doubtful ;
the obscurity attending the doctrine of metamorphosis did not
fail to cause misunderstandings in phytotomy, as it did in the
morphology of organs. Meyen makes only the striated and
pitted vessels in the wood convey air, the true spiral vessels
sap. That vessels are formed from cells, as Mirbel had already
maintained and Treviranus had partly observed, Meyen
intimates indeed, but not with an air of entire conviction.

The different forms of laticiferous organs are examined
under the head of the ' system of circulation in plants.' Meyen
sees in this system the highest product of the plant, being
fully persuaded with Schulz, that the latex (milk), or as he also
terms it the life-sap, is in constant circulation, like the blood
in the veins. He gives a more summary account than is his
wont of the course of the laticiferous organs, but bestows
more care on the nature of the latex, and on the structure of
the receptacles that contain it. That some of these are
produced by cell-fusion, that others represent intercellular
spaces, while others again are long branched cells, was not
known to Meyen or even to later phytotomists before i860.

This condensed account of the contents of Meyen's * Phy-
totomie ' shows a striking mixture of advance and retrogression,
when compared with what had been achieved before his time ;
by the side of the fact established by Treviranus that the
epidermis does not consist of a single membrane but of a layer
of cells, to which Meyen assents, we find the gross mistake of
taking the guard-gells of stomata for cuticular glands, the

Chap. III.] of Cell-membrane in Plants. 291

apertures in which he considers as of secondary importance. It
is still more striking that Meyen expressly rejects on page 120
the fact established two years before by von Mohl that the pits
of parenchyma are thinner spots, and treats the various pit-
formations of the cell-wall as raised portions of the surface.

In the first volume of his later work the ' Neues System,'
Meyen gives a detailed account of phytotomy, which accords
on the whole with the scheme developed in the book we have
been examining, and as might be expected he corrects many
errors, adduces many new observations, and introduces us to
many steps in advance of former knowledge ; we shall recur
to some of his later views in ensuing portions of this history
with which they are more in connection, remarking only here,
that Meyen paid more attention to the contents of the cell
than his contemporaries, and especially made a number of
observations on the streaming movement, without however
recognising the peculiar nature of the protoplasm which is its
substratum. The cell-wall, which he had once considered to
be homogeneous, he afterwards believed to be composed of
fine fibres, a view resting on correct but insufificient observation
and aftenvards set right by von Mohl and Nageli.

It is scarcely possible to imagine a more striking contrast
between two men pursuing the same science than that between
Meyen and his much more important contemporary Hugo von
Mohl ; Meyen was more a writer than an investigator ; von Mohl
wrote comparatively little in a long time, and only after most
careful investigation ; Meyen attended more to the habit, the
collective impression produced by objects seen with the micro-
scope, von Mohl troubled himself little about this, and always
went back to the foundation and true inner connection of the
structural relations ; Meyen quickly formed his judgment, von
Mohl often delayed his even after long investigation ; Meyen
was not critical, though always prone to opposition, in von Mohl
the critical power much overweighed that of constructive
thought. Meyen has not so much contributed to the definitive

u 2

29 2 Examination of the Matured Framework [Book ii.

settlement of important questions, as brought to light manifold
phenomena, and so to speak accumulated the raw material ; von
Mohl on the other hand aimed from the first at penetrating as
deeply as possible into vegetable cell-structure, and employing
all the anatomical facts in framing a coherent scheme.

We have already called attention to Hugo von Mohl's^
pre-eminent position in the history both of this and also of the
succeeding period. Occupying himself for the most part with
phytotomical questions which had been already investigated,
he made the solid framework of cellulose the object of special
and searching examination, and completed the work of his
predecessors on this subject ; he thus laid a firm foundation
for the researches into the history of development afterwards
undertaken by Nageli. Von Mohl, like former phytotomists,
generally connected his researches into structural relations
with physiological questions ; but there was one great and
unmistakable difference ; he never forgot that the interpreta-

* Hugo Mohl (afterwards von Mohl) was bom at Stuttgart in 1805, ^^^^l
died as Professor of Botany in Tubingen in 1872. His father held an im-
portant civil office under the Government of Wiirtemberg. Robert Mohl,
also in the service of the Government, Julius Mohl, the Oriental scholar,
and Moritz Mohl, the political economist, were his brothers. The instruc-
tion at the Gymnasium at Stuttgart, which he attended for twelve years, was
confined to the study of the ancient languages ; but Mohl early evinced a
preference for natural history, physics, and mechanics, and devoted himself
in private to these subjects. He became a student of medicine in Tiibingen
in 1823, and took his degree in 1S28. He then spent several years in
Munich in intercourse with Schrank, Martins, Znccharini and Steinheil and
obtained abundant material for his researches into Palms, Ferns, and
Cycads. He became Professor of Physiology in Berne in 1832, and Pro-
fessor of Botany in Tiibingen after Schiibler's death in 1835, and there he
remained till his death, refusing various invitations to other spheres of
work. He was never married, and his somewhat solitary life of devotion to
his science was of the simplest and most uneventful kind. He was intimately
acquainted with all parts of botanical science, and possessed a thorough
knowledge of many other subjects ; he was in fact a true and accomplished
investigator of nature. A very pleasing sketch of his life from the pen of
De Bary is to be found in tlie ' Botanische Zeitung ' of 1872, No. 31.

Chap. Ill] of Cdl-memhrane in Plants. 293

tion of visible structure must not be disturbed by physiological
views ; he used therefore his thorough physiological knowledge
chiefly to give a more definite direction to his anatomical
researches, and to illustrate the connection between structure
and function in organs. By scarcely any dther phytotomist
was the true relation between physiological and anatomical
research so well understood and turned to such practical
account as by von Mohl, who was equally averse to the entire
separation of phytotomy from physiolog)', and to the undue
mixing up of the one with the other, which has led his
predecessors, Meyen especially, into misconceptions.

His anatomical researches profited by his extraordinary
technical knowledge of the microscope ; he could himself
polish and set lenses, which would bear comparison with the
best of their time. As the majority of botanists from 1830 to
1850 had little knowledge of the kind, there was no one so
well qualified as von Mohl to give instruction in short treatises on
the practical advantages of a particular instrument, to remove
prejudices and finally as in his ' Mikrographie ' (1846) to give
detailed directions for the management of the instrument.

But his mental endowments were of course of the higher
importance, and it is difficult to imagine any more happily
suited to the requirements of vegetable anatomy during the
period from 1830 to 1850. At a time when men were building
fanciful theories on inexact observations, when Gaudichaud was
once more explaining the growth in thickness of the woody
portions of the plant after the manner of Wolff and Du Petit-
Thouars, when Desfontaines' account of the endogenous and
exogenous growth of stems was still accepted, when Mirbel was
endeavouring to support his old theory of the formation of
cells by new observations and beautiful figures, when Schulz
Schulzenstein's wildest notions respecting laticiferous vessels
were being rewarded with a prize by the Paris Academy, when
Schleiden's hastily adopted views respecting cells and fertilisa-
tion appeared on the scene with great external success, von

294 Exammation of the Matured Framework [book ii.

Mohl, for ever going back to exact observation, was cutting away
the ground from under ill-considered theories in careful mono-
graphs, and at the same time bringing to light a mass of well-
established facts leading to further and serious investigation.
These theories have now only a certain historical interest, while
von Mohl's contemporaneous works are still a rich repertory of
useful observations, and true models of clear exposition.

His written productions were preceded by a careful study of
all branches of botanical knowledge and the auxiliary sciences.
That he not merely acquired knowledge in this way, but
trained the powers of his understanding also, is shown by
the striking precision and clearness of his account of his first
investigations. At a time when the nature-philosophy and
Goethe's doctrine of metamorphosis in a distorted form were
still flourishing, von Mohl in spite of his youth approached the
subjects of his investigation with a calmness and a freedom
from prepossessions, which are the more remarkable when we
observe that his friend Unger was at first quite carried away
by the stream, and only slowly managed to reach the firm
ground of genuine inductive enquirj'.

Owing to the extravagances and aberrations with which he
made acquaintance as a young man in the nature -philosophy,
von Mohl contracted an aversion to all philosophy, evidently
taking the formless outgrowths from the doctrines of Schelling
and Hegel for something inseparable from it, as we may gather
from his address at the opening of the faculty of natural history
in Tilbingen, which had been separated at his instance from
that of philosophy. His dislike to the abstractions of phi-
losophy was evidently connected with his distaste for far-
reaching combinations and comprehensive theories, even
where they are the result of careful conclusions from exact
observations. Von Mohl was usually satisfied with the establish-
ment of separate facts, and in his speculative conclusions he
kept as closely as possible to what he had actually seen, for
instance, in his theory of the thickening of cell-walls; and

Chap. III.] of Ccll-membraiic in Plants. 295

where new views opened before him as a result of his exact
observation, he cautiously restrained himself and was generally
content to hint at matters which bolder thinkers afterwards pro-
ceeded to investigate ; such a case occurred in his examination
of cell-membranes by polarised light. Hence we miss to some
extent the freer flight of imaginative genius in von Mohl's
scientific labours ; but there is more than sufficient compensation
for this want in the sure and firm footing which he offers to the
reader of his works ; if we pass from the study of the writings
of phytotomists before 1844 to those of von Mohl, we are sensible
of one predominant impression, that of security ; we have the
feeling that the observer must have seen correctly because the
account which he gives of the matter before us seems so
thoroughly natural and almost necessarily true, and all the
more because he himself notices all possible doubts, and lets
those which he cannot remove remain as doubts. In these
points von Mohl's style resembles that of Moldenhawer, but in
von Mohl it attains to a mastery which is wanting in the other.

There is an evident connection between von Mohls di.slike of
far-reaching abstractions and philosophic speculation on the
results of observation and the fact, that in the course of more
than forty years' unintermitted application to phytotomy he
never composed a connected general account of his subject.
His efforts as a writer were confined to monographs usually
connected with questions of the day or suggested by the state
of the literature. In these he collected all that had been
published on some point, examined it critically, and ended by
getting at the heart of the question, which he then endeavoured
to answer from his own observations.

For the purpose of these observations he looked about in
every case for the most suitable objects for examination, a
point to which former phytotomists, with the exception of
Moldenhawer, had paid little attention ; he then studied these
objects thoroughly, and thus prepared the way for the examin-
ation of others, which presented greater difficujties. Every

2g6 Examination of the Matured Framework [Book it.

monograph of this kind was a nucleus, round which a larger
number of observations might afterwards gather. In a long
series of such solid productions he treated conclusively all the
more important questions of phytotomy.

Von Mohl's extraordinary carefulness was not however able to
guard him, calm observer though he was, from some serious
mistakes, at least in his earlier years, such as those which occur
in his first theory of intercellular substance (1836), and in his
earliest views on the nature of the cell-membrane of the pollen-
grain (1834). These and some other errors on the part of
a gifted and truly inductive enquirer are instructive, since they
show that observation without any ground-work of theory is
psychologically impossible ; it is a delusion to suppose that an
observer can take the phenomena into himself as photographic
paper takes the picture ; the sense-perception encounters views
already formed by the observer, preconceived opinions with
which the perception involuntarily associates itself. The only
means of escaping errors thus produced lies in having a distinct
consciousness of these prepossessions, testing their logical
apphcability and distinctly defining them. When von Mohl
laid down his theory of intercellular substance, there evidently
floated before his mind indistinct, half-conscious ideas of the
kind that Wolff and Mirbel entertained of the structure of the
vegetable cell ; and as he considered the cell-membrane of the
pollen-grain to consist of a cell-layer, he summarised its obscure
structural relations under the then very obscure conception of
the cell. As a true investigator of nature, who adheres always
and firmly to the results of further observation, and endeavours
to clear his ideas by their aid, conceding only a relative value to
every view, von Mohl soon escaped from these errors, and him-
self supplied proofs of the incorrectness of his former opinion.
The number of really erroneous statements in his works is
wonderfully small considering the very large number of investi-
gations in which he engaged.

In examining the part which von Mohl played in the general

Chap. 111.] of Cell-membrane in Plants. 297

development of phytotomy we can distinguish satisfactorily two
periods in his scientific career, the first of which extends from
1827 to about 1845. Before 1845 he was acknowledged to be
the first of phytotomists, decidedly superior to all rivals ; his
authority, though often attacked by unimportant persons, grew
from year to year. This period may be said to close with the
publication of his ' Vermischte Schriften ' in 1845. Up to that
time investigations into the form of the solid framework of cell-
membrane had chiefly attracted the interest of phytotomists,
and in this subject there was no one who could measure him-
self with von Mohl. Vet he began soon after 1830 to study the
history of development in plants; in 1833 he described the
development of spores in a great variety of Cryptogams, in
1835 the multiplication of cells by division in an alga, and the
cell-division in the formation of stomata in 1838 ; in this period
appeared Mirbel's first observations on the formation of pollen-
cells (1833). Von Mohl too was the first, if we disregard
Treviranus' somewhat imperfect notices of the origin of vessels
in 1806 and 181 1, who explained the history of the development
of those organs ; and his theory of the thickening of cell-mem-
branes, the principles of which are to be found in his treatise
on the pores in cellular tissue (1828), may also be regarded as
a mode of conceiving the sculpture of the cell-membrane from
the point of view of the history of development.

Ever since 1838 Schleiden had raised the history of develop-
ment to the first rank in botanical investigation, but he had
proposed a thoroughly faulty theory of cell-formation, to which
von Mohl at first at least did not withhold his assent in spite of
previous and much better observations ; but after 1842 Nageli
devoted himself still more thoroughly and with more lasting
results to the study of the development both of vegetable cells
and tissue-systems, and of the external organs. He introduced
new elements into phytotomic research, and it soon became
apparent that even the questions hitherto examined must be
grappled with in a different fashion. Von Mohl did not hold aloof

298 Examination of the Matured Framework [Book ii,

from the new direction, but completed a series of excellent
investigations connected with the new questions in the theory
of cell-formation. The most important of these was his enquiry
into the nature of protoplasm, to which he gave the name still
in use. In his treatise, ' Die Vegetabilische Zelle,' which came
out in 1 85 1 in Wagner's Dictionary of Physiology, he even
gave an excellent account of the modern theory of cell-forma-
tion ; but notwithstanding all this, and the great authority
which he rightly continued to enjoy, he was no longer the
guide who led the way in the domain of phytotomy, as he had
been before 1845.

His zeal as an observer had at all times been chiefly attracted
to the solid framework of vegetable structure in its matured
condition, though a number of his most important works were
devoted to the study of cell-contents.

Except in his 'Anatomic der Palmen' (1831), where he ex-
pended much and to some extent even unnecessary labour on
figures representing the general appearance of the tissue (histo-
logic habit), von Mohl's microscopic drawings do not aim at
giving the collective impression, but at facilitating the under-
standing of the delicate structure of single cells and their combi-
nations by aid of the simplest possible lines. He always despised
pictures from the microscope, such as were introduced at a later
time by Schacht, — a kind of artistic restoration of the originals
and to some extent a playing with science ; and in his later
publications he was more sparing of illustrations or omitted them
altogether, in proportion as he acquired the power of giving
clear verbal explanations of even difficult structural conditions.

Von Mohl's scientific activity was so wonderfully productive
that it is not easy to present the reader with a clear account of it ;
but we must endeavour at least to furnish such a summary of
its chief results as may serve to give a general idea of his
importance in the history of our science. We may here pass
over such of his treatises as do not bear on the main questions
of phytotomy, and notice only those that relate to the structure

Chap. III.] of Cell-membrane in Plants. 299

of the solid framework of plants, because the historical signifi-
cance of his investigations into the history of development can
only be understood in connection with the questions to be
treated in the following chapter. But we shall not limit our-
selves to publications which appeared before 1845, though we
may be thus compelled to notice researches which in succession
of time belong to the next period, and indeed almost to the
present moment.

I. The view that the cell is the sole and fundamental
element in vegetable structure had been already maintained
by Sprengel and Mirbel, but not supported by exact observa-
tions. Treviranus too had shown that the vessels in wood
are formed by the union of rows of cell-like tubes, but he had
never arrived at a thoroughly clear conception of the matter.
On the one side was the theory that the plant consists entirely
of cells, on the other, and for long the old and strange view,
that the spiral thread was an independent elementary organ of
vegetable structure, — a view which Meyen still maintained in
1830. Von Mohl must be regarded as the first who took up the
all-important position, that not only the fibrous elements of
bast and wood, which had long been considered to be elon-
gated cells, but the vessels of the wood also are formed from
cells ; and we may on this point give great weight to his own
assertion that he was the first who observed the formation of
vessels from rows of closed cells. This discover)' happened
in the year 1831, and he describes distinctly, though briefly,
the decisive observations in his treatise on the structure of the
palm-stem. At the points of constriction in the vessels he saw
the dividing walls, the existence of which had been denied by
all former phytotomists ; 'these dividing walls,' he says, 'are
entirely different from the rest of the membranes of the plant,
being formed of a network of thick fibres with openings
between them.' He studied the history of the development
of these vessels both in palms and in dicotyledonous plants.
* In the young shoot,' he says, ' are found at the spots, where

300 Examination of the Matured Framework [book ii.

afterwards there are large vessels, perfectly closed large cylin-
drical tubes with a transparent and very delicate membrane.'
He then shows how by degrees the sculpture peculiar to the
walls of vessels is formed on the inside of these tubes, and he
takes the opportunity of saying that a metamorphosis in time
from one form of vessel into another is entirely out of the
question, as Treviranus also and Bernhardi had maintained. 'The
dividing walls (transverse septa),' he continues, ' are formed in
a precisely similar manner to the side-walls of vessels ; only the
original tender membrane of the septa is usually lost in the
meshes of the network of fibres.' From that time no phytoto-
mist capable of an independent judgment has had any doubt
with regard to this view of the formation of the vessels in wood.
It is however striking enough that von Mohl, who thought it so
important to show that the cell is the sole foundation of veget-
able structure, never extended the proof to milk-vessels and
other secretion-canals in order to show whether and how these
also are formed from the cells. In his treatise on the vegetable
cell (185 1 ) he still expressed doubt about Unger's assertion,
that the milk-vessels are also formed from rows of cells that
coalesce with one another, and held rather to the view of
an anonymous writer in the ' Botanische Zeitung ' of 1846,
page 833, that these vessels are membranous linings of gaps
in the cell-tissue. He might well lose his taste for the exam-
ination of these and similar organs after Schultz Schultzenstein
had by his various treatises, written after 1824, on the so-called
vital sap and the circulation which he attributed to it, made
this part of phytotomy a very quagmire of error, and had not
refrained from replying in an unbecoming manner to von Mohl,
who repeatedly opposed his views ; moreover Schultz's essay
'Ueber die Circulation des Lebenssafter' (1833), which teems
with absurdities, had received a prize from the Academy of Paris.
2. The growth in thickness of the cell-membrane, and the
sculpture caused by it was a subject that is more or less con-
nected with most of von Mohl's writings. He developed the

Chap. III.] of Cell-membrane in Plants. 301

chief features of his view in 1828 in his first work, ' Die Poren
des Pflanzengewebes !' The way in which he represented to him-
self the growth in thickness of cell-membranes at a later time
may be expressed as follows. All elementary organs of a plant
are originally very thin-walled perfectly closed cells, which in
the tissue are separated by walls formed of two laminae' ; on
the inside of these primary cell-membranes, after they have
ceased to increase in circumference, new layers of membranous
substance are formed, which lying one upon another adhere
closely together, and represent the whole amount of secondary
thickening layers ; on the inner side of the membrane thus
thickened by apposition there may usually'* be perceived a
tertiary layer of a different character.

But there are certain sharply defined spots on the original
cell-wall, where this thickening does not take place ; in such
spots the cell is still bounded only by the primary membrane ;
it is these thin spots which bear the name of pits, and which
Mirbel, and in some cases Moldenhawer, took for holes, but
von Mohl considered that it was only in very exceptional cases
that they were really changed into holes by resorption of the
thin primary wall. In accordance with this theory, the spiral,
annular, and reticulated vessels are produced by deposition of
thickening matter in the form suitable to each case on the
inside of the originally smooth thin cell-wall. But like Schlei-
den and other phytotomists, von Mohl was not quite clear in his
views either of the origin or mode of formation of matured
bordered pits ; it was supposed that the two laminae of the
dividing wall parted from one another at certain spots in such
a manner that a lenticular hollow space was formed between
them, and that this space answered to the outer border of the

* But von Mohl expressed some doubts on this point in 1844 ('Botanische
Zeitung,' p. 340).

^ This tertiary layer was at first supposed by Theodor Hartig to be of
general occurrence; von Mohl in 1844 considered it to be present only in
certain cases.

302 Examination of the Matured Framework [Book ii.

pit, while the inner border was the result of ordinary pit-
formation. This view, which could be shown to be incorrect
by the history of development, arose in fact from inexact obser-
vation,— a rare case with von Mohl ; the true course of events
in the formation of bordered pits was first described by
Schacht in i860.

It was mentioned above, that Meyen in his ' Neues System
der Physiologie' of 1837, i. p. 45, made cell-membranes con-
sist of spirally wound fibres; von Mohl had described in 1836
the structural relations of certain long fibrous cells of Vincaand
Nerium, which might be provisionally explained in this way ;
he was led by Meyen's ideas on the subject to a renewed and
minute examination of the more delicate structure of the cell-
membrane in 1837 ; he first of all cleared the ground round
the question, by distinguishing the cases in which real spiral
thickenings lie on the inner side of the membrane, from those
in which the membrane is smooth on the outside, but shows an
inner structure of fine spiral lines ; in these cases he assumed
a peculiar arrangement of the molecules of cellulose, and
endeavoured to illustrate the possibility of such a disposition by
the phenomena of cleavage in crystals (' Vermischte Schriften,'
p. 329) ; but he did not succeed in explaining these very delicate
conditions of structure, which we now call the striation of the
cell-membrane, so clearly as Nageli afterwards did in connection
with his molecular theory.

3. The question of the substance and chemical nature of cell-
membranes was intimately connected with von Mohl's theory
of its growth in thickness ; he was engaged in 1840 in minutely
studying the reactions which various cell-membranes exhibit
with iodine solution under different conditions, — a question on
which Schleiden and Meyen had recently disagreed ; von Mohl
arrived at the result, that iodine imparts very various colours to
vegetable cell-membrane, according to the quantity in which it
is absorbed ; a small amount produces a yellow or brown, a
larger a violet, a still larger a blue tint ; this depends partly on

Chap. III.] of Cell-membrane in Plants. 303

the extent to which the membrane is capable of distention ; the
blue colour especially depends on the absorption of a sufficient
quantity of iodine. Greater interest, excited at first by a very
important work by Payen' in 1844, was taken in the question
of the chemical nature of the solid framework of the vegetable
body, in which it was shown that the substance of all cell-
membranes exhibits a similar chemical composition when
freed from foreign elements. Payen considers that this
material, cellulose, is present in a tolerably pure form in the
membranes of young cells, but is rendered less pure in older
ones by ' incrusting substances,' whose presence changes the
physical and chemical characters of cell-membranes in various
ways. These incrusting substances may be more or less
removed by treating the membranes with acids, alkalies,
alcohol, and ether, while other inorganic matters remain
behind after combustion as an ash-skeleton. This theory,
which has been more perfectly worked out in modern times,
was soon afterwards met by Mulder with the assertion, that a
large part of the layers composing the walls of cells consist
from the first of other combinations and not of cellulose ; he
at the same time deduced from this view certain conclusions
respecting the growth in thickness of cell-walls. He and
Harting, relying on microscopic examination, maintained that
the innermost tertiary layer in thickened membranes is the
oldest, and that the other layers are deposited on the outside
of this, and are not composed of cellulose. Von Mohl opposed
this view decidedly and successfully in the Botanische Zeitung of
1847 5 he likewise in his work on the vegetable cell (p. 192),
refuted the view of the varying substance of cell-membrane,

* Anselm Payen (i 795-1871) was born at Paris and was Professor of In-
dustrial Chemistry in the Ecole des Arts et Metiers in that city. His most
important botanical works were his ' Memoire sur I'amidon,' etc., Paris
(1839., and his ' Memoire sur le developpement des Vegetaux,' published in
the Memoirs of the Academy of Paris.

■304 Examination of the Matured Framework [Book ii.

which Schleiden had founded on some obscure chemical
grounds.

It would carry us much too far to enter into the details of
this scientific dispute ; Payen's view of the chemical nature of
the vegetable cell-wall, which von Mohl adopted and elaborated,
has maintained itself to the present day, and is generally con-
sidered to be the true one ; on the other hand, the foundations
of von Mohl's theory of growth in thickness were shaken in 1858
by Nageli's observations, and we may say that on the whole it
has been for ever superseded. It has been nevertheless of
great service in the development of our views on cell-structure
in plants ; keeping closely to the facts directly observed, it
served to bring almost all the conditions of the sculpture of
cell-walls under one point of view, and to refer their formation
to one general and very simple scheme ; every such theory
helps to advance science, because it facilitates mutual under-
standing ; in this case, when Nageli proposed his more pro-
found theory of intussusception, the understanding of it was
essentially assisted by a previous exact knowledge of von Mohl's
theory in its principles and results. In conclusion it may be
mentioned here that von Mohl afterwards in his investigation
into the occurrence of silica in cell-membranes made a large and
important addition to the knowledge of their more delicate
structure, and of the way in which incrusting substances are
deposited in them (Botanische Zeitung, 1861).

4. The views of phytotomists on the so-called intercellular
substance during the twenty years from 1836 to 1856 were closely
connected with the older theories of cell-formation, but were
opposed to the modern doctrine of the cell founded by Nageli
in 1846. Von Mohl himself had introduced this idea for the first
time into the science in 1836 in one of his earlier and inferior
essays, ' Erlauterung meiner Ansicht von der Structur der Pflan-
zensubstanz,' rather in opposition to than in connection with his
own theory of the growth and structure of cell-walls. Setting
out from modes of formation of cell-membranes in some Algae,

Chap. III.] of Ccll-membrane in Plants. 305

difficult to understand and in some respects quite peculiar,
von Mohl believed that he saw in many cases in the higher
plants also between the sharply-defined membranes, which
bound the cell-spaces and which he regarded as the entire cell-
membranes, a substance in which the cells are imbedded, for
such is its appearance when it is largely developed ; when it
lies in small quantity only between cells in close apposition, it
looks like a thin layer or cement. After Meyen in his ' Neues
System,' pp. 162, 174 had declared against this view in 1837,
von Mohl too abandoned it more and more, and afterwards
limited the occurrence of intercellular substance to certain
cases, being convinced that much that he had before taken
for it consisted only of layers of secondary thickening, between
which he still saw the primary lamina of the cell-membrane.
The theory of intercellular substance was taken up and further
developed by other phytotomists, by Unger especially in the
Botanische Zeitung for 1847, p. 289, and afterwards chiefly by
Schacht ; Wigand came forward as an opponent of it in 1854 in
his 'Botanische Untersuchungen,' p. 65, and logically following
out von Mohl's theory of the cell-membrane declared the thin
layers of intercellular substance as well as the cuticle, which had
been first correctly distinguished by von Mohl, to be laminae of
primary cell-membrane, the substance of which had undergone
profound chemical change. These ideas also of the intercellular
substance and the cuticle assumed an entirely different aspect
when Nageli introduced his theory of intussusception.

The limits imposed on this history render it necessary to be
content with these indications of von Mohl's share in the working
out of the theory of cells in its connection with the structure
of the solid framework of cell-membrane; we shall return
again to his observations on the formation of individual cells.

5. Forms of tissue and comparative anatomy. Phytotomy
up to 1830 had been weak in its classification of tissues,
in its ideas as to their arrangement, and consequently in
its histological terminology ; the inconvenience arising from

X

3o6 Examination of the Matured Framework [Book it.

this state of things was most distinctly felt when it became
necessary to compare the structure of different classes of
plants, Cryptogams, Conifers, Monocotyledons and Dicoty-
ledons, and to establish their true differences and actual
agreements. How little phytotomy had advanced in this
respect is shown plainly in the account of tissues given by
Meyen in his ' Neues System ' in 1837. To von Mohl belongs
the merit of having perceived at an early period in his scientific
career, and more clearly than his contemporaries, the value of
a natural and sufficient discrimination of the various forms of
tissue, and the necessity of obtaining a correct view of their
relative disposition ; he thus showed the way to an under-
standing of the general structure of the higher plants, and
rendered it possible to make a scientific comparison of the
structure of different classes of plants.

Von Mohl, like Moldenhawer long before, showed from the
first a correct apprehension of the peculiar character of the
vascular bundles as compared with other masses of tissue.
He, too, examined them first in Monocotyledons, and gave an
account of them in his treatise on the structure of Palms
(1831), and also in his later essays on the stems of Tree-ferns,
Cycads, and Conifers and on the peculiar form of stem in
Isoetes and Tamus elephantipes, to be found in his 'Ver-
mischte Schriften' of 1845. His just conception of them as
special systems composed of various forms of tissue has made
his account clear and intelligible, and his whole treatment of
the subject appears new in comparison with that of every pre-
vious writer except Moldenhawer. If these labours of von Mohl
are surpassed in value by later studies of the history of deve-
lopment, they served for the time as a nucleus for further
investigations, especially into the nature of stems. It con-
tributed in a high degree to a correct insight into the structure
of the stem, that von Mohl, agreeing in this with Moldenhawer,
distinguished the portion belonging to the wood from the
portion belonging to the bast in the vascular bundles, and

HAP. 111.] of Ccll-membranc in Plants. 307

regarded both as essential constituents of a true vascular
bundle. Not less important were his enquiries into the
longitudinal course of the vascular bundle in the stem and
leaf, which showed that in the Phanerogams the bundles in
the stem are only the lower extremities of the bundles, the
upper extremities of which bend outwards into the leaves,
and that the Monocotyledons and Dicotyledons agree in this
particular, though the course of the bundle differs considerably
in the two cases. He obtained an important result in this
respect in his researches on palm-stems in 1831, when he
proved the incorrectness of the distinction between endogenous
and exogenous growth in thickness, which had been laid down
by Desfontaines, and even employed by De CandoUe in fram-
ing his system. According to Desfontaines, the wood of
Monocotyledons appears as a collection of scattered bundles,
of which those that run out above into the leaves come from the
centre of the stem. From this very imperfect observation
he deduced the view, that the bundles of vessels in Mono-
cotyledons originate in the centre of the stem, and that they
continue to be formed there, until the older hardened bundles in
the circumference form so solid a sheath that they withstand
the pressure of the younger ; then all further growth in thick-
ness must cease, and hence the columnar form of the mono-
cotyledonous stem. This doctrine found general acceptance,
and was employed by De Candolle to divide vascular plants
into Endogens and Exogens, in accordance with the very
general inclination felt in the first half of the present century
to distinguish the great groups of the vegetable kingdom by
anatomical characters. It is true that Du Petit-Thouars had
already shown that some monocotyledonous stems have un-
limited growth in thickness ; neither his nor Mirbel's later
observations succeeded in shaking the theory, the adherents of
which met such cases by assuming a peripherical as well as a
central growth. Then von Mohl in the treatise above-mentioned
demonstrated the true course of the vascular bundles in the

X 2

3o8 Examination of the Matured Framework [book ii.

stem of Monocotyledons, and at once did away with the whole
theory of endogenous growth in the opinion of all who were
capable of judging, though some even eminent systematists
for a long time maintained the old error. The results which
von Mohl obtained from his study of the comparative anatomy
of the stem, rested mainly on careful observation of the
mature tissue-masses, and when he studied the history of deve-
lopment, he was not in the habit of going back to the very
earliest and most instructive stages. Hence he failed to ex-
plain fully the real points of agreement and difference of
structure between Tree-ferns and other Vascular Cryptogams
and Phanerogams, and in like manner he stopped half-way when
engaged in explaining the secondary growth in thickness of di-
cotyledonous stems from the nature of their vascular bundles,
and the formation of cambium. The account of growth in
thickness which he still gave in 1845 (' Vermischte Schriften,'
p. 153), and which rests less on observation than on an
ideal scheme, is highly obscure, and even in the treatise which
he published in the Botanische Zeitung in 1858 on the
cambium-layer of the stem of Phanerogams, and in which he
criticises the newer doctrines of Schleiden and Schacht, the
subject is far from being fully cleared up, though the views
there advocated are decidedly superior to his former ones. A
satisfactory conclusion with respect to growth in thickness of
the woody body and of the rind was not reached till the history
of development in vegetable histology began to be more
thoroughly studied.

As von Mohl had from the first laid special stress on the peculiar
character of the vascular bundles as compared with other tissue-
masses, so he perceived that the structure of the epidermis and
of the different forms of exterior tissue was thoroughly charac-
teristic, and he succeeded in arriving at a clearer understanding
of the matter in this case than in the other. Very confused
ideas had prevailed on the subject before he took it up, and we
owe to him the best and most important knowledge which we

Chap. III.] of Cell-membrane in Plants. 309

at present possess. Especially important were his researches
into the origination and true form of stomata (1838 and
1856), and into the cuticle and its relation to the epidermis
(1842 and 1845). He brought entirely new facts to light by
his study of the development of cork and the outer bark in
1836; these tissues had scarcely been examined with care
till then, and their formation and relation to the epidermis and
the cortical tissue were quite unknown. In the latter treatise,
one of his best, the difference between the suberous periderm
and the true epidermis was first shown, the various forms of
the periderm were described, and the remarkable fact esta-
blished that the scaling of the bark was due to the formation
of fine laminae of cork, which, penetrating gradually into the
substance of the cortex, withdraw more and more of it from its
connection with the rest of the living tissue, and as they die off
form by their accumulation a rugged crust, which is the outer
bark surrounding most thick-stemmed trees. The investiga-
tion was so thorough and comprehensive, that later observers,
Sanio especially in i860, could only add to it some more
delicate features in the history of the process. In the same
year appeared his enquiry into the lenticels, where von Mohl
however overlooked what Unger discovered at the same time
('Flora,' 1836), namely, that these forms arise beneath the
stomata; but he at once corrected Unger's hazardous sup-
position that the lenticels are similar forms to the heaps of
gemmae on the leaves of the Jungermannieae. Unger, for his
part, was not long in adopting von Mohl's explanation of the
lenticels as local cork-formations.

Since von Mohl thus distinctly brought out the special character
of the vascular bundles and of the different forms of epidermal
tissues, it must excite surprise that he, like former phytotomists,
did not find himself under the necessity of framing some con- '
ception of the rest of the tissue-masses in their peculiar grouping
as a whole, as a special system, and of classifying and suitably
naming the different forms that compose them, though his

310 Examination of Matured Framework.

examination of Tree-ferns would seem to have offered him an
occasion for doing so. Von Mohl, Hke his contemporaries, was
satisfied with calHng everything that is neither epidermis, cork
or vascular bundle, parenchyma, without distinctly defining the
expression.

Here we leave von Mohl and his labours for the present, to
return once more in the following chapter to the share which
he took in the further progress of phytotomy. We shall
perhaps best realise his importance in the history of the
science, if we try to think of all that we have now seen him
doing for it as still undone. There would then be a huge gap
in modern phytotomic literature, which must have been filled up
by others before there could be any further addition to the
knowledge of cells and tissues founded on the history of their
development ; for it can hardly be conceived that the advance
to which we owe the present condition of vegetable anatomy,
could have been based upon ideas such as those of Meyen,
Link, and Treviranus, without von Mohl's preliminary dis-
coveries.

CHAPTER IV.

History of Development of the Cell, Formation of
Tissues, Molecular Structure of Organised Forms.

1 840-1 860.

In the period between 1830 and 1840 it had come to be
understood, that the old theories of cell-formation of Wolff,
Sprengel, Mirbel, and others, resting on indistinct perceptions
and not on direct and exact observation, could only give an
approximate idea of the formation of cells. But in the course
of that time really different cases of formation of new cells were
accurately observed by Mirbel, and more especially by von Mohl,
who described different modes of formation of spores, and in
1 835 the first case of vegetative cell-division. Unfortunately these
observations, excellent in themselves, applied to cases of cell-
formation which do not occur in the ordinary multipHcation of
cells in growing organs, and von Mohl guarded himself from
founding a general theory of cell-formation on his observations
on cells of reproduction and on a growing filamentous Alga.
Mirbel also cautiously regarded the formation of pollen-cells
and that which he supposed to be the process in the ger-
mination of spores as cases of a peculiar kind, adhering to
his old theory of the origin of ordinary tissue-cells.

Schleiden's behaviour was different. Having somewhat
hastily observed the free cell-formation in the embryo-sac of
Phanerogams in 1838, he proceeded at once to frame a theory
upon it which was to apply to all cases of cell-formation, and
especially to that in growing organs. The very positive way

312 Development of the Cell and [book ii.

in which he announced this theory and set aside every objec-
tion that was made to it, combined with his great reputation at
the time, at once procured for it the consideration of botanists
generally ; and the most important representatives of phytotomy,
von Mohl himself at first not excepted, allowed that there was
a certain amount of justification for it. It was a question in
which theoretical considerations were not of primary import-
ance; direct and varied observation of careful preparations
with strong magnifying powers could alone form the basis for
further investigation. Unger showed in this way that the pro-
cesses at the growing point of the stem could scarcely be
reconciled with Schleiden's theory, and in this view he was
supported by the English botanist Henfrey; but Nageli was
the first who addressed himself with energy and sound reason-
ing to the important and difficult question, how cells are formed
in reproductive and growing vegetative organs, and how far the
processes are the same in the lower Cryptogams and in the
Phanerogams. He set out by assuming that Schleiden's theory
was in the main correct, but his long-continued investigations
led him finally to the conviction that it must be entirely
abandoned, and he proposed the outlines of the theory
of cell-formation which is accepted at the present time. In
this case, as before in questions of morphology, he applied
himself first, and with great success, to the investigation of the
lower Cryptogams, while Alexander Braun's observations on
some very simple Algae contributed materially to the further
development of the cell-theory, and especially to extending and
correcting the idea of the cell; Hofmeister's researches also in
embryology not only produced great results for morphology,
but at the same time supplied a variety of facts which served
to complete Nageli's view. The further this was worked out,
the more apparent it became that the external circumstances
in the processes of cell-formation might be very various, and
that von Mohl's earlier observations especially gave a correct re-
presentation of individual and typical cases ; but more important

Chap. IV.] Origin of Tissues. 313

than this result was the fact declared by Nageli in 1846, that in
all these different kinds of cell-formation it was only the external
and secondary matters that varied, while the essential part of
the process was in all cases the same, and it was soon per-
ceived that cell-formation in the animal kingdom, which was
now being more thoroughly examined, agreed in the main with
that of the vegetable kingdom, as Schwann and Kolliker had
intimated in 1839 and 1845.

It is unnecessary to give any account here of the totally
different theories which Theodor Hartig and Karsten proposed
about the same time. They do not rest on careful observation,
and we may omit them not merely because they are rejected by
the unanimous judgment of better observers, but because they
had no influence upon the development of the doctrine of
cell-formation, and are therefore without historical interest.

It lies in the nature of the case, that investigations into the
origin and multiplication of cells should turn the attention of
observers more and more to their living contents, for these are
actively and immediately concerned with the formation of new
cells. The various granular, crystalline, and mucilaginous por-
tions of the contents of cells had been repeatedly observed before
1840, and Schleiden and Meyen had specially studied the 'move-
ments of cell-sap '; but it was in the course of observations on
the history of development between 1840 and 1850 that attention
was first called to a substance which plays a regular part in the
formation of new cells, which envelopes the cell-nucleus dis-
covered by Robert Brown, which undergoes the most important
changes as the cell grows, which forms the entire substance of
swarm-spores, and the disappearance of which leaves behind it
a dead framework of cell-membrane. This substance, which is
much more immediately concerned with sustaining the pro-
cesses of life than is the cell-wall, was seen by Schleiden in
1838 and taken for gum. It was more carefully studied by
Nageli between 1842 and 1846, and perceived by him to be
nitrogenous matter. Von Mohl described it in 1844 and 1846

314 Development of the Cell and [Book ii.

from new points of view, gave it the name of protoplasm which
it still bears, and showed that it is this substance, and not the
proper cell-sap, which carries out the movement of rotation
and circulation in cells discovered by Corti in the previous
century, and again observed by Treviranus in 181 1. The
Algae proved highly instructive in the study of this remarkable
substance also. The swarm-spores of Algae and Fungi ob-
served by Alexander Braun, Thuret, Nageli, Pringsheim, and
De Bary showed that protoplasm is not dependent on the cell-
membrane for its vitality, that by virtue of its own internal
powers it can alter its form, and even move in space. In 1855
Unger in his ' Lehrbuch ' pointed out the resemblance of this
substance to the matter known as sarcode in the lower forms
of animals, a resemblance brought out more plainly in 1859,
when De Bary's studies of the Myxomycetes proved that the
substance of these forms was protoplasm, which continues to
live for a considerable time, and often in large masses, before
it forms cell-membranes. Zootomists now began to take an
interest in these results of botanical research ; Max Schulze
(1863), Briicke, and Klihne studied animal and vegetable
protoplasm, and the conviction gained ground more and more
in the years from i860 to 1870 that protoplasm is the imme-
diate principle of vegetable and animal life. This discovery is
one of the most important results of research in modern
natural science.

Not less important were the results obtained from the study
of the rest of the organised contents of cells ; von Mohl
proved that chlorophyll-corpuscles, the most considerable
organs of nutrition in the plant, are formed of protoplasm,
and Theodor Hartig, though his cell-theory was a mistake, did
good service by his discovery of aleurone-grains in seeds and
of the crystalloids which sometimes occur in the grains,
and which are also formed of protoplasm and renewed from
protoplasm. Radikofer, Nageli, and others added to our
knowledge of the form and chemical composition of these

Chap. IV.] Origin of Tissues. 315

aleurone-grains. To starch-grains, which had been frequently
examined, by Payen especially, Nageli devoted an investiga-
tion at once comprehensive and profound, and obtained results
of extraordinary value ; these were given to the world in an
exhaustive work published in 1858 under the title 'Die
Starkekorner,' and form an epoch not in phytotomy only,
but in the general knowledge of organised bodies. By
the application of methods of research unknown before in
microscopy, Nageli arrived at clear ideas of the molecular
structure of the grains, and of their growth by the introduction
of new molecules between the old ones. This theory of intus-
susception founded on the observation of starch-grains derives
its great importance from the fact that it served directly to
explain the growth of cell-membrane, could be applied generally
to molecular processes in the formation and alteration of
organic structures, and accounted for a long series of remark-
able phenomena, especially the behaviour of organised bodies in
polarised light. Niigeli's molecular theory is the first successful
attempt to apply mechanico-physical considerations to the ex-
planation of the phenomena of organic life.

While men of the highest powers of mind were devoting
themselves to the solution of these difficult problems, the study
of tissues was not neglected in the years after 1840, and here
too it was Nageli who gave the chief impulse and the direction
to further development. In the periodical which he published
in conjunction with Schleiden he had already (1844-46) given
an account of some searching enquiries which he had made
into the first processes in the formation of vascular bundles
from uniform fundamental tissue ; in the Cryptogams he
observed the production of the tissue of the whole plant from
the apical cell of the growing stem, and this discovery, still
further pursued by Hofmeister especially, has given rise during
the last twenty years to a copious literature, which has been
of service to the theory of the formation of tissues, to
morphology, and consequently also to systematic botany.

3i6 Development of the Cell and [Book ii.

The researches of Hofmeister, Nageli, Hanstein, Sanio, and
others into the first formation of vascular bundles from the
fundamental tissue of young organs led to important results
for morphology, in so far as it was now for the first time
possible to judge of the morphological value of anatomical
and histological relations. The growth in thickness of woody
plants, a question of primary importance to vegetable physi-
ology, was first made intelligible by the discovery of the mode
of formation of vascular bundles and their true relation to
cambium ; Hanstein and Nageli, and afterwards Sanio espe-
cially, cleared up the questions connected with growth in
thickness in their main features before and after i860.

When we pass on to show how the great results above-
mentioned were attained, we encounter some difficulties.
After 1840 botanical literature multiplied to an extent before
unknown ; it is from elaborate monographs on single subjects
in phytotomy, from some text-books, and especially from smaller
essays in botanical periodicals that we must gather an account
of the further development of scientific thought. Much as the
founding of scientific periodicals has facilitated communication
between professed botanists, yet this form of literature makes
it more difficult to see the way clearly through the work of
earlier periods and to discover the historical connection in the
science, not to speak of the harm that usually results from it to
young and inexperienced students.

Such being the nature of the sources from which we must
draw our information, we shall obtain a better general view of
the whole subject if we depart from the practice of former
chapters, and follow out the more important questions in their
historical development instead of connecting them directly
with leading persons. Such a treatment of the subject is
indeed suggested by the fact that we are now no longer on

Chap. IV.] Origin of Tissues. 317

pure historic ground ; for the majority of the men who have
developed modern doctrines since 1840 are still alive, and it
must be uncertain whether the account here attempted may
not be impugned on some ground or other. Owing to the
extraordinary diversity of opinion that exists among botanists
even on the most general questions in the science, it is
extremely difificult to ascertain what can be considered as
a common possession, — an unfortunate condition of things,
from which no science perhaps suffers so much as botany.

The extent to which individual botanists have contributed
to the advance of phytotomy during the period under consider-
ation will appear of itself from the following narrative ; and
if we speak almost exclusively of Germans, it is for the simple
reason that Englishmen from Grew's time till now can scarcely
be said to have added anything to our knowledge of phyto-
tomy ; the Italians also, once so gloriously represented by
Malpighi, scarcely come under consideration in the questions
now to be dealt with, while French botanists, represented
by Mirbel in the preceding period, though they have produced
many works on phytotomy since his time, have had no impor-
tant share in deciding the fundamental questions of modern
science.

In the preceding period it was necessary to take into
consideration the increasing improvement of the microscope,
in order to understand the development of opinion on
vegetable structure; but it is scarcely needful to do so after
1840. Since that time good and serviceable instruments with
strong magnifying powers and clear definition have been
within the reach of every phytotomist ; and though improve-
ments are still being constantly made, yet the microscopes that
were in the hands of skilful observers between 1840 and i860
were fully adequate to deciding the new questions proposed to
them. The chief improvement effected in the microscope
during this period was the fitting it with apparatus for the
polarisation of light, and for the more convenient measurement

3 1 8 Development of the Cell and [book ii.

of objects ; we shall see presently what influence the former
improvement had on the perfecting of Nageli's molecular
theory. As microscopes improved and the questions to be
solved grew more difficult, it became necessary to bestow
increased care on the preparation of objects ; it was no longer
sufficient to cut or dissect neatly, and so learn the form of the
solid portions of vegetable structure ; measures of precaution
and auxiliary measures of the most various kinds were needed
to obtain a clear view of the soft contents of cells, and to
observe the protoplasm as far as possible in a living state and
protected from prejudicial influences; all sorts of chemical
reagents were applied to make the objects more transparent,
or to show their physical and chemical characters. The
method invented by Franz Schulze before 1851 deserves to be
specially mentioned ; it consisted in isolating the cells in a few
minutes' time by boiling them in a mixture of nitric acid and
potassium-chlorate, and thus shortening Moldenhawer's process
of maceration or superseding it altogether. In a word, the
technicalities of the microscope were perfected in a variety of
ways by Schleiden, von Mohl, Nageli, Unger, Schacht, Hof-
meister, Pringsheim, De Bary, Sanio, and others, and raised to
an art which must be learnt and practised like any other art.
Young microscopists were able after 1850 to learn this art in the
laboratories of their elders, and to profit by their technical
experience and scientific counsels ; schools of phytotomy were
formed at least in the German universities; elsewhere, it is
true, the old condition of things remained in which everyone
had to trust to himself from the beginning.

The general dissemination of good microscopes was accom-
panied by a higher standard of requirement in the execution of
drawings from the instrument, especially after von Mohl had
shown the way ; and the invention of lithography and the
revival of wood-engraving ministered to the needs of science,
supplying the place of the old costly copper-plate printing.
Hence we find an increasing number of beautiful drawings

Chap. IV.] Origin of Tissues. 319

in scientific monographs ; the text-books also could now be ,
supplied svith an abundance of figures, and this greatly pro-
moted the general understanding of things which could other-
wise be seen only under the glass of each observer. From
the close of the i6th century wood-cuts had fallen more and
more into disuse, and had been replaced by copper-plates ;
after 1840 wood-engraving was restored to its old rights and
was found to be a more convenient method of pictorial
illustration, especially for text-books ; thus Schleiden's ' Grund-
ziige ' of 1842, von Mohl's ' Vegetabilische Zelle' of 1851,
Unger's and Schacht's text-books were enriched with many and
sometimes very beautiful wood-cuts. Lithographs were generally
preferred for periodicals and monographs ; the ' Botanische
Zeitung,' founded by Mohl and Schlechtendai in 1843, and
till after i860 the chief organ for shorter phytotomic com-
munications, was illustrated by a large number of beautiful prints
from the establishment of the Berlin lithographer, Schmidt.

I. Development of the Theory of Cell-formation
FROM 1838 to 1851.

Since we are here dealing with questions of fundamental
importance not only to one branch of botanical study but to
the whole science of botany, and even to the rest of the
natural sciences, it seems imperative that we should follow
step by step the founding and perfecting of the theory of the
cell, as far as is possible in the limited space at our com-
mand; we shall deal with the sexual theory further on in a
similar manner.

As usually happens in the inductive sciences, the period of
strict inductive investigation into cell-formation was preceded
by a still longer time, during which botanists ventured to put
forward general theories in reliance on highly imperfect obser-
vations. We have already seen how Caspar Friedrich Wolff
in 1759 made cells originate as vacuoles in a homogeneous

320 Theory of Cell-formation [Book ii.

Jelly, and how this view was adopted in all essential points by
Mirbel at a late period in the i8th century; how Kurt
Sprengel, and with him a number of phytotomists, among
them Treviranus as late as 1830, supposed cells to be formed
from granules and vesicles in the cell-contents, an idea which
Link it is true opposed in 1807, but afterwards accepted to
a great extent. Though Moldenhawer as early as 181 2
(' Beitrage,' p. 70) distinctly rejected these theories, and pub-
lished observations which if followed up would have led to the
right path, yet the botanists above-named and others with them,
long continued to adhere to the earlier views. Kieser, for
example ('Memoire sur I'organisation des plantes,' 181 2) further
developed Treviranus' theory, that the fine granules in the
latex of plants are cell-germs which are afterwards hatched
in the intercellular spaces. Schultz-Schultzenstein in his work
'Die Natur der lebenden Pflanze,' 1823-28, i, p. 607 rejected
this view and adopted that of Wolff and Mirbel. Scarcely
better than the notion of cell-germs represented by Sprengel,
Treviranus, and Kieser was the theory propounded by Karsten
soon after 1840; that of the French botanists Raspail and
Turpin^ (1820-1830), though conveyed in a different termin-
ology, corresponded in its main points with the views of
Sprengel.

It had been the good fortune of Mirbel at the beginning
of the century, and again thirty years later, to promote the
advance of phytotomy by means of important observations,
though he may have interpreted some of them incorrectly ; the
same thing happened again thirty years later, and it was a
German enquirer, von Mohl, who corrected his observations
and views on both occasions.

In his famous treatise on Marchantia polymorpha, which
appeared in 1835 in the Memoirs of the French Institute, the

^ On this point, see von Mohl's citation in 'Flora' of 1827, p. 13. I hiave
not myself been able to consult the originals.

Chap. IV.] fvom 1838 to 185I. 321

first part having been laid before the Paris Academy in 1831-32,
Mirbel distinguished three modes of cell-formation ; in the
germination of the spores of Marchantia new cells are formed
from the germ-tube and new cells again from these by a
similar process, much in the same way therefore as that which
actually occurs in the germination of Yeast-fungi ; he found
a second kind of cell-formation in the production of the
gemmae of Marchantia, where he distinctly observed the
successive appearance of the dividing walls, but formed an
erroneous idea of the proceeding on the whole ; in the further
development of the gemmae and in other cases of growth he
considered that new cells are formed between those that are
already present in the manner supposed in his earlier theory.

Von Mohl's dissertation on the multiplication of vegetable
cells by division, published in 1835 and reprinted in ' Flora' of
1837, shows how strange these processes even then appeared ; in
this work he expresses some doubts about Mirbel's statements,
but he accepts them on the whole, and only makes incidental
mention of his own more numerous and better observations
on the development of spores ('Flora,' 1833), though he had
there seen several cases of cell-division and free cell-formation
with tolerable distinctness. Adolph Brongniart ('Annales des
sciences naturelles,' 1827) also had observed, though imperfectly,
the formation of pollen-grains in their mother-cells in Cobaea
scandens, and Mirbel, in the appendix to the work mentioned
above, had given a correct description and good figures of the
formation of pollen-cells ; and yet von Mohl neglected to com-
pare these important observations of cases of cell-division with
his own ; even in 1845, when he pubhshed the latter in a revised
form in his ' Vermischte Schriften,' he overlooked the close re-
lation between the formation of those pollen-grains and spores,
and the cell-division in Cladophora. Still this treatise of von
Mohl's is of great importance in the history of the theory of cell-
formation, because it described a case of cell-division for the first
time step by step and brought all the saUent points into relief.

y

3aa Theory of Cell-formation [Book ii.

Dumortier had observed the division of cells as early as 1832 \
and Morren had seen it in Closterium in 1836, but had not
given the needful details. Finally, von Mohl applied the
experience which he had gained from Cladophora to other
filamentous Algae, and pointed out the similarity between
these processes and the division of Diatoms, which he con-
sequently claimed as plants in opposition to Ehrenberg, who
considered them to be animals ( ' Flora,' 1836, p. 492).

Meyen next, relying on von Mohl's observations on Clado-
phora, declared in the second volume of his ' Neues System '
that cell-division was a very common occurrence in Algae, Fila-
mentous Fungi and the Characeae, but he neglected any closer
investigation of the processes by which the division is intro-
duced and completed. His comparison of these cases of cell-
formation with the formation of spores, pollen-grains, and endo-
sperm-cells is moreover noticeable as the first attempt to distin-
guish what is now known as free cell-formation from cell-division;
it was obviously the want of this distinction which long pre-
vented clearer views on the whole of this field of observation.
The due separation of these two modes of cell-formation was a
short step after the observations that had been already made ;
and if that step had been taken, Schleiden's theory would have
been impossible, and the development of the cell-theory would
not have been prejudiced by the mistake, introduced by
Schleiden after 1838, of applying the mode of free cell-form-
ation, which he believed he had observed in the embryo-sac of
Phanerogams, to the multiplication of vegetative cells in grow-
ing organs, and regarding it as the only mode of cell-formation.
This would have been the more impossible, since von Mohl in
the same year gave an excellent description of the development
of stomata by division of a young epidermis-cell and the later
separation of the dividing wall into two laminae. But von
Mohl in the years immediately following was over-cautious in

^ See Meyen, ' Neues System/ ii. 344.

Chap. IV.] fvOM 1 83 8 ^0 1 85 1. 323

refraining from all speculative consideration of cases that lay
clearly before him, and his views were still undecided in 1845,
when Unger and Nageli had already made good observations
on the formation of tissue-cells in growing organs (' Vermischte
Schriften,' 1845, p. 336).

Schleiden's theory of cell-formation arose out of a curious
mixing together of obscure observations and preconceived
opinions, and reminds us indeed strongly of the old notions of
Sprengel and Treviranus ; it is true that he distinctly rejected
their views, but he too made new cells arise from very minute
granules, and his theory like theirs did not rest on any thorough
course of observation.

Robert Brown, (see his Miscellaneous Writings, edited by
T. T. Bennett, I.) had discovered the nucleus in the cells
of the epidermis of Orchidaceous plants in 1831, and had
shown that it was very generally present in the tissue-cells of
Phanerogams, but had obtained no results from his discovery.
The cell-nucleus lay undisturbed, till Schleiden suddenly made
it the soul of his theory and the starting-point of all cell-form-
ation. He considered that the nucleus was formed from the
mucilaginous content of the cell, which he assumed on insuf-
ficient grounds to be of the nature of gum ; this he called the
cytoblastem, and the nucleus itself the cytoblast. As he states
that his cytoblastem becomes yellow and granular in solutions
of iodine, we may recognise in it our own protoplasm.

We make acquaintance with Schleiden's theory of cell-form-
ation in its original form, if we turn to his treatise, ' Beitrage
zur Phytogenesis,' (in the Archiv fiir Anatomic, Physiologie, etc.
von Johannes Miiller, 1838). The work begins with some
remarks on the general and fundamental laws of human reason,
etc., discusses the literature of cell-formation in a few lines
without mentioning von Mohl's numerous observations, goes
on to mention the general occurrence of the nucleus which here
receives its new name, then occupies itself with gum, sugar,
and starch, and at last comes to the main subject. There are

¥2

324 Theory of Cell-formation [Book ii.

two spots, says Schleiden, in the plant, where the formation of
new organisation may be most easily and most certainly
observed, the embryo-sac and the end of the pollen-tube, in
the latter of which, according to his theory of fertilisation, the
first cells of the embryo are supposed to be formed, but where
in fact no cells are formed. At both spots small granules soon
arise in the gum-mucilage, which, before homogeneous, now be-
comes turbid, and then single larger and more sharply defined
granules, the nucleoli, appear. Soon after, the cytoblasts
are seen as granular coagulations from the granular mass ;
they grow considerably in this free condition, but as soon as
they have reached their full size, a delicate transparent vesicle
is formed upon them ; this is the young cell, which at first
presents the appearance of a very flat segment of a sphere,
whose plane side is formed by the cytoblast, the convex by the
young cell (the cell-membrane), which rests upon the cytoblast
as a watch-glass on a watch. Gradually the vesicle becomes
larger and of firmer consistence, and now the whole of the wall,
except where the cytoblast forms part of it, consists of a jelly.
By-and-bye the cell grows beyond the edge of the cytoblast
and rapidly becomes so large that the latter appears only as a
small body inclosed in one of the side walls. The shape 'of
the cell becomes more regular with advancing growth and
under the pressure of adjoining cells, and often passes into that
of a rhombododecahedron, which Kieser for reasons drawn
from the nature-philosophy assumed to be the fundamental
form. It is only after the resorption of the cytoblast that the
formation of secondary deposits on the inner surface of the
cell-wall commences, though some exceptional cases are
adduced, Schleiden thinks (p. 148) that he may assume that
the process here described is the general law of formation of
vegetative cell-tissue in Phanerogams. He adds particularly
that the cytoblast can never lie free inside the cell, but is
always enclosed in a duplication of the cell-wall, and he thinks
that it is an absolute law that every cell, except perhaps in

Chap. IV.] from 1838 to 1851. 325

cambium, begins as a minute vesicle, and grows to the size
which it reaches in its matured state. The resemblance of this
view to that of Sprengel and Treviranus is increased by what we
find further on, where we read that from the cell-germs in the
spores of Marchantia usually only from two to four serve to
form cells, the rest becoming overlaid with chlorophyll, and
being consequently withdrawn from the vital process. He who
is acquainted with the modern view of the processes of free
cell-formation founded on the numerous and careful investiga-
tions of later times will scarcely discover in the above account
of Schleiden's theory a single correct observation.

Soon after, von Mohl published in 'Linnaea,' 1839, p. 272,
his observations on the division of the mother-cells of the spores
of Anthoceros ; these were carefully made and were correct in
all the main points ; and in opposition to Mirbel's former state-
ments they establish the fact, that the division is effected by
the mucilaginous conjtents of the cell, and consequently that it
is not a passive division of the contents of the mother-cell pro-
duced by the growth inwards of projections of the cell-wall.

Unger ' was the first to declare distinctly against Schleiden's

^ Franz linger was bom in 1800 on the estate of Amthof, near Leut-
schach in South Steiermark, and was educated up to the age of sixteen in
the Benedictine Monastery of Gratz. Having gone through the three years'
course of ' philosophy,' he turned his attention, by his father's wish, to juris-
prudence; but he abandoned this study in 1820, and became a student
of medicine, first in Vienna, and afterwards in Prague. From the latter
place he made a vacation tour in Germany, and formed the acquaintance of
Oken, Cams, Rudolphi, and other men of science, and in 1825 of Jacquin
and Endlicher, with the latter of whom he maintained an active corre-
spondence on scientific subjects. Having taken his degree in 1827, he
practised as a physician in Vienna till the year 1830, and after that date
was medical official at Kitzbiihl in the Tyrol. During these years he
continued the botanical studies which he had commenced as a youth, and at
Kitzbiihl directed special attention to the diseases of plants, to palaeonto-
logical researches, and to enquiries into the influence of soil on the distribu-
tion of plants. At the end of 1835 he became Professor of Botany at the
Johanneum in Gratz, and devoting himself there especially to the study of

326 Theory of Cell-formation [book ii.

doctrine, and his observations on the punctum vegetationis
appeared in the 'Linnaea' of 1841, p. 389 ; from the size and
position of the cells he concluded that the tissue-cells in this
case are formed by division, and not in the manner alleged by
Schleiden. Soon after Nageli also ('Linnaea,' 1842, p. 252)
observed the processes of cell-formation in the extremities of
roots, but he did not conceive them to be cases of division ; he
saw two nuclei form in each mother-cell, and a new cell form
round each nucleus, and explained the origin of the dividing
wall as due to the meeting together of the two new cells ; he
thought that a similar process takes place in stomata and in
the mother-cells of pollen ; this conception was not absolutely
incompatible with Schleiden's theory, but there was this differ-
ence, that in Nageli's case essential processes were correctly
observed, but were to some extent incorrectly interpreted. In
the same year appeared the first edition of Schleiden's ' Grund-
ztige der wissenschaftlichen Botanik,' in ^ which his theory of
cell-formation was repeated in a more precise form. That he
was thoroughly in earnest to maintain it is shown by the fact
that he gave still another exposition of it in his ' Beitrage zur
Botanik' in 1844, where he insists that his method of cell-
formation is the general one, though it has been distinctly
ascertained in the Phanerogams only. But how completely an
observer may be led captive by a preconceived opinion may be
learnt from Schleiden's suggestion, that the formation of zygo-
spores in Spirogyra is in accordance with his views, though it

palaeontology, he soon became the most eminent authority on that subject.
Having been made Professor of Vegetable Physiology in Vienna in 1849,
he applied himself more to physiology and phytotomy. He retired from
this position in 1866, and from that time forward lived as a private in-
dividual in Gratz, promoting scientific knowledge by the publication of
popular treatises and the delivery of lectures. He died in 1870. Informa-
tion respecting his personal character and his varied and copious labours in
many departments of botanical science is given by Leitgeb in the ' Botan-
ische Zeitung' of 1870, No. 16, and by Reyer, ' Leben und Wirken des
Naturhistoriker Unger,' Gratz, 1871.

Chap. IV.] from T838 fo 1851. 327

is impossible to conceive of a case of cell-formation more easy
to observe, or less reconcilable with Schleiden's theory. It
was mentioned in the first book, that Hedwig and Vaucher
were acquainted with the remarkable process of the formation
of zygospores in the alga-genus Spirogyra ; but this as late as
Schleiden's time was not regarded as an example of cell-forma-
tion, and his view was really a step in advance, since it brought
a process, so highly peculiar according to existing ideas, under
the general conception of cell-formation.

The systematic elaboration of the theory of cells, founded on
careful observation and mature reflection, began with the year
1844. Almost at the same time in this year appeared Nageli's
detailed enquiries into the occurrence of the cell-nucleus and
into cell-division, von Mohl's observations on the primordial
utricle and its behaviour in the process of cell-division in young
tissue, and lastly those of Unger on merismatic cell-formation
(cell-division) as a general mode of proceeding in the growth of
organs. As these observers were chiefly concerned to test the
correctness and general applicability of Schleiden's theory, they
necessarily paid special attention to the general occurrence of
the cell-nucleus and to its position on the side of the cell-
wall, for these were the points most accessible to observation
and criticism. The discussion of these observations disclosed a
defect in the current phraseology, in which the word cell was
commonly understood to mean only the cell-membrane, but
sometimes included everything belonging to and contained in
the cell ; hitherto moreover the protoplasm of the cell had not
been sufficiently distinguished from the rest of the cell-contents.
Nageli and von Mohl arrived simultaneously at a clearer
understanding of these points ; von Mohl recognised the
primordial utricle (1844) as a component part of the cell-
contents and not belonging to the cell-wall, and explained the
part which it plays in cell-division ; in 1846 he arrived at a clear
conception of the protoplasm as a peculiar substance distinct
from the other contents of the cell and gave it the name it still

328 Theory of Cell-formation [Book ii.

bears. Meanwhile Nageli had also distinguished the protoplasm
from everything else in the cell, and noticed its pre-eminent
importance in cell-formation and its nitrogenous character.

We. must not omit to mention here, that investigations into
the processes of cell-formation compelled observers to search
for the spots where cell-formation actually takes place, and
thus the fact was ascertained, that cells in statu nascendi are
not to be found in all parts, not even in all growing parts of
the plant, but that we must look for them in the so-called
puncta vegetationis in the stem and root, in the youngest
lateral organs, and between the bark and the wood in woody
plants. About this time a new idea began to be attached to
the word cambium, which Mirbel had used in the sense of a
nourishing juice saturating the plant; it was now applied to
the tissue-masses in which the formation of new cells takes
place, and specially to the very thin layer of tissue lying
between the wood and the rind, from which new layers of
wood and rind in woody plants are formed— a layer, which
according to Mirbel's theory had been a mass of sappy matter,
in which new cells arise as vacuoles.

Unger in an enquiry into the growth of internodes ('Bota-
nische Zeitung,' 1844) again declared himself as an opponent of
Schleiden's theory. He maintained first of all and erroneously
that the cell-nucleus is not of general occurrence in tissue where
division is taking place, but he argued rightly from the position
of the cells, from the difference of thickness in their walls, and
from their relative size, in favour of their multiplication by
the formation of dividing walls ; he noticed the part played by
the cell-contents in the multiplication of cells in hairs, and
asserted that merismatic cell-formation (cell-division) is the
general rule in the growth of organs of vegetation, while he
distinctly declared that it was not possible to bring all that is
actually seen at the spots where formation of cellular tissue is
taking place into agreement with Schleiden's theory. But
Unger did not observe the processes that take place in cell-

Chap, IV.] from 1 838 to 1851. 329

division step by step ; his observations sufficed to make
Schleiden's theory very improbable without offering enough
foundation for a new one, and Schleiden did not fail to reply
to Unger's objections in the second edition of his 'Grundziige'
in 1845.

Earlier in the same year, von Mohl published in the ' Bota-
nische Zeitung' the treatise on the primordial utricle which
has been already mentioned ; by the term primordial utricle he
meant partly the very thin layer of protoplasm, which in large
cells full of sap lines the inside of the cell-wall, and partly an
outer layer of the protoplasm in young cells, which are still
rich in that substance. It is true that the distinguishing the
primordial utricle was not a very important matter ; but von
Mohl applied it with his usual thoroughness to obtaining a
better insight into cell-formation by calling attention (p. 289) to
the circumstance, that the cells of the cambium-layer between
the rind and the wood fit into one another and leave no inter-
cellular spaces ; from this he concluded that there are only two
possible modifications of cell-multiplication, either division of
cells by formation of a dividing wall or formation of cells
within cells ; in each of these young cells is a primordial
utricle, the origin of which must at least be contemporary with
that of the cell (cell-membrane). ' Could it then be distinctly
shown, that two primordial utricles exist side by side in cells,
which are in the act of multiplying, before a partition-wall is
formed between them, it would be evident that in the cambium
layer and at the points of the stem and root the formation of the
primordial utricle precedes that of the cell.' Von Mohl believed
that he had seen this process, but was not perfectly satisfied as
to the correctness of his observation ; but he continues : ' Since
every young cell contains a primordial utricle, this must either
be absorbed before a multiplication of the cell commences in
order to make way for two new ones formed in its stead, or the
old primordial utricle must separate into two.' He considered
the first supposition to be the probable one, rejecting Unger's

^^o Theory of Cell-formation [book ii.

statement that the nuclei are formed after the division. It is
surprising that after these considerations von Mohl thought that
his own observations necessarily confirmed Schleiden's theory of
cell-formation, although he noticed beside that the nucleus
never forms a part of the cell-wall, an essential feature in that
theory ; but in fact von Mohl took the membrane which accord-
ing to Schleiden separates from the nucleus for the primordial
utricle. But these mistakes are soon followed by the right
conjecture, that the substance of the primordial utricle may be
identical with the mucilaginous mass, which commonly encloses
the nucleus, and so with that which von Mohl two years later
named protoplasm. In this later treatise (' Botanische Zeitung,'
1846), in which he proves that the well-known movements in
the interior of cells are made not by the watery cell-sap but by
the protoplasm, he states (p. 75) that it is the protoplasm which
produces the nucleus, that the organisation of the nucleus
ushers in the formation of the new cell, and that contrary to
Schleiden's theory the protoplasm completely envelopes the
nucleus, which always occupies the centre of very young cells,
as is the case especially in the endosperm-cells observed by
Schleiden. He then shows how the protoplasm of young cells
at first solid afterwards forms sap-cavities and stretches between
them in walls, bands or threads, the substance of which exhibits
the streaming movement. Von Mohl strangely neglected on
this occasion to compare carefully his former observations on
the origin of spores and the division of Alga-cells with his new
results, and to seek for the essential resemblances between
them ; on the contrary he said emphatically that the cell-division
in Cladophora is probably a quite different process from the
multiplication of tissue-cells in higher plants.

The discoveries of Unger and von Mohl up to the year 1846
were quite sufficient to refute Schleiden's theory, but not to
give a clear and general view of the processes in the formation
of cells; the different kinds of cell-formation were neither
carefully distinguished from one another, nor could they be

Chap. IV.] fvom 1 838 to 185I. 33 1

referred to a common principle. Both observers had en-
deavoured to conjecture the course of events from certain data,
supplying by inference what they had not directly observed.

Nageli about the same time took up a different position as
an opponent of Schleiden's theory. In an exhaustive treatise
on the cell-nucleus, cell-formation, and cell-growth in plants,
the first part of which appeared in 1844 in the periodical
founded by himself and Schleiden, he collected together all
that had hitherto been observed by himself and others from
various points of view. All sections of the vegetable kingdom
were once more systematically examined with reference to the
occurrence of the cell-nucleus and the different kinds of cell-
formation ; all cases of the latter were carefully compared
together in their resemblances and differences, in order to
deduce from the observed phenomena that which was essential
and universal. The first result was, that Schleiden found
himself obliged, in the second edition of his ' Grundziige ' in
1845, to accept the cell-division established by Nageli in Algae
and the mother-cells of pollen as a second kind of cell-forma-
tion ; thus began the movement in retreat which was destined
to end in the following year with the overthrow of Schleiden's
theory. This was effected by the continuation of Nageli's
treatise in the third volume of the periodical for 1 846. In the
first part of his work Nageli had set out by assuming the
correctness of Schleiden's assertions, though he was even then
compelled to modify them considerably. In the second part,
however, in consequence of further observations Schleiden's
theory was declared in plain terms to be utterly incorrect, and
was refuted point by point. But Nageli was not obliged to
confine himself to this negative result ; his comprehensive
investigations supplied material at the same time for construct-
ing a new theory of cell-formation, which not only took in all the
various cases, but declared the principle which lay at the root
of all. If we compare this second part of Nageli's treatise with
von Mohl's publications from 1833 to 1846, we shall see that

^^2 Theory of Cell-formation [Book ii.

von Mohl had observed with accuracy a number of important
facts, but that NageH added largely to them, and, which is the
main point, elaborated them into a comprehensive theory em-
bracing all kinds of cell-formation. How important the correct
distinction of the protoplasm from the rest of the cell-contents
was for the perfecting of the theory of cells is seen from Nageli's
declaration, that he retracts his former view which rested on
the authority of Schleiden, because it sprang from a time when
he was ignorant of the significance of the mucilage-layer (the
protoplasm), though it is true that he indicates at the same
time other points and new considerations which definitively set
aside Schleiden's theory. After investigating the different
modes of free cell-formation and finding the processes there
quite different from Schleiden's account of them, he proceeded
to search for free cell-formation where Schleiden had affirmed
that it invariably occurs, namely in growing vegetative organs
in the higher plants. But this investigation led him to the
conclusion that all vegetative cell-formation is true cell-division,
and that even the reproductive cell-formation in some Algae
and Fungi is effected by division ; the reproductive cells of
most plants are the result of free cell-formation, but it should
be observed that the term free cell-formation is here used not
exactly in the modern sense, inasmuch as Nageli included in it
the formation of four-fold grains (tetrads) in spores and pollen.
If the distinction between cell-division and free cell-formation
had often been suggested by former observers, Nageli was the
first who distinctly defined it, though not exactly as it is now
defined. ' In cell-division the contents of the mother-cell
separate into two or more portions ; a perfect membrane forms
round each of these portions, which at the moment of its
appearance rests partly on the wall of the mother-cell and
partly on the adjacent walls of the sister-cells. In free cell-
formation a smaller or larger part of the contents of a cell, or
even the whole of them becomes isolated. On its surface is
formed a perfect membrane, which is everywhere free on its

Chap. IV.] from 1 838 to 1851. 0^'}^'^

outer face. There are two processes in the formation of a
cell ; the first is the isolation or individualising of a part of the
contents of the mother-cell, the second the formation of a
membrane round the individualised portion.' He then proceeds
to show that the cell-wall is formed by the separation of non-
nitrogenous molecules from the nitrogenous mucilage (proto-
plasm). These sentences contain all that is general and
essential in vegetative cell-formation. Further on he notices
the peculiarities in the various processes in cell-formation ; he
says that the individualising of the cell-contents assumes four
forms ; first, single small portions of the contents separate
themselves inside the rest, as occurs in the formation of free
germ-cells in Algae, Fungi, and Lichens, and of endosperm-
cells in Phanerogams ; secondly, the whole contents of one
cell, or of two by conjugation of associated cells, collect into a
free spherical or ellipsoidal mass, as in the formation of germ-
cells in the Conjugatae ; thirdly, the whole contents of a cell
separate into two or more portions, which is now called cell-
division ; from this Nageh distinguishes as his fourth form, the
process known as abscision (Abschniirung), which occurs in
the formation of germ-cells in many Algae and Fungi.

Schleiden had declared it to be a general law in plants, that
cells are only formed inside mother-cells. Meyen however,
Endlicher, and Unger, had recently assumed the formation
of new cells between the older ones ; Nageli maintained that
all normal cell-formation, vegetative and reproductive, takes
place only within mother-cells.

In opposition to the long-cherished notion that there
must be one general and fundamental form of cell, Nageli
pointed to the fact that cells have very different forms at the
moment of their production. Those which arise by free
cell-formation are, he says, at first always spherical or ellip-
soidal ; those produced by cell-division have a shape neces-
sarily conditioned by the form of the mother-cell and the
manner of division. He showed further that changes in the

334 Theory of Cell-formation [book ii,

shape of cells with advancing growth depend materially on
whether they enlarge equally in all parts of their circumference
or not. These considerations, obvious as they are, were now
for the first time pointed out and fully appreciated.

The reader who is already familiar with our subject will
recognise in the passages adduced from Nageli without further
explanation the essential principles of the modern theory of
cells, especially if he compares them with the views pro-
pounded at the same time and previously by Schleiden,
Unger, and von Mohl. But, as might be expected, the further
investigations, which were pursued with zeal during the suc-
ceeding twenty years and produced a considerable literature,
did much to enlarge and perfect Nageli's theory in many
of its details and to correct it in some minor points; the
theory itself facilitated this process by supplying a scheme
to which the investigation of special questions could readily
be referred. Whether the nucleus is a solid body or a ve-
sicle, whether in the division of a mother-cell into compart-
ments the wall of partition always grows from without inwards
or is formed simultaneously over its whole surface, whether it
is originally composed of two laminae or of one which is
afterwards differentiated, — these and many other questions
were decided in course of time.

Schleiden's theory was now definitively set aside, a deeper
insight was obtained into the nature of the cell, and the ideas
connected with the word became broader and more profound.
The knowledge of the formation of cells showed that the cell-
walls, which had been hitherto regarded as the important part,
are only secondary products, that the true living body of
the cell is represented by its contents and especially by the
protoplasm. Alexander Braun, relying on numerous re-
searches into the lower Algae, expressed himself in 1850
(' Verjiingung,' p. 244) to the effect that it is an inconvenience
that the word cell is used at one time to designate the cell
with its wall, at another time the cell without its wall, or again

Chap. IV.] from 1838 tO 185I. 'i^'>^^

the wall without the cell. Since the contents are the essen-
tial part of the cell and form a separate and individual whole
which has its own membrane-like boundary, the primordial
utricle, before the secretion of the membrane of cellulose, we
must either confine the term cell to the enveloping mem-
brane or to the chamber which it forms and find another
name for the body of the contents, or else call this the true
and proper cell. This, which presents itself at once as the
correct mode of conception to anyone who observes the
formation of swarm-spores in Algae and Fungi and many
other cases of cell-formation, was from this time forward a
vital point in the doctrine of the cell. Braun contributed
also to the clearing up of the ideas of botanists on this sub-
ject by bringing together under one systematic view and
classifying all the varieties of cell-formation which were known
to him up to the year 1850, and especially by a more
searching investigation into modes of conjugation. Henfrey's
contributions ('Flora' of 1846 and 1847) rested entirely
on the observations of German botanists, and brought to
light nothing that was independently and essentially new.
On the other hand Hofmeister's new observations on the
development of pollen (1848), and his many remarks on
cell-formation in his epoch-making researches into embryo-
logy in 1 85 1, contributed repeatedly to the deciding of doubtful
points, especially in the behaviour of the nucleus in cell-forma-
tion and the production of the dividing walls. Von Mohl,
who in spite of his own excellent observations maintained up
to 1846 a somewhat undecided attitude of mind in respect
to Schleiden's theory, which was at that time still in vogue,
pubhshed in 185 1, in his treatise 'Die vegetabilische Zelle,'
an excellent summary of the results which had been so
far achieved. In describing cell-division he notices speci-
ally that the new nuclei occupy the centres of the future
daughter-cells before the division of the contents commences;
but he still clung to his old view, that in every instance of

^^6 Theory of Cell-formation [Book ii.

cell-division the parting-wall must form progressively from
without inwards, as in Cladophora, contrary to Nageli's and
Hofmeister's correct statements, that cases also occur of
simultaneous formation at every point of the surface of the
partition-wall. As usual, however, von Mohl rested his opposi-
tion on a good observation, and showed that in the case
of the formation of pollen in dicotyledonous plants it is
possible to burst the membrane of a mother-cell in the act
of dividing, and set free the protoplasm when it is already
deeply divided into the four parts, and so to see the half-
formed partition-walls ; but this only proved that such was the
process in the cases observed, the formation of the partition-
walls being simultaneous in others. It may be mentioned
in this place, that the idea of special mother-cells in the
formation of pollen introduced by Nageli in 1842 was in
entire accordance with the condition of the science at the
time, since he meant by the term the laminae of membrane
formed during the successive divisions of the mother-cell.
To call these still special mother-cells, as some modern phy-
totomists do, is quite unjustifiable, because since 1846, when
Nageli propounded his theory, the word cell, as we have
seen, no longer designated the mere membrane but the
whole body of the cell, while the expression special mother-
cell rests on the older phraseology, in which cell and cell-
membrane are identical.

The additions made to the doctrine of cell-formation during
the greater part of the twenty years after 1851 were unimpor-
tant in comparison with the mighty development which it
had experienced during the preceding ten years. These
years had indeed been marked by the greatest possible
activity and fruitfulness in results in all parts of botanical
study. By the labours of Unger, von Mohl, Nageli, Braun,
and Hofmeister, not only were the foundations laid for a true
theory of cells, but the details were worked out, and the
conceptions connected with them finally cleared up. Text-

Chap. IV.] from 1838 ^ 185I. '>,'>^']

books could now disseminate the new teaching through
wider circles, and with these works may be classed von Mohl's
treatise already mentioned on the vegetable cell, since it came
much into use in a later and special edition, and was made by
many teachers of botany the foundation and guide in their
lectures. It was now become the fashion to compose not
general text-books of botany, but compendia of anatomy and
physiology, and thus morphology and systematic botany were
neglected, as anatomy and physiology had been in the period
immediately preceding Schleiden's time. Whoever therefore
wished to consult a complete manual of general botany was
for some time obliged to be content with Schleiden's ' Grund-
ziige'; and this had a great deal to do with keeping alive
his erroneous doctrines on cells and fertilisation among
general readers, while the professed botanists had long given
in their adherence to more modern and more correct views.
It is a misfortune in our science to be singularly poor in good
text-books, which might have given a general account from
time to time of the existing condition of research ; this is one
of the reasons why for some time past even official representa-
tives of botanical science often differ so much from one
another in their fundamental views on method, and on the
question of how much has been actually established and how
much still remains doubtful in the main divisions of the
subject, that a mutual understanding seems often impossible.
That a better state of things in this respect prevails in zoology,
physics, and chemistry, is certainly not a little due to the many
good compendia and text-books, which endeavour to give some
account of the progress of those sciences from year to year.

However, during the period from 1850 to 1870 Schacht
and Unger attempted to make the results of modern phyto-
tomic investigation accessible to general readers by means
of text-books. Such was the nature of Schacht s^ work,

* Hermann Schacht was born at Ochsenwerder in 1824, and died in 18^14
in Bonn, where he had been Professor of Botany since 1859.

Z

338 Theory of Cell-formation [Book ii.

' Die Pflanzenzelle,' published in 1852, a book which claimed
to expound all parts of phytotomy by the aid of the author's
own observations, with occasional reference only to the
writings of others ; the attempt was so far impossible, as
the essential points had already been fully cleared up by
the labours of other botanists. The work had however the
advantage of attracting the attention of the reader by nume-
rous good original drawings, and the style was enlivened
by the constant appeal to original observation ; at the same
time, through insufficient use of the available literature, the
author's views not unfrequently fell short of the existing
standard of knowledge. Worse than this however was a
certain defect of education, which led the writer into self-
contradiction and to incorrect classification of his facts ; things
fundamentally important were sometimes neglected for un-
important details, and a certain unreflecting empiricism was
apparent in the whole work, in marked contrast with the
logical exactness of von Mohl, Nageli, and Hofmeister. In
the second edition of the work, published in 1856 under the
title, ' Lehrbuch der Anatomic und Physiologic der Gewachse,'
we find many improvements in the details, but still on the whole
the same formal defects. It is not unimportant in a historical
point of view to notice this character of Schacht's writings, be-
cause during this period most young botanists and other persons
also derived their knowledge of phytotomy and of the nature
of cells chiefly from him ; his books did not truly represent the
condition of the science; their defective reasoning had an
injurious effect on the minds of younger readers, and they intro-
duced into phytotomy and vegetable physiology a habit of ac-
cumulating a mass of undigested facts, such as has for some time
marked the condition of morphology and systematic botany.

Unger's text-book ' Anatomic und Physiologic der Pflanzen '
(1855) was superior in conception and execution. It intro-
duced the beginner to the doctrine of cells with careful
attention to all that was known on the subject, if sometimes

Chap. IV.] fvom 1 838 tO 185I. 339

with some hastiness of decision, while it brought the really
important points everywhere into prominence and employed
individual facts to explain the general propositions, as should
always be done in a work intended for learners. But in
addition to this Unger's book contained much that was really
new and valuable, and among other things some very im-
portant remarks on the physiological characteristics of proto-
plasm ; and it pointed out for the first time the similarity
between vegetable protoplasm and the sarcode in Rhizopods,
which Max Schulze had before carefully described. In this
year Nageli also published investigations into the primordial
utricle and the formation of swarmspores in his ' Pflanzen-
physiologische Untersuchungen,' Heft I, which gave a new
insight into the physical and physiological characteristics of
protoplasm. It has been mentioned above that De Bary's
investigations into the Myxomycetes in 1859 had thrown
new light on the subject of protoplasm, and had called at-
tention to vital phenomena connected with it, which, though
analogous to what had been before observed, were rendered
very striking from the circumstance that in this case the
protoplasm was not in microscopically small portions enclosed
by firm cell-walls, but moved about and showed changes
of shape in large, sometimes in very large, masses, that were
entirely free and unconfined. Here was the best opportunity
for making a nearer acquaintance with protoplasm and for
learning to recognise it as the immediate support of all
vegetable and animal life ; in succeeding years the zootomists
and physiologists Max Schulze, Briicke, Kiihne, and others
established the fact that the substance which lies at the
foundation of cell-formation in animals agrees in its most
important characteristics with the protoplasm of vegetable
cells. A more detailed account of modern researches on this
subject, which would moreover involve the examination of
Hofmeister's work of 1867, 'Die Lehre von der Pflanzen-
zelle,' does not fall within the limits of our history.

z 2

340 Development of Opinion on the Nature [book ii.

2. Further Development of Opinion on the Nature
OF the Solid Framework of Cell-Membrane in
Plants after 1845.

Between 1840 and 1850 the most eminent representatives of
phytotomy were chiefly engaged, as we have seen, in observing
the formation of vegetable cells, and in framing the true theory of
the subject by process of induction. It was not to be expected
that, while these labours were bringing year by year new things
to light and keeping opinion on the formation of cells in a con-
stant state of fluctuation, their results would lead to very
important changes in the theory of the solid framework of cell-
membrane founded by von Mohl. On the contrary, it was at
this time that his views such as we have seen them on the con-
nection of cells one with another, on the configuration of their
partition-walls and on their growth in thickness, attained their
greatest influence. His theory seemed to stand firm and
complete when contrasted with the unsettled state of opinion
respecting the origin of cells, and the question, how far it could
be made to agree with the new observations on the history of
cell-formation, was hardly raised. In the midst of the strife of
opinion on the latter subject appeared von Mohl's ' Vermischte
Schriften ' in 1845, in which his views on the structure of mature
vegetable tissue were produced in a series of monographs as
the apparently irrefragable result of his observations. And in
fact phytotomic research up to i860 followed the train of
thought initiated by von Mohl, till at last the inadequacy of
his views was rendered apparent between 1858 and 1863 by
Nageli's new theory of growth by intussusception, and by the
profounder insight obtained into the nature of cell-formation.

A sufficient proof of the correctness of these remarks is to be
found in the further development of the views of botanists on
the intercellular substance and the cuticle, which might have
adapted themselves before 1850 to the new theory of cells, but

Chap. IV.] of the Cell-tissuc in Plants after 1845. 341

instead of doing so were moulded by the ideas current before
1845. It has been shown in the preceding chapter how von
Mohl gradually restricted the theory of intercellular substance
which he had proposed in 1836, and had come in 1850 to regard
this substance as only a cement which might in many cases be
perceived between the cell-walls. It should be added here,
that Schleiden in connection with his theory of cells considered
both the intercellular substance and the cuticle to be supple-
mentary secretions from the cells, and made the former fill the
intercellular spaces, just as laticiferous and resiniferous passages
are filled with secretions from the adjacent cells (1845). Unger
too in 1855 (' Anatomic und Physiologic der Pflanzen ') thought
the existence of a cement between the cells necessary to pre-
vent their falling asunder. Schacht, who in his ' Pflanzenzelle '
of 1852 had followed Schleiden in explaining the intercellular
substance and the cuticle aS secretions or excreta from the cells
of the plant, still kept on the whole to this view in 1858,
though he modified it in some important points. This theory
of Schleiden and Schacht was first opposed by Wigand in a
series of essays (i 850-1 861), in which in strict adherence to
von Mohl's theory of apposition he sought to prove, that the
layers which are visible in wood-cells as intermediate laminae in
the partition-walls, and which till then had been regarded as a
cement between contiguous cells, an intercellular substance,
were nothing else than the thin primary membranous laminae
formed in the process of cell-division, and subjected to subse-
quent chemical change, while the secondary layers of thickening
in von Mohl's sense lie on both sides of them. The cuticle
on the epidermis was explained in a corresponding manner.
Though Sanio in 1863 raised a variety of objections to Wigand's
view, he still adhered to it in principle, and found a strong con-
firmation of it in the fact, that he succeeded in producing the
well-known cellulose-reaction in the intercellular substance of
wood-cells when freed from foreign admixtures.

The researches of Wigand and Sanio w^ere sufficient to over-

343 Development of Opinion on the Nature [Book ii.

throw von Mohl's account of the intercellular substance and the
cuticle, but they had not proved that the intermediate laminae
are in fact the primary partition- walls on which von Mohl's secon-
dary thickening-layers had been deposited, on both sides in the
case of the intercellular substance, on one side in that of the
cuticle. The structure of the partition- walls and the existence of
the cuticle could be explained in a totally different way from the
point of view now opened by Nageli's theory of intussusception;
there was no need now to see either a secretion or a primary
cell-wall in the intermediate lamina of thickened cells or in the
cuticle, for it was possible that this lamination might be due to
subsequent chemical and physical differentiation of membranes
thickened by intussusception. As phytotomists are not yet
quite agreed as to the correctness of this view, we must be con-
tent with observing here that in the matter of the cuticle and the
intercellular substance lies one of the points, the determination
of which will involve the question of von Mohl's earlier theory
of apposition. It is not the purpose of this history to give the
more modern views that have asserted themselves since i860,
especially where the question is still in debate.

It was a part of von Mohl's idea of the cell-tissue and one
to which he had firmly adhered since 1828, that except in the
cross walls of genuine wood-vessels and some very isolated cases
the partition-walls in cellular tissue are never perforated ; that
both simple and bordered pits always remain closed by the
very thin primary lamina of cellulose. But between 1850 and
i860 several cases were discovered which were at once excep-
tions to von Mohl's rule, and of great importance to physiology.
Theodor Hartig, in his ' Naturgeschichte der forstlichen Kul-
turpflanzen Deutschlands ' (1851), described peculiar rows of
cells in the bast-system, in which the transverse and sometimes
the longitudinal walls appear to be pierced like a sieve by
numerous minute holes, and to these cells he gave the name
of sieve-tubes. Von Mohl (1855), while in other points con-
firming and extending Hartig's discovery, declared against

Chap. IV.] oj the Cell-ttssue in Plants after 1845. 343

the perforation of the walls, believing that the appearances
were due to lattice-like thickenings of the cell-walls ; he
proposed therefore to call Hartig's sieve-tubes latticed cells.
Then Nageli showed in 1861 that in some cases at least
there can be no doubt that the walls are actually perforated,
and that the sieve-plates serve for the passage of mucilaginous
matter in bast-tissue, and the author of this history, it may
be remarked in passing in 1863, and Hanstein in 1864, sug-
gested means by which it may be ascertained with certainty
that Hartig's sieve-plates are perforated. Meanwhile a number
of laticiferous organs had been recognised as forms of vessels
in von Mohl's sense, and it was found that such canals are pro-
duced by dissolution of the septa of adjacent cells. But the
knowledge of the laticiferous organs continued till towards
1865 to be very unsettled and defective, and the examination of
resin-passages, and the discovery that they are formed by simple
parting of cells from one another, belong to modern phytotomy ;
Hanstein, Dippel, N. J. C Miiller, Frank, and others have
since i860 enlarged our knowledge of these forms of tissue.
Schacht in i860 established one of the most important excep-
tions to von Mohl's view above-mentioned, by demonstrating the
formation and true form of bordered pits in the wood of Coni-
fers and in dotted vessels in Angiosperms from the history of
their development, and by showing moreover that in all cases
where bordered pits are formed on both sides of a partition-wall
and the adjacent cells afterwards convey air, there the original
very thin partition-wall in the bordered pit disappears, and that
consequently in such cases the bordered pits represent so many
open holes, through which adjacent cells and vessels com-
municate. At the same time another hitherto inexplicable
phenomenon received its explanation. Malpighi, and after
him the phytotomists at the beginning of the present century
had remarked, that the large vessels in the wood are not
unfrequently filled with parenchymatous cell-tissue, for the
origin of which no one could account. The phenomenon,

344 Development and [book ii.

however, could now be explained quite simply after Schacht's
discovery ; the formation of thylosis in vessels only takes place
when these border on closed parenchyma-cells in the wood;
when this is the case, the very thin membrane which separates
the bordered pits from the contiguous cells is not absorbed,
but it bulges inwards into the cavity of the vessel under the
pressure of the sap of the neighbouring parenchyma-cell, there
swells up like a bladder, and may by the formation of partition-
walls give rise to parenchymatous tissue; this, if proceeding
from a number of pits, fills up the cavity of the vessel.

3. History of Development and Classification
OF Tissues.

It has been already stated, that the first step to a real under-
standing of the structure as a whole of the higher plants was
made by Moldenhawer, who beginning with the study of the
Monocotyledons, first formed an idea of the vascular bundles
as a distinct whole, a system composed of various forms of
tissue, and applied this idea to explain the construction of the
stems of Dicotyledons, upsetting thereby Malpighi's earlier
theory of the growth in thickness of stems. It was also ob-
served, that von Mohl, advancing further in the same direction,
gave a more exact description of the epidermis and of the
tissues connected with it, and classified them, that is, intro-
duced a terminology founded on real investigation, but did not
succeed in bringing the subject to an entirely satisfactory con-
clusion ; this could in fact be reached only by the study of the
history of development, the only decisive method of investiga-
tion, whether the object be to determine the true nature of
cells and their subordinate forms, or the solid fabric of vege-
table structure, or as in the present case to distinguish and
classify forms of tissue ; it is this method which supplies the
morphological points of view necessary for the understanding
of the inner structure of the plant by investigating tissues in

Chap. IV.] Classification of Tissues. 345

those states of development, in which they are not yet adapted
to subsequent physiological functions. The combination of
morphological and physiological points of view in the determin-
ation of facts has maintained itself longer in this part of
botanical study than in any other ; but here too ideas and
opinions were gradually sifted and cleared up under the influ-
ence of the modern study of the history of development,
though it was not till after 1850 that the determination of the
chief points in the theory of cell-formation left the leading
phytotomists at hberty to devote themselves to histological
questions.

How little advance had been made towards the true under-
standing of the varieties of forms of tissue in the higher plants
before 1850 is shown, for instance, by Schleiden's account of
tissues on page 232 of his 'Grundziige' of 1845, where
parenchyma, intercellular substance, vessels, vascular bundles,
bast-tissue, bast-cells in Apocyneae and Asclepiadeae, latici-
ferous vessels, felted tissue, epidermal tissue, are discussed in
this succession in co-ordinated sections of the text. It is
obvious that no well-ordered view of the whole cellular
structure of a plant of the higher order could be obtained in
this way. Further on in the same work, where Schleiden
attempts a classification of vascular bundles, which he dis-
tinguishes into closed and open, and assigns the latter to
Dicotyledons, we find the cambium-layer named as the outer
boundary of these open vascular bundles ; the bast which lies
outside the cambium was therefore not considered to be a part
of the open vascular bundles, and this necessarily excluded
any profitable comparison of the circumstances in Monocoty-
ledons and Dicotyledons. The case is still worse in many
respects in Schacht's work already mentioned, 'Die Pflanzenzelle'
of 1852, where under the heading 'Kinds of vegetable cells'
the histology is discussed in the following co-ordinated sections ;
the swarm-filaments of Cryptogams, the spores of the same,
pollen-grains, cells and tissue of Fungi and Lichens, cells and

346 Development and [Book ii.

tissue of Algae, parenchyma and its cells, vessels of the plant,
wood and its cells, bast-cells, stomata, appendicular organs of
the epidermis, cork; then follows a paragraph on the thick-
ening-ring, and then to the no small astonishment of the
reader comes an account of the vascular bundles, after the
vessels, the wood, and the bast-cells have been already dis-
missed. That such a mode of presenting the subject is due to
the little insight possessed by the writer into the structure of
the plant as a whole is apparent from simply reading the book,
and a similar confusion of ideas is found in his text-book of
1856.

We find a much better classification of tissues in 1855 in
Unger's ' Anatomic und Physiologie der Pflanzen ' ; an account
of cells is followed by a description of cell-complexes, as one
of the chief divisions of the book, and herein of cell-families,
cell-tissues, and cell-fusions. Another chief section is occupied
with cell-groups, and here epidermal formations, air-spaces,
sap-receptacles, glands and vascular bundles are noticed ;
here certainly the fact has been overlooked that vascular
bundles may be co-ordinated with epidermal formations, but
not air-spaces, sap-receptacles and glands. His last chief
division gives an account of tissue-systems and of the way in
which the vascular bundles are united together in different
plants, and secondary growth in thickness and the activity of
the cambium-layer are described quite in the right connection.

In this branch of the science, as in every case where it is a
question of establishing fundamental conceptions, of surveying
facts from extensive points of view, and of seeking the requisite
principles by means of the history of development, we find that
it is Nageli who opens the way and lays the foundation. In
his ' Beitrage zur wissenschaftlichen Botanik' of 1858, he pro-
posed a classification of tissues from purely morphological
points of view. His first division was into generating and
permanent tissue ; in each section he distinguished two forms,
prosenchymatous and parenchymatous tissue. Parenchymatous

Chap. IV.] Classification of Tissues. 347

generating tissue, the original component of every j^oung organ,
he named primary meristem as distinguished from prosen-
chymatous generating tissue, which is differentiated in the
form of strands and layers, and received from him the general
name of cambium ; this was certainly not a happy distinction,
because Nageli's cambium by no means consists entirely of
prosenchymatous tissue. By the term secondary meristem
Nageli designated the tissue-strands and tissue-layers which
are formed between the permanent tissue of older parts. The
cambium he regards as the first product of the primary meristem.
The second chief form, permanent tissue, he divides into two
classes, not according to the form of the cells or physiological
relations, but according to its origin ; all permanent tissue,
which is derived immediately from primary meristem, is
protenchyma, all that comes directly or indirectly from cam-
bium is epenchyma. And since the tissue-strands, till then
known as vascular bundles, do not contain vessels only but
always fibrous elements also, as Bernhardi had shown in 1805,
Nageli thought that they should therefore be called fibrovascular
strands. If it cannot be denied that the obvious distinction
between epidermal and other tissue did not find suitable
expression in this classification, and though other points of
view may at the present day be proposed for the genetic
arrangement of tissues, yet Nageli's classification and ter-
minology have the merit of having for the first time exhibited
the general histology of plants on comprehensive and genetic
principles. It contributed materially to impart a better under-
standing of the collective structure of plants.

The vascular bundles or fibrovascular strands especially de-
manded further investigation of the genetic and morphological
kind ; for a correct insight into the origin and subsequent trans-
formation of this tissue-system is as important for phytotomy
as a similar knowledge with respect to the bony system in
vertebrate animals is for zootomy. But a knowledge of the
vascular bundles and their course in the stem has a special im-

348 Development and [Book ii.

portance in phytotomy, because it is the only way to the under-
standing of secondary growth in thickness in true woody plants.
It was noticed above, that von Mohl had proved in 1831
the separate character of the bundles which begin in the stem
and bend outwards into the leaves where they end, so that the
entire system of bundles in a plant consists of single bundles
isolated when formed and subsequently brought into connection
with one another. Nageli had already examined the correspond-
ing circumstances in the vascular Cryptogams in 1846, when
Schacht took the retrograde step of making the vascular
system in the plant originate in repeated branching, instead of
in subsequent blending of isolated strands ; Mohl declared
unhesitatingly against this mistake in 1858, but it was refuted
at greater length and still more clearly by Johannes Hanstein
in 1857, and by NageU in 1858. Hanstein in a treatise on the
structure of the ring of wood in Dicotyledons confirmed
Nageli's previous statements, and proved in the case of
Dicotyledons and Conifers that the first woody circle in the
stem is formed from a number of vascular bundles, which are
identical with those of the leaves and originate in the primary
meristem of the bud. These primordial bundles pass down-
wards through a certain number of internodes in the stem
independent and separate, and either retain their isolation to
the point where they end below or unite with adjacent bundles
which originated lower down. Hanstein happily termed the
portions of the vascular bundles, which enter the stem from
the base of the leaf and traverse a certain portion of it in a
downward direction, leaf-traces, so that it may be stated
briefly, that the primary wood-cylinder in Dicotyledons and
Conifers consists of the sum of the leaf-traces. Nageli's observa-
tions were of a more comprehensive character, and supplied,
as we have seen, a terminology for tissues. He distinguished
three kinds of vascular bundles according to their course ; the
common bundles, which represent Hanstein's leaf-traces in the
stem, and whose upper ends bend outwards into the leaves ;

Chap. IV.] Classification of Tissues. 349

the cauline bundles, which extend above to the punctum
vegetationis of the stem without bending outwards into leaves ;
and leaf-bundles, which belong to the leaves only. He laid it
down as a general rule as regards the common bundles in
Dicotyledons and Conifers that they begin to form where their
ascending and descending halves meet, at the spot therefore
where they bend outwards into the leaf, and continue to form
as they descend into the stem and ascend into the leaf by
differentiation of suitable tissue. It follows from the nature of
these common bundles, that a more thorough understanding
of their course and origin presupposes a more accurate know-
ledge of the order of formation of the leaves at the end of the
stem and of the changes in the phyllotaxis during growth ;
these relations Nageli took into detailed consideration, and
even derived from them new points of view for the examina-
tion of the genetic arrangement of leaves, pointing out at the
same time the unsatisfactory nature of the principles of the
doctrine propounded by Schimper and Braun. Nageli was
also the first who compared the anatomical structure of roots
with that of stems, and drew attention to the peculiar character
of the fibrovascular body in these organs. As his previous
discovery of the apical cell and its segmentation promoted
further research, so now his treatise on fibrovascular strands
called forth many others from various quarters ; among them
that of Carl Sanio on the composition of the wood ('Bota-
nische Zeitung,' 1863) must be mentioned as one of the
first and most important, and as serving in conjunction with
the works of Hanstein and Nageli to throw light upon the
processes of growth in thickness of stems. It has been already
said that neither von Mohl nor Schleiden, neither Schacht nor
linger succeeded in finding the true explanation of growth in
thickness. It was impossible that they should do so, for they
were insufficiently acquainted with the origin, true course, and
composition of the vascular bundles before growth in thickness
commences ; the study of the subject was greatly perplexed by

350 Ndgeli's Theory of Molecular Structure [Book ii.

the confounding together in thought and language of totally
different things which came under consideration, the so-called
thickening-ring, in which the first vascular bundles were sup-
posed to originate close under the summit of the stem, being
confounded with the cambium of true woody plants which is
formed at a much later period, and both of them again with the
very late-formed meristem-layer in arborescent Liliaceae, in
which new vascular bundles are continually being produced
and cause a peculiar enlargement of the stem\ Sanio's treatise
first removed this confusion of ideas, which appears in von
Mohl himself to some extent even in 185S, by sharply dis-
tinguishing the thickening-ring beneath the point of the stem,
in which the vascular bundles begin to be formed, from the
true cambium, which is formed at a later time in and between
the vascular bundles, and produces the secondary layers of
wood and rind ; Sanio also occupied himself with submitting
the various elements of the wood to a more careful examination,
and with giving them a better classification and terminology.
The peculiar instance of secondary growth in thickness in the
arborescent Liliaceae, which had long been known and had
helped to mislead von Mohl and Schacht, was fully explained
for the first time by A. Millardet in 1865. The later works
of Nageli, Radlkofer, Eichler and others on abnormal wood-
formations contributed materially to enlarge the knowledge
of normal growth also; but these coming after i860, and
Hanstein's later investigations into the differentiation of tissues
at the end of the stem in Phanerogams, do not fall within the
limits of our history.

4. Nageli's theory of Molecular Structure and of
growth by intussusception.
This theory, the importance of which to the further develop-
ment of phytotomy and vegetable physiology has been already

^ See Sachs, ' Lehrbuch der Botanik,' ed. 4(1874), p. 129 (p. 128 of 2nd
English edition).

Chap. IV.] and of Gvowth by Intussusception. 351

pointed out, will form the conclusion of our history of the
anatomy of plants. It was a remarkable coincidence that this
molecular theory of organic forms, which is not without results
for zootomy also, was brought to completion at about the same
time, namely, the year i860, that Darwin first published his
theory of descent. At the first glance the two theories seem
to have no connection with one another, and so the coincidence
in time appears to be quite accidental. But if we go deeper
into the matter, we find a resemblance between them which is
of great historical importance ; they both of them exchange the
purely formal consideration of organic bodies, which had pre-
vailed up to that time, for a consideration of causes ; as Darwin's
doctrine endeavours to account for the specific forms of animals
and plants from the principles of inheritance and variability
under the disturbing or favouring influence of external circum-
stances, so the object of Nageli's theory is to refer the growth
and inner structure of organised bodies to chemical and
mechanical processes. The future will show, whether the views
which we owe to Nageli will not contribute to the laying a
deeper foundation for the theory of descent, since it is not im-
probable that a more thorough understanding of the molecular
structure of organisms may add light and certainty to the still
obscure conceptions of inheritance and variation.

The first beginnings were, as is usual in similar cases,
small and inappreciable, and no one could have foreseen from
the first observations of the facts in question what the ultimate
development would be. We have said above, that von Mohl
observed as early as 1836 the striation of certain cell-walls, and
that this led Meyen, on the ground of further but to some
extent inaccurate observations, to conceive of vegetable cell-
walls as composed of spirally twisted threads. It was also
noticed that von Mohl next distinguished true striation from
spiral thickenings (1837), the two having been confused
together by Meyen, and advanced so far as to form some idea of
the molecular structure of cell-walls, without arriving however at

^^2 Ndgelts Theory of Molecular Struchtre [Book ii,

any satisfactory conclusion. Agardh, who discovered some new
instances of cell-striation, was still less successful in his specula-
tions. Von Mohl resumed the subject in 1853 in the ' Bota-
nische Zeitung,' and insisted on the fact that it was not possible
to separate the striae or apparent fibres by mechanical or chemi-
cal means, but he left it still undecided whether the lines which
cross each other in the surface-view belong to the same or to
different layers of membrane. The communications of Criiger
and Schacht, made shortly after, did not help to advance the
question ; Wigand also took part in the discussion in 1856, but
wandered at once from the right path by supposing the cross-
striations to belong to different layers of membrane. As long
as botanists adhered to von Mohl's theory, that the concentric
stratification of cell-walls was due to deposition of new layers,
it was scarcely possible for them to arrive at a correct decision
with respect to striation; it became possible, when Nageli proved
in his great work 'Die Starkekorner ' (1858) that the con-
centric stratification of starch-grains and of cell-membranes
generally does not mean, that similar layers lie simply one on
another, but that denser and less watery layers alternate with
layers that are less dense and contain more water ; and that it
is not possible to explain this mode of stratification by deposi-
tion as understood by von Mohl, but that it may be explained
by intercalation of new molecules between the old ones and by
corresponding differentiation of the amount of water. That
surface-growth in cell-walls does take place by this kind of
intussusception had been incidentally suggested by linger, and
the appearance, known as the striation of the cell-wall might
now be referred to the same principle as the concentric
stratification, namely to the intercalation of more and less
watery matter in regular alternation. But Nageli pointed out
a fact which had escaped other observers, namely, that the
difference of structure which usually appears on the surface-
view as double cross-striation, passes through the whole
thickness of a stratified cell-wall. Thus Nageli arrived at a

Chap. IV,] and of growtli by intussusception. '>,^'>f

differentiation in three directions in space of the substance of
every minute portion of cell-membrane, and made better use
than von Mohl himself had made of the comparison which he
had suggested, namely, that the structure of a cell-wall with
cross-striation and at the same time with concentric stratification
resembles that of a crystal cleaving in three directions. He
first gave expression to this conception of the structure of the
cell- wall in 1862 in his ' Botanische Untersuchungen,' I. p. 187,
and further developed it in the second volume of the same
work at p. 147.

But the true starting-point of Nageli's theory of molecular
structure is to be found in his searching investigations in 1858,
into the constitution of starch-grains. From the way in which
they resist the effects of pressure, drying, distention, and with-
drawal of a part of their substance, he arrived at the conclusion
that the whole substance of a starch-grain is composed of
molecules, whose shape must be not spherical but polyhedral,
that these are separated from one another in their normal
condition by envelopes of water, and that the amount of water
in the stratified substance depends on the size of these
molecules, the water being less when the molecules are larger ;
this view could at once be applied to the structure of the cell-
wall, the growth of which may be explained as the increase in
size of the molecules already present, and the intercalation of
new small molecules between the old ones. These molecules
of Nageli are themselves very compound bodies, for the smallest
of them would consist of numerous atoms of carbon, hydrogen
and oxygen, and ordinarily a molecule would be composed of
thousands of those aggregates of atoms, which the chemists
call molecules.

In examining starch-grains Nageli came to the conclusion
that molecules of different chemical character are grouped
together at every visible point; the material which colours
blue with iodine, the granulose, could be removed from the
grains, and then there remained behind a skeleton of the

A a

354 NdgeWs theory of molecular structure [Book ii.

starch-grain very poor in substance, but showing exactly the
original stratification and giving no blue colour with iodine ;
this Nageli named starch-cellulose. It followed from this
behaviour, that two chemically different molecules lie every-
where side by side in the grain of starch, much as if red and
yellow bricks had been so employed to build a house, that
when all the yellow bricks were afterwards removed, the red
alone would still represent the wall in its original form as a
whole though in a looser condition. He arrived at similar
results in the case of the crystalloid proteid bodies, v^hich
Theodor Hartig discovered, and Radlkofer had examined
crystallographically, Maschke chemically. Since it is possible
in the same manner to extract the so-called incrusting matters
from cell-membranes without essentially altering their form,
and to obtain ash-skeletons of them which imitate all the
delicacies of their structure, the comparison adopted above
may also be applied in still more complex manner to the
molecular structure of these membranes ; and indeed many
considerations lead to the belief, that the ideas which Nageli
obtained from starch-grains may be applied with some modifica-
tions to the structure of protoplasm also.

We said that the appearances in the starch-grains led Nageli
to suppose that their molecules are not spherical but poly-
hedral, and the question naturally arose whether they are
really crystalline. The point could be settled by the use of
polarised light, to which different observers had already turned
their attention. Erlach in 1847, Ehrenberg in 1849, had em-
ployed polarised light for the determination of microscopic
objects, without however arriving at any conclusions on the
subject of molecular structure ; Schacht indeed at a later time
declared such observations to be a pretty amusement, but
without scientific value. But soon we have once more one of
von Mohl's careful and solid investigations ('Botanische Zeitung,'
1858), in which with the aid of technical improvements in
the apparatus he arrived at conclusions respecting the nature

Chap. IV.] and of gvowth by intussusception. ^tSS

and substance of cell-membranes, starch-grains, &c., which
proved that in the hands of a reflecting observer perfectly
familiar with the physics of polarised light the instrument is no
toy, but a means for penetrating deeply into nature's secrets.
Yet on this occasion also appeared that peculiarity in von Mohl
which twenty years before had prevented him from founding a
conclusive theory upon his profound and extended observa-
tions on cell-formation ; he was content once more to observe
thoroughly and correctly, to describe what he observed care-
fully, and to connect it with proximate physical principles
in such a manner as to supply rather a classification of pheno-
mena, than a new and deeper insight into the essence of the
matter. He wanted the creative thought, the intense mental
effort, to arrive by analysis at the ultimate elements in the results
of his investigations and to frame for himself a clear represen-
tation of the inner structure of the organised parts. Von Mohl
in this case also stopped short at induction and did not pass on
to deductive and constructive elaboration of the question before
him ; this was left to Nageli, as we shall see.

Meanwhile a more exhaustive work appeared in 1861 from
the pen of Valentin on the investigation of vegetable and
animal tissue in polarised light, in which the author, equipped
with great knowledge of the subject itself and its literature,
examined in detail the phenomena of polarisation, gave a good
account of the instrument and the mode of using it, and
explained generally the theory and practice of investigations of
the kind. But he overlooked one fact noticed by von Mohl,
that vegetable cell-membranes, through which rays of polarised
light pass perpendicularly to their surface, show interference-
colours, and this was sure to lead him to an incorrect
explanation of their inner structure.

NageK from 1859 onwards made the phenomena of polarisa-
tion the subject of protracted study, practical and theoretical ;
the results were published in 1863 in his ' Beitrage,' Heft 3,
but he had in the previous year made known that portion

A a 2

^S^ Ndgelis theory of molecular structure.

of them which bore on the molecular structure of cell-walls
and starch-grains (' Botanische Mittheilungen,' 1862). The
phenomena of polarisation led him once more and by a
different path to the view that the organised parts of the
vegetable cell consist of isolated molecules surrounded by
a fluid, and his renewed investigations of these phenomena
resulted in more definite conceptions of the nature of these
molecules, which from the optical behaviour of the objects
examined he concluded were not only polyhedral but crystal-
line ; in effect, the molecules of the substance of the organised
parts of plants behave, according to Nageli, as crystals with
two optic axes, which therefore possess three different axes
of elasticity ; in starch-grains and cell-membranes these
crystalline molecules are so arranged that one of these axes
is always perpendicular to the stratification, while the two
others lie in its plane. The effect of the organised parts of the
cells on polarised light is the sum of the effects of the single
molecules, whereas the fluid that lies between them is optically
inactive, and only comes into consideration because according
to its quantity the molecules separate more or less far from or
approach one another.

THIRD BOOK

HISTORY OF VEGETABLE
PHYSIOLOGY

(1583-1860)

INTRODUCTION.

All that was known in the i6th and at the beginning of the
17th centuries of the phenomena of hfe in plants was scarcely
more than had been learnt in the earliest times of human
civilisation from agriculture, gardening, and other practical
dealing with plants. It was known, for instance, that the
roots serve to fix plants in the soil and to supply them with
food ; that certain kinds of manure, such as ashes and, under
certain conditions, salt, strengthen vegetation ; that buds
develope into shoots ; and that the blossom precedes the
production of seeds and fruits. These and a variety of minor
physiological phenomena were disclosed by the art of garden-
ing. On the other hand, the physiological importance of
leaves in the nourishment of plants was quite unknown, nor
can we discover more than a very indistinct perception of the
connection between the stamens and the production of fruitful
seeds. That the food-material taken up from the soil must
move inside the plant in order to nourish the upper parts was
an obvious conclusion, which it was attempted to explain
by comparing it with the movement of the blood in animals.
Writers on the subject up to the end of the 17th century
make very slight mention of the influence of light and warmth
on the sustentation and growth of plants, though doubdess the
operation of these agencies in the cultivation of plants, as in
other matters, must have been early recognised.

So scanty was the stock of knowledge which the founders of
vegetable physiology in the latter half of the 17th century
found ready to their hand. While the physiological signi-
ficance of the different organs of the human body and of most

360 Introduction. [Book III.

animals were known to every one, at least in their more
obvious features, the study of vegetable life had to begin with
laborious enquiries, whether the different parts of plants are
generally necessary to their maintenance and propagation,
and what functions must be ascribed to individual parts for
the good of the whole. It was no easy matter to make the
first step in advance in this subject ; something can be learnt
of the functions of the parts of animals from direct observa-
tion, scarcely anything in the case of plants ; and it is only
necessary to read Cesalpino and the herbals of the i6th
century to see how helpless the botanists were in every case
in presence of questions concerning the possible physiological
meaning of vegetable organs, when they ventured beyond the
conceptions of the root as the organ of nourishment, and
of the fruit and seeds as the supposed ultimate object of
vegetable life. The physiological arrangements in vegetable
organs are not obvious to the eye ; they must be concluded
from certain incidental circumstances, or logically deduced
from the result of experiments. But experiment presupposes
the proposing a definite question resting on a hypothesis ;
and questions and hypotheses can only arise from previous
knowledge. An early attempt to connect the subject with
existing knowledge was made in the use of the comparison
of vegetable with animal life, a comparison which Aristotle
had employed with small success. Cesalpino, provided with
more botanical and zoological knowledge, endeavoured to
arrive at more definite ideas of the movement of the nutrient
juices in plants, and when Harvey discovered the circulation
of the blood in the beginning of the 1 7th century, the idea at
once arose that there might be a similar circulation of the sap
in plants. Thus a first hypothesis, a definite question was
framed, and attempts were made to decide it by more exact
observation of the ordinary phenomena of vegetation, and
still better by experiment ; and though a discussion which
lasted nearly a hundred years led to the opinion that there is

Book III.] Introduction. ■^6i

no circulation of sap in plants corresponding to the circulation
of blood in animals, the result was obtained by the aid of this
hypothesis derived from a comparison between animals and
plants. The important discovery that leaves play a consider-
able part in the nourishment of plants, was to some extent an
incidental product of the investigation of the former question,
and it preceded that of the decomposition of carbon dioxide
by the green parts of plants by more than a hundred years.
To give another example ; it was obviously a comparison
of certain phenomena in vegetable life with the propagation of
animals which paved the way for the discovery of sexuality
in plants ; long before Rudolf Jacob Camerarius made his
decisive experiments (1691-1694) on the necessary co-opera-
tion of the pollen in the production of seeds capable of
germination, the idea had been entertained that there might
be an arrangement in plants corresponding to the sexual re-,
lation in animals, though that idea was highly indistinct and
distorted by various prepossessions. In like manner the interest
excited by the discovery of the irritability of the Mimosae in
the 17th century, and of similar phenomena of movement in
plants at a later time, was mainly due to the striking resem-
blance suggested between animals and plants ; and the first
researches into the subject were obviously intended to answer
the question whether the movements in plants are due to con-
ditions of organisation similar to those in animals. In all
cases of this kind it was matter of indifference whether
the analogies presupposed were finally confirmed after pro-
longed investigation, as in the question of sexuality, or dis-
proved as in that of the circulation of the sap. The result
was of less importance than the obtaining points of departure
for the investigation. It answered this purpose to adopt cer-
tain actual or only apparent analogies between plants and
animals, and to assume, to some extent to invent, certain
functions for the apparently inactive organs of plants, and
to interrogate them upon the point. Scientific activity was

362 Introduction. [Book III.

set in motion, and it mattered not what the result might be.
In all questions connected with the phenomena of life, our own
life is not only the starting-point but also the standard of our
conceptions ; what animate nature is as opposed to inanimate
we discern first by comparing our own being with that of other
objects. From our own vital motions we argue to those of the
higher animals, which we comprehend immediately and in-
stinctively from their conduct ; by aid of these the motions
of the lower animals also become intelligible to us, and
further conclusions from analogy lead us finally to plants,
whose vitality is only in this way made known to us. While
plants were thus even in ancient times regarded as living
creatures and allied to animals, further reflection naturally
suggested the idea that the phenomena of animal life would
be reproduced in plants even in details. We learn from the
•botanical fragments of Aristotle that this was in fact the way
in which the first questions in vegetable physiology arose ;
they assumed a more definite form with Cesalpino, and later
physiologists repeatedly made use of similar conclusions from
analogy. The historian of this branch of botanical science
must seek no other beginning of it, for it had no other and
could have no other from the nature of the case. And if
preconceived analogies between plants and animals often
proved deceptive and mischievous, yet continued investigation
gradually brought to light more important and more essential
points of agreement between the two kingdoms ; it has be-
come more and more evident in our own days, that the
material foundations of vegetable and animal life are in the
main identical, — that the processes connected with nourish-
ment, movement of juices, sexual and asexual propagation
present the most remarkable similarities in both kingdoms.

If the first founders of scientific vegetable physiology sur-
rendered themselves thoroughly to teleological views, this was
owing to the circumstances of the time, and it served indeed
to promote the first advances of the science. There was no

Book III.] Introduction. 363

need in the 17th and i8th centuries that a man should be
an Aristotehan to presuppose design and arrangements in
conformity with design in all parts of physiological investiga-
tion. This is everywhere and always the original point of
view which precedes all philosophy ; but it is the part of
advanced science to abandon this position ; and as early
as the 1 7th century philosophers recognised the fact that the
teleological mode of proceeding is unscientific. But the
first vegetable physiologists were not philosophers in the
stricter sense of the word, and in their investigations they
accepted the teleological conception of organic nature without
question, because they regarded it as a self-evident fact, that
every organ must be purposely and exactly so made as to
be in a condition to perform the functions necessary for the
permanence of the whole organism. This conception was
in accordance with views then prevaihng, and was even useful;
it was no disadvantage in the first beginnings of the science,
that it should be supposed that every, even the minutest, part
of a plant was expressly contrived and made for maintaining
its life, for this was a strong motive for carefully examining
the organs of plants, which was the first thing requisite. This
is exemplified in Malpighi, Grew, and Hales, and we shall
see that even towards the end of the 17th century Konrad
Sprengel made splendid discoveries respecting the relations
of the structure of the flower to the insect world, while strictly
carrying out his teleological principles. The teleological
view was injurious to the progress of morphology from the
first, though the history of systematic botany shows how hard
it was for botanists to free themselves from such notions.
The case was different with physiology ; so long as it was
a question of discovering the functions of organs, and learning
the connection between the phenomena of life, teleology
proved highly useful if only as a principle of research. But it
was another matter when it became requisite to investigate
causes, and to grasp the phenomena of vegetation in their

364 Introduction. [Book III,

causal connection. To this the teleological mode of view was
inadequate, and it became necessary indeed to discard it as a
hindrance, in spite of the difficulty of explaining adaptation in
the arrangements of organisms from any other than the teleo-
logical point of view. It is sufficient here to say that this
difficulty is satisfactorily removed by the theory of selection.
This theory is become as important in this respect to physi-
ology, as the theory of descent is to systematic botany and
morphology. If the theory of descent finally liberated the
morphological treatment of organisms from the influence of
scholasticism, it is the theory of selection which has made
it possible for physiology to set herself free from teleological
explanations. Only an entire misunderstanding of the Dar-
winian doctrine can allow anyone to reproach it with falling
back into teleology ; its greatest merit is to have made tele-
ology appear superfluous, where it seemed to naturalists
in former times, in spite of all philosophical objections, to
be indispensable.

If the comparison of plants with animals as well as the teleo-
logical conception of organisms promoted the first attempts at the
physiological investigation of plants, other influences of decisive
importance came into play when the time came for endeavour-
ing to conceive and explain the causes and conditions of the
functions, which had then been ascertained at least in their
most obvious features. Phytotomy was here the chief resource.
In proportion as the inner structure of plants was better known
and the different kinds of tissue better distinguished, it became
possible to bring the functions of organs, as made known by
experiment, into connection with their microscopic structure;
phytotomy dissected the living machine into its component
parts, and could then leave it to physiology to discover from
the structure and contents of the tissues, how far they were
adapted to perform definite functions. Obviously this only
became possible when the phenomena of vegetation had been
previously studied in the living plant. For example, the

Book III.] Introduction. '>fi^

microscopic examination of the processes which take place in
fertiUsation could first be made to yield further conclusions,
after sexuality itself, the necessity of the pollen to the produc-
tion of fruitful seeds, had been proved by experiment ; in the
same way the anatomical investigation of wood could only
supply material for explaining the mode in which water rises in
it, when it had first been ascertained by experiment that this
happens only in the wood, and so in other cases.

The relation between physiology and physics and chemistry
suggests similar considerations ; it is necessary to make some
preliminary remarks in explanation of this relation, because we
often meet with the view, especially in modern times, that
vegetable physiology is virtually only applied physics and
chemistry, as though the phenomena of life could be simply
deduced from physical and chemical doctrines. This might
perhaps be possible, if physics and chemistry had no further
questions to solve in their own domains ; but in fact both are
still as far distant from this goal, as physiology is from hers. It
is true indeed, that modern vegetable physiology would be
impossible without modern physics and chemistry, as the earlier
science had to rely on the aid of the physics and chemistry of
the day, when she was engaged in forming a conception of
ascertained vital phenomena as operations of known causes.
But it is equally true, that no advance which physics and
chemistry have made up to the present time would have pro-
duced any system of vegetable physiology, even with the aid of
phytotomy ; history shows that a series of vital phenomena in
plants had been recognised in the 17th and i8th century, at a
time when physics and chemistry had little to offer, and were
in no condition to supply explanations of any kind to the
physiologist. The true foundation of all physiology is the
direct observation of vital phenomena ; these must be evoked
or altered by experiment, and studied in their connection,
before they can be referred to physical and chemical causes.
It is therefore quite possible for vegetable physiology to have

366 Introduction. [Book III.

reached a certain stage of development without any explanation
of the phenomena of vegetation from physics or chemistry, and
even in spite of erroneous theories on those subjects. What
Malpighi, Hales, and to some extent Du Hamel produced, was
really vegetable physiology, and of a better kind than some
moderns are inclined to believe ; and their knowledge was
derived from observations on living plants, and not from the
chemical and physical theories of their time. The discovery
even of important facts, for example, that green leaves only
can form the food suitable to effect the growth and formation
of new organs, was made a hundred years before that of the
decomposition of carbon dioxide by the green parts of plants,
at a time indeed when chemistry knew nothing of carbon
dioxide and oxygen. A whole series of physiological discoveries
might be mentioned, which were distinctly opposed to chemical
and physical theories, and even served to correct them. We
may give as examples, the establishment of the facts that roots
absorb water and the materials of food without giving up any-
thing in return, which seemed quite unintelligible on the
earlier physical theory of the endosmotic equivalent ; and that
the so-called chemical rays of the physicists are of subordinate
importance in vegetable assimilation, while contrary to the pre-
vailing notions of physicists and chemists the yellow portions
of the spectrum and those adjacent to it actively promote the
decomposition of carbon dioxide. From what doctrines of the
physicists could it have been concluded, that the downward
growth of roots and the upward growth of stems was due to
gravitation, as Knight proved in 1806 by experiments on living
plants ; or could optics have foreseen that the growth of plants
is retarded by light, and that growing parts are curved under
its influence. Our best knowledge of the life of plants has
been obtained by direct observation, not deduced from chemi-
cal and physical theories. After these preliminary remarks we
may proceed to give a rapid survey of the progress of vegetable
physiology.

Book III.] Introduction. 367

I. That the first beginnings of vegetable physiology were
made about the time that chemistry and physics began to take
their place among the true natural sciences, is no proof that
they called vegetable physiology into existence. She, like
general physiology, mineralogy, astronomy, geography, owed
her origin to the outburst of the spirit of enquiry in the i6th
and 17th centuries, which feeling the emptiness of the scholastic
philosophy set itself to gather valuable knowledge by observa-
tion in every direction. It was in the second half of the 17th
century that societies or academies for the study of the natural
sciences were founded in Italy, England, Germany, and France
under the influence of this feeling ; the first works on vegetable
physiology play a very prominent part in their transactions ; not
to speak of less important cases, it was the Royal Society of
London which published between 1660 and 1690 the memorable
works of Malpighi and Grew ; the first communications of
Camerarius, which form an epoch in the history of the doctrine
of sexuality, appeared in the journals of the German Academia
Naturae Curiosorum, and the French Academy undertook about
the same time to organise methodical researches in vegetable
physiolog)' under Dodart's direction, though the results it is
true did not answer to the goodness of the intention. This
period of movement in all branches of science, when the greatest
discoveries followed one another with marvellous rapidity,
witnessed also the first important advances in vegetable physi-
ology ; such were the first investigations into the ascending and
descending sap, especially those made in England, Malpighi's
theory which assigned to leaves the functions of organs of
nutriment, Ray's first communications on the influence of light
on the colours of plants, and above all the experiments of
Camerarius, which proved the fertilising power of the pollen.
It was the period of first discoveries ; the attempts at explana-
tion were certainly weak ; but phytotomy which was just com-
mencing its own work lent aid from the first to physiology,
while physics and chemistry could do but little for her. On

368 Introduction. [book hi.

the other hand, the predilection for mechanics and mechanical
explanation of organic processes in Newton's age bore fair fruit
in Hales' enquiries into the movement of sap in plants ; his
' Statical Essays' of 1727 connect closely with the works before
mentioned which had laid the foundations of the science, and
with this important performance the first period of its history
reaches a distinctly marked conclusion.

This time of vigorous advance was followed by many years,
in which no notable work was done and no great discovery
effected ; there was active disputation on what had been
already ascertained, but it did not lead to any deeper concep-
tion of the questions or to new experimental determinations.

2. About the year 1760 new life was infused into the con-
sideration of various branches of vegetable physiology. Du
Hamel's 'Physique des arbres ' (1758) gave a summary of
former knowledge and added a number of new observations,
and from that time till the beginning of the present century a
series of important discoveries was made. The doctrine of
sexual propagation, which had scarcely been advanced since
the time of Camerarius, and was disfigured by the theory of
evolution, found an observer of the first rank in Koelreuter
(1760-1770), who threw new light upon the nature of sexuality
by his experiments on the artificial production of hybrids ; he
was the first who carefully studied the arrangements for polli-
nation, and pointed out the remarkable connection between
them and insect-life. These relations were afterwards (1793)
examined in greater detail by Konrad Sprengel, who arrived at
such astonishing and far-reaching results, that they were not
even understood by his contemporaries, nor was their signifi-
cance fully appreciated till quite modern times and in connec-
tion with the theory of descent.

No less important was the advance made in the doctrine of
the nourishment of plants. Between 1780 and 1790 Ingen
Houss proved, that the green parts of plants absorb carbon
dioxide under the influence of light and eliminate the oxygen,

Book III.] Introduction. 369

and thus obtain the carbon which plants accumulate in organic
combinations, but that all parts of plants also absorb at all
times smaller quantities of oxygen, and exhale carbon dioxide,
and so perform a process of respiration exactly corresponding to
that of animals. He was soon followed by Theodore de Saussure
with more thorough investigation of these processes, and with
proofs that the ash-constituents of a plant are no chance or un-
important addition to its food, as had been hitherto commonly
supposed (1804). The influence also of general physical forces
on vegetation was established in some important points, though
not yet submitted to searching examination. Thus Senebier
showed in the period between 1780 and 1790 the great effect
which light exercises on the growth and green colour of plants,
and De CandoUe at a later date discovered its operation in the
case of leaves and flowers that show periodic movements.
Still more important was Knight's discovery in 1806 that the
upright growth of stems and the downward direction of the
main roots are determined by gravitation.

3. This second period of important discoveries was also
followed by a relapse, and again doubts were raised as to the
correctness of the very facts which had been best established ;
attempts were made under the influence of preconceived
opinions to invalidate or ignore these facts, and to substitute
for them theories that wore the guise of philosophy. The so-
called nature-philosophy, which had long been a great hindrance
to morphology, proved in like manner injurious to vegetable
physiology ; the doctrine of the vital force especially stood in
the way of every attempt to resolve the phenomena of life into
their elementary processes, to discern them as a chain of causes
and effects. The ash-constituents of plants, and even their
carbon, were traced to this vital force, and misty notions con-
nected with the word polarity were used to explain the direction
of growth and much beside. In like manner the influence of
the nature-philosophy was brought to bear on the established
results of the sexual theory to the destruction of all sound

Bb

37© Introduction. [book hi.

logic, and the sexuality of plants was once more openly im-
pugned in the face of Koelreuter's investigations. This state of
things continued till some time after 1820, but then it began
to improve once more. L. C. Treviranus examined and
refuted the errors of Schelwer and Henschel in 1822 ; in Eng-
land Herbert conducted new and very valuable investigations
into the question of hybridisation ; and it was in this period
that Carl Friedrich Gartner studied and experimented on
normal fertilisation and the production of hybrids during more
than twenty years ; his conclusions, published in exhaustive
works in 1844 and in 1849, finally settled the more important
questions connected with the sexual theory about the same
time that Hofmeister established the microscopic embryology
of Phanerogams on a firm foundation.

Other parts also of vegetable physiology had been consider-
ably advanced before 1840 ; Theodore de Saussure observed
in 1822 the production of heat in flowers and its dependence
on respiration ; ten years later Goeppert proved the rise of tem-
perature in germinating and vegetating organs. Dutrochet
stimulated enquiry by his researches in various branches of the
science between 1820 and 1840; he was the first to apply the
phenomena of diosmosis to the explanation of the movement of
sap in plants with a lasting influence on the further progress of
physiology. Chemical investigations were less fruitful in
results, though they served to collect a considerable material of
single facts, which could afterwards be turned to theoretical
account.

The close of this period, which began with unprofitable
doubts, but in which much was set in a train for further
development after 1840, is marked by the publication of
some important compilations, in which all that had as yet
been done in vegetable physiology was presented in a con-
nected form. In addition to Dutrochet's collected works (1837)
three comprehensive compendia of vegetable physiology made
their appearance, one by De Candolle, which was translated

Book III.] Introduction. 371

into German by Roeper and published with many improve-
ments and additions in 1833 and 1835 ; this was followed by
a work on vegetable physiology by L. C. Treviranus, 1835-
1838, and lastly by Meyen's ' Neues System der Pflanzenphy-
siologie,' 1 83 7-1 839. These works exhibit the characteristic
features of the period chiefly in this, that physiology finds as
yet no strong support in phytotomy, while the old views of
vital force are brought face to face with more exact physico-
chemical explanations of processes of vegetation.

4. We have already pointed out the wonderful impulse given
to the study of morphology and phytotomy, of embryology
and cells about the year 1840 ; it was shown also that this was
due in a great measure to discarding the errors of the nature-
philosophy and the idea of vital force, and requiring in the
place of such speculations exact observation and systematic
induction, and how Schleiden's 'Grundziige' soon after 1840
vigorously met the demands of the newer time in these
respects, but without satisfying them by the positive results
obtained. The rapid progress made by phytotomy and the
doctrine of cells in the hands of von Mohl and Nageli proved
specially favourable to vegetable physiology, by making it
possible to follow the processes of fertilisation in the interior
of the ovule. The formation of the pollen-tube from the
pollen-grain had been observed long before 1 840, and Schleiden
in 1837 had proposed the view that the embryo of Phanerogams
was formed at the end of the pollen-tube by free cell-formation
after it had entered the embryo-sac. But Amici in 1846 and Hof-
meister in 1849 showed that this notion was erroneous, and
that the germ-primordium is in existence in the embryo-sac
before the arrival of the pollen-tube and is excited by it to
further development, to the forming the embryo. Similarly Hof-
meister's further observations on the embryology of Vascular
Cryptogams and Mosses left no doubt, that the spermatozoids
of these groups of plants discovered by Unger and Nageli
serve to fertilise the germ-cell or egg-cell previously formed

B b 2

373 Introdudmi. [Book hi.

in the female organ and to excite it to further development
(1849, 1851). Soon after the sexual act was observed in
various Algae, and these afforded the best opportunity for
solving by the aid of the microscope the questions which
experiment had still left open. Thuret showed in 1854, how
the large egg-cells in species of Fucus are surrounded and
fertilised by spermatozoids, and he even succeeded in pro-
ducing hybrids by fertilising the egg-cells of one species
with the spermatozoids of another ; but it was still uncertain
whether simple contact of the male and female organs was
sufficient, or whether fertilisation is due to the mingling of
the substance of the spermatozoid and the germ-cell ; the
question was settled by Pringsheim in 1855 j he saw the male
organ of fertilisation of a fresh-water alga penetrate into
the substance of the egg-cell and be dissolved in it, and
this proceeding was afterwards observed in higher Cryptogams
and is represented in its simplest form in the sexual act of
the Conjugatae, which De Bary described at length in 1858
and like Vaucher regarded as a sexual process.

When we consider to what an extent the time and power
of work of the most eminent botanists was devoted after 1840
to long and difficult observations on the minute anatomy of
plants, on cell-formation, embryology and the history of the
development of organs, we cannot wonder if other parts of
vegetable physiology, which require experiments on vegetation
in plants, were cultivated but little and by the way only ; but
these studies also gained firmer footing in the advance of
phytotomy, which supplied the physiologist with a more
definite idea of the organism in which the phenonema of
vegetative life are produced.

The chemistry of the food of plants was one of the strictly
physiological subjects, which like the sexual theory was studied
without intermission and with considerable success in the
period from 1840 to i860, but chiefly or entirely by chemists,
who connected their investigations into the processes of

Book III.] Introduction. 373

nutrition in plants with Saussure's results. Agricultural
chemists were chiefly engaged till nearly i860 with the
questions, whether all or certain constituents of the ash of
a plant are indispensable parts of its food, and whence these
constituents are derived, and with cognate considerations on
the exhaustion of the soil by cultivation and its remedy by
suitable manuring. In France Boussingault had undertaken
experimental and analytical investigations on these subjects
before 1840, and it was he who in the course of the next
twenty years made the most valuable physiological discoveries ;
of these the most important was the fact that plants do not
make use of free atmospheric nitrogen as food, but take up
compounds of nitrogen for the purpose. In Germany the
interest in such questions was increased by the instrumentality
of Justus Liebig, who gathered from the knowledge that had
been accumulated up to 1840 all that was fundamental and
of real importance, and drew attention to the great practical
value of the theory of the nutrition of plants in agriculture
and in the management of woods and forests ; considerable state
provision was soon made for investigations of the kind, but
these often wandered from the right path for the reason, that
being designed to promote practical interests they lost sight
of the inner connection between all vital phenomena. Still
a great mass of facts was accumulated, which careful sifting
might afterwards render serviceable to pure science. Some
of the best agricultural chemists deserve the credit of vindicat-
ing purely scientific as well as practical points of view, and
explained in comprehensive works the general subject of the
nutrition of plants, so far as it was possible to do so without
going deeply into their organisation ; among these wei^e Bous-
singault and the Germans Emil Wolff and Franz Schulze.
But the questions of the nutrition of plants, which are con-
nected with the chemical processes of assimilation and meta-
bolism within them, remained still undecided, though some
valuable preliminary work on these points dates from this time.

374 Introduction. [Book hi.

In comparison with this important advance in the sexual
theory and the doctrine of the nutrition of plants little was
done in the branches of vegetable physiology which remain
to be mentioned, and that little appeared in an unconnected
and fragmentary state ; different observers established the
connection between the temperature of plants' and oxygen-
respiration ; some new single facts were discovered in con-
nection with the downward curvature of roots, Briicke published
in 1848 an excellent enquiry into the movements of Mimosa-
leaves, and Hofmeister showed in 1857 that the phenomenon,
then known as bleeding in the vine and some other trees, takes
place in all woody plants, and not in spring only but in every
period of the year, if the requisite conditions are present.
These and many other isolated observations were very valuable
for the future, but were not used at the time to frame compre-
hensive theories, because no one devoted himself exclusively
to questions of the kind with the perseverance, which in these
difificult subjects can alone lead to certain results and to a
deeper insight into the inner connection of the phenomena.
Surprisingly small was the addition to the knowledge of the
movement of sap in plants, and still less was discovered
respecting the external conditions of processes of growth and
the movements connected with them. The important question
of the dependence of the phenomena of vegetation on temper-
ature, was it is true not wholly neglected ; but the mistake
was made of attempting a short cut by multiplying the total
period of vegetation of a plant by the mean daily temperature,
in the hope of finding in this product an expression for the
total warmth required by a given plant; this mistake was
especially misleading in the geography of plants.

The more valuable knowledge which had been gathered up to
1851 was brought together by vonMohl in his often-mentioned
work on the vegetable cell with equal perspicuity and con-
ciseness, and current views were critically examined ; vegetable
physiology generally was expounded at greater length but with

Book III.] Introduction. 375

less critical sifting in Unger's text-book of 1855 ; these were
the two books which did most to disseminate a knowledge
of the subject up to i860, and they performed their task with
credit ; that which appears in Schacht's books after 1852 under
the head of vegetable physiology rests on such imperfect
acquaintance with this branch of science, as to diminish rather
than increase its reputation.

Passing from this preliminary survey to a more detailed
account of the subject, it will be found necessary to keep
the history of the sexual theory distinct from other questions
in vegetable physiology. This mode of proceeding is required
by the fact, that the establishment and further elucidation
of the decisive points in the sexual theory were made inde-
pendently of the rest of physiology, so that the historical
continuity would be interrupted and the account rendered
obscure by any attempt to connect the development of the
theory chronologically with other topics. In like manner the
doctrine of the nutrition of plants and of the movement of the
sap was developed uninterruptedly and in independence of
other physiological matters ; it will be advisable therefore to
devote a separate chapter to those subjects also. Earlier
discoveries respecting the movements of the parts of plants and
the mechanics of growth will be briefly recounted in a third
chapter.

CHAPTER I.

History of the Sexual Theory.

I. From Aristotle to R. J. Camerarius.

It will contribute to a correct appreciation of the discoveries
made towards the end of the i yth century by Rudolph Jacob
Camerarius and his successors in regard to the sexual relations
of plants, if we first make ourselves acquainted with all that
was known of the matter up to that time from Aristotle down-
wards ; we shall learn at the same time how extremely un-
fruitful was the superficial observation of the older philosophy
in a question in which inductive research only could lead to
real results.

That Aristotle^ like many others after him reckoned sexual
fertilisation among processes of nutrition, and thus failed to
perceive the specific and peculiar character of the latter, is
shown distinctly by his assertion, that the nutritive and propa-
gative power of the soul is one and the same. This hasty
generalisation was associated in Aristotle's mind with another
error arising from very defective experience, which led him
to bring sexuality in organisms into causal connection with
their movement in space. He tells us in his botanical frag-
ments, that in all animals which have the power of locomotion,
the female is distinct from the male, one creature being female,
another male, but both being of the same species, as in
humankind. In plants on the contrary these powers are com-
bined and the male is not distinct from the female; each

^ See Ernst Meyer, ' Geschichte der Botanik,' I. p. 98, &c.

From Aristotle to Camerarius. 377

plant therefore reproduces itself and emits no fertilising
material ; and he adds, that in animals which do not move,
as those that have shells and those that live attached to some
other substance, male and female are not distinguished, for
their life resembles that of plants ; at the same time they
are called male and female by resemblance and analogy, and
there is a certain slight distinction. In like manner some
trees produce fruits while others do not, though they aid
fruit-bearing trees in the production of fruit, as happens in
the case of the fig-tree and the caprifig.

In comparison with these views of Aristotle those of his
disciple Theophrastus ^ appear to some extent enlightened,
and to rest on a wider experience, but even his observation
supplies nothing of interest on the subject : for he says that
some blossoms of the ' niali medicae ' produce fruit, and
that some do not, and that it should be observed whether
the same thing occurs in other plants, which he might
easily have done for himself in his own garden. He is more
concerned with putting his knowledge into logical order, than
with answering the question whether there is any sexual
relation in plants. It is certain, he says, that among plants
of the same species some produce flowers and some do not ;
male palms, for instance, bear flowers, the female only fruit ^ ;
and he concludes the sentence by the remark, that in this
lies the difference between these plants, and those which
produce no fruit, and that it is obvious that there must be a
great difference in the flowers. In his third book ' De Causis '

1 The edition here used is that of Gottlob Schneider, ' Theophrasti Eresii
quge supersunt opera,' Leipzig, 1818. See in addition to the passages
noticed in the text the ' De Causis,' 1. I. c. 13. 4, and 1. IV. c. 4, and the
' Historia Plantarum,' 1. II. c. 8.

•^ It should be understood that neither Theophrastus nor the botanists of
the 1 6th and 17th centuries considered the rudiments of the fruit to be part
of the flower ; this, which was pointed out in the history of systematic
botany, seems to have been overlooked by Meyer, ' Geschichte,' I. p. 164.

378 History of the Sexual Theory. [Book hi.

(c. 15, 3) he says, that terebinths are some male and some
female, and that the former are barren and are therefore
called male. That Theophrastus in all these matters trusted
to the relations of others is shown by a passage in the same
book (c. 18, i), where he says, 'What men say, that the fruit
of the female date-palm does not perfect itself unless the
blossom of the male with its dust is shaken over it, is indeed
wonderful, but resembles the caprification of the fig, and it
might almost be concluded that the female plant is not by
itself sufficient for the perfecting of the foetus ; but this cannot
be the case in one genus or two, but either in all or in many.'
We observe the grand style in which the Greek philosopher
dismisses this important question, and how far he is from
condescending to make an observation for himself.

It appears that in Pliny's time the hypothesis of a sexual
difference in plants had grown up and become confirmed in
the minds if not of writers, yet of those who occupied them-
selves with nature ; Pliny in his ' Historia Mundi,' describing
the relation between the male and female date-palm, calls the
pollen-dust the material of fertilisation, and says that naturalists
tell us that all trees and even herbs have the two sexes ^

If this theme supplied little material for reflection to philo-
sophers, it did not fail to excite the fancy of the poets. De
Candolle cites the verses of Ovid and Claudian on the
subject, and passing over the intervening centuries for a
very sufficient reason notices the lively poetic description of
two date-palms in Brindisi and Otranto by Jovianus Pontanus
in 1505. But nothing was gained in this way for natural
science.

Treviranus in his 'Physiologic der Gewachse^ ' (1838), II. p.
371, has well described the state of knowledge on this subject

* The passage is quoted in full in De Candolle's ' Physiologic vegetale,'
1835, ii- P- 44- It is said there of the pollen, ' Ipso et pulvere etiam
feminas maritare.'

Chap. I.] FroM Aristotle to Camerariiis. 379

among the botanists of Germany and the Netherlands in the
1 6th century. 'The idea of a male sex in such plants as
Abrotanum, Asphodelus, Filix, Polygonum mas et femina, was
founded only on difference of habit, and not on the parts
which are essential to it. But it should be observed that it
is the less learned among the older botanists, Fuchs, Mattioli,
Tabernaemontan, who make most frequent use of this mode
of designating plants ; the more learned, as Conrad Gesner,
de I'Ecluse, J. Bauhin employ it only in the case of a plant
already known. De I'Ecluse it is true in describing the plants
which he found often notes the form, colour, and even the
number of the stamens ; in Carica Papaya he calls the in-
dividual with stamens the male, and the one with carpels
the female, since he holds them to belong to different sexes,
though of the same species ; but he is satisfied with saying,
that it is affirmed that the two are so far connected, that the
female produces no fruit if the male is separated from it by
any great distance (' Curae posteriores,' 42).

The case of the botanists above-mentioned is simply one of
ignorance; in the botanical philosopher Cesalpino on the
contrary we see a consequence of the Aristotelian system,
which leads him distinctly to reject the hypothesis of separate
sexual organs in plants as opposed to their nature. It is diffi-
cult to understand how De Candolle, at page 48 of his
' Physiologic vegetale,' can say that Cesalpino recognised the
presence of sexes in plants. His conception of vegetable
seed-grains as analogous to the male seed in animals must
have made it impossible for him to understand sexuality in
plants. So too his notion that the seed is derived from the
pith as the principle of life in plants, in connection with which
he says at page 11 of the first of his sixteen books; 'Non
fuit autem necesse in plantis genituram aliquam distinctam
a materia secerni, ut in animalibus, quae mari et femina
distinguuntur.' He regarded the parts of the flower which
surround the ovary, or are separate from it, together with

380 History of the Sexual Theory. [Book hi.

the stamens as simply envelopes of the foetus ; and though
he knew, as has been already shown, that in some plants,
the hazel, chestnut, Ricinus, Taxus, Mercurialis, Urtica,
Cannabis, Mais, the flowers are separate from the fruit, and
even mentions that the barren individuals are called male,
and the fruit-bearing female, he understood this only as a
popular expression, without really admitting a sexual relation.
Respecting the words male and female he says at page 15 :
' Quod ideo fieri videtur quia feminae materia temperatior
sit, maris autem calidior ; quod enim in fructum transire
debuisset, ob superfluam caliditatem evanuit in flores, in
eo tamen genere feminas melius provenire et fecundiores
fieri aiunt, si juxta mares serantur, ut in palma est animad-
versum, quasi halitus quidam ex mari efflans debilem feminae
calorem expleat ad fructificandum.'

There is no mention of the pollen here, still less any attempt
to extend what had been observed in dioecious plants to the
ordinary cases, in which flowers and pistil, as Cesalpino
would say, are united in the same individual. His view of
the relation between the seed and the shoot, cited above on
page 47, shows that he conceived of the formation of seeds as
only a nobler form of propagation than that by buds, but not
essentially distinct from it. The idea of sexuality in plants
was not in fact consonant with Cesalpino's interpretation of
Aristotelian teaching.

Prosper Alpino's account (1592) of the pollination of the
date-palm contains nothing new, except that he had seen it in
Egypt himself.

The Bohemian botanist Adam Zaluziansky'^ made no obser-
vations of his own, but attempted in 1592 to reduce the

' See De Candolle, ' Physiologie vegetale,' p. 47.

^ His 'Methodus Herbaria' is said to have been published in 1592.
The remarks in the text are made in reliance on a long quotation from it in
Roeper's translation of De Candolle's ' Physiologie,' ii. p. 49, who had
before him an edition of 1604.

Chap. I.] FroM Avistotle to Camerarius. 381

traditional knowledge on the subject to some kind of theory.
The foetus, he says, is a part of the nature of plants, which
they produce out of themselves, and is thus distinguished
from the shoot which grows from the plant, as a part from
the whole, but the other as a whole from a whole. He quotes
Pliny almost word for word where he says, that observers of
nature maintain that all plants are of both sexes, but in some
the sexes are conjoined, in others they are separate ; in many
plants the male and female are united, and these have the
power of propagation in themselves, like many androgynous
animals ; and he explains this, more explicitly than i\.ristotle,
from defect of locomotion in plants. This is the case, he says,
with the majority of plants. In some, as the palm, the
male and female are separated, and the female without
the male produces no fruit, and where the dust from the
male does not reach the female plant by natural means,
man can assist. Zaluziansky like other writers is anxious that
plants of different sexes should not be taken for different
species. He refers also to the popular distinction of many
plants into male and female according to certain external
peculiarities.

Jung again must certainly have known the facts and views that
were current in his time ; but there is nothing in his botanical
waitings to show that he entertained the idea of a real sexuality
in plants, of the necessity of the co-operation of two sexes in
the work of propagation. It might almost be believed that
the most learned and serious men, such as Cesalpino and
Jung, were just those, who regarded the hypothesis of
sexuality in plants as an absurdity, and shrunk from its con-
sideration. This impression is conveyed too by Malpighi's
' Anatomie des Plantes.' It was Malpighi who gave the first
careful account of the development of the seed, and studied
the earlier stages in the growth of the embryo in the embryo-
sac ; and yet even he says nothing of the co-operation of the
dust contained in the anthers in the formation of the embryo.

382 History of the Sexual Theory. [Book hi.

and does not once mention the views of former writers. Mal-
pighi, like Cesalpino, regarded the formation of seeds as only
another kind of ordinary bud-formation, and propagation as
only another kind of nutrition. He mentions (p. 52) inci-
dentally that plants with unfruitful flowers are designated as
male, but treats this as a popular expression merely, and
ultimately propounds the theory that the stamens and the
floral envelopes remove a portion of the sap from the flower,
in order to purify the sap for the production of the seeds

(p. 56).

In all accounts of the theory of sexuality in plants, a botanist
otherwise unknown in history, Sir Thomas Millington, is named
as the person who first claimed for the stamens the character
of male organs of generation. The only record of the fact,
however, is contained in the following words of Grew in his
'Anatomy of Plants' (1682), ch. 5, sect. 3, p. 171 : 'In con-
versation on this matter (namely the connection of the stamens,
called by Grew the attire \ with the formation of seeds) with
our learned Savilian Professor Sir Thomas Millington, he told
me he was of opinion that the attire served as the male organ
in the production of the seed. I replied at once, that I was
of the same opinion, and gave him some reasons for it,
answering at the same time some objections that might be
brought against it.' Grew gives on p. 172 the following sum-
mary of his ideas on the subject ^ ; it would appear, he says,
that the attire serves to remove some superfluous parts of the
sap, as a preparatory process to the production of seed. As
the floral envelopes (foliature) serve to remove the volatile
and saline sulphur-parts, so the attire serves to lessen

^ In the ' Compositae,' however, Grew called the single flowers the florid
attire, see p. 37.

^ We may compare with this, pp. 38 and 39 of the iirst part of the work
which appeared in 1671, where Grew ascribed no sexual significance to the
stamens.

Chap. I.] FroHi AHstotlc to Camerarius. 383

and adjust the gaseous, in order that the seed may become
more oily and its principles be better fixed. Here we find
ourselves on the ground of the chemistry of the day, in which
sulphur, salt, and oil play the chief parts. Consequently, con-
tinues Grew, the flower has usually a stronger smell than the
attire, because the saline sulphur is stronger than the gaseous,
which is too subtle to affect the sense. Closely adhering to
Malpighi's view he goes on to compare these processes in
the flower with processes in the ovary of animals, inasmuch
as they qualify the sap in the ovary for the approaching
formation of seed, and he says that as the young and early
attire before it opens contains the superfluous part of the
female organ, so after it is opened it probably performs the
ofifice of the male. But how confused his ideas still were on
this point may be further seen by examination of the passage
which follows in his book (page 172, section 7), where, speak-
ing of the single flowers in the head of the Compositae, he
regards the blade, that is the style and stigma, of the floral
attire as a portion of a male organ, and the globulets (pollen-
grains) and other small particles upon the blade and in the
thecae (anthers) of the seed-like attire as a vegetable sperm,
which subsequently when the parts are duly matured falls
down upon the seed-case and so touches it with a prolific
virtue.

He meets the objection, that the same plant must con-
sequently be both male and female, with the fact, that snails
and other animals are similarly constituted. That the pollen-
grains communicate a prolific virtue to the ovary (uterus) or to
its juices by simply falling upon it, he thinks is rendered
probable by comparing this with the process of fertilisation in
many animals, and here Grew has some curious remarks.
The section closes with the observation that to expect com-
plete similarity in this matter between plants and animals, is
to require that the plant should not only resemble an animal,
but should actually be one.

384 History of the Sexual Theory. [Book hi.

If now we ask ourselves, what it really was that was gained
from Millington and Grew, we find that it was simply the
conjecture, that the anthers produce the male element in
fertilisation, and that this view was closely connected in their
minds with the strangest chemical theories and analogies from
animal life. It is remarkable by what indirect ways science
sometimes advances. If Grew had only been prepared to
assume some kind of sexuality in plants, he need only have
taken up Theophrastus' statement, that the anther-dust of the
male palm is shaken over the female to produce fertilisation ;
and since both Grew and Malpighi observed the pollen in the
anthers, they might at once and in reliance on this experiment
of a thousand years before have come to the conclusion that
the stamens are the male organs. But Grew never mentions
the ancient views and experiences. Like other writers before
Camerarius, he made no attempt to answer the question by
experiment. It was a step in advance, when Ray in his
'Historia Plantarum' (1693), I. cap. 10, p. 17; II. p. 1250,
threw some light on the very obscure train of thought in
Grew's mind, and did something to put it on the right track,
by referring to the case of dioecious plants and to the old
experience of the date-palm, but he too made no attempt to
settle the question by experiment. The true discoverer of
sexuality in plants, Camerarius, was however engaged in the
experimental solution of the problem two years before the
appearance of Ray's ' Historia Plantarum.' Ray's remarks on
the subject in the preface to his 'Sylloge Stirpium' (1694) are
only assertion founded on no experiments. But if any are
prepared to attribute greater value to the utterances of Grew
and Ray, the comparison of them with the way in which
Camerarius addressed himself to the question will show at
once, that it was he who so far advanced the theory of the
subject as to make it accessible to experimental treatment, as
he undoubtedly was the first who not only undertook experi-
ments on the subject but carried them out with the skill which

Chap. I.] Rudolph Jacob Camerarius. 385

will appear in the following section. Linnaeus was right when
he says in his ' Amoenitates ' (1749), I. p. 62, that it was
Camerarius who first clearly demonstrated {perspicue demon-
stravit) the sexuality of plants and the mode of their pro-
pagation.

2. Establishment of the Doctrine of Sexuality

IN Plants by Rudolph Jacob Camerarius.

1691-1694.

We have seen that all that was known with regard to
sexuality in plants up to 169 1 was comprised in the facts
related by Theophrastus concerning the date-palm, the tere-
binth, and the ' malus medica,' and in the conjectures of Mil-
lington, Grew, and Ray, while Malpighi's views in opposition
to these later authors were considered to be equally well
founded. The sexuality of plants could only be raised to the
rank of a scientific fact in one way, that namely of experiment ;
it had to be shown that no seed capable of germination could
be formed without the co-operation of the pollen. All historic
records concur in proving, that Camerarius was the first who
attempted to solve the question in this way, and that he fol-
lowed up this attempt by many other experiments. It is quite
another question how the fertilising matter reaches the germ
which is capable of being fertilised, and this could not be
entertained till experiment had established the fact, that the
pollen is absolutely indispensable to fertilisation.

To Johann Christian Mikan, Professor of Botany in Prague,
is due the merit of having collected the scattered and therefore
almost forgotten writings of Rudolph Jacob Camerarius^ and

^ Rudolph Jacob Camerarius was bom at Tubingen in 1665 and died
there in 1 7 2 1 . Having completed the course of study in philosophy and medi-
cine, he travelled from 1685 to ^^87 in Germany, Holland, England, France,
and Italy. In 1688 he became Professor Extraordinary and Director of the
Botanic Garden in Tiibingen j in 1689 Professor of Natural Philosophy;

C C

386 History of the Sexual Theory. [Book hi.

published them, together with some similar works of Koelreuter,
at Prague in 1797 under the title, 'R. J. Camerarii Opuscula
Botanici Argumenti.' This book, apparently little known, will
be my principal authority for the following remarks. The
short preliminary communications are printed without alteration
from the ninth and tenth year of the second, and from the fifth
and sixth year of the third decury of the Ephemerides of the
Leopoldina; the letter to Valentin, which will be noticed
again further on, together with an abstract of the same and an
answer of Valentin, are given according to Gmelin's edition of
1749.

Camerarius had observed, that a female mulberry-tree once
bore fruit, though no male tree (amentaceis floribus) was in
its neighbourhood, but that the berries contained only abor-
tive and empty seeds, which he compared to the addled eggs
of a bird. His attention was roused, and he made his first
experiment on another dioecious plant, Mercurialis annua ; he
took in the end of May two female specimens of the wild
plant (they were usually called male, but he knew them to be
the female) and set them in pots apart from others. The
plants throve, the fruit was abundant and filled out, but when
half ripe they began to dry up, and not one produced perfect
seeds ; his communication on this subject is dated December
28, 1691. In the third decury of the Ephemerides, year 5, he
relates that in a sowing of spinach he had found monoecious
as well as dioecious plants, as Ray had observed in Urtica
romana, and he himself again in three other species. The dis-
regard of this fact was afterwards the cause of erroneous in-
terpretation of the experiments and of doubt about sexuality.

and finally, in 1695, First Professor of the University, in succession to his
father, Elias Rudolph Camerarius. He was afterwards succeeded by his
son Alexander, one of ten children. There is an article on Camerarius in
the ' Biographie Universelle,' from the pen of Du Petit-Thouars. His
works on other subjects, as well as those on the question of sexuality in
plants, are distinguished by ingenious conception and lucid exposition.

Chap. I.] RiidolpJi Jacoh Camerariiis. 387

But Camerarius' chief composition on the subject of sexuality
in plants is his letter ' De sexu Plantarum,' which is often men-
tioned but apparently little read, and which he addressed to
Valentin, Professor in Giessen, on Aug. 25, 1694. It is the
most elaborate treatise on the subject which had as yet been
written, or indeed which appeared before the middle of the i8th
century, and contains more profound observations than were
made by any other botanist before Koelreuter. The style con-
trasts favourably with the style of the writers of the time, and is
thoroughly that of modern natural science ; it combines perfect
knowledge with careful criticism of the literature of the subject ;
the construction of the flower is explained more clearly than it
had ever been before, or was again for a long time after, and
expressly for the purpose of making the meaning of his experi-
ments on sexuality intelligible. The whole tone of the letter
shows that Camerarius was deeply impressed with the extra-
ordinary importance of the question, and that he was concerned
to establish the existence of sexuality by every possible means.

After detailed examination of the parts of the flower, the
anthers and pollen, the behaviour of the ovules before and
after fertilisation, the phenomena of double flowers and similar
matters, from all which he cautiously deduces the meaning
of the anthers (apices), he proceeds to bring forward direct
proofs. He says, ' In the second division of plants, in which
the male flowers are separated from the female on the same
plant, I have learnt by two examples the bad effect produced
by removing the anthers. When I removed the male flowers
(globulos) of Ricinus before the anthers had expanded, and
prevented the growth of the younger ones but preserved the
ovaries that were already formed, I never obtained perfect seeds,
but observed empty vessels, which fell finally to the ground
exhausted and dried up. In like manner I carefully cut off
the stigmas of Mais that were already dependent, in consequence
of which the two ears remained entirely without seeds, though
the number of abortive husks (vesicularum) was very great.'

c c 2

388 History of the Sexual Theory. [Book in.

He then refers to his former communications to the Epheme-
rides on dioecious plants, and says that the case of the spinach
confirmed these results. After alluding to similar relations in
animals he continues, ' In the vegetable kingdom no production
of seeds, the most perfect gift of nature, the general means
for the maintenance of the species, takes place, unless the
anthers have prepared beforehand the young plant contained
in the seed (nisi praecedanei florum apices prius ipsam plantam
debile praeparaverint). It appears, therefore, justifiable to give
these apices a nobler name and to ascribe to them the signifi-
cance of male sexual organs, since they are the receptacles in
which the seed itself, that is that powder which is the most
subtle part of the plant, is secreted and collected, to be after-
wards supplied from them. It is equally evident, that the ovary
with its style (seminale vasculum cum sua plumula sive stilo)
represents the female sexual organ in the plant.' Further on he
assents to Aristotle's theory of the mixture of sexes in plants,
and adduces Swammerdam's discovery of hermaphroditism in
snails, which he says is the exception in animals but the rule
in plants. One erroneous notion which was only seen to be
erroneous a hundred years later by Konrad Sprengel, and not
finally refuted till within the last few years, was his belief that
hermaphrodite flowers fertilise themselves, and this by com-
parison with the snails he thinks is strange, though most
botanists till down to our own times, in spite of Koelreuter and
Sprengel, did not find it strange. That sexuality in plants was
admitted by botanists, Ray excepted, at the close of the 17th
century at most in a figurative sense, but that Camerarius con-
ceived of it as in the animal kingdom, and sought to make this
conception prevail, is apparent from the strong expressions,
which he uses to show that in dioecious plants the distinction
between male and female plants is not to be understood
figuratively. He says that the new foetus, the young plant
contained in the seed, is formed inside the coat of the seed
after the plant has flowered, exactly as the new foetus is formed

Chap. I.] Rudolph Jacoh Camerarius. 389

in animals. The authority of the ancients was still great at
that time, for Camerarius thinks it necessary to insist that the
views of Aristotle, Empedocles, and Theophrastus are not
opposed to his sexual theory. Camerarius appears as the
true investigator of nature, endowed with the true discerning
spirit in disregarding the question which had already been
raised with respect to animals, whether the ovum or the sper-
matozoid (vermis) produces the foetus, because the first thing
to be done was to establish the fact of a sexual difference, not
the mode of generation ; he thinks it certainly desirable to
examine and see what the pollen-grains contain, how far they
penetrate into the female parts, whether they advance uninjured
as far as the seed which receives them, or what they discharge
if they burst before reaching it. He does full justice to Grew's
services in connection with the knowledge of the pollen and its
function.

It does all honour to the scientific spirit in Camerarius, that
he raises a number of objections to his own theory ; one was,
that Lycopods and Equisetaceae produce, as he thinks, no
young plants from their pollen ; he suspected therefore that
they have no seed. It should be remembered that the germi-
nation of Equisetaceae and Lycopods was not observed till the
19th century. An objection, more important at the time, was
that a third ear of a castrated maize plant contained eleven
fertile seeds, of whose origin he could give no account. He
was even more disturbed by finding that three plants of hemp
taken from the field and cultivated in the garden produced
fertile seeds, and he tries to explain it by supposing various
ways in which pollination might have taken place unobserved.
This led him to make a fresh experiment ; next year he placed
a pot containing seedHngs of hemp in a closed room ; three
male and three female plants grew up ; the three male were cut
off" (not by himself) before their flowers opened ; the female
produced a great number of abortive seeds, but also a good
many fruitful ones. His opponents and those who sought to

39© , History of the Sexual Theory. [Book in.

appropriate his honours fastened, as is usual, on these failures,
without being able to account for the experiments which had
been successful. The statement of his failures is our best
proof of the exactness of his observations, for we now know
the cause of failure, which Camerarius himself observed, but
did not apply in explanation. We may assume that he would
have cleared up this point in his splendid investigations in a
quieter time, for at the end of his letter he laments the unjust
war then raging ; it was the time of the predatory campaign of
Louis XIV, To his letter is appended a Latin ode of twenty-
six stanzas by an unknown poet, probably a pupil of his own; it
is an epitome of the ' Epistola de sexu Plantarum,' as Goethe's
well-known poem contains the chief points of his doctrine of
metamorphosis, but it resembles Goethe's composition in no
other respect ; it begins

Novi canamus regna cupidinis,
Novos amores, gaudia non prius

Audita plantanim, latentes

Igniculos, veneremque miram.

3. Dissemination of the New Doctrine; its
Adherents and Opponents, i 700-1 760.

No part of botany has so often engaged the pen of the
historian, as the doctrine of sexuality in plants ; but the
majority of writers have not gone to the original sources for
their information, and the consequence has been that the
merits of the real founders and promoters of the doctrine have
often been thrown into the shade for the benefit of others ;
even German botanists have ascribed the services of Camera-
rius to Frenchmen and Englishmen, because they were unac-
quainted with his writings, or were unable to judge of the
question and its solution. We shall here endeavour to show
from the records of the i8th century how far anyone before
Koelreuter really contributed anything of value ta the estab-

Chap. I.] Adherents and Opponents of Sexuality. 391

lishment of the sexual theory. As is usually the case in great
revolutions in science, some simply denied the new theory,
many adopted it without understanding the question, others
formed a perverse and distorted conception of it under the
influence of reigning prejudices, while others again sought to
appropriate to themselves the merit of the real discoverer ;
there were but few who with a right understanding of the
question advanced it by new investigations.

The botanists who endeavoured to aid in determining the
matter by their own observations may be distinguished into
those, to whom the important point was the enquiry whether
the pollen is absolutely necessary to the formation of seed,
such as Bradley, Logan, Miller, and Gleditsch, and those who
like Geofifroy and Morland assumed that sexuality was no
longer an open question, and who were bent on observing in
what way the pollen effects fertilisation in the ovule. But
there was another class of writers altogether, who, believing
that they could deal with the subject without making observa-
tions and experiments of their own, either like Leibnitz,
Burckhard, and Vaillant, simply accepted the results of the
observations of others on general grounds, or like Linnaeus
and his disciples, endeavoured to draw fresh proofs from
philosophical principles, or like Tournefort and Pontedera,
simply rejected the idea of sexuality in plants. Lastly, we might
mention Patrick Blair who did nothing himself, but merely
appropriated the general results of Camerarius' observations,
and has had his reward in being quoted even by German
writers as one of the founders of the sexual theory \

We have now to see what was really brought to light by
further experiment and observation. Bradley appears to have
been the first who experimented on hermaphrodite flowers
with a view to establish the sexuality of plants (' New improve-

1 See Patrick Blair's ' Botanic Essays,' in two parts (1720), pp. 242-276.
Even the Latin ode is borrowed without acknowledgment.

392 History of the Sexual Theory. [book hi.

ments in Gardening' (171 7), I. p. 20). He planted twelve
tulips by themselves in a secluded part of his garden, and as
soon as they began to flower removed the anthers ; the result
was, that not one of them produced seeds, while four hundred
tulips in another part of the same garden produced seeds in
abundance.

Twenty years pass by before another experiment is made.
James Logan \ Governor of Pennsylvania, an Irishman by
birth, set some plants of maize in each corner of a plot of
ground, which was forty feet broad, and about eighty long, and
experimented on them in various ways. In October he noted
the following results : — the cobs of the plants, from which he
had removed the m.ale panicles when the stigmas were already
dependent, presented a good appearance ; but closer examina-
tion showed that they were unfertilised, with the exception of
one which was turned in the direction from which the wind
might have conveyed pollen from other plants. On the cobs,
from which he had removed some of the stigmas, he found
exactly as many grains as he had left stigmas. One cob, which
had been wrapped in muslin before the appearance of the
stigmas, produced only empty husks.

Miller's experiments in 1751, which Koelreuter has extracted
from the 'Gardener's Dictionary,' part IP, are specially inter-
esting, because the aid of insects in pollination was then
observed for the first time. Miller planted twelve tulips, six
or seven ells apart, and carefully removed the stamens as soon
as the flowers began to open ; he imagined that he should thus
entirely prevent fertilisation ; some days after he saw some bees

* The account in the text is taken from Koelreuter's report in his ' Historic
der Versuche iiber das Geschlechte der Pflanzen,' as given at p. 188 of
Mikan's ' Opnscula Botanici Argumenti.' Logan's work, ' Experimenta et
Meletamata de Plantarum Generatione,' unknown to me, is said by Pritzel
to have been published at the Hague in 1739. Koelreuter cites from a
London edition of 1 747.

^ Koelreuter's report in Mikan's collection is again the authority which is
here relied on.

Chap. I.] Adherents and Opponents of Sexuality. 393

load themselves with pollen in an ordinary tulip-bed and fly
over to his imperfect flowers. After they were gone, he
observed that they had left on the stigmas a quantity of pollen
sufficient for fertilisation, and these tulips did in fact produce
seed. Miller also kept some female plants of spinach apart
from the male, and found that they bore large seeds without
embryos.

Professor Gleditsch, Director of the Botanic Garden in Ber-
lin, described in the same year (' Histoire de 1' Academic royale
des sciences et des lettres ' for the year 1749, published in 1751
at Berlin), an experiment on the artificial fertilisation of Palma
dactylifera folio flabelliformi, which was no doubt our Chamae-
rops humilis, since he says himself in page 105 that it was
Linnaeus' Chamaerops, and Koelreuter speaks of the plant in
his report by that name. This treatise, in point of scientific
tone and learned handling of the question, is the best that
appeared between the time of Camerarius and that of Koel-
reuter. We learn from the introduction, that in the year 1749
there were few who doubted the existence of sexuality in plants.
The author says that he has endeavoured to attain to perfect
conviction on the point by many years' experiments with plants
of the most various kinds. Of late years he had chiefly selected
dioecious plants for investigation, Ceratonia, Terebinthus,
Lentiscus, and the species of date-palm which is commonly
called Chamaerops. After relating the formation of fertile
seeds in Terebinth and the mastic-tree produced by artificial
pollination, he turns to Chamaerops, of which species Prince
Eugene had repeatedly caused specimens of considerable size
to be brought over from Africa ; a specimen cost as much as a
hundred pistoles; but they died without flowering. 'Our
palm in Berlin,' he continues, ' is a female, and may be eighty
years old ; the gardener asserts that it has never borne fruit,
and I have myself never seen fertile seeds on it during fifteen
years.' As there was no male tree of the kind in Berlin, Gle-
ditsch procured some pollen from the garden of Caspar Bose

394 History of the Sexual Theory. [book hi.

in Leipslc. In the course of the nine-days' journey the greater
part of the pollen escaped from the anthers, and Gleditsch
feared that it was spoilt ; but he was reassured by the Leipsic
botanist Ludwig, who had had experience in Algiers and Tunis,
and who informed him that the Africans usually employ dry
pollen that has been kept for some time for the purpose of fertili-
sation. Though the flowering of the female tree was nearly over,
he strewed the loose pollen on its flowers, and tied the withered
inflorescence of the male plant to a late-blowing shoot of the
female. The result was that fruit ripened in the following
winter, and germinated in the spring of 1750. A second
attempt conducted in a similar manner produced an equally
favourable result^.

Koelreuter, who repeats this account in his 'Historic der
Versuche,' a record of the experiments made between the
years 1691 and 1752 on the sexes of plants, ends his nar-
rative with these words : ' These are, as far as I know, all the
attempts which have been made and described since the year
1 69 1 to prove the existence of sexes in plants.' Koelreuter's
book was written to show that experiment only can determine
the question of sexuality in the vegetable kingdom, and that
no one beside Camerarius, Bradley, Logan, Miller, and Gle-
ditsch had pursued this method up to 1752.

While these botanists occupied themselves with the ques-
tion whether there was a distinction of sexes in the vegetable
kingdom, we meet with two writers at the beginning of the
1 8th century who regard sexuahty as proved, and who take up
the question of the mode in which the pollen brings about the
formation of the embryo. Both were adherents of the theory of
evolution, bad observers, and not familiar with the literature
of the subject. The first is Samuel Morland. In the

* Koelreuter says that he sent pollen of Chamaerops in 1766 to St.
Petersburg and to Berlin, where it was successfully employed by Ecklebea
and Gleditsch. He wished to try how long the pollen retains its efficacy.

Chap, I.] Adherents and Opponents of Sexuality. 395

'Philosophical Transactions' of 1702 and 1703, p. 1474, he
names Grew as the man who had observed that the pollen
answers to the male semen, but he makes no allusion to
Camerarius' experiments, the only ones which had as yet been
made. He himself suggests that the young seeds may be
compared to unfertilised ova, while the pollen-dust (farina)
contains embryo plants, one of which must find its way into
every ovule (ovum) in order to fertilise it. If so, the style
must be a tube through which the embryos pass into the ova.
He supposes the pollen in Fritillaria imperialis to be washed
by wind and rain from the stigma through the style into the
ovary, without reflecting that the movement must be an up-
ward one in the hanging flower. If I could prove, he says,
that embryos are never found in unfertilised seeds, this would
be a demonstration ; but I have never been so fortunate as to
settle this point. He does not mention that Camerarius had
shown this ten years before ; he can only give as the main
argument for his conjecture, that in beans the embryo lies
near the orifice of the seed-coat (the micropyle), which
shows that he was not aware that the two large bodies in
the seed of the bean (the cotyledons) belong to the embryo, a
fact which his countrymen Grew and Ray had already pointed
out. It appears therefore, that Morland supplied no answer to
the question how fertihsation takes place ; his treatise contains
nothing more than the assertion that the embryo is already
contained in the pollen-grain, and that it reaches the seed
through a hollow style and is there developed, an entirely
erroneous and not even an original idea, for it was the oft"-
spring of the theory of evolution which was at that time in
vogue.

Geoffroy's communications (' Histoire de 1' Academic
royale des sciences,' Paris, 17 14, p. 210) contain a few
more facts. He mentions neither Grew, Camerarius, nor
even Morland, but connects his own observations of 171 1 on
the structure and purpose of the more important parts of the

39^ History of the Sexual Theory. [book hi.

flower with those of Tournefort, who was a decided opponent
of the doctrine of sexuahty in plants. The parts of the
flower are hastily described, figures are given of some forms
of pollen-grains, and the notion that the style is a tube re-
ceives some apparent confirmation from the experiment of
drawing water through the style of a lily. The view that the
pollen is not an excrement, as Tournefort and Malpighi had
maintained, is defended partly by arguments which prove
nothing, for instance, by the erroneous assertion that the
anthers are always so disposed that the extremity of the pistil
must necessarily receive their dust. The only proof offered
for the fact that seeds are infertile if deprived of the co-
operation of the pollen, is a very hasty account of some ex-
periments with maize and Mercurialis. The result of these
experiments, as well as some other remarks of Geoffroy, re-
mind us of the text of Camerarius' letter to an extent which
mere accident will hardly account for. If Geoffroy really
made these experiments, which is open to some doubt, yet
they were made fifteen years later than those of Camerarius,
who did make the same experiments among others and has
described them better. Geoffroy next endeavours to show
how the pollen effects the fertilisation, and offers two views on
the subject ; first, that the dust contains much sulphur and is
decomposed on the pistil, the more subtle parts forcing their
way into the ovary, where they set up a fermentation and
cause the formation of the embryo ; the second view is, that
the pollen-grains already contain the embryos, which find their
way into the seeds and are there hatched. This is Morland's
notion, who however is not mentioned. Geoffroy considers
the latter to be the more probable hypothesis, chiefly because
no embryo is found in the ovule before fertilisation, and also
because the seed of the bean has an orifice (the micropyle) ;
it does not occur to him that these facts speak as much for the
first as for the second view.

Enough has been produced to show that Morland and

Chap. I.] Adherents and Opponents of Sexuality. 397

Geoffroy contributed nothing either to the establishment of
the fact of sexuality in plants, or to the decision of the question
how the pollen effects fertilisation in the ovule. Neverthe-
less I have mentioned these two men immediately after those
who really developed the sexual theory, because they at least
took their stand on experience, and endeavoured, though
unsuccessfully, to demonstrate conditions of organisation which
should explain the process of fertilisation. We come now to
the names of men — Leibnitz, Burckhard, Vaillant, Linnaeus —
who are usually supposed to have aided in establishing the
sexual theory, but who may be proved to have contributed
nothing whatever to the scientific demonstration of that
doctrine. First as regards the philosopher Leibnitz ; he
says in a letter of 1701, from which Jessen has quoted the
most important parts in his * Botanik der Gegenwart und
Vorzeit,' 1864, p. 287 : 'Flowers are closely connected with
the propagation of plants, and to discover distinctions in the
mode of propagation (principiis generationis) is very useful,'
etc, ; again, ' A new and extremely important point of com-
parison will be hereafter supplied by the new investigations
into the double sex in plants,' alluding, according to Jessen,
to those of Camerarius and Burckhard. We shall not expect
to find that Leibnitz made experiments himself, and the
words quoted merely indicate that he wished to see the
parts of the flower employed for purposes of classification,
because according to the observations of others they are the
instruments of propagation. The remark applies in a still
higher degree to Burckhard, who in his letter to Leibnitz of
1702, quoted above on p. 83, further developed the idea
intimated by Leibnitz, for he too accepted the sexuality of
plants as an established and self-evident truth. The address
with which Sebastian Vaillant opened his lectures at the
Royal Gardens in Paris in 171 7 has often been noticed
by the historians of botany. De CandoUe, who assigns to
him an important share in developing the sexual theory.

398 History of the Sexual Theory. [Book hi.

says\ that in this address he propounded the sexuality of plants
most expressly and as an acknowledged fact, and that he
described very graphically the way in which the anthers fer-
tilise the pistil, into which description little that was correct
probably found its way, since it required Koelreuter, Sprengel,
and the botanists of quite modern times to clear up this
point. Vaillant therefore can only have the credit of an
eloquent description of what was then accepted. However,
De CandoUe goes on to say what Vaillant's discoveries were,
and on the following page we read that Linnaeus confirmed
these discoveries in the year 1736 in his 'Fundamenta Bota-
nica,' and made skilful use of them in the year 1735 in laying
the foundations of his sexual system. We have already in the
second chapter of the first book explained the confusion of
ideas which lies at the bottom of these and many similar
statements, and in the same chapter have sufficiently indicated
our opinion respecting Linnaeus' share in the establishment of
the doctrine of sexuality. It was the character of Linnaeus'
mind to attach slight value to the experimental proof of a fact,
even when, like that of sexuality, it could only be proved
by experiment ; from the point of view of his scholastic
philosophy it was more important with him to deduce the
existence of this fact, in what seemed to him the philosophic
way, from the idea of the plant or from reason, and in doing
so to drag in a variety of analogies from the animal king-
dom ; hence he acknowledged the services rendered by Came-
rarius, but troubled himself little about his experiments which
alone could decide the question, while he undertakes himself
to prove the existence of sexes in plants on grounds of reason
and the like in his peculiar fashion. How he did this in the
* Fundamenta ' and in the ' Philosophia Botanica ' has been
already shown. Here we will briefly notice the often-quoted

* See Vol. II. p. 502, of the * Physiologie vegetale.'

Chap. I.] Adherents and Opponents of Sexuality. 399

dissertation, 'Sponsalia Plantarum,' in the first volume of
the ' Amoenitates Academicae ' (1749). He first gives the
views of MiUington, Grew, Camerarius and others ; then on
p. 63 he accepts the statement of Gustav Wahlboom, that
he, Linnaeus, had devoted infinite labour to this question
in 1735 in the 'Fundamenta Botanica,' and had there (§§ 132-
150) proved the sexes of plants with so great certainty that no
one would hesitate to found on it a detailed classification
of plants. Here then we have once more the construction of
Linnaeus' so-called sexual system introduced into the ques-
tion of sexuality, as if it had anything whatever to do with the
establishing the existence of sexes in plants, and as to the
infinite labour (infinito labore) which Linnaeus is supposed
to have given to the question, the paragraphs cited from the
' Fundamenta ' contain the scholastic subtleties quoted in
Book I. chap. 2, but not one single really new proof. The
arguments in the dissertation we are considering are of exactly
the same kind, and it is itself only a lengthy paraphrase
of Linnaeus' propositions in the ' Fundamenta Botanica,' illus-
trated by experiments made by others, and with the addition
of a few unimportant observations, some of which are mis-
interpreted. We read, for instance, p. loi, ' Nectar is found
in almost all flowers, and Pontedera thinks that it is absorbed
by the seeds that they may be the longer preserved ; it might
seem that bees must be hurtful to flowers, since they carry away
the nectar and the pollen ; ' but Linnaeus, differing from Ponte-
dera, remarks that 'bees do more good than harm, because they
scatter the poflen on the pistil, though it is not yet ascertained
what is the importance of the nectar in the physiology of the
flower.' This fact of the assistance rendered by insects,
which was soon afterwards better described by Miller, is
not further examined in this place, for Linnaeus goes on to
speak of gourds, that they do not perfect their fruit under
glass, because the wind is prevented from effecting the pollina-
tion.

400 History of the Sexual Theory. [Book hi.

One experiment only is mentioned, but not the person by
whom it was made. We read at p. 99 that in the year 1723
in the garden of Stenbrohuld, the male flowers of a gourd
in bloom were daily removed, and that no fruit was formed.
Soon after allusion is made to the artifices used by gardeners
to obtain hybrid varieties of tulips and cabbage, but the matter
is treated rather as agreeable trifling. In the third volume of
the Amoenitates of the year 1764, in which Koelreuter's first
enquiries into hybridisation had been already published, we
find a dissertation on hybrids by Haartman, which was cer-
tainly written as early as 1751. In this treatise the necessary
existence of hybrid forms is concluded from philosophic
principles, as Linnaeus had deduced sexuality from similar
principles ; no experiments are made, but certain forms are
arbitrarily assumed to be hybrids ; a Veronica spuria gathered
in the garden at Upsala in 1750 is asserted to be the product
of Veronica maritima as the mother and of Veronica offici-
nalis as the father, but the only reason for assigning the
paternity to the latter plant is that it grew close by. We
find also a Delphinium hybridum stated on similar grounds
to be the offspring of Delphinium elatum fertilised by Aconi-
tum napellus, and a Saponaria hybrida to have arisen from
the pollination of Saponaria officinalis by a Gentiana ; and we
are told among other things that Actaea spicata alba is the
offspring of Actaea spicata nigra fertilised by Rhus toxicoden-
dron. It is obvious that in all this there was no observation
of decisive facts, but simple conclusions from arbitrary pre-
mises.

We conclude therefore that neither Linnaeus nor his
disciples in the interval that elapsed between the labours
of Camerarius and Koelreuter contributed a single new or
valid proof to the establishment of the fact, that there is a
sexual difference in plants and that hybrids are formed be-
tween different species ; and if many later botanists talked
of the great services rendered by Linnaeus to the sexual

Chap. I.] Adherents and Opponents of Sexuality. 401

theory, and even regarded him as its most eminent founder,
this arose partly from the fact that they were unable to
distinguish between his scholastic deductions and scientific
proof, and partly from that confusion of the idea of sex-
uality with a classification of plants founded on the sexual
organs, to which we have before called attention. Such a
confusion of ideas gave rise to the claims which Renzi as-
serted on behalf of Patrizi, but which Ernst Meyer, in
his ' Geschichte der Botanik,' iv. p. 420, has refuted on this
very ground. Even in our own century De Candolle has
been blamed by Johann Jacob Roemer for not giving Lin-
naeus the credit of being the actual founder of the sexual
theory.

A few words in conclusion on those writers, who after
Camerarius' investigations still denied sexuality in plants,
because they knew nothing of what had been written on the
subject or were incapable of appreciating scientific proof.
Tournefort must first be mentioned on account of the great
authority which he enjoyed with botanists during the first
half of the 1 8th century. In his ' Institutiones rei herbariae '
of the year 1700 (Book I. p. 69), with which we have already
made acquaintance, he treats of the physiological significance
of the parts of the flower, apparently in entire ignorance of
Camerarius' researches, and at any rate with a leaning to
Malpighi's views. He makes the petals take up nourishment
from the flower-stalks, which they further digest and supply to
the growing fruit, while the unappropriated parts of the sap
pass through the filaments into the anthers and collect in the
loculaments, to be afterwards discharged as excreta. Tournefort
even doubted the necessity of the pollination of the female
date-palm. The truth is that he was not well acquainted with
the facts, and was led astray by his preconceptions. The
same was the case with the Italian botanist Pontedera ; in his
* Anthologia ' of 1720 he reproduces Malpighi's unlucky notion,
and at the same time makes the ovary absorb the nectar for

Dd

402 History of the Sexual Theory. [Book hi.

the perfecting of the seed ; he regarded the male flower in
dioecious plants as a useless appendage.

Valentin, to whom Camerarius addressed his famous letter
' De sexu plantarum ' in 1694, did his correspondent a dis-
service in publishing a short abstract of it, which contained
some gross misapprehensions of the facts'. Alston in 1756
relying on these incorrect statements disputed the conclusions
of Camerarius, and doubted the sexual importance of the
stamens on very insufficient grounds. More reasonable doubts
were suggested by a German botanist, Moller, who observed
that female plants of spinach and hemp produced seeds even
after the removal of the male plants, and appealed to the
apparently asexual propagation of Cryptogams ; these objections
were answered by Kastner of Gottingen, who pointed to the
fact that dioecious plants, the willow for instance, sometimes
bear hermaphrodite flowers. The botanists in question would
never have entertained these doubts, if they had read and
understood the writings of Camerarius, or had been acquainted
with the literature of the subject.

4. The theory of Evolution and Epigenesis.

We have already observed the influence of the theory of
evolution on the doctrine of the fertilisation of plants in the
case of Morland and Geoffroy. We learn more about it in the
work, already quoted, of the philosopher Christian Wolff,
'Verniinftige Gedanken von den Wirkungen der Natur,'
Magdeburg, 1723; it will be well to give his own words, for
they will serve to show at the same time the amount of know-
ledge possessed by a cultivated and well-read man in the
country of Camerarius and thirty years after the appearance of
his treatise on the sexuality of plants. In the second chapter
of the fourth part, which treats of the life, death, and genera-

1 See Mikan, ' Opuscula Botanici Argumenti,' p. 180.

Chap. I.] Theory of Evolution and Epigenesis. 403

tion of plants, Wolff says : ' Ordinarily plants are produced
from seeds, for the seed not only contains the plant in embryo
but also its first food.' He says that propagation by means of
buds is equally natural, for each bud contains a branch in little.
' We find inside in the flower a number of stalks disposed in a
circle, and something at the top of each, which is full of dust
and lets the dust fall on the upper part of that which holds the
seed ; this organ is compared by some to the genitals of the
animal, and the dust to the male seed ; they think also that the
seed is made fruitful by the dust, and that therefore the embryo
must be conveyed by the dust into the seed-case and there be
formed into seeds. I have proposed to examine into the
matter, but I have always let it escape me.' . . . 'Since all
that has been hitherto adduced is found also in flowers which
spring from bulbs, and it is also certain that the leaves of bulbs
have consequently embryos in them ... it is easy to see that
the embryos must come from the leaves of the bulbs. And
since they could as easily be conveyed from there into the
seed-grains with the sap, as into the dust which is produced in
the upper part of the flower, I am inclined to think that this
is the true account of the matter and that it will be confirmed
by experience. But now comes the main question, whence
come the embryos into the sap; since they have not an
external figure only but an internal structure also, it is not
plain how they can be formed either by the mere inner move-
ment of the sap, or by separation of certain parts. . . . And this
is certainly more credible, that the embryos already exist in
little in the sap and the plant, before they are brought by some
change into the condition in which they are met with in the
seed and in buds. But there is the further question where
they were previously. They must either lie one in another in a
minute form, as Malebranche especially maintains, or they are
brought from the air and the earth with the nourishing sap
into the plant, an idea which Honoratus Fabri advanced and
Perrault and Sturm developed after him. According to the

D d 2

404 History of the Sexual Theory. [Book in.

first opinion the first seed-grain must have contained everything
in itself, which has grown from it to this hour.' But this
demand goes beyond even WolfPs powers of belief ; for, says
he, it is too great a tax on the imagination to conceive of this
inclosing of germs one in another like box within box. It is well
known that such notions as these were very prevalent in the i8th
century, and that the spermatozoids of animals were thought to
lend considerable support to them ; even Albert Haller after
1760 was an adherent of the theory of evolution. However con-
fused Wolffs general train of thought may be, we should notice
his perception of the fact, that the theory of evolution does away
with the sexual significance of the anthers. We shall see by-
and-bye, that Koelreuter was able to form a very different idea
of sexual propagation. His great importance in the history of
the sexual theory will be best learnt from a consideration of
the speculative views of his predecessors and contemporaries.
It will not be amiss therefore to disregard chronology for a
while, and to notice here the views of the Baron von Gleichen-
Russworm, and the feeble arguments of Kaspar Friedrich
Wolff against the theory of evolution. The first-named writer
in his work 'Das Neueste aus dem Reich der Pflanzen,' 1764,
relying principally on microscopic observation of the contents
of pollen-grains, supported the view that the granules in them
answer to spermatozoids in animals, and that they find their
way into the ovule and are there developed into embryos.
Yet Gleichen was at the same time a zealous supporter of the
sexual theory, and endeavoured to meet well-known objections
to it by pointing to the occurrence of female flowers on male
plants of spinach ; he also made some experiments on maize
and hemp in the interests of the theory. He did not perceive
that hybrids supply convincing proof against the theory of
evolution, but he rightly appealed to them as affording strong
arguments in favour of sexuality. His real knowledge of
hybrids is partly drawn from the statements of Linnaeus, with
which we have already made acquaintance ; he even describes

Chap. I.] Theory of Evolution and Epigenesis. 405

a hybrid between a goat and a cow, and other similar ones,
and he is angry with Koelreuter for fixing such narrow limits
to the occurrence of hybrids ; thus the first person who
produced hybrids systematically in the vegetable kingdom
must submit to be scolded for refusing to accept the imaginary
hybrids of his contemporaries. Gleichen's book and the
selection from his microscopic discoveries, which appeared in
1777, abound in good detached observations ; he was the first
who saw and figured the pollen-tubes of Asclepias, without of
course suspecting their real nature and importance.

Kaspar Friedrich Wolff is usually said to be the writer who
refuted the theory of evolution. It is certainly true that in
his dissertation for his doctor's degree in 1759, the well-known
' Theoria generationis,' he appeared as the decided opponent
of evolution ; but the weight of his arguments was not great,
and the hybridisation in plants which was discovered at
about the same time by Koelreuter supplied much more
convincing proof against every form of evolution. Wolff
conceived of the 'act of fertilisation as simply another form of
nutrition. Relying on the observation, which is only partly
true, that starved plants are the first to bloom, he regarded the
formation of flowers generally as the expression of feeble
nutrition (vegetatio languescens). On the other hand the
formation of fruit in the flower was due to the fact, that the
pistil found more perfect nourishment in the pollen. In this
Wolff was going back to an idea which had received some
support from Aristotle, and is the most barren that can be
imagined, for it appears to be utterly incapable of giving any
explanation of the phenomena connected with sexuahty, and
especially of accounting for the results of hybridisation. Wolff
may have rejected the theory of evolution on such grounds as
these, but he failed to perceive what it is which is essential
and peculiar in the sexual act.

4o6 History of the Sexual Theory. [Book hi.

5. Further development of the sexual theory by Joseph

Gottlieb Koelreuter, and Konrad Sprengel.

1761-1793.

Camerarius had shown by experiment that the co-operation
of the pollen is indispensable to the production in plants of
seeds containing an embryo, and later observers had confirmed
the fact of sexuality by further and varied experiments. The
next step in the strict scientific investigation of the matter was
to determine by the same method of experiment the share of
each principle, the male and the female, in the formation of
the new plant which resulted from the sexual act. When
pollen and ovule belong to the same individual plant, the
offspring assumes the same form and the question remains
undecided. It was necessary to bring together the pollen and
ovule of different plants ; this must show whether some
characters are derived to the offspring from the pollen, and
others from the ovule, and what the characters are which are
thus distinguished, supposing of course that such a union of
different forms is possible. The answer to these questions
could only be obtained by experiment, that is by artificial
hybridisation ; for until hybrid forms had actually been
produced in this manner, it must be quite unsafe to assume
that certain wild plants owed their origin to cross-fertilisation.

Camerarius had already raised the question in his letter,
whether cross-fertilisation in plants is possible, and had added
another, whether the progeny varies from its parents (an et
quam mutatus inde prodeat foetus). Bradley is our authority
for the statement that a gardener in London had obtained a
hybrid between Dianthus caryophyllus and Dianthus barbatus
by artificial means as early as 17 19; but Koelreuter^ was

' Joseph Gottlieb Koelreuter was bom at Sulz on the Neckar in 1733,

and died at Carlsrnhe in 1806, where he was Professor of Natural History,

and from 1768 to 1786 Director also of the Botanic and Grand-ducal

■ Gardens. On giving up the latter position he continued his experiments in

his own small garden till the year 1790. Karl Friedrich Gartner in his work

Chap. I] Joseph G. Koelreuter and Kofirad Spvengel. 407

the first who investigated the question scientifically and
thoroughly. He was the first moreover who recognised all its
importance, and he appHed himself to it with such admirable
and unexampled perseverance and judgment, that the results
which he obtained are still the best and most instructive,
though a thousand similar experiments have been made
since his time. He also made the first careful study of the
different arrangements inside the flower in their connection
with the sexual relation, discovered the purpose of the nectar
and the co-operation of insects in pollination, and proposed that
view of the sexual act, which with some considerable modifica-
tion we must still in the main consider to be the true one,
namely, that it is a mingling together of two different sub-
stances.

If we compare Koelreuter's writings, which are full of matter
in a small compass, with all that was produced after Camerarius,
we are astonished not only at the abundance of new thoughts,
but still more at their wonderful clearness and perspicuity, and
the sureness of the foundation laid for them in observation and
experiment. In reading the observations of Linnaeus, Gleichen,
and Wolff on the sexual theory we step into a world of thought
which has long been strange and is scarcely intelligible to us,
and which in the present day possesses only a historical
interest. Koelreuter's works on the contrary seem to belong
to our own time ; they contain the best knowledge which we
possess on the question of sexuality, and have not become
antiquated after the lapse of more than a hundred years. We
see by his example that one really gifted thinker with the
requisite perseverance will effect more in a few years, than

' Ueber Bastardzeugung ' of 1849, at p. 5 says that after the latter date Koel-
reuter occupied himself with experiments in alchemy ; but this must be a
mistake. Gartner, loco cit., and the ' Flora ' of 1839, P- 24.^, supply all that
seems to be known of the life of this distinguished man. The ' Biographic
Universelle ' contains no account of him. It would appear that he was
in St. Petersburg before 1766.

4o8 History of the Sexual Theory. [Book hi.

many less gifted observers in the course of many years. But
the same thing happened now, which happens often in similar
cases and which happened to Camerarius ; a much longer time
elapsed before others learnt to understand the meaning and
importance of Koelreuter's labours, than he had found necessary
for making his discoveries.

Koelreuter's most important and best-known work appeared
in four portions in 1761, 1763, 1764 and 1766 under the title,
' Vorliiufige Nachricht von einigen das Geschlecht der Pflanzen
betreffenden Versuchen und Beobachtungen ' ; we shall en-
deavour to give a brief summary of the more important
results.

At different places in this work occur remarks and experi-
ments on arrangements for pollination, which up to that time
had been seldom and only hastily observed. As the pollen-
tube had not yet been discovered, and Koelreuter himself set
out with the view, that a fluid finds its way from the pollen-
grains as they lie on the stigma to the ovules, it was important
first of all to determine the quantity of pollen which is required
for the complete fertilisation of an ovary ; with this object
in view Koelreuter counted the pollen-grains formed in a
particular flower and compared them with the number required
to be applied to the stigma in order to effect complete
fertilisation, and he found that the latter number was much
the smaller. For instance, he counted four thousand eight
hundred and sixty-three pollen-grains in a flower of Hibiscus
venetianus, while from fifty to sixty were sufficient to produce
more than thirty fertile seeds in the ovary ; in Mirabilis jalapa
and Mirabilis longiflora he counted about three hundred grains
of pollen in the anthers, while from two to three or even one
sufficed for fertilisation in the one-ovuled ovary. He also tried,
whether in flowers with divided and even deeply-cleft styles
fertilisation could be effected in all compartments of the ovary
through one of them only, and he found that it could.

Koelreuter directed special attention to the arrangements,

Chap. I.] Joscpli G. Koelveuter and KoHvad Spvcngel. 409

by which in the natural course of things the pollen finds its
way from the anthers to the stigmas. He ascribed perhaps too
much to the agency of the wind and the oscillations of the
flower from any cause ; at the same time he was the first
who recognised the great importance of the insect-world to
polUnation in flowers. ' In flowers,' he says, ' in which pollin-
ation is not produced by immediate contact in the ordinary
way, insects are as a rule the agents employed to effect it,'
(later observation has shown that they are generally so
employed even in cases where actual contact is possible),
' and consequently to bring about fertilisation also ; and it is
probable that they render this important service if not to the
majority of plants at least to a very large part of them, for
all the flowers of which we are speaking have something in
them which is agreeable to insects, and it is not easy to find
one such flower, which has not a number of these creatures
busy about it.' He noticed the dichogamous construction
in Epilobium, but did not further pursue his observation. He
next examined the substance in flowers Avhich is agreeable to
insects ; he collected the nectar of many flowers in con-
siderable quantities, and found that it gave after evaporation
of the water a kind of sweet-tasted honey ; this honey was
unpalatable only in Fritillaria imperialis, which is avoided
by the humble-bees. He had no doubt therefore, that bees
procure their honey from the nectar of flowers. How greatly
he was interested in the relations between the existence of
certain plants and that of certain animals, relations which were
neglected till Darwin once more brought them into notice in
quite recent times, is shown by his investigation into the pro-
pagation of the mistletoe (1763) ; he calls special attention to
the fact, that not only must the pollination of this plant be
effected by insects, but that the dissemination of its seeds
is also exclusively the work of birds, and that the existence
of the plant therefore is dependent on two different classes
of living creatures.

4IO History of the Sexual Theory. [Book in.

Again we find observations on the movements of anthers
and stigmas, especially those caused by sensitiveness. Count
Giambattista dal Covolo had made the first observations in
1764 on the sensitiveness of the anthers of thistle-like plants,
and had endeavoured to explain their mechanism. Koelreuter
did not trouble himself about this point, so much as about
the connection between the irritability of the anthers and the
pollination of the stigmas. He took into consideration the
sensitive stamens of Opuntia, Berberis and Cistus, which Du
Hamel had already noticed, and discovered for himself the
irritability of the lobes of the stigma in Martynia proboscidea
and Bignonia radicans. He noticed that the lobes when
touched close, but soon open again ; but if pollen is placed
upon them, they remain closed till fertilisation is secured.

How perfectly insects effect the pollination of flowers he
showed by a comparative trial, in which he applied pollen
himself to three hundred and ten flowers with a brush, while
he left the same number to the operation of insects ; the
number of seeds formed in the latter case was very little less
than in the former, though the insects had to contend with
unfavourable weather.

He endeavoured also to ascertain the time required for the
quantity of ' seminal matter ' sufficient for fertilisation to reach
the ovary after pollination ; he also showed that pollination
is followed by fertilisation without the aid of light; later
botanists incorrectly maintained the contrary.

Koelreuter was less successful in his observations on the
structure of pollen-grains ; here the microscope was indis-
pensable and microscopes were still very imperfect. Never-
theless he discovered that the outer covering of the pollen-grain
consists of two distinct coats, and noticed the spines and
sculpturings on the outer coat and its elasticity ; he observed
the lids of the orifices in the exine of Passiflora coerulea, and
went so far as to see the inner coat in moistened pollen-grains
protrude in the form of conical projections, which then however

Chap. I.] JosepJi G. Koelreuter and Kourad Spreugel. 411

burst and allowed the contents to escape. But he explained
the pollen-tube, which he had thus seen, incorrectly by sup-
posing that these projections were intended to prevent the
bursting of moistened grains. It was not till sixty or seventy
years later that the matter was fully understood. Koelreuter
supposed the contents of the pollen-grain to be a 'cellular
tissue,' and the true fertilising substance to be the oil which
adheres to the outside of the grains, but is formed inside them
and finds its way out through fine passages in the coat. The
bursting of the pollen-grains, which his opponent Gleichen
thought must take place to allow of the escape of his supposed
spermatozoids, seemed to him an unnatural proceeding.

Starting from the hypothesis, that the oil which clings to
the pollen-grains is the fertilising substance, Koelreuter pro-
pounds his view of the process of fertilisation in accordance
with the chemical notions of the day ; he first rejects the
idea that the pollen-grains themselves can reach the ovary,
and then says : ' Both the male seed and the female moisture
on the stigmas are of an oily nature, and therefore when they
come together enter into a most intimate union with one
another, and form a substance which, if fertilisation is to ensue,
must be absorbed by the stigma and conveyed through the
style to the so-called ovules or unfertilised germs.' Koelreuter
therefore made the fertilisation really take place on the stigma,
the mingled male and female substance making its way into the
ovary and there producing the embryos in the seed. He had
expressed this view before in 1761; he repeated it in 1763
with the idea that the male and female moistures unite together,
as an acid and an alkali unite to form a neutral salt ; a new
living organism is the result at once or later of this union.
In an investigation which he made in 1775 into the conditions
of pollination in Asclepiadeae he reverted to this idea, and
insisted that the act of fertilisation in the whole vegetable and
animal kingdom is a mingling of two fluids. But at a later
period he seems to have no longer considered the moisture

412 History of the Sexual Theory. [Bookiii.

of the stigma to be the female principle, for experiment had
taught him, that if a stigma exchanges the moisture from
another stigma for its own, and is then dusted with its own pollen,
no hybrid form is produced \ In any case Koelreuter had a
more correct idea of the nature of sexual fertilisation than any
of his predecessors, and it was one specially adapted to enable
his contemporaries to understand the results of experiments
in hybridisation, while the hybrids themselves suppHed most
convincing arguments against the prevailing theory of evolution.
We have arrived at Koelreuter's most important performance,
the production of hybrids. Here was a case for skilful ex-
perimentation, not for microscopic observation, and here he
obtained results in which nothing afterwards required to be
changed, but which when combined with later observations
have been used for the discovery of general laws in hybrid-
isation. The first hybrid which he obtained by placing the
pollen of Nicotiana paniculata on the stigmas of N. rustica,
produced pollen that was impotent ; but he soon after obtained
hybrids from the two species which produced seeds capable
of germination, and in 1763 he described a considerable
number of hybrids in the genera Nicotiana, Kedmia, Dianthus,
Matthiola, Hyoscyamus, and others. In the last portion of
his great work (1766) he speaks of eighteen attempts to obtain
hybrids with five native species of Verbascum, and submits
Linnaeus' views on hybrid plants, which we have already
described, to a withering criticism. He shows at the same
time from experiment, that if the stigma of a plant receives
its own pollen and pollen from another plant at the same
time, the former only is effectual, and that this is one reason
why hybrids which can be raised artificially are not found in
nature. We must not attempt to give a detailed account of
his famous hybrids of the third, fourth, and fifth degrees, nor
of his experiments on other points, such as the reverting of

* See G.artner, ' UeberBastardzeugung ' (1849 > P- 62. I have unfortunately
been unable to meet with the second continuation of Koelreuter's work.

Chap. I.] Joscph G. Koelreutev Qud KoHvad Spvengel. 413

hybrids to the original form by the repeated employment of
its pollen ; the value of these experiments for theoretical
purposes was afterwards fully brought out by Nageli.

It is impossible to rate too highly the general speculative
value of Koelreuter's artificial hybridisation. The mingling of
the characters of the two parents was the best refutation of
the theory of evolution, and supplied at the same time pro-
found views of the true nature of the sexual union. It was
shown by his numerous experiments that only nearly allied
plants and not always these are capable of sexual union, which
at once disposed of Linnaeus' vague ideas in the judgment of
every capable person, though it was long before science
candidly accepted Koelreuter's results. The plant-collectors
of the Linnaean school as well as the true systematists at the
end of the i8th century had little understanding for such
labours as Koelreuter's, and incorrect ideas on hybrids and
their power of maintaining themselves prevailed in spite of
them in botanical literature. Hybrids were necessarily in-
convenient to the believers in the constancy of species ; they
disturbed the compactness of their system and would not fit
in with the notion that every species represented an ' idea.'

Koelreuter's doctrines however did not always fall on un-
fruitful soil ; two botanists at least were found in Germany
who adopted them, Joseph Gartner the author of the famous
Carpology and father of Carl Friedrich Gartner who at a later
time spent twenty-five years in experimenting on fertilisation
and hybridisation, and Konrad Sprengel who took up Koel-
reuter's discovery of the services rendered by insects and
arrived at some new and very remarkable results.

Joseph Gartner made no fresh observations on sexuality
himself, but in the Introduction to his ' De fructibus et semi-
nibus plantarum' (1788) he made use of Koelreuter's results for
the purpose of distinguishing more clearly between different
kinds of propagation, and strengthening his own attack on the
theory of evolution. The germ-grains or spores of cryptogamic

414 History of the Sexual Theory. [Book iii.

plants were at that time often regarded on insufficient grounds
as true seeds ; Gartner distinguished them from seeds, because
they are formed without fertiUsation and yet are capable of
germination, whereas ovules become seeds capable of germina-
tion only under the influence of the pollen. He distinctly denied
the sexuality of the Cryptogams ; it was not till fifty years later
that strict scientific proof was substituted in this department
of botany for vague conjecture, and it was more in the interest
of true science in Gartner's day to deny sexuality in the Cryp-
togams altogether, than to take the stomata in Ferns with
Gleichen, or the indusium with Koelreuter, or the volva in
Mushrooms for the male organs of fertilisation. Gartner rightly
appealed to Koelreuter's hybrids against the defenders of the
theory of evolution; and to those who saw in the seed only
another form of vegetative bud, he said, that the bud can
produce a new plant without fertilisation but that the seed
cannot. We have already given an account in the chapters on
Systematic Botany of the services rendered by Gartner to the
knowledge of the seed in its immature and in its mature
condition ; as regards the process of fertilisation he adopted in
the main Koelreuter's view, that it is the result of the union
of a male and female fluid, from which the germ-corpuscle in
the ovule is developed by a kind of crystallisation. Konrad
Sprengel also fully committed himself to this view, and was
thereby prevented from understanding the process of fertilisa-
tion in Asclepiadeae.

In Konrad Sprengel^ we encounter once more an observer

^ Christian Konrad Sprengel, bom in 1750, was for some time Rector at
Spandau. There he began to occupy himself with botany, and devoted so
much time to it that he neglected the duties of his office, and even the
Sunday's sermon, and was removed from his post. He afterward lived a
solitary life in straitened circumstances in Berlin, being shunned by men
of science as a strange, eccentric person. He supported himself by giving
instruction in languages and in botany, using his Sundays for excursions,
which any one who chose could join on payrnent of two or three groschen.
He met with so little support and encouragement that he never brought out

Chap. I.] Joseph G. Koelreuter ttud Konvad SpreHgcl. 415

of genius, like Camerarius and Koelreuter, who however sur-
passed them both in boldness of conception and was therefore
even less understood by his contemporaries and successors^ than
they had been by theirs. The conclusions, to which his in-
vestigations led him, were so surprising, they suited so little
with the dry systematism of the Linnaean school and with
later views on the nature of plants, that they had become quite
forgotten when Darwin brought them again before the world
and showed their important bearing on the theory of descent.
As Camerarius first proved that plants possess sexuality, and
Koelreuter showed that plants of different species can unite
sexually and produce fruitful hybrids, so now Sprengel showed
that a certain form of hybridisation is common in the vegetable
kingdom, namely the crossing of different flowers or different
individuals of the same species. In his work, 'Das neu ent-
deckte Geheimniss der Natur in Bau und Befruchtung der
Blumen,' Berlin, 1793, he says at page 43 : 'Since very many
flowers are dioecious, and probably at least as many herma-
phrodite flowers are dichogamous, nature appears not to have
intended that any flower should be fertilised by its own
pollen.' This was however only one of his surprising con-
clusions ; still more important perhaps was the view, that the
construction and all the peculiar characters of a flower can
only be understood from their relation to the insects that visit
them and effect their pollination ; here was the first attempt to
explain the origin of organic forms from definite relations to
their environment. Since Darwin breathed new life into these
ideas by the theory of selection, Sprengel has been recognised
as one of its chief supports.

It is highly interesting to read, how this speculative mind

the second part of his famous work ; his publisher did not even give him a
copy of the first part. Natural disgust at the neglect with which his work
was treated made him forsake botany and devote himself to languages. He
died in 1816. One of his pupils wrote a very hearty eulogium on him in the
' flora' of 1819, p. 541, which has supplied the above facts.

41 6 History of the Sexual Theory. [BookIII.

by the study of structural relations in flowers, which were
apparently trivial and open to the eyes of all men, first arrived
at ideas which in the course of a few years were to lead to such
far-reaching results. He says : 'In the summer of 1787 I was
attentively examining the flowers of Geranium sylvaticum, and
observed that the lower part of the petals was provided with
slender rough hairs on the inside and on both edges. Con-
vinced that the wise framer of nature has not produced a single
hair without a definite purpose, I considered what end these
hairs might be intended to serve. And it soon occurred to
me, that on the supposition that the five drops of juice which
are secreted by the same number of glands are intended for
the food of certain insects, it is not unlikely that there is some
provision for protecting this juice from being spoiled by rain,
and that the hairs might have been placed where they are for
this purpose. Since the flower is upright, and tolerably large,
drops of rain must fall into it when it rains. But no drop of
rain can reach one of the drops of juice and mix with it,
because it is stopped by the hairs, which are over the juice-
drops, just as a drop of sweat falling down a man's brow is
stopped by the eye-brow and eye-lash, and hindered from
running into the eye. An insect is not hindered by these hairs
from getting at the drops of juice. I examined other flowers
and found that several of them had something in their structure,
which seemed exactly to serve this end. The longer I con-
tinued this investigation, the more I saw that flowers which
contain this kind of juice are so contrived, that insects can
easily reach it, but that the rain cannot spoil it ; but I gathered
from this that it is for the sake of the insects that these flowers
secrete the juice, and that it is secured against rain that they
may be able to enjoy it pure and unspoilt.' Next year, following
out an idea suggested by the flowers of Myosotis palustris, he
found that the position of spots of different colours on the
corolla have some connection with the place where the juice is
secreted, and with the same ready reasoning as before he came

Chap. I.] Joscph G. Koelrciiter and Konrad Sprengel 417

to the further conclusion : ' If the corolla has a particular
colour in particular spots on account of the insects, it is for
the sake of the insects that it is so coloured; and if the
particular colour of a part of the corolla serves to show an
insect which has lighted on the flower the direct path to the
juice, the general colour of the corolla has been given to it, in
order that insects flying about in search of their food may see
the flo\vers that are provided with such a corolla from a long
distance, and know them for receptacles of juice.'

He afterwards discovered that the stigmas of a species of
Iris were absolutely unable to be fertilised in any other way
than by insects, and further observation convinced him more
and more, 'that many, perhaps all flowers, which have this
juice, are fertilised by the insects which feed on it, and that
consequently this feeding of insects is in respect of themselves
an end, but in respect of the flowers only a means, but at the
same time the sole means to a definite end, namely, their
fertilisation ; and that the whole structure of such flowers can
be explained, if in examining them we keep in sight the fol-
lowing points, first, that flowers were intended to be fertilised
by the agency of one or another kind of insects, or by several ;
secondly, that insects in seeking the juice of flowers, and for
this purpose either alighting upon them in an indefinite
manner, or in a definite manner either creeping into them or
moving round upon them, were intended to sweep ofl" the dust
from the anthers with their usually hairy bodies or with some
part of them, and convey it to the stigma, which is provided
either with short and delicate hairs, or with a viscid moisture,
that it may retain the pollen.'

In the summer of 1790 he detected dichogamy, which he
first observed in Epilobium angustifolium. He found, 'that
these hermaphrodite flowers are fertilised by the humble-bee
and by other bees, and that the individual flower is not fer-
tilised by its own pollen, but the older flowers by the pollen
which the insects convey to them from the younger.' Having

E e

41 8 History of the Sexual Theory. [Book in,

observed the same thing in Nigella arvensis, he afterwards
found exactly the opposite arrangement in a species of Eu-
phorbia, in which the stigmas can receive the pollen by the
aid of insects only from older flowers.

He goes on to say that he grounds his theory of flowers on
these his six chief discoveries made in the course of five years ;
he then gives his theory at length, first of all explaining the
nature of juice-secreting glands (nectaries^ and organs for
receiving or covering the nectar, and the contrivances for
enabling insects to find their way readily to the juice. He
calls attention to Koelreuter's excellent observations on the
fertilisation of nectar-bearing flowers by insects, and notices
that no one has hitherto shown that the whole structure of
such flowers has this object in view, and can be fully explained
by it. He finds the chief proof of this important proposition
in dichogamy.

'After the flower,' he says, 'has opened in dichogamous
plants, the filaments have or assume either all at once or one
after another a definite position, in which the anthers open
and offer their pollen for fertilisation. But at this time the
stigma is at some distance from the anthers and is still small
and closed. Hence the pollen cannot be conveyed to the
stigma either by mechanical means or by insects, for there is
as yet properly no stigma. This condition of things continues
a certain time. When that time is elapsed, the anthers have
no longer any pollen, and changes take place in the filaments
the result of which is that the anthers no longer occupy their
former position. Meanwhfle the pistil has so changed that
the stigma is now exactly in the place where the anthers were
before, and as it now opens, or expands the parts of which it
is composed, it often fills about the same space as the anthers
filled before. Now the spot, which was at first occupied by
the ripe anthers and is now occupied by the ripe stigma, is so
chosen in each flower, that the insect for which the flower is
intended cannot reach the juice without touching with a por-

Chap. I.] JoscpJi G. Koclreuter and Konrad Sprengcl. 419

tion of its body the anthers in a young flower, and the stigma
in an older ; it thus brushes the pollen from the anthers and
conveys it to the stigma, and so the pollen of the younger
flower fertilises the older.' It has been already said, that
Sprengel was also acquainted with the opposite form of dicho-
gamy ; and the result of his explanation of both kinds is the
conclusion, that some flowers can only be fertilised by the aid
of insects, and he adds that some cases are to be found, in
which the arrangements in the flower are of such a nature as
to involve the injury and even the death of the insect that
gives its services. Further on he tells us, that all flowers,
' which are without a proper corolla and have no calyx of any
importance in its place, are destitute of nectar, and are not
fertilised by insects but by some mechanical means, as by the
wind, which either blows the pollen from the anthers on to
the stigmas, or shakes the plant or the flower and makes the
pollen fall from the anthers on to the stigmas.' He observes,
that such flowers always produce a light pollen and in large
quantities, whereas the pollen of nectar-bearing plants is heav)\
Then he shows how his principles explain all the physiological
characters of flowers, position, size, colour, smell, form, time
of flowering and the like.

Sprengel set out with the idea, that the nectar and certain
arrangements in flowers are expressly intended for the service
of insects ; but his investigations led him ultimately to the
conclusion, that insects themselves serve not only to effect
the fertilisation of plants generally, but also in all ordinary
cases to bring about the crossing of different flowers of the
same plant or of different plants of the same species. There
remained a question, which from Sprengel's strictly teleological
point of view especially required an answer, what was the
object of this crossing of flowers or individual plants ? Sprengel
was content, as we have seen, with simply stating the fact, and
with saying, that nature apparently did not choose that any
flower should be fertilised by its own poUen. Who would

E e 2

420 History of the Sexual Theory. [Book hi.

make it a reproach to the discoverer of such remarkable and
widely-prevalent phenomena in nature, that he did not answer
this question and give the iinal touches to the body of doctrine
which he created, and which could only be developed by
many experiments and the labour of long years ? Neither his
worldly circumstances nor the reception accorded to his work
with all its genius were such as to encourage him to undertake
the solution of this last and most difficult problem, even if he
had been inchned to do so. Botanists were just at that time
and for some time after preoccupied with views, which allowed
such biological and physiological facts in vegetable life to lie
neglected, nor were Sprengel's results at all favourable to the
doctrine of the constancy of species ; from that point of view
the wonderful relations between the organisation of flowers
and that of insects must have seemed absurd and repulsive.
In such cases it is the character of less-gifted natures, rather
to deny the facts or to disregard them, than to sacrifice their
own favourite views to them ; this is one explanation of the
neglect which Sprengel's book met with everywhere. Then
notwithstanding the labours of a Camerarius and a Koelreuter
there were many even at the beginning of our own century
who still doubted the sexuality of plants. Even after Knight
and William Herbert, with a right understanding of the ques-
tion left open by Sprengel, had obtained experimental results
which helped to answer it, the new doctrine did not make its
way. The earlier simple-minded but consistent teleology had
been succeeded by a rejection of all teleological explanations
in the treatment of physiological questions, and this spirit
conduced to make Sprengel's results seem inconvenient in
proportion as they appeared to admit only of such explanation.
With regard to phenomena of this kind botanists before i860
were in a position, in which they were without the means of
forming a judgment ; they shrank from the teleological point
of view and from believing with Konrad Sprengel, that every,
even the least-obvious, arrangement in an organism was the

Chap. I.] Joseph G. Koelreuter and Konrad Sprengel. 421

direct work of a Creator ; but they had nothing better to put
in the place of this idea, and hence Sprengel's discoveries not
being understood were neglected till Darwin recognised all
their importance, and by opposing the theory of descent and
selection to the principle of design was in a position not only
to show that they had a scientific meaning, but also to employ
them as powerful supports of the theory of selection. Then,
too, it became possible rightly to appreciate the contributions
of Knight, Herbert, and K. F. Gartner to the further com-
pletion of Sprengel's doctrine, for their discoveries also were
for a while neglected. A few years after the appearance of
Sprengel's book, Andrew Knight^ relying on the results of
experiments made for the purpose of comparing self-fertilisa-
tion and crossing in the genus Pisum, laid down the principle,
that no plant fertilises itself through an unlimited number of
generations; in 1837 Herbert summed up the results of his
numerous experiments in fertilisation in the statement, that he
was inclined to believe that he attained a better result, when
he fertilised the flowers from which he wished to obtain seeds
with pollen from another individual of the same variety or at
least from another flower, than when he fertilised it with its
own pollen ; K. F. Gartner came to the same conclusion after
experiments in fertilising Passiflora, Lobelia, and species of
Fuchsia in 1844. In these observations lay the first germ of
the answer to the question left undecided by Sprengel, why
most flowers are so constructed that fertilisation can only be
fully effected by the crossing of different flowers or of different
plants of the same species ; the artificial crossings of this kind,
which Knight, Herbert, and Gartner compared with the self-
fertilisation of single flowers, showed that crossing procures
a more complete and vigorous impregnation than self-fertilisa-
tion. It was but a short step from this fact to the idea, that

* See Hermann Miiller, ' Befruchtung der Blumen durch Insecten,' Leip-
zig (1873), p. 5-

423 History of the Sexual Theory. [Book iii.

the arrangements in the flower discovered by Sprengel together
with the aid of insects serve to secure the strongest and most
numerous progeny possible. Darwin was the first who fixed
his eye distinctly on this idea also, in order to employ it in his
theory of selection, and sought support for it in a number of
experiments made after 1857.

6. New opponents of Sexuality and their refutation
by experiments. 1785-1849.

Those who have read the writings of Camerarius and Koel-
reuter carefully find it difficult to believe, that after their time
doubts were still entertained not about the manner in which
the processes of fertihsation are accomplished but about the
actual existence of difference of sex in plants. And yet such
doubts were expressed repeatedly during the succeeding sixty
years in various quarters and with the greatest confidence, and
this not in consequence of increased accuracy in experimental
research or of contradictions that could be proved in the views
of the founders of the sexual theory, but because a number
of observers made unskilful experiments and obtained con-
tradictory results, or made inaccurate observations on the
plants on which they experimented, and generally had not the
requisite experience and circumspection. Such were Spallan-
zani and later Bernhardi, Giron de Bouzareingue and Ramisch.
Schelver, his pupil Henschel, and their adherents erred still
more grossly and from a diff"erent cause ; they thought them-
selves justified by preconceived opinions and conclusions from
the nature-philosophy in denying facts established by experi-
ment. The destructive effects of the nature-philosophy on the
powers of the understanding at the beginning of the 19th
century was shown in the case of many botanists, who were no
longer able to estimate the result of simple experiments, and
to trace back the phenomena of nature to the scheme of
causes and effects. As Linnaeus once imagined that he could

Chap. 1.] Opponents of Sexuality, i'j8j-i84<). 423

prove sexuality in plants on philosophical grounds and paid
comparatively slight attention to their behaviour as shown by
experiment, so we have in Schelver a nature-philosopher who
conversely endeavoured to prove the impossibility of sexuality
in plants on philosophical grounds. As Linnaeus deduced
sexuality from the nature or idea of the plant, Schelver denied
it from the same nature or idea ; as a matter of logic one was
as much in the right as the other, but the question could not
be decided in this way but only by experiment. However our
nature-philosophers thought it advisable to get some empirical
support for their theories, and they found it in Spallanzani \
He published his enquiries into fertilisation in animals and
plants under the title ' Experiences pour servir a I'histoire de
la generation des animaux et des plantes,' Geneva, 1786; his
account of those relating to plants, with which only we are
concerned, betrays a very defective acquaintance with botanical
literature, for he reckons Cesalpino among those who had
admitted sexuality in plants. His experiments themselves
testify to very slight knowledge of the biological considerations
by which the cultivation of plants for experiment must be
guided, and generally little botanical acumen, as is often the
case with amateurs who without sufficient preparation suddenly
turn, their attention to questions of vegetable physiology; his
treatment of his topics is superficial, his criticism of others is
dogmatic and bitter without exciting confidence in the author's
own skill and judgment. His experiments were often under-
taken in haste and with little consideration, and some of them
were made on plants the least suitable for such investigations, as

^ Lazaro Spallanzani was born at Scandiano in Modena, and died at
Pa via in 1799, where he was for a long time Professor of Natural History.
He made researches in very various questions of natural science, and
especially in animal physiology ; but they seem to have been conducted
with the same want of care and deliberation which appears in his experi-
ments on sexuality in plants. A long article in the ' Biographie Univer-
selle ' gives a detailed account of his scientific labours.

424 History of the Sexual Theory. [Book hi.

for instance on Genista, beans, peas, radishes, Basilicum, Del-
phinium. It is no matter of surprise therefore that in the
case of some plants, as Mercurialis and Basilicum, he arrived
at the conclusion that the pollen is necessary to the production
of fertile seeds, while he makes others, as the gourd, the
water-melon, hemp, and spinach produce such seeds without
fertilisation. His countryman Volta, a greater man, repeated
his experiments and impugned the results which he had
obtained from them.

Such was the character of the experiments to which Franz
Joseph Schelver, Professor of Medicine in Heidelberg appealed
in his ' Kritik der Lehre von dem Geschlecht der Pflanzen,'
1812. It is unnecessary to give a detailed account of this
strange production of a mind misled, even though a consider-
able number of German botanists as late as 1820 took its
nonsense for profound wisdom, Schelver dismissed the ex-
periments of Camerarius in four lines, and while he treated
Koelreuter with contempt, he praised Spallanzani as the
weightiest author on the subject. The statements of Came-
rarius and Koelreuter are true, he said, but they do not prove
the fertilisation. He is more concerned to decide the question
from the nature of vegetative life, and from this nature con-
structed by himself he concludes that the organs of plants are
of no use at all, that they cannot even tend to be of use to
one another and to propagate life together, because this one
end of their action can be a living one only where all the
parts are present at the same time, which of course disposes of
the fertihsing effect of the pollen ; accordingly he does not
refer the effect of a male plant on a neighbouring female plant,
which results in the formation of seeds, to pollination by the
former, but it is the proximity itself which has the fertilising effect.
But these are very insufficient specimens of his reasoning.

The writings of his pupil HenscheP are even worse than

* August Henschel was a practising physician and a University teacher in
Breslau.

Chap. I.] Opponents of Sexuality, 1^8^-184^. 4^5

those of his master, and the worst of these is his large work
'Von der SexuaHtat der Pflanzen ' of 1820. He thought him-
self obliged to prove the doctrines of the nature-philosophy by
countless experiments ; but the way in which these are devised,
managed and described displays the extreme of dulness and
incapacity to form a sound judgment. The doubt which must
occasionally rise in the mind of the reader as to the accuracy
of his reports, and the remarks which have been made on this
point by Treviranus and Gartner, are not needed to disgust
him with the scientific efforts of this writer.

It would be superfluous to give an account of the contents
of Henschel's book, which is interesting from the pathological
rather than from the historical point of view. To what an
extent better men than Henschel even later than 1820 lost
under the influence of the nature-philosophy their capacity for
judging such questions as we are discussing, how even in-
vestigators of merit thought it worth while to treat the pro-
ductions of Schelver and Henschel with a certain respect, is
shown among other works, by a collection of letters, which
were published by Nees von Esenbeck as a second supple-
ment to the 'Regensberg Flora' of 1821, and by the later
remarks of Goethe on the metamorphosis of plants, to be
found in Cotta's edition of his works in forty volumes (vol.
xxxvi. p. 134) under the title ' Verstaubung, Verdunstung,
Vertropfung.' But there were some who set themselves dis-
tinctly against these pernicious ideas, such as Paula Schrank
('Flora,' 1822, p. 49) and C L. Treviranus, who published in
1822 a full refutation of Henschel in his ' Lehre von dem
Geschlecht der Pflanzen in Bezug auf die neuesten Angriffe
erwogen.' A few stray supporters of the dying nature-philo-
sophy were still to be found at a later time ; among them
Wilbrand, Professor in Giessen, who ('Flora,' 1830, p. 585)
adopted the very subtle distinction that there is in plants
something analogous to sexuality in animals, but no real
sexuality. We see in the whole literature of the nature-

426 History of the Sexual Theory. [Book til

philosophy an incapabihty of judging of experiments simply
with the sound human understanding; an imaginary some-
thing was constantly introduced into the results of experiments
which had not the remotest connection with their conditions
and results.

The doubts expressed by Bernhardi in 1811, by Girou in
1828-30, and by Ramisch in 1837 were of a different kind;
these men made experiments and judged of them in a scientific
manner ; but they were insufficiently acquainted with what
had been done before them, and their experiments were not
devised with the requisite knowledge of the conditions of the
problem, or carried out with sufficient precautions. Came-
rarius and Ray had noticed in the previous century the occa-
sional occurrence of male flowers on female plants of spinach,
hemp and mercury ; and yet the observers above mentioned
chose these plants for their experiments without being on their
guard against the possible appearance of these exceptional
circumstances, or of other means of pollination.

We see then that doubts were entertained till as late as
after 1830 with regard either to sexuality in plants altogether,
or to its general prevalence in Phanerogams ; the Cryptogams
were not mentioned, for they were assumed to be devoid of
sex in spite of many valuable observations of earlier times.
The great majority of botanists however admitted the sexual
significance of the organs of the flower ; most of them rested
in entire faith on Linnaeus' authority, while some were able to
appreciate the experimental proofs of Camerarius, Bradley,
Logan, Gleditsch and Koelreuter. But all who took up the
subject in earnest between 1820 and 1840 were naturally led
to desire that the question should once more be thoroughly
examined. The Berlin Academy of science had offered in
1 8 19 at Link's suggestion a prize for an essay on the question,
whether there is such a thing as hybrid fertilisation in the
vegetable kingdom, in the hope of stimulating botanists to
new investigations into the decisive points in the sexual

Chap. I.] Karl FriedHck Gartner. 427

theory. The only reply to this offer, an essay by Wiegmann
which was not sent in till 1828, did not come up to the re-
quirements of the Academy, and was rewarded with only half
the prize. The Dutch Academy at Haarlem was more suc-
cessful when induced by Reinwardt in 1830 to propose the
question in a somewhat altered form and in connection with
practical horticulture. This prize was contended for by Karl
Friedrich Gartner Vvhose essay delayed by circumstances till
1837 received the prize of honour and an extraordinary reward.
But the whole body of his results, derived from the experi-
mental researches of five-and-twenty years, were not published
till 1 849 and then in a large volume, ' Versuche und Beobach-
tungen iiber die Bastardzeugung,' Stuttgart, 1849, having been
preceded by an introductory work of equal extent, ' Versuche
und Beobachtungen iiber die Befruchtungsorgane der voll-
kommeneren Gewachse und iiber die natiirliche und kiinstliche
Befruchtung durch den eigenen Pollen.' The two works
together are the most thorough and complete account of ex-
perimental investigation into sexual relations in plants which
had yet been written. They are a brilliant termination of
the period of doubt with respect to sexuality in plants which
succeeded to the age of Koelreuter — a termination which
coincides in time with the lively discussion which was being
maintained on the strength of microscopical investigations by

1 Karl Friedrich Gartner, son of Joseph Gartner, was born at Calw in
1772, and died there in 1850. He attended lectures on natural science at
the Carlsacademie at Stuttgart, and then went first to Jena for medical
instruction, and in 1795 to Gottingen, where he was a pupil of Lichtenberg.
He took a degree in 1796 and settled as a physician in his naiive town.
Here he occupied himself at first with questions of human physiology, and
afterwards worked at the supplement to his father's ' Carpologia.' He
collected notices and extracts for a complete work on vegetable physiology.
This design was never fulfilled, but it led to his taking up the question of
sexuality in plants, to which he devoted twenty-five years ('Jahresheft
des Vereins fiir vaterl. Nalurkunde in Wiirtemberg,' 1852, vol. viii,
p. 16).

428 History of the Sexual Theory. [Book hi.

Schleiden and Schacht on the one side and by Hofmeister on
the other respecting the processes in the formation of the
embryo.

Gartner's writings derive their importance not so much from
new and surprising discoveries or brilliant ideas and un-
expected combinations, as from their very searching exami-
nation into all the circumstances and relations which can
come under consideration in the sexual propagation of
Phanerogams. His experiments in hybridisation, of which he
kept most exact accounts, exceeded the number of nine
thousand ; in these and in normal cases of pollination he
studied all the sources of error which could in any way affect
his experiments, and took into careful consideration all the
conditions of fertilisation connected with the development of
the plant itself and with its external circumstances ; at the
same time he examined critically all that had been written on
the subject, and submitted every experiment reported by
former observers to the test of his own wide experience. The
volume on self-fertilisation is a complete account of the biology
and physiology of flowers. The phenomena connected with
the unfolding and fertilisation of the flower are described from
the writer's own observations, some of which are quite new ; it
specially investigates the relations between the calyx, the
corolla, the secretion of nectar and the opening of the anthers,
also the temperature of flowers and the physiological processes
in the ovary, the style and the stigma; all that was then
known of irritability and the phenomena of movement in the
flower and in the organs of fructification was collected together
and elucidated by fresh observations, and thus a picture was
drawn complete to the smallest detail of the life of a flower,
such as we do not yet possess of any other organ. It would
be idle to think of giving in a small compass a clear idea of
the wealth of these observations. But all this was only pre-
liminary to the main point, the proof that Camerarius was
right, that notwithstanding the objections of a hundred years

Chap. I.] KaH FricdricJi Gartner. 429

the co-operation of the pollen is indispensable to the formation
of the embryo in the growing seed, and that plants therefore
have sexuality exactly as animals have it. Gartner did not
content himself with simply making new experiments in fertili-
sation ; he refuted the objections of Spallanzani, Schelver,
Henschel, Girou and others in detail from fresh experiments
and from other sources of information, paying particular regard
to all the circumstances which could come under consideration
in each case ; he exposed the inaccuracy of the observations of
the opponents of sexuality point by point, and finally called at-
tention to a number of remarkable phenomena observable in the
ovary even before fertilisation, and to the circumstances under
which the pollen may find its way to it in cases where ordinary
pollination has been apparently prevented. These observations
once more confirmed the existence of sexuality in plants, and
in such a manner that it could never be again disputed.
When facts were observed in i860, which led to the pre-
sumption that under certain circumstances in certain indi-
viduals of some species of plants the female organs might
produce embryos capable of development without the help of
the male, there was no thought of using these cases of
parthenogenesis to disprove the existence of sexuality as the
general rule ; men were concerned only to verify first of all
the occurrence of the phenomena, and then to see how they
were to be reasonably understood side by side with the
existing sexuality, as had to be done also in the corresponding
cases in the animal kingdom.

Gartner's work on hybridisation had been preceded by other
enquiries into the same subject^ those namely of Knight men-
tioned above at the beginning of the century, and Herbert's
more ample investigations published in his work on Amaryl-
lideae in 1837. Gartner did not neglect to compare his
observations at all points with the results of his predecessors,
especially those of Koelreuter, and he deduced from the
astonishing mass of material a number of general propositions

43© History of the Sexual Theory. [Book hi.

respecting the conditions under which the production of hy-
brids is possible, the results of crossing, and the causes of
failure. A special interest attaches to his mixed and com-
pound hybrids, to his experiments on the various degrees of
influence which foreign pollen exercises on the behaviour of
the female organ, and the connection of this point with the
formation of varieties. It is impossible to give a more distinct-
account of Gartner's results without entering into discussions
which would exceed the limits of a historical survey. It is the
less necessary to do so, since Niigeli undertook in 1865 to
give a summary view of all the important results to be found
in the wealth of material supplied by Koelreuter, Herbert and
Gartner^. Gartner's experiments in hybridisation were con-
ducted at Calw in Wiirtemberg, the place where Koelreuter
had made his in 1762 and 1763. And thus it was in two
small cities of Wiirtemberg that the foundations of the sexual
theory were laid and the theory itself perfected, as far as it
could be by experiment only, by three of the most eminent
among observers. Camerarius in Tiibingen, Koelreuter and
K. F. Gartner in Calw contributed so largely to the empirical
establishment of the theory, that all that was done by others
would seem of small importance, if artificial pollination only
were in question. But Koelreuter was imperfectly acquainted
with the methods by which pollination is usually effected in
nature ; Sprengel was the first who saw into all their more
important relations, and the fact must not be concealed, that
Gartner in regarding Konrad Sprengel's observations as un-
worthy of serious consideration, neglected the most fruitful
source of new and magnificent results. His careful study of
the secreting of nectar and of the sensitiveness of the organs of
fertilisation, and his many observations on other biological re-
lations in flowers, would have found their natural termination,
if he had connected them at all points with Sprengel's general

' See also Sachs, ' Lehrbueh der Botanik,' Leipzig, 1874.

Chap. I.] Investigation of tlic fertiUsation-proccss. 431

conclusions respecting the relation of the structure of the
flower to the insect world. This Gartner entirely failed to do,
and hence in this case also it was reserved for Darwin"s
wonderful talent for combination to sum up the product of the
investigations of a hundred years, and to blend Koelreuter's,
Knight's, Herbert's, and Gartner's results with Sprengel's
theory of flowers into a living whole in such a manner, that
now all the physiological arrangements in the flower have
become intelligible both in their relations to fertilisation, and
in their dependence on the natural conditions under which
pollination takes place without the aid of man. Here, as in
morphology and systematic botany, Darwin found the pre-
misses given and drew the conclusion from them ; here too
the certainty of his theory rests on the results of the best
observers, on investigations which find in that theory their
necessary logical and historical consummation.

7. Microscopic investigation into the processes of
fertilisation in the phanerogams; pollen-tube
and egg-cells^. 183o-1850.

Those who were convinced of the sexuality of plants had
endeavoured as early as the previous century to form some
idea with the help of the microscope of the way in which the
pollen effects the formation of the embryo in the ovule. We
may pass over Morland's and Geoffrey's very rude attempts in
this direction; Needham (1750), Jussieu, Linnaeus, Gleichen,
and Hedwig imagined that the pollen-grain bursts upon the
stigma, and that the granules it contains make their way down-

■ The more important works referred to in this section are Robert Bro\vn's
'Miscellaneous Writings,' edited by Bennett, 1866-67; von Mohl on G.
Amici, in the ' T.otanische Zeitung,' 1863, Beilage, p. 7 ; Schleiden, ' Ueber
die Eildnng des Eichens \\\v\ Entstchung des Embryos,' in 'Nova Acta
Academiae Leopoldinensis/ 1839, vol. xi, Abtheilung, i ; Hofmcister, ' Zur
Uebersicht der Geschichte von der Lehre der Pflanzenbefruchtung,' in
' Flora' of 1867, p. 119.

432 History of the Sexual Theory. [Book hi,

wards through the style to the ovules, and are there either
hatched into embryos or assist in their production. This way
of conceiving the matter was closely connected with the theory
of evolution which then prevailed, and seemed to find some
countenance in the seed-corpuscles of animals ; it was also
supported by the observation that pollen-grains placed under
the microscope in water often burst and discharge their con-
tents in the form of a granular mucilage. It has been already
mentioned that Koelreuter rejected this view ; he declared the
bursting of the pollen-grains to be contrary to nature, and con-
sidered the oil which exudes from the grains to be the fertilising
substance. This view was adopted by Joseph Gartner and
Sprengel, but it fell into disesteem, while that of Needham and
Gleichen commanded some assent some years longer. The
next question was, how the granular contents of the pollen-
grain reach the ovules. Accident supplied a starting-point for
further consideration. Amici, who was examining the hairs on
the stigma of Portulaca for another purpose, saw on that
occasion (1823) the pollen-tube emerge from the pollen-grain,
and the granular contents of the latter, commonly known as
the fovilla, execute streaming movements like the well-known
movement in Chara. The desire to verify this remarkable
fact, and to discover how the fertilising substance is absorbed
by the stigma, led Brongniart in 1826 to examine a great
number of pollinated stigmas. He succeeded in establishing
the fact that the formation of pollen-tubes is a very frequent
occurrence. The want of perseverance in following out his
observation and a prepossession in favour of Needham's old
theory prevented him from discovering the course of the
pollen-tubes all the way to the ovules; he supposed, indeed,
that after penetrating into the stigma they open and discharge
their granular contents, and he maintained distinctly that these
are analogous to the spermatozoids in animals, and are the
active part of the pollen. But now Amici addressed himself
more earnestly to the question, and in 1830 he not only

Chap. I.] Investigation of tlu fertiUzation-process. 433

followed the pollen-tubes into the ovary, but also observed
that one finds its way into the micropyle of each ovule.

Thus the question was suddenly brought near to its solution,
when observers began to wander from the right path in
different directions. Robert Brown showed in 1831 and 1833
that the grains in the pollen-masses of Orchids and Asclepiads
put forth pollen-tubes as in other plants, and that fine tubes
are found in the ovary of Orchids in which pollination has
taken place ; but he was in doubt about the connection of
these tubes with the pollen-grains, and rather inclined to think
that they were formed in the ovary, though possibly in con-
sequence of the pollination of the stigma. Schleiden went
wrong in a very different way, and by so doing made the
question as prominent in botanical research, as was that of the
origin of cells at this time. He published in 1837 some ex-
cellent investigations into the origin and development of the
ovule before fertilisation, certainly the best and most thorough
of the day. He at the same time showed that Brongniart's
and Brown's doubts were unfounded, and confirmed the state-
ment of Amici, that the pollen-tubes make their way from the
stigma to the ovule, which they enter through the micropyle.
But he made them push forward a little too far, for he asserted
positively that ' the pollen-tube pushes the membrane of the
embryo-sac before it, making an indentation, and its extremity
then appears to lie in the embryo-sac. The extremity of the
tube now swells out into a round or oval shape, and cell-tissue
forms from its contents ; the lateral organs, one or two coty-
ledons, are then produced, the original apical point remaining
more or less free and forming the plumule. The portion of
the tube underneath the embryo and the fold of the embryo-
sac which envelopes it are divided off sooner or later and dis-
appear, so that the embr>'0 now really lies in the embryo-sac'
This view, which appears to rest on direct observation and is
illustrated by figures which answer to the description, corre-
sponds with the old theory of evolution and has a striking

Ff

434 History of the Sexual Theory. [Book hi.

approximation to the ideas of Morland and Geoffroy ; and if it
were correct, it would like these imply the necessity of pollina-
tion to the formation of seeds that should contain embryos, but
at the same time it would do away with that which is the essen-
tial point in the sexuality of plants, for the ovule would merely
be the spot adapted to the hatching of the embryo formed from
the pollen. Schleiden's idea was at once adopted by Wydler,
Gelesnow and various other botanists, and especially by
Schacht, but the most eminent microscopists withheld their
assent. Amici was the first who openly opposed the new doc-
trine; before the Italian congress of savants at Padua in 1842
he endeavoured to prove that the embryo is not formed at the
end of the pollen-tube, but from a portion of the ovule which
was already in existence before fertilisation, and that this part
is fertilised by the fluid contained in the pollen-tube. But the
choice of a gourd, a plant eminently unsuitable for his pur-
pose, prevented his discovering the exact details of the process,
and Schleiden did not hesitate to denounce his assertions in
1845 in the plainest terms. But in the next year (1846) Amici
produced decisive proof for the views which he had maintained ;
he showed from the Orchidaceae, which were peculiarly well
adapted for such investigations, not only that Robert Brown's
doubts above mentioned were without foundation, but, which
is the main point, that a body, the egg-cell, is present in the
embryo-sac of the ovule before the arrival of the pollen-tube,
and that this body is excited by the presence of the pollen-tube
to further development, the formation of the embryo. He
gave a connected account on this occasion for the first time of
the whole course of these processes from the pollination of the
stigma to the perfecting of the embryo.

The correctness of the account given by Amici was con-
firmed in the following year by von Mohl and Hofmeister, the
latter of whom described in detail the points which were
decisive of the question from a variety of plants, and illustrated
them by very beautiful figures in a more copious work, ' Die

Chap. I.] Investigation of the fertiUzation-proccss. 435

Enstehung des Embryo der Phanerogamen,' Leipzig, 1849.
Tulasne also came forward in opposition to Schleiden's theory,
being thoroughly convinced that there was no actual contact of
the pollen-tube with the egg-cell, denying indeed the existence
of the egg-cell before fertilisation. Thus a vehement contro-
versy arose on the subject ; a prize offered by the Institute of
the Netherlands at Amsterdam was awarded to an essay of
Schacht's in 1850, which defended Schleiden's theory, and
illustrated it by a great number of drawings giving incorrect
and indeed inconceivable representations of the decisive points.
Von Mohl says very admirably on this occasion (' Botanische
Zeitung,' 1863, Beilage, p. 7) : ' Now that we know that
Schleiden's doctrine was an illusion, it is instructive, but at the
same time sad, to see how ready men were to accept the false
for the true ; some renouncing all observation of their own
dressed up the phantom in theoretical principles ; others with
the microscope in hand, but led astray by their preconceptions,
believed that they saw what they could not have seen, and
endeavoured to exhibit the correctness of Schleiden's notions
as raised above all doubt by the aid of hundreds of figures,
which had every thing but truth to recommend them ; and
how an academy by rewarding such a work gave fresh con-
firmation to an experience which has been repeatedly made
good especially in our own subject during many years past,
namely that prize-essays are little adapted to contribute to the
solution of a doubtful question in science.' In this case the
prize-essay had been refuted before it appeared by von Mohl,
Hofmeister and Tulasne. Schacht adhered all the more firmly
to Schleiden's theory ; after further controversy, in which other
writers of less authority took part, Radlkofer published in 1856
a complete review of the question, which fully confirmed Hof-
meister's observations, and gave incidentally an account of
Schleiden's views in the altered form which they had by that
time assumed ; this account showed in fact that Schleiden had
completely retracted his former opinions, and in this rctracta-

F f 2

436 History of the Sexual Theory. [Book hi.

tion Schacht was soon after compelled to follow him, having be-
come acquainted with facts observed in the ovule of Gladiolus,
which were obviously irreconcilable with Schleiden's theory.

Hofmeister had from the first directed special attention to
the questions, whether any bodies are found in the pollen-tube
which answer in any way to spermatozoids, and whether any
opening can be perceived at the end of the tube. He found
indeed forms in Coniferae in 1851, which reminded him of
the male organs of fertilisation in the higher Cryptogams ; but
the pollen-tube was closed both in them and in the rest of the
Phanerogams, in which moreover its outer coat attains to a
considerable thickness. There remained therefore only the
hypothesis, that a fluid substance passes through the walls of
the pollen-tube and of the embryo-sac and effects the fertilisa-
tion of the egg-cell ; thus it was not the theory of preformation
of the last century, to which Brongniart still adhered, but the
view represented by Koelreuter, which ultimately proved to be
nearer the truth, though it may be said that all that remained
of that view was, that the fertilising substance in the Phane-
rogams is a fluid. The granular contents of the pollen-grains,
which were supposed to be spermatozoids, have since been
partly found to be only innocent starch-grains and drops of oil.

8. Discovery of Sexuality in the Cryptogams.
1837-1860.

By the year 1845 "O o^^^ capable of forming a judgment on
the question any longer doubted the existence of different
sexes in Phanerogams. But it was not so with the Cryptogams,
though a number of facts were acknowledged at this time
which seemed to point to the conclusion, that a moment
arrives sooner or later in the course of their development also,
when a sexual act is accomplished. But the question had not
as yet been systematically studied; no experimental investi-
gations had been made, or observations of such a kind as to
demonstrate the necessity of sexual union.

Chap. I.] Sextiality in Cryptogams. 437

The great majority of botanists in the second half of the
1 8th century had no longer any doubt that the stamens were
organs of reproduction, and they were anxious to prove the
existence of similar organs in the Cryptogams ; they rested in
this matter on external resemblances and analogies, which they
interpreted in a more or less arbitrary manner. The obvious
external resemblance between the antheridia and archegonia in
Mosses and the sexual organs in the Phanerogams led Schmidel
and Hedwig to consider them to be stamens and ovaries, and
the conjecture was correct, though the true nature of the moss-
fruit had to be learnt in another way. Micheli, Linnaeus
and Dillen, trusting still more to external appearance and with
slight knowledge of these plants, had before this taken the
fruit for a male flower, and in the case of the rest of the
Cryptogams the best botanists were only feeling their way in
the dark with no certain experience to guide them. It is not
necessary to give a particular account of the views which
originated in this way ; one or two may be mentioned by way
of example. Koelreuter regarded the volva of Mushrooms,
Gleditsch and Hedwig certain tube-like cells in their lamellae,
as the male organs of fertilisation. Gleichen took the stomata,
Koelreuter the indusium, Hedwig even the glandular hairs of
Ferns for anthers. It was not yet suspected that the course of
development and the whole morphology of the Cryptogams
could not be so compared with that of the Phanerogams;
correct and incorrect assumptions with regard to the sexual
organs of the Cryptogams were alike devoid of scientific value,
being mere guesses and vague conjectures. Nor was the state
of things much better even in the first years of the 19th
century ; and if by that time a number of occasional obser-
vations had been made which could afterwards be turned to
scientific account, these were as yet only isolated facts without
scientific connection, and every one was at liberty to concede
or to refuse sexual organs to the Cryptogams generally at his
own discretion. Meanwhile observations gradually accumu-

438 History of the Sexual Theory. [Book hi.

lated, and towards 1845 it began to be possible by critical
examination of them to arrive at something like a clearer
understanding of this part of botany. The majority of
botanists readily accepted Schmidel's and Hedwig's opinion
with respect to the Mosses; Vaucher had as early as 1803
maintained that the long-known conjugation of Spirogyra was a
sexual act; Ehrenberg observed in 1820 the conjugation of a
Mould, Syzygites ; Bischoff and Mirbel explained the organ-
isation of the antheridia of the Liverworts in 1845, while Nees
von Esenbeck saw the spermatozoids of Sphagnum in 1822
and Bischoff those of Chara in 1828, though they were at first
taken for Infusoria, an opinion maintained by Unger as late as
1834. But it was Unger \ who in 1837, after careful study of
the spermatozoids of the Mosses in 1837, declared them to be
the male organs of fertilisation; in 1844 Nageli discovered
corresponding forms on the prothallium of Ferns, which had
till then been called a cotyledon, and in 1846 the spermatozoids
of Pilularia, the products of the small spores which Schleiden
had explained to be the pollen-grains of that plant.

These facts were of the highest importance, but little was to
be made of them as long as the female organ in the plants in
question, the Mosses excepted, was unknown, and meanwhile
it was only the resemblance between vegetable and animal
spermatozoids which led to the conjecture, that the one had
the same sexual significance as the other.

Light was suddenly thrown upon the subject, when Count
Lesczyc-Suminsky discovered in 1848 on the supposed cotyledon
(prothallium) of Ferns both the antheridia and the peculiar
organs, inside which the embryo or young fern is formed.
Though the statements respecting the structure and develop-
ment of these female organs and of the embryo were inaccurate
in some important points, yet the place was now indicated

^ The authorities for these statements are collected by Hofmeister in
•Flora,' 1857, p. 120, etc.

Chap. I.] Scxiiality in Cryptogams. 439

where it might be presumed that the fertilisation by the
spermatozoids takes place; and as the history of the germi-
nation of the rest of the vascular Cryptogams was to some
extent known through the earlier labours of Vaucher and
Bischoff, the organs of fructilication of these plants might now
be sought, where they are really to be found. But an erroneous
idea respecting the meaning of the small spores of the Rhizo-
carps propounded by Schleiden had first to be put out of the
way, and this was done by an appeal to the discovery of Nageli
mentioned above and by the investigations of Mettenius. Then
in 1849 Hofmeister supplied a connected description of the
germination of Pilularia and Salvinia, in which the decisive
points as regards the sexual act were clearly set forth, and the
connection of the spermatozoids with the fertilisation of the egg-
cells in the archegonium was established. He did the same
for Selaginella, which is very unlike the Rhizocarps and Ferns,
and in which the spermatozoids are developed from smaller
spores, and fertilise the egg-cells in archegonia formed in the pro-
thallium of the large spores. By comparing the processes of
germination in these plants with those of Ferns and Mosses,
he succeeded in throwing entirely new light on the whole of the
morphology of these classes of plants, and thus made it possible
for the first time to compare them with one another and with
the Phanerogams, and to form a right estimate of the sexual
act in the Muscineae and Vascular Cryptogams in its relation
to the history of the development of these plants. Hofmeister
arrived at the following conclusion from his observations in
1849: 'The prothallium in the vascular Cryptogams is the
morphological equivalent of the leaf-bearing Moss-plant, while
the leafy plant of a Fern, of a Lycopodium and a Rhizocarp
answers to the capsule of the Moss. In Mosses as in Ferns
there is an interruption of the vegetative development by
sexual procreation, an alternation of generations ; this takes
place in the Vascular Cryptogams very soon after germination,
in the Mosses much later,' The vast importance of this dis-

440 History of the Sexual Theory. [Book hi.

covery to systematic botany has been already noticed. The
conception of these relations developed by Hofmeister was not
less important to the doctrine of the sexuality of plants ; it
swept away at one stroke all the old false analogies between
Phanerogams and Cryptogams and brought to light the real
agreement ; Hofmeister had detected in the archegonium of
the Cryptogams the body which is developed there, as in the
ovule of the Phanerogams, into an embryo after fertilisation,
namely the germinal vesicle or egg-cell. Here was the point of
departure for all further systematic comparison in the sexual
propagation of Cryptogams and Phanerogams. All beside was
of secondary importance, even the fact, that the fertilisation
of the egg-cell in the Cryptogams is not effected by a pollen-
tube, but by spermatozoids. It was now easy to show the
corresponding relations of generation in the other cases which
Hofmeister had not yet observed.

Hofmeister's statements and conclusions respecting Sela-
ginella and Isoetes were confirmed and some additions made
to them by Mettenius in 1850, and in 1851 appeared Hof-
meister's exhaustive work ' Vergleichende Untersuchungen,'
in which the mode of production of the embryo in Coniferae
was represented as an intermediate form between those of
Phanerogams and Cryptogams. Further contributions were
made to the knowledge of the subject; Henfrey confirmed
Hofmeister's results in the case of Ferns ; Hofmeister him-
self and Milde observed in 1852 the history of fertilisation
in Equisetaceae, and the former supplied at the same time a
more complete account of the development of Isoetes; in 1855
he described the decisive points in Botrychium and Mettenius
in 1856 those in Ophioglossum.

The processes of development before and after fertilisation
were now cleared up by all these discoveries, but the direct
observation of the act of fertilisation was still wanting.
Hofmeister ('Flora,' 1857, p. 122) describes the state of affairs
in the following terms : ' While numerous investigations had

Chap. I.] Scxiialtty in Cryptogams. 441

thrown a clear light on the character of the male and female
organs, and on the way in which the embryo is formed by
repeated division of the egg-cell present before fertilisation, we
continued quite in the dark respecting the particular nature
of the fertilisation. Observation and experiment had estab-
lished the fact, that the influence of the spermatozoids on the
archegonia was required to produce an embryo in the latter.
Female moss-plants' separated from the male, macrospores in
the Vascular Cryptogams separated from the microspores, had
in all cases proved unproductive ; but it was not even certainly
known to what point in the female organ the spermatozoids
force their way. It is true that Lesczyc and after him
Mercklin had seen the entry of moving spermatozoids into
the mouth of archegonia in Ferns ; but Lesczyc's account of
the part which he supposed them to play there afterwards, was
proved to be an illusion. I had myself observed motionless
spermatozoids halfway down the neck of archegonia of an
Equisetum ; but nothing was to be learnt of the manner in
which the spermatozoid affects the egg-cell. Then it happened
that in the spring of 185 1, being engaged in observing the
development of the organs of vegetation of Ferns, I repeatedly
saw spermatozoids moving about in the basilar cells which en-
close the egg-cell in the archegonia of Ferns, and the majority of
them even playing about the egg-cell. Their movements were
put an end to during the observation by the commencement of
changes, which the contents of young vegetable cells which
have been cut open usually experience under the prolonged
influence of water.' Later observations leave no doubt now
that in the Muscineae and Ferns single spermatozoids force
their way into the naked egg-cell of the archegonium.

* W. P. Schimper, in his ' Recherches anatomiques et morphologiques
sur les Mousses' of 1850, had made some important statements respecting
the sterility of female moss-plants growing at a distance from male speci-
mens, and proved that the presence of male plants among females that are
otherwise barren renders them fruitful.

442 History of the Sexual Theory. [Book hi.

The question was first set at rest in the Algae, where the pro-
cess of fertiUsation could be seen directly and without exposing
the objects to destructive influences. That sexual propaga-
tion occurs in the Algae also had seemed probable, since
Decaisne and Thuret in 1845 discovered organs in species
of Fucus, and Nageli in 1846 in Florideae, which scarcely
admitted of any other explanation. Alexander Braun also had
called attention to the formation of two kinds of spores in a
large number of freshwater Algae. But as yet there was only
conjecture. Then Thuret proved by experiment in 1854, that
in the genus Fucus the large egg-cells must be fertilised by very
small swarming spermatozoids, in order to set up germination ;
both organs can be collected separately and in numbers in this
genus, and be brought together at pleasure ; Thuret even
succeeded in obtaining hybrids. Pringsheim first observed in
1855 the formation of spermatozoids in the little horns of
Vaucheria and established the fact that spores capable of germ-
ination are not formed unless the spermatozoids approach the
egg-cell. To Thuret's statements he added the very important
one, that the remains of spermatozoids may be recognised on the
surface of the contents of the fertilised egg-cell of Fucus, which
is already surrounded by a membrane. About the same time
Cohn published his observations on Sphaeroplea annulina,
which confirmed the fact of the approach of the spermatozoids
to the egg-cells, which consequently, as in Fucus and Vau-
cheria, form a cell-wall and are rendered capable of further
development.

Still the decisive observation had not yet been made; no
one had yet seen how the two fertilising elements behaved at
the moment of fertilisation. Pringsheim had the good fortune
to make this observation in one of the commonest of fresh
water Algae, Oedogonium. There he saw the moving sperma-
tozoid first come into contact with the protoplasmatic substance
of the egg-cell, and then force its way into it, blend with it
and dissolve. And thus the first observation was made, which

Chap. I.] Scxuality in Cryptogams. 443

proved decisively that a real intermixture takes place of the
male and female elements of fertilisation ; this important fact
was confirmed by De Bary in the same year.

Now that it was once established, that fertilisation in
Cryptogams consists in the blending together of two naked
bodies of protoplasm, the spermatozoid and the egg-cell, it
was reasonable to conclude that conjugation in Spirogyra and
generally in Conjugatae, was an act of fertilisation, only in this
case the two fertilisation-elements are not of different size
and shape, but similar in appearance. To this conclusion De
Bary arrived in 1858 in his monograph of the Conjugatae.
This extension of the idea of fertilisation to cases in which the
uniting cells are to outward appearance alike, was of special
value to the theory of sexuality, as was seen in the sequel,
when other forms of fertilisation were observed which made it
necessary still further to extend the idea of sexuality. In 1858
Pringsheim discovered arrangements for fertilisation in another
group of Algae, the Saprolegnieae, which to outward appearance
at least departed widely from those hitherto known in the
lower plants.

Thus between the years 1850 and i860 a number of funda-
mental facts were discovered, and were afterwards confirmed
and extended by fresh observations in the course of the follow-
ing years. It does not fall within the limits of this work to
notice the many discoveries that were made in this part of
botanical science after i860 ; we will only remark, that between
i860 and 1870 the processes of fructification were observed
by Thuret and Bornet in Florideae, and especially by De
Bary and his pupils in Fungi, in some of which very peculiar
forms were brought to light. No doubt any longer exists that
difference of sex prevails generally in the Thallophytes also,
though it is still an open question, whether it may not be
wanting in some of the very simplest and smallest kinds.

One of the most important results of these investigations
is obviously the striking resemblance between many of

444 History of the Sexual Theory.

the processes of fertilisation in Cryptogams and in the lower
animals ; here is another confirmation of the fact, often
brought out in other ways by modern zoological and botanical
research, that the points of resemblance in the vegetable and
animal kingdoms appear most plainly, if we compare together
the simplest forms to be found in both ; we have in this fact a
plain proof also, that both kingdoms have been developed from
like common elements, as the theory of descent implies. With
respect to the true nature of fertilisation itself, which is evidently
a similar process in the main in animals and plants, we can
only say at present, that it amounts in all cases to a material
blending together of the contents of two cells, neither of which
is capable of further development by itself, while the product
of the combination is not only capable of such development,
but unites in itself the characteristics of the two parent forms
and transmits them to its descendants. That fertilisation is
not the intimate union of two bodies possessing a definite
form, but that the male fertilising substance at least may be a
simple fluid, appears to be distinctly shown by the process in
Phanerogams ; and we may assume, that in Cryptogams also,
the sexual act is not affected by the form of the fertilisation-
elements, though a certain shape and power of movement is
necessary for the conveyance of the fertilising substance to that
which is to be fertilised.

CHAPTER II.

History of the Theory of the Nutrition of Plants.
1583-1860.

That plants take up certain substances from their environ-
ment for the purpose of building up their own structures
could not be a matter of doubt even in the earliest times ; it
was also obvious, that movements of the nutrient material must
be connected with this proceeding. But it was not so easy to
say, what was the nature of this food of plants, in what manner
it finds its way into and is distributed in them, and what are
the forces employed ; it was even for a long time undecided,
whether the food taken up from without suffers any change
inside the plant, before it is applied to purposes of growth.
Such were the questions which had engaged the attention of
Aristotle, and which formed the chief subject of Cesalpino's
physiological meditations.

But the questions respecting the nutrition of plants acquired
a much more definite shape in the latter half of the 17th
century, when the various phenomena of vegetation began to
be more closely observed, and some attempt was made to
understand their relations to the outer world. Malpighi, the
founder of phytotomy, was the first who undertook to explain
the share which belongs to the different organs of the plant in
the whole work of nutrition ; guided by analogy, he perceived
that the green leaves are the organs which prepare the food,
and that the material so prepared by them passes into all parts
of the plant, there to be stored up or employed for purposes

446 History of the Theory of [Book hi.

of growth. But this gave no insight into the nature of the
substances from which plants prepare their food. On this
point Mariotte endeavoured to give such information as could
be obtained from the chemistry of his day; and he has the
merit of having shown, in opposition to the old Aristotelian
notion, that plants convert the food-material which they derive
from the ground into new chemical combinations, while the
earth and the water supply the same elements of nutrition to
the most different kinds of plants. It could not escape the
notice of physiologists even of that time, that the water which
plants take up from the ground introduces into them but very
small quantities of matter in solution. Van Helmont in the
first half of the 17th century had shown this by an experiment,
the results of which, however, led him to think that plants
were able to produce both the combustible and incombustible
parts of their substance from water. Hales at the beginning
of the 1 8th century formed a different opinion, being led by
the evolution of the gases in the dry distillation of plants to
conclude, that a considerable part of their substance was
absorbed in a gaseous form from the atmosphere.

The views propounded by Malpighi, Mariotte, and Hales
contained the most important elements of a theory of the
nutrition of plants ; fully understood they would have taught
that one part of the food of plants comes from the earth and
the water, and another part from the air; that the leaves
change the materials thus obtained in such a manner as to
produce from them the substance of plants and to apply this
to the purposes of growth ; but the ideas were not combined
in this way, for during some years after their time botanists
were chiefly engaged in observations on the movement of the
sap in plants, and they arrived even on this point at very
obscure and even contradictory results, because they overlooked
the function of the leaves which had already been recognised
by Malpighi. All insight not only into the chemical processes
in the nutrition of plants, but also into the mechanical laws of

Chap. II.] the Nutrition of Plants. 447

the movement of the sap, and generally into the whole internal
economy of plants, depends on a knowledge of the fact, that it
is only the cells which contain chlorophyll, and therefore in
the higher plants the leaves chiefly as consisting largely of
such cells, which have the power of converting the gaseous
food supplied by the atmosphere into the substance of the
plant with the aid of the materials taken up from the soil.
This fact is of fundamental importance to the whole theory of
the nutrition of plants ; it is only by a knowledge of it that we
can explain the movement of material connected with nutrition
and growth, the dependence of vegetation on light, and to a
great extent also the function of the roots.

But this principle could not be discovered till the new
chemical system founded by Lavoisier took the place of the
old phlogistic chemistry, and it is remarkable that the dis-
coveries, which laid the foundation of modern chemistry in the
period between 1760 and 1780, contributed essentially to the
establishment at the same time of the modern doctrine of the
nutrition of plants. Ingen-Houss, in reliance on Lavoisier's
antiphlogistic views on the composition of air, water, and the
mineral acids, succeeded in proving that all parts of plants are
continually absorbing oxygen and forming carbon dioxide, but
that the green organs at the same time under the influence of
light absorb carbon dioxide and exhale oxygen ; and as early
as 1796 he considered it probable that plants obtain the whole
mass of their carbon from the carbon dioxide of the atmosphere.
Soon after (1804) de Saussure proved, that plants, while they
decompose carbon dioxide, increase in weight by a greater
amount than that of the carbon which they retain, and that
this is to be explained by the fact that they at the same time
fix the elements of water. He likewise showed that the small
quantities of saline compounds, which plants take up from the
soil, are a necessary part of their food, and that it was at least
probable, that the nitrogen of the atmosphere does not contribute
to the formation of nitrogenous substances in plants. Senebier

448 History of the Theory of [Book hi.

had before insisted on the fact, that the decomposition of
carbon dioxide under the influence of Hght only takes place in
green organs.

Thus the most important points in the nutrition of plants
were discovered by Ingen-Houss, Senebier and de Saussure.
But, as often happens in the case of discoveries of such
magnitude, their ideas were for a long time exposed to great
misunderstanding. They were better appreciated in France
than in any other country ; Dutrochet and De CandoUe were
able to see the importance of the interchange of gases in the
green organs to the general nutrition and respiration; but
others, and especially German botanists, were not content with
these simple chemical processes as the foundation of the whole
system of nutrition and consequently of the whole life of the
plant ; the theory of the vital force, which was elaborated in con-
nection with the nature-philosophy during the first years of the
19th century, and was generally accepted by philosophers and
physiologists, chemists and physicists, preferred to supply the
plant with a mysterious substance for its food, which had its
source in the life itself and which it called humus. The most
obvious considerations, which must at once have shown that
this humus-theory was absurd, were entirely overlooked ; and
thus in the face of de Saussure's results the food of plants was
once more referred entirely to the soil and the roots, as it was
in the earliest times ; one of the consequences of this humus-
theory in combination with the vital force was that the ash-
constituents of plants were supposed to be merely accidental
admixtures or stimulants, or to be directly produced in the
plant by the vital force.

In the period between 1820 and 1840 the reaction set in
from different quarters against the theory of vital force;
chemists succeeded in producing by artificial means certain
organic compounds, which had hitherto been regarded as
products of that force ; Dutrochet discovered in endosmose a
process, which served to refer various vital phenomena in

Chap. II.] the Nutrition of Plants. 449

plants to physico-mechanical principles ; de Saussure and others
showed that the heat of plants is a product of respiration, and
by 1840 the earlier theory of a vital force might be looked
upon as antiquated and obsolete. It remained to restore to
their rights the observations of Ingen-Houss and de Saussure,
which under the influence of that theory and of the notions
respecting the humus had been so utterly misconstrued.
Liebig set aside the humus-theory in 1840, and referred the
carbon of plants entirely to the carbon dioxide of the atmosphere,
and their nitrogenous contents to ammonia and its derivatives ;
he claimed the components of the ash as essential factors in
the nutrition, and taking his stand on the general laws of
chemistry endeavoured to obtain chiefly by the method of
deduction an insight into the chemical processes of assimilation
and metabolism. The whole theoretical value of the facts
discovered by Ingen-Houss, Senebier and de Saussure was
first made apparent by the connection which Liebig succeeded
in establishing between the phenomena of nutrition. The
doctrine of nutrition burst suddenly into new life ; firm
ground was gained, and the botanist, no longer distracted by
the difficulties raised by the vital force but resting on physical
and chemical principles, might now resume the task of in-
vestigation. Oxygen-respiration denied by Liebig was first
of all re-established by von Mohl and others. Liebig's views
on the source of nitrogen in plants and on the importance of
the ash-constituents rested chiefly on general considerations
and observations and on calculation, and had now to be tested
by systematic investigation and especially by experiments on
vegetation in individual plants. And here the place of honour
must be assigned to Boussingault, who pursued the path of
pure induction as contrasted with Liebig's deductive mode of
proceeding, gradually improved the methods for experimenting
on vegetation, and soon succeeded in so producing plants in a
purely mineral soil free from all humus, that he finally settled
the question of the derivation of the carbon from the atmosphere

Gg

45o Theory of the Nutrition [Book hi.

and of the source of the nitrogen also. He showed from the
plants thus artificially nourished, and with due consideration
of the many sources of error which beset the question, that the
uncombined nitrogen of the atmosphere does not contribute to
the nutrition of plants, but that a normal increase in the
nitrogenous substances in a plant takes place when the roots
take up nitrates as well as the necessary constituents of the ash.
With the exception of some doubts which still remained
respecting the necessity of certain constituents of the ash,
such as sodium, chlorine and silicic acid, the source of the
materials which take a part in the chemistry of the nutrition of
plants was known before i860; but the knowledge obtained
with regard to processes in the interior of the plant, the
origination of organic substances in the processes of assimila-
tion, and the further changes which they undergo was still
fragmentary and uncertain, and led to no general and conclusive
results.

I. Cesalpino.

Aristotle had sought to determine the nature of the
materials which plants take up as food, and had laid down the
proposition, that the food of all organisms is not simple but
composed of various substances. This view was correct, but
he united with it the erroneous notion, that the food of plants
is elaborated beforehand in the earth, as in a stomach, and is
made applicable to purposes of growth, so as to exclude the
necessity of any separation of excrements in the plant ; this
error was refuted by Jung, as we shall see, but nevertheless
it continued to hve as late as into the i8th century, and
ultimately quite spoilt Du Hamel's theory of nutrition.

Cesalpino, whom we have learnt to regard as a faithful and
gifted disciple of Aristotle, directed his speculations to the
mechanical rather than to the chemical side of the question,
and chiefly tried to explain the movement of the nutrient sap
in plants. He had a larger stock of material drawn from

Chap. II.] of Plants. Cesalpino. 45 1

experience at his disposition than his master, and it is instruc-
tive therefore to make a nearer acquaintance with his views,
because they show how far the old philosophy was in a con-
dition to turn better empirical knowledge than Aristotle
possessed to a satisfactory use; they will also show that
Cesalpino's first essays led him to views which can no longer
be said to be strictly Aristotelian.

In the second chapter of the first book of the work from which
we have already quoted, 'De plantis libri XVI,' 1583, he raises the
question, in what way the food of plants is taken in and their
nutrition accomplished. In animals we see the food conveyed
from the veins to the heart, which is the laboratory of the warmth
of the body, and after it has been finally perfected there,
spread abroad through the arteries into all parts of the
body ; and this is effected by the operation of the force
(spiritus) which is generated in the heart from the food. In
plants on the contrary we see no veins, or other channels, nor
do we feel any warmth in them, so that it is difficult to under-
stand how trees grow to so great a size, since they seem to
have much less natural heat than animals. Cesalpino explains
this enigma by saying, that animals require much food for
maintaining the activity of the senses and the movements of
their organs. The larger quantity of animal food also requires
larger receptacles, namely the veins. Plants on the other
hand need less food, because this is only used for purposes of
nutrition, or to a very small extent for the production of
internal heat as well, and therefore they grow more vigorously
and bear more fruit than animals. At the same time plants
are not without internal heat, though it cannot be perceived
by the touch because all objects seem cold to us, which are
less warm than our organ of feeling. That plants moreover
have veins, though only narrow ones in accordance with the
small mass of their food, is shown by those which yield a
milky juice, such as Euphorbia and Ficus, which when cut
bleed hke the flesh of animals ; Cesalpino adds ' and this is

Gg 2

453 Theory of the Nutrition [Book hi.

very frequent also in the vine,' which shows that he made no
distinction between milky juice and the exuding water of the
weeping vine-stock. These narrow veins cannot be seen on
account of their fineness ; but in every stem and in every root
things may be discerned which like nerves in animals can be
split longitudinally and are called the nerves of the plant, or
also certain thicker things, such as those which branch in
most leaves and are there called veins. These should be
considered as food-passages and as answering to the veins
in animals ; but plants have no main vein like the vena
cava in animals, but many fine veins pass from the root to
the heart of the plant (cor, root-neck, see above, Book I.
chap. 2), and ascend from it into the stem ; for it was not
necessary that the food should be collected in a common
receptacle in plants, as it is in the heart in animals, where this
is necessary for the production of the spiritus, but it was
sufficient that the fluid in plants should be changed by contact
with the medulla cordis (in the root-neck), as it is changed
in animals in the marrow of the brain or in the liver ; and in
these organs the veins are very narrow, as they are in plants.

Since plants have no sense-perception, they cannot seek
their food like animals, but they draw up the moisture from
the ground into themselves in a way of their own ; but it is
not easy to see how this takes place. Cesalpino, in trying to
explain this, gives us a glimpse into the physics of the day,
and we observe also to our surprise an attempt made to
explain phenomena in living creatures by physical laws, a step
beyond the limits of Aristotelian modes of thought and in the
right direction. It is not the ratio similitudinis, which draws
iron to the magnet, that can cause the attraction of the juice
by the roots, for then the smaller would be drawn to the
larger ; and if the attraction of the fluid of the earth by the
roots were the same thing as the attraction of the iron by the
magnet, the moisture of the earth would draw out the juice
from the plant, which is just what does not happen. Nor can

Chap. II.] of Plants. Ccsalpino. 453

it be the ratio vacui ; for since not moisture only but air also
is contained in the earth, the plant would be filled not with
juice but with air. But Cesalpino hits upon a third kind of
cause by which juices may be drawn into the plant. Do not
many dry things, he says, in accordance with their nature
attract moisture, as linen, sponge and powder, while others
repel it, as the feathers of many birds and the herb Adiantum,
which are not wetted even when dipped in water; but the
former absorb much water, because they have more in com-
mon with it than with air ; of this kind Cesalpino thinks those
parts of plants must be, which the nourishing soul employs to
take in food. Therefore these organs are not traversed by a
continuous canal such as the veins in animals, but formed like
the nerves of a fibrous substance ; and thus the power of
suction (bibula natura) conveys the moisture continually to
the place, where the principle of internal heat is placed, just as
may be seen in the flame of a lantern, to which the wick
continually conducts the oil. The absorption of the moisture
is also increased by the outer warmth, for which reason plants
grow more vigorously in spring and summer.

That Cesalpino had no suspicion of the use of the leaves in
the nutrition of plants appears incontestably from his repeat-
ing the Aristotelian idea, that the leaves are only for the
protection of young shoots and fruits from air and sun-light ;
this idea is no result of speculation, but came simply from
observing a vineyard in a hot country.

2. First inductive experiments and opening of new

POINTS OF view in THE HiSTORY OF THE THEORY OF

THE Nutrition of Plants.

All that Aristotle and his school, Cesalpino not excepted, are
able to tell us about the phenomena of vegetable life, was the
result of the most every-day observations, none of which were
critically and exactly tested to ascertain their actual correctness,

454 Theory of the Nutrition [Book hi.

while the larger part of their physiological axioms were not
derived from observations on plants at all, but from philosophi-
cal principles, and especially from analogies taken from the
animal world.

The first step towards a scientific treatment of the doctrine
of nutrition was an enlargement and critical examination of the
materials to be gained from experience ; nor were any difficult
observations or experiments needed to discover contradictions
between the truths of nature and the old philosophy ; all that
was necessary was to look into things more closely and to judge
of them with less prejudice.

In this way Jung was led to oppose one important point
of the Aristotelian account of nutrition. In the second frag-
ment of his work ' De plantis doxoscopiae physicae minores '
is to be found a remark, which is evidently directed against
the notion that plants receive their food already elaborated
from the earth, and therefore give off no excrements ^ Plants,
says Jung in accord with Aristotle, appear not to need a
thinking soul (anima intelligente), which would be able to
distinguish wholesome from unwholesome food, and Aristotle
therefore provided them with food which had already been
perfectly prepared in the earth. But Jung takes another
view founded on actual observation. It is very possible, he
says, that the openings in the roots which take in liquid matter
are so organised, that they do not allow every kind of juice to
enter, and who can say that plants have the peculiarity of only
absorbing what is useful to them, for like all other living crea-
tures they have their excreta, which are exhaled through the
leaves, flowers, and fruits. But among these he reckons the
resins and other exuding liquids, and says that it is possible
after all that a large part of the juices of plants escapes by
imperceptible evaporation, as happens in animals.

' See the Fragments of Aristotelian phytology in Meyer's ' Geschichte der
Botanik,' 1. p. 120.

Chap. II.] of Plants. Van Helmont. 455

According to Aristotle's view the plant itself was quite pas-
sive in the work of nutrition ; since food was offered to it which
had been already prepared for it in the earth, growth was to
some extent merely a process of crystallisation unaccompanied
by chemical change. In pointing to the formation of excreta
Jung on the contrary ascribed a chemical activity to the plant,
And by supposing that the organisation of the root was such
as to prevent the entrance of certain matters and to favour that
of others, he made the plant co-operate in its own nourish-
ment, though he did not assume that it needed a thinking soul
for this purpose.

Johann Baptist van Helmont', physician and chemist, and a
contemporary of Jung, took up a position still more decidedly
opposed to Aristotelian doctrines. He rejected the four
elements of that philosophy, and regarding water as a chief
constituent of all things he considered that the whole substance
of plants, the mineral parts (the ash) as well as the combustible,
was formed from water. Thus while Aristotle made the com-
ponent parts of plants be introduced into them by water in a
state ready for use, Van Helmont, on the contrary, ascribed to
the plant the power of producing all kinds of material from
water. It would scarcely have been necessary to mention this
resistance to old dogmas, originating as it did in the notions of
the alchemists, if Van Helmont had not made an attempt to
establish his views by experiment ; this was the first experiment
in vegetation undertaken for a scientific purpose of which we
have any information, and it was repeatedly quoted by many
later physiologists, and employed in support of their theories.
He placed in a pot a certain quantity of earth, which when
highly dried weighed two hundred pounds; a willow-branch

1 J. B. van Helmont was born at Brussels in 1577, and died at Villvorde
near Brussels in 1644. He was a leading representative of the chemistry of
his day. Kopp, in his ' Geschichte der Chemie,' 1S43, i. p. 117, lias given
a full account of his life and labours.

45^ Theory of the Nutrition [Book hi.

weighing five pounds was set in this pot, which was protected
by a cover from dust, and daily watered with rain-water. In
five years' time the willow had grown to be large and strong,
and had increased in weight by a hundred and sixty-four pounds,
though the earth in the pot, when once more dried, only showed
a loss of two ounces. Van Helmont concluded from this
experiment that the considerable increase of weight in the plant
had been gained entirely at the cost of the water, and conse-
quently that all the materials in the plant, though distinct from
water, nevertheless come from it.

These objections to Aristotelian teaching on the part of
Jung and Van Helmont remained isolated and unproductive.
But an incentive to new investigations in vegetable physiology
was supplied from a different quarter, and its influence lasted
till far into the i8th century. This was the suggestion, that
not only does a nutrient sap taken up by the roots ascend to
the leaves and fruits of plants, but that there is also a move-
ment of the same sap in the opposite direction in the rind.
But this idea assumed from the first two different forms. Some
botanists, evidently resting on the analogy of the circulation of
the blood in animals, supposed that there was also an actual
circulation of the sap in plants ; others on the contrary were
content with supposing that while the watery sap absorbed by
the roots rises in the wood, an elaborated sap capable of
ministering to growth moves in the rind, the laticiferous vessels,
and the resin-ducts. The two views were at a later time
repeatedly confounded together, and those who refuted the
first believed that they had refuted the other also. It appears
that a physician from Breslau, Johann Daniel Major \ Pro-

^ J. D. Major, who was bom at Breslau in 1639, ^'^^ ^^^^ ^^ Stockholm
in 1693, is quoted by Christian Wolff, as well as by Reichel (' De vasis
plantarum.' 1758, p. 4) and others, as the founder of the theory of circula-
tion, which he propounded in 1665 in his ' Dissertatio Botanica de planta
monstrosa Gottorpiensi,' etc. Kurt Sprengel (' Geschichte der Botanik, ii.
p. 7) classes him also among tlie defenders of the doctrine of palingenesia, a

Chap. II.] of Plauts. Majov, Malpigki. 457

fessor in Kiel, first gave expression to the opinion, that there is a
circulation of the nourishing substance in plants as in animals ;
and from this time to the end of the i8th century the circula-
tion of the juices of plants was a favourite subject of discussion,
but more often chosen by the impugners of the doctrine than
by its defenders.

The better form of the idea, namely, that there is a return-
movement of material towards the root, combined with the view,
that the leaves are the organs which produce the substances re-
quired for growth from the crude material supplied to them, was
expressed by Malpighi as early as 1 7 7 1 in the shape of a well-
considered theory. In his 'Anatomes plantarum idea ' of that
year he devotes the last pages to a short account of the theory
of nutrition, as he understood it. He regarded the fibrous
constituents of the wood as the organs for conducting the sap
taken up by the roots, and the vessels as air-passages, which he
named tracheae on account of their resemblance to the tracheae
of insects. He was in doubt whether the air came from the earth
through the roots, or from the atmosphere through the leaves, for
he had never succeeded in finding openings for the entrance of
air in the roots or the leaves ; but he thought it more probable
that the air is absorbed by the roots, because they are well
supplied with tracheae, and air has besides a tendency to ascend.
Beside these fluid-conducting fibres and air-conducting tracheae
in the wood he called attention to the existence of special
vessels, which conduct peculiar juices in many plants, as the
laticiferous vessels, gum-passages, and turpentine-canals.

Respecting the movement of the juices, he notices that the
direction may be reversed, because shoots planted upside down
send out roots into the earth from what is organically their
upper end, and grow into trees ; and though they do not grow
vigorously, yet the experiment proves that the movement of
the sap in them is in the reverse direction.

superstitious belief in the reproduction of plants and animals from their
ashes, which was used to prove the resurrection of the dead.

458 Theory of the Nutrition [Book hi.

After these preliminary remarks he proceeds to prove, that
it is in the leaves that the crude juices of nutrition undergo the
change which fits them for the maintenance of growth. The
way in which Malpighi arrives at this view is as simple as it is
original. He considers the cotyledons of young plants to be
genuine leaves (in leguminibus seminaHs caro, quae folium est
conglobatum), as is shown in the gourd, where the cotyledons
grow into large green leaves. Liquid is conveyed to them
through the radicle, and a portion of the substances which they
contain passes from them into the plumule to make it grow,
which it will not do if the cotyledons are removed ; hence he
concludes that all other leaves also are intended to elaborate
(excoquere) the nutritive juice contained in their cells, which
the woody fibres have conveyed to them. The liquids mingled
together in their long passage through the network of fibres are
changed in the leaves by the power of the sun's rays, and
blended with the sap before contained in their cells, and thus
a new combination of the constituent parts is effected, trans-
piration proceeding at the same time ; he compares the whole
process with that which goes on in the blood of animals.

We see that Malpighi's view of the function of the leaves in
nutrition approaches very closely to the truth, as closely indeed
as was at all possible in the existing condition of chemical
knowledge. He w^as induced by the results of anatomical
investigation to carry this view farther and indeed correctly ;
he supposed that the parenchymatous tissue of the rind acts in
the same way as the leaves ; but he went a step too far in
assigning the function of the leaves to the colourless parenchy-
ma also, which only serves for the storing up of assimilated
matter. He says we must ascribe a character similar to that of
the leaf-cells to the corresponding cells in the rind and to those
also which lie transversely in the wood (the medullary and
cortical rays), and that it is not unreasonable to conclude that
the food of the plant is elaborated and stored up in these cells.
As he makes no sharp distinction between elaboration and

Chap. II.] of Plants. Malpighi. 459

mere storing up, he ascribes the function of the leaves to the
parenchyma of fleshy fruits also and to the scales of bulbs ; he
concludes from the exudations from stumps of trees and from
the cut surfaces of other parts of plants, that they are filled with
reserve-matter (asservato humore turgent).

Thus the essential points in Malpighi's theory of nutrition in
the year 1671 were, that the vessels of the wood are primarily
air-conducting organs, that the leaves elaborate the crude sap
for purposes of growth, that the sap so elaborated is stored up
in different parts of the plant, and that the fibrous elements of
the wood convey upwards to the leaves the crude materials of
nutrition which are absorbed by the roots. No mention is
made of a circulation of juices, comparable to the circulation of
the blood, though this idea was in later times often imputed to
him ; and we find by his later remarks, that while he was in no
doubt as to the elementary organs which convey the ascending
sap, he confined himself to conjecture with respect to the way by
which the sap elaborated in the cell-tissue of the leaves, rind and
parenchyma generally is carried on its further course. But he
was in no doubt about the direction of that course ; he believed
that this sap forces itself downwards through the stem into the
roots, and upwards in the branches above the leaves and so
into the fruit. Thus Malpighi had formed a more correct idea
of the movement of assimilated matter than the majority of his
successors who introduced the verj' unsuitable expression,
' descending sap.' He further thought it probable that the
elaborated sap passes through the bast-bundles^ but without a
continuous flux and reflux (absque perenni et considerabili
fluxu et refluxu) ; that it rests to some extent in the laticiferous
vessels, but that it is also driven sometimes, when occasion
requires, by transpiration and external causes into the higher

1 He says, ' in mediis vasculis reticularibus,' which when taken in con-
nection with his general histology, must be understood to mean the bast-
bundles.

460 Theory of the Nutrition [Book hi.

parts of the plant, where it is the means of maintaining growth
and nutrition. These later remarks also are better than much
that was said about the movement of the sap in the i8th and
even in the 19th century, and at all events they prove that to
speak of Malpighi as a defender of the circulation of the sap in
Major's sense, as was often done in later times, was an entire
misunderstanding of his views.

Malpighi published his theory in a brief and connected form
in 1671 ; it appeared again further worked out in detail in the
fuller edition of the Phytotomy in 1674 ; he attributed a special
value to his discovery, that plants require air to breathe as
much as animals, and that the vessels of the wood answer in
function to the tracheae in insects and to the lungs in other
animals ; he recurs also several times to the importance of
leaves as organs for the elaboration of the food.

If we compare Malpighi's theory of the nutrition of plants
with the views of his predecessors, we cannot help seeing, that
it was an entirely new creation, in which Aristotelian doctrines
had no share. If his successors had apprehended the impor-
tant and essential points in his doctrine and had striven by
experimenting on living plants to support and illustrate them
by new facts, we should have been spared many erroneous
notions which established themselves in the theory, and made
it a perfect chaos of misconceptions. That particular miscon-
ception, which we have already mentioned more than once,
namely, that Malpighi, like Major and Perrault after him,
assumed a continuous circulation of the juices of the plant,
necessarily involved an incorrect idea of the function of the
leaves ; that function was by many later writers either quite
neglected, or sought for chiefly in transpiration, the chemical
activity of the leaves being quite overlooked.

Malpighi's theory can hardly be said to take into considera-
tion the chemical nature of the food of plants ; it is chiefly
occupied with the relation of the organs to the main points in
the nutritive process ; its foundations are for the most part

Chap. II.] ofPlmtts. MaHotte. 461

laid in the anatomy of the plant. Grew, who in all essential
points adopted Malpighi's views, but without doing much to
advance them by his lengthy discussions on particular ques-
tions, made some attempt to extend the knowledge of the
chemistry of the subject; but his notions were entirely
borrowed from the corpuscular theory of Descartes, and
he may be said to have constructed his own chemical pro-
cesses ; the consequence was that he usually overlooked the
points that were of fundamental importance, and brought
nothing to light that could assist the further development of
the theory of nutrition. But there is another writer, whose
name is in the present day known to few in the history of
vegetable physiology, but whose ideas on the chemistry of
plants are of great interest. This writer is Mariotte\ the
discoverer of the well-known law of gases, one of the greatest
physicists of the latter half of the 17th century, who also
enriched the physiology of the human body with some
valuable discoveries. We have a tolerably copious treatise
of Mariotte's in the form of a letter to a M. Lantin in the
year 1679, to be found in the ' CEuvres de Mariotte,' Leyden,
1717, under the title, 'Sur le sujet des plantes.' It is highly
instructive to gather from this letter the ideas of one of the
most famous and ablest of the natural philosophers of that day
on chemical processes and conditions in the nutrition of plants,
a few years after the appearance of Malpighi's great work and
about the time that Grew's Phytotomy was being published.
It is to be expected that Mariotte should give but an incidental
and superficial attention to the more delicate structure of

* The date of the birth of Edme Mariotte is not known. He was a
native of Burgund)', and lived in Dijon at the time of his earliest scientific
labours. He was an ecclesiastic and became Prior of St. Martin sous
Beaune near Dijon ; he was a Member of the Academy of Sciences in Paris
from its foundation in 1666, and was one of the first PVenchmen who
experimented in physics and applied mathematics to them. He died in
Paris in 1684 (' Biographic Universelle ').

462 Theory of the Nutrition [Book hi.

plants ; but we are compensated for this by his making us
acquainted with everything fundamentally important and new
which could at that time be said on the chemistry of the food
of plants. Speaking of the ' elements ' or ' principles ' of plants,
Mariotte propounds three hypotheses. The first is, that there
are many immediate principles (principes grossiers et visibles,
evidently what we should call proximate constituents) in plants,
such as water, sulphur or oil, common salt, nitre, volatile salt or
ammonia, certain earths, etc. ; and that each of these immediate
constituents is a compound of three or four more simple prin-
ciples, which have united together into one body ; nitre for in-
stance has its ' phlegma ' or tasteless water, its ' spiritus,' its fixed
salt, and other things ; common salt in the same way has the
like constituents, and it may be assumed with much probability,
that these more simple principles also are compounds of parts
that differ among themselves, but are too small to be distin-
guished by any artificial means as to figure or any other
characters. Having shown how certain principles unite together,
he goes on to say, that he is unwilling to ascribe to them any
sort of consciousness (connaissance) by which they seek to
unite together ; but he thinks that they are endowed with
a natural disposition to move towards one another, and to
unite closely as soon as they touch one another ; though it is
very difficult to define the nature of this disposition, it is enough
to know that there are many instances of such movements to
be found in nature ; thus heavy bodies move towards the
centre of the earth, and iron to the magnet ; nor are these
movements more difficult to conceive, than that of the planets
in their courses or of the sun round its axis, or that of the
heart in a living animal. With this first hypothesis Mariotte
places himself, in opposition to the Aristotelian doctrine with its
entelechies and final causes which prevailed at that time
among botanists and physiologists, upon the firm ground of
modern science with its atoms, and its assumption of necessarily
active forces of attraction.

Chap. II.] of Plants. Mariotte. 463

Mariotte's second hypothesis more specially concerns the
chemical nature of plants ; he supposes that several of his
principes grossiers are contained in every plant, and he endea-
vours first to explain their source ; the motes in the air, he
says, which when burnt by lightning smell of sulphur, are
carried by rain into the earth, and parts of them are taken up
into the plant. Moreover distillation in all plants produces a
water, w4iich the chemists call phlegma, and also acids and
ammonia, and if the residuum is burnt there remains an ash,
from which we obtain an earth which is without taste and
insoluble in water, and fixed salts ; these salts differ from one
another according as they are mixed with more or less acid and
ammoniacal spirit or other unknown principles, which the fire
could not volatilise. It is not to be wondered at that these
principles are found in plants, since they derive their food from
the earth which contains them. We see how great has been
the advance since the time when Van Helmont believed that he
had proved by his experiment, that all the materials in plants
come from pure water.

It remained to confront one view of the source of the
substances in plants, which was also drawn from the treasure-
house of Aristotelian conceptions, and was still in vogue. It was
supposed that the very materials of which the plant is composed
were contained in their own form in the earth, and had only
to be taken up by the roots. Aristotle had himself said : 'Every-
thing feeds on that of which it consists, and everything feeds
on more than one thing ; whatever appears to feed only on
one thing, as the plant on water, feeds on more than one thing,
for earth in the case of the plant is mixed with the water ;
therefore the country-people water plants with mixtures of
things.' This passage might leave some doubt about x\ristotle's
view, if we did not find the following : ' As many savours as
there are in the rinds of fruits, so many it is plain prevail also
in the earth. Therefore also many of the old philosophers
said, that the water is of as many kinds as the ground through

464 Theory of the Nutrition [Book hi.

which it runs'.' These passages taken with those quoted above
show that Aristotle made the substances required for the
growth of plants reach them from the earth ready elaborated,
as has been before observed ; and this view, still maintained in
Mariotte's time, may yet be met with among those who are
ignorant of physiology. It is interesting then to see, how
vigorously Mariotte exposes the incorrectness and absurdity of
this idea, though he has no new discovery to help him. In his
third hypothesis he maintains, that the salts, earths, oils, and
other things, which different species of plants yield by distilla-
tion, are always the same, and that the differences are due
entirely to the way in which these principes grossiers and their
simplest parts are united together or separated, and he proves
it thus : If a bonchretien pear is grafted on a wild one, the
same sap, which in the wild plant produces indifferent pears,
produces good and well-flavoured pears on the graft ; and if
this graft has a scion from the wild pear again grafted on it,
the latter will bear indifferent fruit. This shows that the same
sap in the stem assumes different qualities in each graft.' But
still more forcible is his proof of the fact, that plants do not
take their substance direct from the earth, but produce it
themselves by chemical processes. Take a pot, he says, with
seven to eight pounds of earth and grow in it any plant you
like ; the plant will find in this earth and in the rain-water which
has fallen on it all the principles of which it is composed in its
mature state. You may put three or four thousand different
kinds of plants in this earth ; if the salts, oils, earths were
different in each species of plant, all these principles must be
contained in the small quantity of earth and rain-water which
falls upon it in the course of three or four months, which
is impossible ; for each of these plants would yield in the
mature state a dram of fixed salt at least and two drams of

^ See the Fragments of Aristotelian phytology in Meyer's ' Geschichte
der Botanik/ i. pp. 119, 125.

Chap. II.] of Plants. Mariotte. 465

earth, and all these principles together with those which are
mixed with the water would weigh at least from two to three
ounces, and this multiphed by four thousand, the number of
the species of plants, would give a weight of five hundred
pounds.

These arguments like those of Jung, and in the main also
those of Malpighi, rested on facts which were on the whole as
well known in ancient times as in the 1 7th century ; but no
one had before given heed to considerations, which were
in themselves quite sufficient to do away with the Aristotelian
teaching on the subject of the nutrition of plants.

In the second part of his letter Mariotte discusses the
phenomena of vegetation which depend on nutrition ; he com-
pares the endosperm in the seed with the yolk of the egg in
animals, and the entrance of the water into the roots with its
rising in capillary tubes; he takes the milky juice to be the
nutrient sap and compares it with arterial blood, the other
watery juices answering to venous blood. He says something
quite new about the pressure of the sap ; he notices the high
pressure at which the sap stands in plants, and concludes
from it that there must be contrivances in them, which allow
of the ingress of the water but not of its egress. The exist-
ence of the pressure is well demonstrated by the outflow from
plants which contain milky juice when they are wounded, and is
compared with the pressure on the blood in the veins. Equally
striking is his further conclusion, that the pressure of the sap
expands the roots, branches, and leaves, and so contributes to
their growth. The sap, he adds, would not be able to remain
at this pressure, if it did not enter by pores, which forbid its
return. In these remarks lay the first germs of speculation on
the growth of plants, such as we shall meet with in Hales also
in a somewhat different form, but in the backward state in
which phytotomy then was they could not at present be further
developed ; we shall recur to them further on, though in a
different connection.

Hh

466 Theory of the Nutrition [Book m.

Mariotte concluded that the primary sap finds its way into
the plant through the leaves as well as through the roots from
the fact, that if a branch is taken from a tree, and one of its
smaller branches kept in water, another will remain fresh for
some days ; the conclusion was not quite justified, as the
future showed. His remarks on the necessity of sunlight
to nutrition, on the ripening of fruit, and other matters, rests
on very imperfect experience and need not be noticed.

The characteristic and the important point in Mariotte's
theory of nutrition is the marked contrast between his point of
view in natural science and the Aristotelian and scholastic
doctrines still widely diffused, and thus he is led to declare
war also against Aristotle's vegetable soul. He connects his
remarks on this point with a fact which excites his astonish-
ment, namely that every species of plant reproduces its proper-
ties so exactly ; no explanation of this fact, he says, is gained
by the assumption of a vegetable soul, of which no one knows
what it is. He declares as decidedly against the theory of
evolution, also much in vogue in his day. In opposition to
the notion that all future generations are shut up one inside
another in the seeds of a plant, he thinks it much more
probable that the seeds only contain the essential substances,
and that their influence on the crude sap brings about the
successive formation of the rest of the constituents of the plant,
a view which we may still allow to be correct. He regards the
whole process of nutrition and life in plants as a play of phy-
sical forces, as the combination and separation of simple
substances, but he believes at the same time that he can
prove the commonly received doctrine of spontaneous gener-
ation to be a necessary conclusion from this view. On this
point he went wrong from want of sufficient and well-sifted
experience, for he regarded it as a proof of generatio spontanea
that numerous plants spring up from the soil thrown out from
ditches and swamps that have been laid dry. ' We may there-
fore suppose,' he says, ' that there are in the air, in the water,

Chap. II.] of Plants. Mariotte. 467

and in the earth an infinite number of minute bodies so
fashioned that two or three uniting together may make the
beginning of a plant, and represent the seed of such a plant, if
they find a soil favourable to their growth. But it is not pro-
bable that this little complex body contains already all the
branches, leaves, fruits, and seeds of this plant, and still less
that this seed contains all the branches, leaves, flowers, etc.,
which proceed ad infinitum from the first germination.' The
contrary he thinks is proved by the fact, that a rose-bush which
has lost its leaves in the winter may produce in the next year
nothing but leafy shoots from its flower buds, which shows that
the blossoms were not previously formed in those buds, and
that a similar conclusion is to be drawn from another fact, that
the seeds of one and the same fruit-tree oi of a melon produce
descendants that differ from one another by variation ; here we
have an argument against the theory of evolution much more
to the purpose than the greater part of those which were
alleged against it before Koelreuter obtained his hybrids.

Other prejudices also of his day were opposed by Mariotte,
and on good grounds ; the medicinal effects, commonly known
as the 'virtutes' of plants, played an important part in the botany,
and still more in the medicine and chemistry of that time. He
rejects the old theory of heat and cold, moisture and dryness,
things supposed to be essentially immanent qualities of the
substance of plants and used to explain their medicinal effects,
and pointing to the fact, that poisonous plants grow in the same
soil as harmless ones and side by side with them, he concludes,
as he had before concluded, that different plants do not derive
their peculiar constituents immediately from the soil, but that
they form them themselves by separation and combination of
the common principles. Finally he declared against one of
the grossest errors which had come down from the previous
century, the 'signatura plantarum,' which supposed that the
medicinal properties of plants could be deduced from their
external features, and especially from resemblances between

H h 2

468 Theory of the Nutrition [Book hi.

their organs and the organs of the human body. Mariotte
insists that the medicinal properties of plants are to be ascer-
tained by trying them on sick people.

Mariotte's letter, the most important parts of which have
here been given, presents us with a lively picture of the views
which prevailed in the second half of the 17th century re-
specting the life of plants ; it shows at the same time how an
eminent investigator of nature, adopting the principles of a
more modern philosophy and knowing how to make a skilful
use of the facts that were known to him, was led to oppose
antiquated error, the result of prepossessions and want of re-
flection. If we combine the views of Malpighi on the internal
economy of the plant, derived chiefly from its anatomy, with
the chemical and physical disquisitions of Mariotte, we have
an entirely new theory of the nutrition of plants, not only
antagonistic to the Aristotelian doctrine, but distinguished
from it by a much greater wealth of ideas and by more
sagacious combinations.

These two men had in truth discovered all the principles of
vegetable life and nutrition, w^hich could have been discovered
in the existing condition of phytotomy and chemistry; Mariotte
especially had succeeded in applying the very best that was to
be obtained from the uncertain chemical knowledge of his
day to the explanation of the phenomena of vegetation.
Chemistry was at that time beginning to set herself free from
the notions of the medical science, the iatro-chemistry of a
former age, only to throw herself into the arms of the theory
of the phlogiston ; and how little she could contribute to the
explanation of the processes of nutrition in plants, how little
the methods then in use were adapted to the examination of
organised bodies, may be learnt from a little book published
in 1676 and again in 1679, ' Memoires pour servir k Fhistoire
des plantes,' which appeared indeed in Dodart's name, but
which was compiled and approved by the body of members of
the Academy of Paris. It contains no results of investigation,

Chap. IT.] of Plants. Mariotte. 469

but a detailed scheme for researches into botanical science,
and more particularly into the chemical part of it. There we
read, that plants must be burnt slowly, in order that the de-
stroying and transmuting power of the iire may have less
effect ; the ' virtutes plantarum ' play an important part in the
chemical examination of plants, and blood was mixed with
their juices, in order to discover their properties. A writer
named Dedu in a treatise, ' De I'ame des plantes' (1685) derived
the generation and growth of plants from the fermentation
and effervescence of the acids in combination with the alka-
lies, as Kurt Sprengel informs us. It is by comparison with
these and similar notions that we recognise the full superiority
of the utterances of Malpighi and Mariotte respecting the
nutrition of plants, and their sagacity is still further shown by
the fact, that there are some things which they forebore to say,
evidently because they thought that they were not clearly
proved.

The views of Malpighi and Mariotte on the nutrition of
plants were respected and often quoted by their contempo-
raries and immediate successors ; but as has happened in
other cases unfortunately up to recent times, much that was
fundamentally important and significant in them was neglected
from the first for comparatively unimportant matters, and the
views of these clear thinkers were so mixed up with indistinct
ideas and actual misconceptions, that no real advance was
made, though a variety of new facts were from time to time
brought to light. It has been already noticed that Malpighi's
correct idea of the connection of the leaves with the nutrition
of the plant was at a later time commonly supposed to be
equivalent to Major's theory of circulation, and since the
latter was for various reasons considered to be incorrect, it
was thought that Malpighi's view was dismissed with it. Yet
even Major's theory deserved the preference over the views of
those who assumed only an ascent of the sap in the wood,
because it at least attempted to account for certain phenomena

470 Theory of the Nutrition [Book hi.

of growth. It found a new supporter in 1680 in the person of
Claude Perrault, who does not however appear^ to have added
anything essentially new to Malpighi's conclusive arguments
for a returning sap. Nor did his opponent Magnol in his very
weak treatise published in 1709 succeed in saying anything
that will bear examination against the theory of circulation,
which he too ascribed to Malpighi.

Among the phenomena of vegetation in woody plants, there
is scarcely one so striking as the outflow of watery sap from
wounded vines and from some tree-stems in the spring. This
phenomenon, like the outflow of milky juice, gum, resin and
the like, could not fail to be regarded with lively interest by
those who occupied themselves with vegetable physiology in the
1 7th century. Even supposing the movements of water in the
wood and of the milky and other juices in their passages not
to be necessary accompaniments of the nutrition of plants, yet
it was natural that the physiologists of the 1 7th century should
see in them striking proofs of that movement of the sap which
is connected with nutrition, and should therefore make them
a subject of study. It might also seem to them that the
problem in question was easy to solve, for it was not till long
after that it came to be understood that these movements are
in reality one of the most difficult questions of vegetable
physiology. We discover the interest taken in these matters
from a series of communications in the form of letters from
Dr. Tonge, Francis Willoughby, and especially from Dr.
Martin Lister, to be found in the Philosophical Transactions
for 1670 ^ The phenomenon to which these men chiefly
directed their attention was just the one best calculated to

^ His views are known to me only from Magnol's paper in the ' Ilistoire
de r Academic Royale des Sciences,' 1709, and Sprengel's 'Geschichte der
Botanik,' ii. 20. Perrault's treatise is according to Pritzel's ' Thesaurus ' of
the date of 1680, but is published in the * CEuvres divers de Perrault ' of
1721.

* Especially in pages 1165, 1201, 2067, 2119.

Chap. II.] of Plants. Ray. 47 1

lead to misconceptions respecting the movements of water in
woody plants, namely that which is known as the bleeding of the
wood in winter, and which depends on entirely different causes
from those which produce the weeping of the vine and other
woody plants in spring ; but the two things were supposed to be
identical, and hence arose an unfortunate confusion of ideas.
Lister indeed showed that it is possible to force water out of
the wood of a portion of a branch cut from a tree in winter
time by warming it artificially, and then to cause the water to
be sucked in again by cooling it ; but it was reserved for a
modern physiologist to prove that this phenomenon has nothing
to do with the bleeding of cut stems from root-pressure, and
cannot be used to explain it.

John Ray, who gave a clear and intelligent summary of all
that was known respecting the nutrition of plants in the first
volume of his * Historia plantarum' (1693), also communicated
some experiments made by himself on the movements of water
in the wood. He follows Grew's nomenclature, who called
the ascending sap in the wood lymph and the woody fibres
therefore lymph-vessels, and notices particularly that the lymph
especially in spring cannot be distinguished in taste or in con-
sistence from common water. He agrees with Grew that in
spring the lymph fills the true vascular tubes of the wood and
oozes from them in cross sections, while in summer these are
filled with air, and the lymph at that time, when there is
strong transpiration in woody plants, ascends only in the
lymph-vessels, that is in the fibrous elements of the wood and
the bast. By suitable incisions Ray proved that the lymph
can also move laterally in the wood; and by causing water
to filter in opposite directions through pieces of a branch cut
off at both ends, he refuted those who thought that the cavities
of the wood and especially the vessels were furnished with
valves to hinder the return of the lymph. But his knowledge
of the mechanical causes of the movement of water in the
wood was not very great.

472 Theory of the Nutrition [Book hi.

Some years elapsed before Hales' labours added materially
to the progress which had been already made in the study of
these processes in vegetation. His important services to
vegetable physiology close our present period, but before we
pass on to them, we must first notice a few less important
writers. The pages of Woodward and Beale on transpiration
and the absorption of water are not very valuable contributions
to the theory of nutrition. The fact stated by Woodward,
that a Mentha growing in water took up and discharged by
evaporation through the leaves forty-six times as much water
as it retained in itself, was perhaps the most important of all
that he discovered, but his own conclusions from it were of no
value.

None of Malpighi's doctrines had from the first excited so
much attention as the one which makes the air which is
necessary for the respiration of the plant circulate in the spiral
vessels of the wood, as it does in the tracheae in insects ; while
Grew and Ray after him agreed with Malpighi in the main, his
countryman Sbaraglia in 1704 ventured even to deny the
existence of such vessels, and before long phytotomy was fallen
into such a state of decadence that the question, whether there
were any vessels, or as they were then called spiral vessels, at
all, was repeatedly affirmed and as often denied again, and
ultimately it was thought better in the interest of physiological
questions to take counsel of experiment rather than of the
microscope. Thus in 1715 Nieuwentyt endeavoured with the
help of the air-pump to make the air contained in the vessels
issue in a visible form under a fluid. Here we again en-
counter the philosopher Christian Wolff as a zealous repre-
sentative of vegetable physiology in Germany ; in the third
part of his work, 'Allerhand niitzliche Versuche,' 1721, among
other experiments he mentions some which confirmed the
presence of air in plants ; the question was more interesting,
in the state in which physics and chemistry then were, than
that of the anatomical character of the air-conducting organs.

Chap. II.] of Plaiifs. Christian Wolff. 473

Wolif submitted leaves lying in water containing no air to the
vacuum of the air-pump, and saw air-bubbles issue, especially
on the under side ; but when he allowed the atmospheric
pressure to come into play again the leaves became filled with
water, and a piece of fir-wood treated in a similar manner sank
after the infiltration. In similar experiments with apricots
air issued from the rind and especially from the stalk. Wolff's
pupil Thiimmig described similar experiments in his ' Griind-
liche Erlauterung der merkwiirdigsten Begebenheiten in der
Natur,' 1723, and both continued in this question, as in all
their physiological and phytotomical views, faithful adherents
of Malpighi, as it was wisest then to be. We must linger a
moment longer over Christian Wolff, because he published
a few years later a general view of the nutrition of plants in
a popular form. Wolff's services in the dissemination of
natural science in Germany seem not to have been as highly
appreciated up to the present time as they deserve to be ; his
various works on natural science, some of which took a wide
range and were partly founded on his own observations, were
full of matter and for his time very instructive ; they con-
tributed moreover to introduce more liberal habits of thought
at a time when gross superstitions, such as that of palingenesia,
reigned even among men who published scientific treatises in
the German Academy of Sciences (the 'Acta of the Leopoldina).'
If Wolff's own scientific researches show more good will than
skill, yet he had an advantage over many others in a really
philosophical training, a habit of abstract thought which
enabled him to fix with certainty on what was fundamentally
important in the observations of others, and thus to expound
the scientific knowledge of his day from higher points of view.
For this reason his work which appeared in 1723, ' Verniinftige
Gedanken von den Wirkungen der Natur,' deserves recognition.
It is a work of the kind which would now be called a ' Kosmos,'
and treats of the physical qualities of bodies generally, of the
heavenly bodies and specially of our own planet, of meteor-

474 Theory of the Nutrition [Book hi.

ology, physical geography, and lastly of minerals, plants,
animals and men. In accordance with his chief object,
general instruction, it is written in German and in a good
homely style, and contains the best information that was at that
time to be obtained on scientific subjects ; among these he
gives an account of the processes of nutrition in plants, in which
he made careful and intelligent use of all that had been written
on the subject, bringing together all the serviceable material
which he could gather from Malpighi, Grew, Leeuwenhoek,
Van Helmont, Mariotte and others into a connected system,
and occasionally introducing pertinent critical remarks. If we
consider the state of scientific literature in Germany in the
first years of the i8th century, we shall be inclined to assign
as great merit to comprehensive text-books of this popular
character as to new investigations and minor discoveries.
Wolff's chapter on nutrition has however a special interest for
us, because it contains several observations of value which
were lost sight of after his time. These refer chiefly to the
chemistry of nutrition and touch many problems which were
not solved before our time ; for instance, the statement that it
is a well-known fact that the earth loses its fruitfulness, if
much is grown on it ; that it requires much to feed it, and
must be manured with dung or ashes ; in these few words we
have the questions of the exhaustion of the soil, and the resti-
tution of the substances taken from it by the crop, brought
into notice by Wolff at this early period. ' It should be
particularly noted,' continues Wolff, ' how fruitful nitre makes
the soil; Vallemont has praised the usefulness of nitre, and
has mentioned other things which have a like operation by
reason of their saline and oily particles, such as horn from the
horns and hoofs of animals ; dung hkewise contains saline and
oily particles, which are present in the ash also, and we see
therefore that such particles should not be wanting, if a plant is
to be fed from water. The seed also, which supplies the first food
of the plant, shows the same thing, for there are none which do

Chap. II.] of Plants. Christian Wolff. 475

not contain oil and salt, and there are many from which the
oil may be squeezed out ; and oil and salt are found in all
plants if they are examined chemically.' He insists on the
correctness of the view taken by Malpighi and Mariotte, that
the constituents of the food must be chemically altered in the
plant. Since every plant, he says, has its own particular salt
and its own particular oil, we must readily allow that these are
produced in the plant and not introduced into it. But at the
same time since plants cannot grow where the soil does not
supply them with saline and especially with nitrous particles, it
is from these that the salts and oils in the plant must be pro-
duced, and the water also changed into a nutritious juice.
Further on he alludes to the saline, nitrous and oily particles
which float in the air, and says that daily experience shows that
most of the substance of putrefying bodies passes into the air,
and that if we admit light through a narrow opening into a dark
place, we can see a great number of little particles of dust floating
about ; water also readily takes up salt and earth, and mineral
springs show that metallic particles are mixed with it. There-
fore there is no reason to doubt that rain-water also contains a
variety of matters which it conveys to the plant. Alluding
once more to the chemical changes in the constituents of the
food which must be supposed to take place in the plant, he
connects the subject with some remarks on the organs of
plants, in which he closely follows Malpighi ; he says that these
changes cannot take place in tubes, because the sap merely
rises or falls in them ; we can only therefore suppose that it is
in the spongy substance (the cellular tissue) that the nutrient
sap is elaborated, and accordingly the vesicles or utriculi
are a kind of stomach ; but the change in the water can only
be this, that the particles of various substances which are in
rain-water are separated ffom it and united together in some
special manner, and this cannot be effected without special
movements. But his ideas on these movements in the sap
are somewhat obscure. He employs the expansion of the

47 6 Theory of the Nutrition [Book hi.

air and the capillarity of the woody tubes as his moving forces.
He agrees decidedly with those who postulated a returning
sap as well as an ascending crude sap, but he appeals in this
matter to Major, Perrault, and Mariotte, and not to Malpighi ;
yet like Malpighi he notices the growth of trees set upside
down as a proof that the juices can move in opposite directions
in the conducting organs, and with Mariotte he ascribes the
enlargement of growing organs to the expanding power of the
juices which force their way into them.

But these well-meant efforts on the part of Christian Wolff,
and indeed all that was done from Malpighi and Mariotte to
Ingen-Houss to advance the knowledge of the nutrition of
plants, was thrown into the shade by the brilliant investigations
of Stephen Hales \ in whom we see once more the genius of
discovery and the sound original reasoning powers of the great
explorers of nature in Newton's age. His ' Statical Essays,'
first published in 1727, reappeared in two new editions in
English, and afterwards in French, Italian and German trans-
lations ; in the last with a preface by Christian Wolff. This
was the first work devoted to a more complete account of the
nutrition of plants and of the movements of the sap in them,
and while it noticed what had been already written on the
subject, it was chiefly composed of the author's own investi-
gations. An abundance of new experiments and observations,

* Stephen Hales was born in the county of Kent in 1677 and was educated
at home without showing any special ability. At the age of nineteen he
became a member of Christ's College in Cambridge, and there showed his
taste for physics, mathematics, chemistry, and natural history. Nevertheless
he took orders and held Church preferment in different counties. He
became a Member of the Royal Society in 1718, and read before it his
'Statical Essays.' His 'Hemostatics' appeared in 1733. He made and
published other investigations and discoveries of very various kinds before
his death in 1761. He was buried in his church at Riddington, which he
had rebuilt at his own cost, and the Princess of Wales caused an inscription
to his memory to be placed in Westminster Abbey. See his Eloge in ' His-
toire de 1' Academic Royale des Sciences,' 1762.

Chap. II.] of Plants. Hales. 477

measurements and calculations combine to form a living
picture of the whole subject. Malpighi endeavoured to dis-
cover the physiological functions of organs by the aid of
analogies and a reference to their structure; Mariotte discerned
the main features of the connection between plants and their
environment by combining together physical and chemical
facts ; Hales may be said to have made his plants themselves
speak ; by means of cleverly contrived and skilfully managed
experiments he compelled them to disclose the forces that
were at work in them by effects made apparent to the eye, and
thus to show that forces of a very peculiar kind are in constant
activity in the quiet and apparently passive organs of vegetation.
Penetrated with the spirit of Newton's age, which notwith-
standing its strictly teleological and even theological conception
of nature did endeavour to explain all the phenomena of life
mechanically by the attraction and repulsion of material
particles, Hales was not content with giving a clear idea of the
phenomena of vegetation, but sought to trace them back to
mechanico-physical laws as then understood. He infused life
into the empirical materials which he collected by means of
ingenious reflections, which brought individual facts into
connection with more general considerations. Such a book
necessarily attracted great attention, and for us it is a source
of much valuable instruction on matters of detail, though we
now gather up the phenomena of vegetation into a somewhat
differently connected whole.

His investigations into transpiration and the movement of
water in the wood were greeted with the warmest approbation.
He measured the quantity of water sucked in by the roots and
given off by the leaves, compared this with the supply of
moisture contained in the earth, and endeavoured to calculate
the rapidity with which the water rises in the stem, and to
compare it with the rapidity of its entrance into the roots and
its exit by the leaves. The experiments, by which he showed
the force of suction in wood and roots, and that of the root-

478 Theory of the Nutrition [Book hi.

pressure in the case of the bleeding vine, were particularly
striking and instructive. His measurements and the figures, on
which he founded his calculations, were not so exact as they were
often at a later time supposed to be, but he was himself satisfied
with obtaining round, approximative numbers ; these under
given circumstances supplied a sufficient basis for propositions
which were new and afforded a certain amount of insight into the
economy of the plant. This mode of proceeding showed his
understanding ; for the case of living bodies is different from
that of metals and gases ; in. these we seek for constants which
can then be inserted in general formulae, and to which there-
fore the nicest accuracy is applied ; but in plants we have to
deal with individual cases, and it is from a right interpretation
of the measurements taken from them that we can arrive at
general laws of vegetation.

To show that the forces of suction and pressure which
operate in plants are not something sui generis, but prevail also
in dead matter, in other words that they are an example of the
general attraction of matter, a subject of particular interest at
that time. Hales observed the absorption of water by substances
with fine pores ; and measured the force employed. These
processes he compared with the force which swelling peas
exert on the obstacles which they encounter, and thus obtained
a more correct idea of the forces concerned in the movement
of water in the plant than that given by the capillarity of glass-
tubes, which Mariotte and Ray had employed to illustrate
them.

Hales failed to appreciate the value of Malpighi's obser-
vations on the function of leaves, and was induced by the
copiousness of the evaporation of water from their surfaces
to overrate the physiological importance of that process ; hence
he saw in leaves chiefly organs of transpiration, which raise the
sap by suction from the roots through the stem. In accord-
ance with this view he denied the existence of a descending
sap in the bark, and only admitted that the ascending sap

Chap. II.] of Plauts. HttleS.

479

in the wood might possibly sink in the night in consequence
of the lowering of the temperature, like the quicksilver in a
thermometer, and that so far there might be a return-movement.
This was the weak point in Hales' system.

One of his most important discoveries has generally been
overlooked even in modern times, probably because it was
entirely neglected by his successors in the i8th century; he
was the first who proved, that air co-operates in the building up
the body of the plant, in the formation of its solid substance,
and that gaseous constituents contribute largely to the nourish-
ment of the plant ; consequently that neither water, nor the
substances which it carries with it from the earth, alone supply
the material of which plants are composed, as had been
generally imagined. He showed also with the aid of the
air-pump, and better than Nieuwentyt and Wolff, that air
enters the plant not only through the leaves but also through
apertures in the rind, and circulates in the cavities of the
wood. He then connected this with the fact which he had
confirmed by numerous experiments, that large quantities of
'air' are obtained from vegetable substance by fermentation
and dry distillation ; the air thus set free by fermentation and
heat must in his opinion be condensed and changed to a
sohd condition during the period of vegetation. He says in
chap. 7, that we find by chemical analysis (dry distillation) of
vegetables, that their substance is composed of sulphur, volatile
salt, water and earth ; these principles are all endowed with
mutual power of attraction (of their parts). But air also
enters into the composition of the plant, and this in its solid
state is powerfully attractive, but in an elastic condition has
the highest powers of repulsion. It is on infinitely various
combinations, actions, and reactions of these principles that
all activity in animal and vegetable bodies depends. In
nutrition the sum of the forces of attraction is greater than
that of the forces of repulsion, and thus the viscid ductile
parts are first produced, and then by evaporation of the water

480 Theory of the Ntitrition [Book hi.

the harder parts. But if the latter again absorb water, and the
forces of repulsion consequently gain the preponderance, then
the consistence of the vegetable parts is dissolved, and this
decomposition restores to them the power of forming new
vegetable products ; therefore the stock of nutritive substance
in nature can never be exhausted ; this stock is the same in
animals and plants, and is fitted by a small change of texture
to feed the one or the other.

He goes on to say, that it results from his experiments, that
leaves are very useful for the nourishing of the plant, inasmuch
as they draw up the food from the earth ; but they seem also
to be adapted to other noble and important services ; they
remove the superfluous water by evaporation, retaining the
parts of it that are nutritious, while they also absorb salt, nitre,
and the like substances, and dew, and rain ; and since, like
Newton, he regarded light as a substance, he concludes by
asking : ' may not light, which makes its way into the outer
surfaces of leaves and flowers, contribute much to the refining
of the substances in the plant ? '

It might be gathered from these expressions that Hales
attributed importance for purposes of nutrition only to the
substances suspended in the air ; but this was not the case ;
for we read in the 6th chapter, that he had proved by
experiment that a quantity of true permanently elastic air is
obtained from vegetable and animal bodies by fermentation
and dissolution (dry distillation) ; the air is to a great extent
immediately and firmly incorporated with the substance of
these bodies, and it follows therefore that a large quantity of
elastic air must be constantly used in forming them.

But Hales not only regards the air as a nourishing
substance, but he sees also in its elasticity, which counteracts
the attraction of other substances, the origin of the force
which maintains the internal movements in the plant. He
says that if all matter were endowed only with forces of
attraction, all nature would at once contract into an inactive

Chap. II.] of Plants. Hales. 481

mass; it was therefore absolutely necessary in order to set in move-
ment and animate this huge mass of attracting matter, that a
sufficient quantity of strongly repellent and elastic matter should
be mixed with it ; and since a large portion of these elastic
particles are constantly changing to a solid condition through
the attraction of the other parts, they must be endowed with
the power of again assuming their elastic condition, when they
are set free from the attracting mass. Thus the formation and
dissolution of animal and vegetable bodies go on in constant
succession. Air is therefore very important to the production
and growth of animals and plants in two ways \ it invigorates
their juices while it is in the elastic state, and contributes
much to the firm union of the constituent parts, when it has
become fixed.

We see what good use Hales could make of the small stock
of ideas in physics and chemistry at his disposal, and that he
succeeded with their help in rising to a point of view, from
which he was able to form some idea of the phenomena of
vegetation in their most important relations to the rest of
nature, and in their inner course and connection. But his
successors did not comprehend the fundamental importance of
these considerations, and made no use of the pregnant idea, that
a much larger part of the substance of plants comes from the air
and not from the water or the soil; they were for ever wonder-
ing that so little is furnished by the soil to the plant, as Van
Helmont had shown, though they did not confess to supposing
that the water was changed into the substance of the plant, as
he had imagined. Thus physiologists lost sight of the principle,
which might long before the time of Ingen-Houss have suffi-
ciently explained the most important of all the relations of the
plant to the outer world, namely that it derives its food from
the constituents of the atmosphere, and so neglected further
experimental enquiry into the matter ; they quoted and re-
peated Hales' experiments and observations again and again,
but forgot that which in his mind bound all the separate facts
together. i i

48a Theory of the Nutrition [Book hi.

Hales is the last of the great naturalists who laid the
foundations of vegetable physiology. Strange as some of their
ideas may seem to us, yet these observers were the first who
gained any deep insight into the hidden machinery of vegetable
life, and handed down to us a knowledge both of individual facts
and of their most important relations. If we compare what
was known before Malpighi's time with the contents of Hales'
book, we shall be astonished at the rapid advance made in less
than sixty years, while scarcely anything had been contributed
to the subject in the period between Aristotle and Malpighi.

3. Fruitless attempts to explain the movement of
the sap in plants. 1730-1780.

If those, who studied the nutrition of plants and especially
the movement of their sap in the period between Hales and
Ingen-Houss, had kept a firm hold on Malpighi's view, that
the nutritive substances are elaborated in the leaves, and had
combined it with Hales' idea, that plants derive a large portion
of their substance from the air, they would have had a principle
to guide them in their investigations into the movement of the
sap; and by experimenting on living plants they might have
succeeded in giving a more definite expression to these ideas,
even though chemistry and physics supplied during that time
no new aids. We have said already that such was not the
course of events ; physiologists confined their attention to the
obvious phenomena of vegetation, and trusted in so doing to
gain a firmer footing, but in this they never got beyond a
commonplace and unreflecting empiricism, because their
observation was without an object, and their conclusions
without a principle. They wandered from the right direction,
as always happens when observation is not guided by a well-
considered hypothesis ; and their conceptions were rendered
more obscure by their imperfect acquaintance with one of the
most important aids to understanding the movement of the

Chap. II.] of Plafits. Dc la Bttisse. 485

sap, namely the structure of the more delicate parts of the
plant, the knowledge of which had not advanced since the
days of Malpighi and Grew. Since most of them made no
phytotomical investigations of their own, and only partially
understood the descriptions of those writers, they had to be
content with misty and often quite inaccurate ideas of the
inner structure of wood and bark, and yet expected to obtain
an insight into the movement of the sap in them. In reading
the writings of Malpighi, Grew, Mariotte, Hales and even
Wolff, notwithstanding many mistakes in details we find a
pleasure in the connected reasoning, and in the sagacity which
knew how to distinguish between what was important and
what was not ; whereas the observers, whom we have now to
mention, give us only isolated statements, nor have we the
satisfaction of feeling that we are conversing with men of
superior understanding.

We may pass over the unimportant writings of Friedrich
Walther (1740), Anton Wilhelm Platz (1751) and Rudolph
Bohmer (1753), as merely barren exercises; but some notice
should be taken of those of De la Baisse and Reichel, since
these authors at least endeavoured to bring to light something
new. But the method which they employed of making living
plants suck up coloured fluids was calculated to give rise
to serious errors both at the time and afterwards. Magnol
had mentioned experiments of the kind in 1709, and the
Jesuit father Sarrabat, known by the name of De La Baisse,
occupied himself with them and described them in a treatise,
'Sur la circulation de la seve des plantes,' 1733, which received
a prize from the academy of Bordeaux \ He set the roots
of different plants in the red juice of the fruit of Phytolacca,
and found that in two or three days the whole of the bark of
the roots and especially the tips of the root-fibres were coloured

1 See Sprengel, ' Geschichte der Botanik,' i. 229, and Reichel's and
Bonnet's works mentioned below.

484 Theory of the Nutrition [book hi.

red inside. It was a natural conclusion at that time, that
it was these parts which chiefly absorbed the red colouring
matter, and in fact this opinion was maintained till quite
recent times, and it was on such results that Pyrame de
Candolle founded his theory of the spongioles of the root,
which is still accepted in France. At present it is known,
that the bark and especially the youngest tips of the fibres
of the root are not coloured under these circumstances, until
they have been first poisoned and killed by the colouring
matter ; these experiments therefore, which have been fre-
quently repeated since De la Baisse's time, prove nothing
respecting the action of living roots, but they were from the
first the cause of a pernicious error in vegetable physiology,
which as we shall see gave rise to others also. One result
however of De la Baisse's experiments was less misleading ;
he placed the cut ends of branches of woody plants in the
coloured fluid, and found that not only the general body of
the wood, but the woody bundles which pass from it into the
leaves and parts of the flowers, were coloured red, while the
succulent tissue of the bark and leaves remained uncoloured.
It appeared therefore that the red juice passed only through
the wood, and. a somewhat bold analogy might lead to the
further conclusion that this is true also of the nutrient sub-
stances dissolved in the watery sap ; but the view so stated
is not at present considered to be correct, and that the sap
which ascends from the roots to the leaves, the water especially,
is conveyed through the wood only, and not through the rind,
had been already sufficiently proved by the experiments of Hales
and others. The uncritical treatment of experiments of this kind
by Georg Christian Reichel^ afterwards led to new errors,
though his dissertation, ' De vasis plantarum spiralibus,' shows
to advantage by the side of similar productions of the day

^ Georg Christian Reichel was born in 1727 and died in 177 1. He was
Professor in the University of Leipsic.

Chap. II.] of Plants. Rcichel. 485

owing to its careful notices of the literature, and the author's
original researches in phytotomy. Reichel was not satisfied with
the arguments of Malpighi, Nieuwentyt, Wolff, Thiimmig and
Hales for the view that the vessels of the wood contain air.
He observed quite correctly, that if branches are cut off from
woody and herbaceous plants and the cut surfaces are placed
in red decoction of brazil-wood, the red colouring matter spreads
through all the vascular bundles, even those of the flowers and
fruit ; but on examination with the microscope he found the
red fluid to some extent in the cavities of the vessels, and
hastily concluded that they too in the natural condition convey
sap and not air. His description and his drawing show
however, that only some vessels had received any of the
red fluid and that none of these were filled with it. Reichel
and the many who repeated his statements forgot to ask
whether the vessels had contained air or fluid before the
experiment, or whether the result would have been the same,
if plants with uninjured and living roots had absorbed the
coloured fluid, and no divided vessels had therefore come
in contact with it. There was no reason why observers of
that day should not have been alive to the simple consider-
ation, that the vessels of a branch parted from the stem and
placed in a fluid muSt necessarily show the capillary action of
narrow glass tubes if they are filled with air in their natural
condition, and that in the experiment the transpiration of the
leaves must favour the ascent of the red juice in the cavities of
the vessels, as was to be gathered from other and better ex-
periments made by Hales. But these obvious reflections were
not made ; the supposed results of the experiment were heed-
lessly accepted, and the unfounded notion, that vessels are
natural sap-conducting organs, was set up in opposition to the
trustworthy decision of Malpighi and Grew, that they convey
air. Thus on the strength of badly interpreted experiments
one of the most important of physiological discoveries was
called in question, and a hundred years later there were persons,

486 Theory of the Nutrition [Book hi.

who, relying on the same experiments as Reichel, supposed
that the vessels of the wood convey the ascending sap, a view
which made it impossible from the first to arrive at any real
understanding of the movement of the sap in plants provided
with organs of transpiration. But even the other great dis-
covery which we owe to Malpighi, that leaves are organs for
elaborating the food, was denied by Bonnet, who substituted
for it the utterly false view, that they chiefly serve to absorb
rain-water and dew. Bonnet^, who had previously done good
service to insect-biology, and had discovered the asexual
propagation of aphides, having injured his eyes in these studies,
found an agreeable pastime in a variety of experiments on
plants. Much that he did was unimportant, yet he obtained
some results, which could afterwards be turned to account
by more competent persons, for the weakness of his own
judgment is shown even in his more serviceable observations,
such as those on the curvature of growing plants. We notice
the same defect in his observations on the part played by
leaves in the nutrition of the plant. It shows the character of
the time that a book like Bonnet's ' Recherches sur I'usage
des feuilles des plantes,' a mere accumulation of undigested
facts, should have been generally considered an important
production. He tells us, that his attention was called by
Calandrini to the fact, that the structure of the under side
of leaves seems to show that they were intended to absorb
'the dew that rises from the ground' and introduce it into
the plant. Starting from this sensible suggestion, as he calls
it, he proceeded to make a variety of senseless experiments

* Charles Bonnet, bom at Geneva in 1720, sprang from a wealthy family,
and was intended for the profession of the law, but gave himself up from
an early age to scientific pursuits, and especially to zoology. He was after-
wards a member of the great council of Geneva, and wrote various treatises
on scientific subjects, psychology, and theology. He died on his property at
Genthod near Geneva in 1793. See the 'Biographic Universelle' and
Carus, ' Geschichte der Zoologie,' p. 526,

Chap. II.] of Plants. Bonnet. 487

with leaves, which were cut off from their plants, and having
been smeared over with oil or other hurtful substances were
laid on water, some on their upper -some on their under side,
the object being to note the time which they took to perish.
It is impossible to imagine worse-devised experiments on
vegetation ; for if Bonnet wished to test Calandrini's ' sensible '
conjecture, he ought certainly to have left the leaves on the
living plants and have observed the effect of the supposed
absorption of dew on the vegetation. It is to be observed,
that by rising dew he evidently meant aqueous vapour, for the
real dew descends chiefly on the upper side of the leaf; and
what could he have expected to learn by laying cut leaves
on water ? how could this prove that leaves absorb dew ?
Nevertheless Bonnet came to the conclusion that the most
important function of leaves was to absorb dew, and in order
to make this result agree with Hales' investigations on trans-
piration, he propounded the theory^, that the sap which rises
by day from the roots into the stem is carried by the woody
fibres assisted by the air-tubes into the under side of the leaves,
where there are many stomata to facilitate its exit (evaporation).
At the approach of night, when the leaves and the air in the
air-tubes are no longer under the influence of heat, the sap
returns to the roots ; then the under side of the leaves com-
mences its other function ; the dew slowly rising from the
earth strikes against it, condenses upon it, and is detained
there by the fine hairs and by other contrivances (this really
takes place to a much greater extent on the upper side). The
fine tubes of the leaves absorb it at once, (this is evidently not
so, since the dew increases in quantity till sunrise), and conduct
it to the branches, whence it passes into the stem. He
thought so highly of this strange theory, that he believed
he found in it a teleological explanation of the heliotropic
and geotropic curvature of leaves and stems, two things which

1 See p. 35 of the German translation by Arnold, 1762.

488 Theory of the Nutrition [Book hi.

he did not distinguish, and of the position of leaves on the
stem. Bonnet's view of the functions of leaves, foolish as
it is, is historically important and therefore required to be
noticed, because it was really accepted during many years
in preference to the older and better ideas, and because it
shows how the power of judging of such matters had fallen
off since Malpighi's time. It appears to have been the praise
lavished on Bonnet by his contemporaries that made later
physiologists, who might have known better, take him for
an authority on the nutrition of plants. His experiments on
the growth of plants in another material than earth are if
possible more worthless than those with cut leaves. Here too
the idea was not his own j for hearing that land-plants had
been grown in Berlin in moss instead of earth, he made
numerous experiments of the kind, and found that many
plants grow vigorously in this way, and bloom and bear seed.
But the theory of nutrition gained nothing by these experi-
ments, which were only a childish amusement. The few pages
which Malpighi wrote on the nutrition of plants are worth
more than all Bonnet's book on the use of leaves ; the former
by the help of some simple considerations and conclusions
from analogy really discovered the use of leaves ; Bonnet on
the faith of many unmeaning experiments ascribed to them
another function than the true one.

We are unable to pass a much more favourable judgment on
the views respecting the nutrition of plants of another writer,
who otherwise did good service to vegetable physiology, and
to whom we shall return in our last chapter. It is true that
Du Hamel\ of whom we speak, was not an investigator of

^ Henri Louis du Hamel du Monceau was born at Paris in 1 700 and died
in 1781. He had an estate in the Gatinais, and turned his studies in
physics, chemistry, zoology, and botany to account in the composition of a
number of treatises on agriculture, the management of woods and forests,
naval affairs, and fisheries. He was made Member of the Academy in 1728

Chap. II.] of Plauts. Du Hamcl. 489

nature, as were Malpighi, Mariotte or Hales ; compared with
those great thinkers he was only a compiler, and a somewhat
uncritical one. But he was not a dilettante in science, like
Bonnet ; he made the vegetable world the subject of serious
and diligent study, and he endeavoured to turn the results
of that study to practical account. Long familiarity with plants
gave him a kind of instinct for the truth in dealing with them,
as is shown in his observations and experiments, many of
which are still instructive ; but he had neither that faculty
of combination which can alone bring a meaning out of
experiments and observations in physiological investigations,
nor the power to distinguish between matters of fundamental
and secondary importance. So thinks also his biographer
Du Petit-Thonars.

The merits and the faults here mentioned are combined in
an especial degree in Du Hamel's most famous work, ' Phy-
sique des arbres,' which appeared in two volumes in 1758 and
is a text-book of vegetable anatomy and physiology with
numerous plates. His remarks on the nutrition of plants
and the movement of the sap are a lengthy compilation chiefly
from Malpighi, Mariotte and Hales, though he has not suc-
ceeded in appropriating exactly that which is theoretically
important or adopting the most commanding points of view.
He introduces the results of his own experiments into his
account, and these are often instructive in themselves, but are
never made use of to establish a definite view with respect
to the connection between the processes of nutrition. He
hits upon the right view only when he is dealing with plain
and obvious matters ; for instance, he restores the vessels
of the wood to their old rights, and concludes from experi-
ments, as had been already done in the 17 th century, that
an elaborated sap moves in the reverse direction in the rind ;

on presenting to it an essay on a disease then raging in the saffron-plantations,
and caused by the gTO\vth of a fungus (* Biographie Universelle ';.

49° Theory of the Nutrition [book hi.

so too he perceives that if bulbs, tubers, and roots, with or
without the help of water which they have absorbed, produce
shoots and even flowers, this must be done at the expense
of material laid up in reserve, but he does not turn this fact to
any further account. But he utterly spoilt the best part of his
subject ; he made the leaves nothing but pumps that suck
up the sap from the roots ; he quotes Malpighi's better view as
a curiosity, and never mentions it again ; but he accepts
Bonnet's unfortunate theory, though he himself adduces many
facts, which make for Malpighi's interpretation of the leaves.
He is almost more unsuccessful with chemical points in
nutrition ; he repeats Mariotte's statements with regard to the
necessity of a chemical change in the nutrient substances in
the plant, and even supplies further proof of it ; but he cannot
shake off the Aristotelian dogma, that the earth like an animal
stomach elaborates the food of plants, and that the roots
absorb the elaborated matter like chyle-vessels (II. pp. 189,
230). He concludes from his own attempts to grow land-plants
without earth and in ordinary water that the latter supplies
the plant with very little matter in solution, but he makes
no use of Hales' statements with regard to the co-operation
of the air in the building up of the plant, and ends by saying
(II. p. 204) that he only wished to prove that the purest and
simplest water can supply plants with their food, which his
experiments do not prove. Thus almost all that Du Hamel
says on the nutrition of plants is a mixture of right observations
in detail with wrong conclusions, and reflections which never
rise above the individual facts and give no account of the
connection of the whole. These faults appear in a still higher
degree in a later and almost more comprehensive work, the
'Traite theorique et pratique de la vegetation' of Mustel
(1781). The further the distance from the founders of vege-
table physiolog}', the larger were the books that were written
on the subject; but the thread that held the single facts
together became thinner and thinner, till at last it broke.

Chap. II.] of Plants. Ingen-Hoitss and de Saussitre. 491

The theory of nutrition, Uke a forced plant, needed Hght that
it might recover strength. This hght came with the discoveries
of Ingen-Houss, and with the mighty strides made by chemistry
after 1760 in the hands of Lavoisier.

4. The modern theory of nutrition founded by Ingen-
Houss AND Theodore de Saussure. 17 79-1 804.

The two cardinal points in the doctrine of the nutrition of
plants, namely that the leaves are the organs which elaborate
the food, and that a large part of the substance of the plant is
derived from the atmosphere, were established, as we have seen,
by Malpighi and Hales, and employed by them in framing
their theory ; it remained to supply a direct and tangible proof
of the fact that the green leaves take up a constituent of the
atmosphere and apply it to purposes of nutrition. It was evi-
dently the want of such direct proof which caused the suc-
cessors of the first great physiologists to overlook the import-
ance of the propositions thus obtained by deduction, and so
to grope their way in the dark with no principle to guide them.

The discoveries of Priestley, Ingen-Houss and Senebier, and
the quantitative determinations of de Saussure in the years be-
tween 1774 and 1804, supplied the proof that the green parts
of plants, and the leaves therefore especially, take up and
decompose a constituent of the air, while they at the same time
assimilate the constituents of water and increase in weight in a
corresponding degree ; but that this process only goes on
copiously and in the normal way, when small quantities of
mineral matter are introduced at the same time into the plant
through the roots. The discoveries and facts, from which this
doctrine proceeded, were those which overthrew the theory of
the phlogiston, and from which Lavoisier deduced the prin-
ciples of modern chemistry ; the new theory of the nutrition of
plants was indeed directly due to Lavoisier's doctrines, and it
is necessary therefore to take at least a hasty glance at the

492 Theory of the Nutrition [Book hi.

revolution which was effected in chemistry between 1770 and
1790. It is a well-known fact^ that this revolution dates from
the discovery of oxygen-gas by Priestley in 1774. Priestley
himself was and continued to be a stubborn adherent of the
phlogiston ; but his discovery was made by Lavoisier the basis
of an entirely new view of chemical processes. By the com-
bustion of charcoal and the diamond, Lavoisier proved as early
as 1776 that 'fixed air' was a compound of carbon and 'vital
air.' In like manner phosphoric acid, sulphuric acid and, after
a preliminary discovery by Cavendish, nitric acid also were
found to be compounds of phosphorus, sulphur and nitrogen
with vital air; in 1777 Lavoisier showed that fixed air and
water are produced by the combustion of organic substances,
and after establishing within certain limits the quantitative
composition of fixed air, he named it carbonic acid, and the
gas which had up to that time been known as vital air he called
oxygen. Cavendish in 1783 obtained water by the combustion
of hydrogen-gas, and then Lavoisier proved that water is a
compound of hydrogen and oxygen. These discoveries not
only did away step by step with the old theory of the phlo-
giston, and supplied the principles of modern chemistry, but
they also affected exactly those substances which play the most
important part in the nutrition of plants ; every one of these
discoveries in chemistry could at once be turned to account in
physiology. In 1779 Priestley discovered that the green
parts of plants occasionally exhale oxygen, and in the same
year Ingen-Houss described some fuller investigations, which
showed that this only takes place under the influence of light,
and that the green parts of plants give off carbon dioxide in the
dark, as those parts which are not green do both in the light
and the dark. A correct interpretation of these facts was not
however possible in 1779 ; it was not till 1785 that Lavoisier

^ See Kopp, ' Geschichte der Chemie' (1843), i. p. 306, and ' Entwick-
lung der Chemie in der neuerenzeit ' (1873), p. 138.

Chap. II.] of Plants. Priestley. 493

succeeded in setting himself quite free from the old notions,
and developed his antiphlogistic system into a connected
whole. It should be mentioned that he had discovered in
1777 that the respiration of animals is a process of oxidation
which produces their internal heat, heat being the product of
every form of combustion. This fact was equally important
for vegetable physiology, but it was some time before it was
used to explain the life of plants.

The establishment of the fact, that parts of plants give
off oxygen under certain circumstances, did little or nothing to
further the theory of their nutrition ^ ; and that was all that
vegetable physiology owes to Priestley. Ingen-Houss on the
other hand determined the conditions under which oxygen is
given off, and further showed that all parts of plants are con-
stantly giving rise to carbon dioxide ; on these facts rests the
modern theory of the nutrition and respiration of plants, and
we must therefore consider that Ingen-Houss was the founder
of that theory. But since we are dealing here with a discovery
of more than ordinary importance, it seems necessary to go
more closely into the details.

A work of Priestley's appeared in 1779, which was translated
into German in the following year under the title, ' Versuche
und Beobachtungen iiber verschiedene Theile der Naturlehre,'
and contained among other things the writer's experiments on
plants. His way of managing them was eminently unsuitable,
nor did he arrive at any definite and important result, though
he expressed the idea which had led him to make them clearly
enough, where he says, ' If the air exhaled by the plant is of
better character (richer in oxygen) than atmospheric air, it
follows that the phlogiston of the air is retained in the plant

^ Still less was gained from an obser\'ation made by Bonnet, that leaves
exposed to sunlight in water containing air show bubbles of gas on their
upper surface. Bonnet expressly denied the active participation of the
leaves in the phenomenon, since the same thing happens with dead leaves
in water containing air.

494 Theory of the Nutrition [Book hi.

and used there for its nourishment, while the part which
escapes, being deprived of its phlogiston, necessarily attains a
higher degree of purity.' After he had ceased his experiments
with plants in 1778, he observed that there was a deposit of
matter in the water in some vessels which he had used for
them, and that it gave off a very ' pure air ' ; a number of
further observations taught him that this air was given off only
under the influence of sun-light ; Priestley himself did not sus-
pect that the deposit in question, afterwards known as Priest-
ley's matter and found to consist of Algae, was a vegetable
substance.

In the same year (1779) appeared the first book by Ingen-
Houss ^, in which the subject was treated at length ; it was
called, ' Experiments on Vegetables, discovering their great
power of purifying the common air in the sunshine and of
injuring it in the shade and at night,' and was at once trans-
lated into German, Dutch and French. The title itself shows
that the author had observed more and more correctly than
Priestley. But he did not come to an understanding of the
inner connection of the facts, till Lavoisier completed his new
antiphlogistic theory. He says himself in his essay, ' On the
nutrition of plants and the fruitfulness of the earth,' which
appeared in 1796, and was translated into German with an
introduction by A. v. Humboldt in 1798, that when he pub-
lished his discoveries in 1779, the new system of chemistry
was not yet fully declared, and that without its aid he had
been unable to deduce the true theory from the facts ; but
that since the composition of water and air had been dis-
covered, it had become much easier to explain the phenomena
of vegetation. But in order to establish his priority he says on
p. 56, that he had been fortunate enough to find out the real

* Jan Ingen-Houss, physician to the Emperor of Austria, practised first
in Breda, and afterwards in London. He was bom at Breda in Holland in
1730, and died near London in 1799.

Chap. II.] of Plants. Senehier. 495

cause why plants at certain times vitiate the surrounding air,
a cause which neither Priestley nor Scheele had suspected.
He had discovered, he says, in the summer of 1779, that all
vegetables incessantly give out carbonic acid gas, but that the
green leaves and shoots only exhale oxygen in sun-light or clear
day-light. It appears therefore that Ingen-Houss not only dis-
covered the assimilation of carbon and the true respiration of
plants, but also kept the conditions and the meaning of the
two phenomena distinct from one another. Accordingly he
had a clear idea of the great distinction between the nutri-
tion of germinating plants and of older green ones, the in-
dependence of the one, the dependence of the other, on light ;
and that he considered the carbon dioxide of the atmosphere
to be the main if not the only source of the carbon in the
plant, is shown by his remark on a foolish assertion of Hassen-
fratz that the carbon is taken from the earth by the roots ; he
replied that it was scarcely conceivable that a large tree should
in that case find its food for hundreds of years in the same
spot. There was a certain boldness in these utterances of
Ingen-Houss, and a considerable confidence in his own con-
victions, for at that time the absolute amount of carbon dioxide
in the air had not been ascertained, and the small quantity of
it in proportion to the other constituents of air would certainly
have deterred some persons from seeing in it the supply of the
huge masses of carbon which plants accumulate in their
structures.

Before Ingen-Houss in the work last mentioned explained
the results of his observations of 1779 in accordance with the
new chemical views, and laid the foundations of the doctrine
of nutrition in plants, Je.\n Senebier \ of Geneva, made pro-

^ Jean Senebier, born at Geneva in 1742, was the son of a tradesman, and
after 1 765 pastor of the Evangelical Church. On his return from a visit to Paris
he published his ' Moral Tales,' and at the suggestion of his friend Bonnet
competed for a prize offered at Haarlem for an essay on the Art of Observation.
He was awarded the second place in this competition. In 1769 he became

496 Theory of the Nutrition [Book hi.

tracted researches into the influence of Hght on vegetation
( 1 782-1 788), and founded on their results a theory of nutri-
tion, which he pubhshed in 1800 in a tediously prolix work in
five volumes entitled, 'Physiologic vegetale.' In this work
some valuable matter was concealed in a host of unimportant
details and tiresome displays of rhetoric, which for the most
part are beside the question. But it must be acknowledged
that Senebier was better provided with chemical knowledge
than Ingen-Houss, and that he brought together all the scat-
tered facts that the chemical literature of the day offered, in
order to obtain a more complete representation of the pro-
cesses of nutrition. It was of especial importance at that time
to insist on the principle that the processes of nutrition within
the plant must be judged by the general laws of chemistry ;
organised beings, said Senebier, are the stage, on which the
affinities of the constituents of earth, water, and air mutually
influence each other ; the decompositions however are gene-
rally the result of the influence of light, which separates the
oxygen of the carbon dioxide in the green parts of plants. He
insists (II. p. 304) upon this among other facts, that the simple
constituents of all plants are the same, and the differences are
only quantitative. He then brings before us the simple and
compound constituents of plants one after the other, and
among them light and heat figure as material substances, in ac-
cordance with the view of the time. He treats at great length the
old question of the meaning of the salts in the plant, and it is

pastor at Chancy, and in 1773 librarian of Geneva. At this time, among
other literary labours, he translated Spallanzani's more important writings ;
he also studied chemistry under Tingry, and carried out his researches into
the influence of light. In 1791 he wrote an article for the 'Encyclopaedic
methodique ' on vegetable physiology. The revolution in Geneva drove him
into the Canton Vaud, and there he composed his ' Physiologic vegetale,'
in five volumes. He returned to Geneva in 1799 and took part in a new
translation of the Bible. He died in that city in 1809 (' Biographic
Universelle ').

Chap. II.] of Plants. Dc Saussure. 497

instructive to observe how he tries to decide whether the
nitrates, sulphates and ammonia, which are found in the sap of
plants, are introduced from without, or are formed in them
from their constituent elements ; he concludes finally that the
former is the more probable opinion. That the greater part at
least of the carbon of plants comes from the atmosphere could
scarcely be a matter of doubt with those who knew the writings
of Ingen-Houss ; but Senebier devotes special attention to this
question; he endeavours to take all the co-operating factors
into the calculation, and especially to prove once more that the
oxygen given off from the plant in light comes from the carbon
dioxide which has been absorbed, that the green parts only
and no others are able to effect this decomposition, and that
there is a sufficiency of carbon dioxide in nature to supply the
food of plants. But although he convinced himself that green
leaves decompose the carbon dioxide which surrounds them in
a gaseous form, he supposed that it is chiefly through the roots
that this substance finds its way with the ascending sap into
the leaves, and this view often gave occasion to further error in
later writers.

The tedious prolixity of Senebier's book was one reason
why it never enjoyed the measure of appreciation and influence
which it deserved; but it was also thrown into the shade by
the appearance of a work of superior excellence, distinguished
at once by the importance of its contents, by condensation of
style, and by perspicuity of thought. This work was the
'Recherches chimiques sur la vegetation' of Theodore de
Saussure^ (1804), which contained new observations and new

' Nicolas Theodore de Saussure was bom at Geneva in 1767, and died
there in 1845. He was the son of the famous explorer of the Alps, and
assisted his father in his observations on Mont Blanc and the Coldu Geant,
In 1797 he wrote his treatise on carbonic acid in its relation to vegetation,
a prelude to his ' Recherches chimiques ' ; the latter work received great
attention from the scientific world, and he was made a corresponding
member of the French Institute. He was a man of literary tastes, and took

Kk

49^ Theory of the Nutrition [Book hi.

results, and what was still more important, a new method.
Saussure adopted for the most part the quantitative mode of
dealing with questions of nutrition; and as the questions
which he put were thus rendered more definite, and his ex-
periments were conducted in a most masterly manner, he
succeeded in obtaining definite answers. He knew how to
manage his experiments in such a manner that the results were
sure to speak plainly for themselves ; they had not to be
brought out by laborious calculation from those small and, as
they are called, exact data, which less skilful experimenters use
to hide their own uncertainty. The directness and brevity with
which precise quantitative results are expressed, the close reason-
ing and transparent clearness of thought, impart to the reader of
de Saussure's works a feeling of confidence and security such as
he receives from scarcely any other writer on these subjects
from the time of Hales to our own. The ' Recherches chi-
miques' have this in common with Hales' 'Statical Essays,'
that the statements of facts which they contain have been made
use of again and again by later writers for theoretical purposes,
while the theoretical connexion between them was constantly
overlooked, as we shall have reason to learn in the following
section. It is not every one who can follow a work like this,
which is no connected didactic exposition of the theory of
nutrition, but a series of experimental results which group
themselves round the great questions of the subject, while
the theoretical connection is indicated in short introductions
and recapitulations, and it is left to the reader to form his own
convictions by careful study of all the details. It was not
de Saussure's intention to teach the science, but to lay its
foundations ; not to communicate facts, but to establish them ;

part also in public affairs, being repeatedly elected to the Council of Geneva.
His preference for a secluded life is said to have been the reason why
he never undertook the duties of a professorship. See the supplement to
the ' Biographie Universelle ' and Poggendorf's ' Biographisch-litterarisches
Handworterbuch.'

Chap. II.] of Plants. De Saussure. 499

the style therefore, as might be expected, is dry and unattrac-
tive; the writer seems to confine himself too anxiously within the
limits of what is given in experience, and there is no doubt that
many errors in later times might have been avoided if the
inductive proof of de Saussure's doctrines had been accom-
panied with a deductive exposition of them of a more didactic
character.

The processes of vegetation examined by de Saussure were,
for the most part, the same as those which Ingen-Houss and
Senebier had studied at length and correctly described in
their general outlines. But de Saussure went beyond this,
and by means of quantitative determinations struck a balance
between the amount of matter taken up and given off by the
plant, thereby showing what it retains. In this way he made
two great discoveries : that the elements of water are fixed in
the plant at the same time as the carbon, and that there is no
normal nutrition of the plant without the introduction of
nitrates and mineral matter. But we cannot form a due idea
of de Saussure's services to physiology without going further into
the detail of his work.

We will first consider his investigations respecting the as-
similation of carbon in plants. Here we have the important
result, that larger quantities of carbon dioxide in the atmo-
sphere surrounding the plants are only favourable to vegetation
if the latter are in a condition to decompose them, that is, if
they are in sufficiently strong light ; that every increase in the
amount of carbon dioxide in the air in shade or in darkness is
unfavourable to vegetation, and that if that increase is greater
than eight times in the hundred it is absolutely injurious. On
the other hand he found, that the decomposition of carbon
dioxide by the green parts in light is an occupation that is
necessary to them, that plants die when they are deprived of
it. The first clear insight into the chemical processes which
accompany the decomposition of carbon dioxide in the interior
of the plant was obtained by perceiving, that plants by appro-

K k 2

5oo Theory of the Nutrition [Book hi.

priating a definite quantity of carbon make a much more than
proportionate addition to their dry substance, and that this is
due to the simultaneous fixation of the component parts of
water. The full significance of this fact could only be appre-
hended at a later time, when the theory of the combinations of
carbon, organic chemistry, had been further developed. As
regards the importance of the decomposition of carbon dioxide
by the green organs under the influence of light to the whole
nourishment of the plant, de Saussure arrived by more definite
proofs than Ingen-Houss had given at the result, that only
a small portion of the substance of plants is derived from the
constituents of the soil in solution in water, but that the great
mass of the vegetable body is built up from the carbon dioxide
of the atmosphere and the constituents of water ; he con-
vinced himself of this partly by considering the small quantities
of matter which the water is able to dissolve from a soil capable
of sustaining vegetation, partly by experiments in vegetation
and considerations of a more general character.

Not less important were de Saussure's investigations into
oxygen-respiration by plants, which taken simply as a fact, had
been previously discovered by Ingen-Houss. But de Saussure
showed that growth is impossible without this process of re-
spiration, even in germinating plants, though these are rich in
assimilated matter. He further showed that green leaves and
opening flowers, and generally the parts of plants which are
distinguished by greater activity of vital processes, require more
oxygen for respiration than those in a less active and resting
state. He determined the loss of weight which the organic
substance of germinating plants suflers from respiration, and
found it to be greater than was proportionate to the weight of
carbon exhaled ; but the chemical science of his day did not
supply him with a certain explanation of this fact. Lastly,
de Saussure at a later time (1822) discovered the chief relations
between the internal heat of flowers and their consumption of
oxygen, and thus we see that he supplied the most important

Chap. II.] of Plants. De Saussurc. 501

elements in the modern theory of the respiration of plants,
though he did not fully explain their mutual connection.

It evidently was the received opinion before the time of
Ingen-Houss, and in spite of Hales' views, that plants derive
the larger part of their food from the constituents of earth and
water. But when it became known that the carbon, which is
the chief constituent of vegetable substance, comes from the
atmosphere, and it was considered that much the larger part of
that substance is combustible, it naturally became a question
whether the incombustible ingredients which form the ash take
any part in the nutrition of plants. This question was by many
physiologists answered in the negative ; but de Saussure main-
tained the contrary view. He insisted that certain ingredients,
which are found in the ash of all plants, must not be regarded
as accidental admixtures, and that the small quantities in which
they occur are no proof that they are not indispensable ; and
he showed from a large number of analyses of vegetable ash,
which for a long time were unsurpassed in excellence, that
there are certain relations between the presence of certain sub-
stances in the ash and the condition of development of the
organs of the plant ; for instance, he found that young parts of
plants capable of development were rich in alkalies and phos-
phoric acid, while older and inactive portions were richest in
lime and silicic acid. Still more important were the experi-
ments in vegetation, by which he showed that plants, whose
roots grow not in earth but in distilled water, only take up as
much ash-constituents as corresponds with the particles of dust
which fall into the water ; and fur. her, that the increase in the
organic combustible substance of a plant so grown is very
insignificant, and consequently that there is no normal vege
tation where the plant does not take up ash-constituents in
sufficient quantity, — a result of the highest importance to the
main question. Unfortunately de Saussure neglected to state
these results with due emphasis and to point out their fun-
damental importance, and consequently doubts were enter-

5oa Theory of the Nutrition [Book hi.

tained even till after 1830 respecting the necessity of the
constituents of the ash to vegetation.

It was known in de Saussure's time that nitrogen entered into
the substance of living plants ; the question was, whence it was
obtained. As it was known that four-fifths of the atmosphere
consists of nitrogen, it was natural to suppose that it is this
which the plant makes use of for forming its nitrogenous sub-
stance. De Saussure endeavoured to settle the question by the
volumetric method, which, as was afterwards discovered, was
not in this case to be trusted. Nevertheless he arrived at the
right conclusion, that plants do not assimilate the nitrogen of
the atmosphere ; this gas must therefore be taken up by the
roots in some form of chemical combination. He made no
experiments on growing plants to decide what that form was,
but contented himself with the conjecture that vegetable and
animal matter in the soil and ammoniacal exhalations from it
supply the nitrogen in plants. This question, first ventilated
certainly by de Saussure, and afterwards the subject of protracted
discussion, was finally settled fifty years later by the experi-
ments of Boussingault.

In connection with his researches into the importance of the
constituents of the ash, de Saussure proposed the question
whether roots take up the solutions of salts and other substances
exactly in the form in which they offer themselves. He found
first of all that very various and even poisonous matters are
absorbed by them, and Ihat there is therefore no such power of
choice, as Jung had once supposed ; on the other hand, it
appeared that the solutions do not enter unchanged into the
roots, for in his experiments in every case the proportion of
water to the salt absorbed was greater than the proportion
between them in the solution, and that some salts enter the
plant in larger, some in smaller quantities, under circum-
stances in other respects the same. But at this time, and for
a long time after, it was not possible to understand and rightly
explain these facts ; the theory of diffusions was not yet known,

Chap. II.] of Plauts. Dc Saussurc. 503

and fifty or sixty years were to elapse before light was thrown
on the questions thus raised by de Saussure.

Such were the most important contents of de Saussure's pub-
Hcation in 1804. His later contributions to the knowledge of
some important questions in vegetable physiology will be men-
tioned further on. A comparison of the contents of the
' Recherches chimiques ' with what was known of the che-
mistry of the food of plants before 1780 excites the liveliest
astonishment at the enormous advance made in these twenty-
four years. The latter years of the iSth century had proved
still more fruitful, if possible, as regards the theory of nutrition
than the latter years of the 17th; both periods have this in
common, that they developed an extraordinary abundance of
new points of view in every branch of botanical science. They
resemble each other also in the circumstance that they were
both followed by a longer period of inactivity ; the time from
Hales to Ingen-Houss was highly unproductive, and so also were
the thirty years that followed the appearance of de Saussure's
great work, though it must be admitted that some good work
was done during that period in France, while in Germany the
new theory was grossly misunderstood by the chief repre-
sentatives of botany, as we shall see in the following section.
It should be mentioned however that one of these misconcep-
tions, which was not removed till after i860, was caused by
de Saussure himself. He had observ^ed that the red leaves of
a variety of the garden Orache disengage oxygen from carbon
dioxide, as much as the green leaves of the common kind. In
this case he was hasty, and concluded from this single ob-
servation that the green colour is not an essential character of
the parts which decompose carbonic acid; if he had only
removed the epidermis of the red leaves he would have found
that the inner tissue is coloured as dark green as the ordinary
green leaves. He who was usually so extremely careful as an
observer was for once negligent, and later writers, as is apt to
happen, fixed exactly on this one weak point, and repeatedly

504 Theory of the Nutrition [Book hi.

called in question one of the most weighty facts of vegetable
physiology, namely, that only cells which contain chlorophyll
eliminate oxygen.

5. Vital force. Respiration and heat of plants.
Endosmose. 1 804-1 840.

During the twenty years that followed the appearance of
de Saussure's chemical researches the theory of the nutrition of
plants can scarcely be said to have been advanced in any one
direction, while much that had already been accomplished was
not even understood. Various circumstances worked together
to introduce misconceptions in this province of botany ; above
all others the inclination, more strongly pronounced than ever
at this period, to attribute to organisms a special vital principle
or force, which was supposed to possess a variety of wonderful
powers, so that it could even produce elementary substances,
heat, and other things out of nothing. Whenever any process
in such organisms was difficult to explain by physical or che-
mical laws, the vital force was simply called in to bring about
the phenomena in question in some inexplicable manner. It
was not that the question was now raised, which at a later time
engaged the attention of profounder thinkers, whether there
was a special agent operating in organic bodies beside the
general forces which govern inorganic nature ; for a careful
examination of this question would certainly have led to the
most earnest efforts to explain all the phenomena of life by
physical or chemical laws. On the contrary, it was found con-
venient to assume this vital force as proved, and to assign it as
the cause of a variety of phenomena, thus escaping the neces-
sity of explaining the way in which the effects were produced ;
in a word, the assumption of a vital force was not a hypothesis
to stimulate investigation, but a phantom that made all intel-
lectual efforts superfluous.

Another hindrance to the progress of physiology, especially

Chap. II.] of Plants. De Saussure. 505

where questions of nutrition turned on the movement of the
sap, was the backward condition of the study of the inner
structure of plants, as described in the second book. For
instance, the question of the descending sap was complicated
in the strangest way by Du Petit-Thouars's theory of bud-roots
that descend between the bark and the wood ; Reichel's un-
founded idea of the rising of the sap in the tubes of the wood
was generally accepted, and a still worse error was maintained
by some, that the intercellular spaces of the parenchyma are
true sap-conveying organs. In 181 2 Moldenhawer had to in-
sist, but without producing any general conviction, that the
vessels of the wood contain air, and Treviranus in 1821 that
the stomata serve for the entrance and exit of air. We need
not notice here what nature-philosophers like Kieser said about
nutrition and the movement of the sap ; but even those who
were far from adopting the extravagancies of this school were
incapable of either making use of or carrying on the labours of
Ingen-Houss, Senebier, and de Saussure. We may adduce in
proof of this statement the remarks of Link on the function of
leaves in his 'Grundlehren der Anatomic und Physiologic,' 1807.
He says at p. 202 that their function is according to Hales
transpiration, according to Bonnet absorption, according to
Bjerkander the exudation and secretion of a variety of fluids,
according to Hedwig the storing up of juices, and inasmuch as
leaves increase the green surfaces of plants, bear stomata and
hairs, and hold a quantity of juices in their abundant paren-
chyma, we may ascribe all these functions, but none of them
exclusively, to leaves ; the only thing peculiar to them is that
they convey elaborated juices to the young parts. Their great
work, the decomposition of carbon dioxide, he does not men-
tion. But this neglect of the doctrines of Ingen-Houss, Sene-
bier, and de Saussure was common, especially in Germany ; it
is seen in the efforts made to prove once more the existence of
a descending sap in the rind, just as it had been proved in the
two previous centuries, by the result of removing a ring of bark

5o6 Theory of the Nutrition [Book in.

from the stem, and by similar experiments ; whereas the
simple consideration that it is only in the green leaves that
carbonaceous vegetable substance is formed, would have made
the existence of what was known as a descending sap appear
to be a matter of course, and must have led to a much clearer
conception of the matter. But this consideration was either
quite overlooked or only mentioned incidentally by those who
occupied themselves with experiments on the movement of the
descending sap. This is the case in Heinrich Cotta's ' Natur-
beobachtungen iiber die Bewegung und Function des Saftes
in den Gewachsen,' 1806, in many respects an instructive
work, and in Knight's otherwise serviceable experiments on
the growth in thickness of trees. It was not till after 1830 that
De CandoUe and Dutrochet perceived that the fact that the
green leaves are assimilating organs must be decisive of the
question of the movement of the sap in the stem.

No progress was made with the general doctrine of nutrition
between 1820 and 1840 except in one point, the absorption of
oxygen by all parts of plants ; here something was done to
consolidate the theory and to enrich it with new facts ; it was
indeed a subject more adapted to the views of the day, because
it at once suggested a variety of analogies with the respiration
of animals. Grischow showed in 1819 that Fungi never de-
compose carbon dioxide, but absorb oxygen and give off
carbon dioxide. Marcet carried the subject further in 1834, after
de Saussure had published in 1822 an excellent investigation
into the absorption of oxygen by flowers ; in this work we
have the basis laid for the theory of vegetable heat, to which
we shall return. But Dutrochet was the first who made an
elaborate comparison of the respiration of plants and animals
(1837), and showed that not only growth, as de Saussure had
already perceived, but also the sensitiveness of plants depends
on the presence of oxygen, that is on their respiration. The
recognition of the fact, that the inhalation of oxygen plays the
same part in plants that it does in animals, prepared the way

Chap. II.] of Plants. De Saussurc. 507

for the view that heat in plants is simply a result of their respi-
ration, as it is in animals. It is not necessary to describe at
length the experiments which were made on heat in plants
before 1822 ; they were one and all vitiated by a want of clear-
ness in the statement of the question, which made success
impossible ; it was assumed that this heat by raising the tem-
perature of the plant would make itself felt by surrounding
objects, and it was sought for exactly where it is least to be
found, in the wood, in fruits and tubers, and generally in resting,
inactive parts. Moreover the previous experiments, collected
in Goeppert's book 'Ueber die Warmeentwicklung der Pfianzen,'
1830, were so unskilfully managed that they could not possibly
lead to any result. Nor could the question whether plants
really develope internal heat, as animals do, be determined by
a few cases of active development of heat in flowers, because
an idea was prevalent at the time in connection with the theory
of a vital force, that flowers as the organs of reproduction alone
possessed the power of generating heat.

Lavoisier had clearly perceived in 1777 that the combustion
of substances containing carbon by inhaled oxygen was the
source of animal heat, and had proved it by experiments.
Senebier, who first observed the rise of temperature in the in-
florescence of Arum by the thermometer, had at least suggested
in his work on physiology of 1800 (iii. p. 315) that a vigorous
absorption of oxygen might be the cause of the phenomenon.
Bory de St. Vincent reported in 1804 that Hubert, the owner
of a plantation in Madagascar, had observed among other things
that the air in which the flowering spike of one of the Aroideae
had developed its heat could support neither animal respiration
nor combustion. These indications were however disregarded,
until de Saussure in 1822 proved directly the connection between
the absorption of oxygen and the rise of temperature in flowers.
It was however a long time before heat in plants was con-
ceived of as a general fact necessarily connected with their
respiration. This conception would have swept away the

5o8 Theory of the Nutrition [Book hi.

whole mass of facts accumulated by Goeppert in his book of 1 830,
from which he tried to prove (p. 228) that plants at no period of
their life possess the power of generating heat — a view which
he retracted however in 1832, when he had observed a rise
of temperature in germinating plants, bulbs, tubers, and in
green plants, when collected into heaps. How difficult it was
for physiologists under the dominion of the 'vital force' to
hold firmly to the simple principle of natural heat, and not to be
led away by isolated observations, is shown by the expressions
of De CandoUe in 1835, and still more by those of Treviranus
in 1838. It is therefore refreshing to see Meyen in his ' Neues
System' (1838), vol. ii, warmly asserting this principle, and
making the development of heat in plants a necessary con-
sequence of their respiration and of other chemical processes.
Meyen himself produced no new observations ; but Vrolik
and De Vriese showed by laborious experiments in 1836 and
1839 the dependence of the generation of heat in the flowers
of Aroideae on the absorption of oxygen. A higher importance
as regards the general principle attaches to the attempt of Du-
trochet in 1840 to prove that even growing shoots generate
small quantities of heat, as shown by a thermo-electric ap-
paratus. Some of the details in these observations are open
to objection ; but it cannot be denied that they are based on a
clear recognition of the general principle, though they ignore
the consideration that the generation of heat in plants is not
necessarily accompanied with a rise in temperature, since
cooling causes may be acting at the same time with greater
effect. However the doctrine of the natural heat of plants
was in the main established by the observations of de Saussure,
Vrolik, De Vriese, and Dutrochet, and by Meyen's and Du-
trochet's assertion of the principle laid down by Lavoisier,
though thirty years elapsed before it became an accepted truth
in vegetable physiology.

The crude idea of a vital force was deprived of one of its
chief supports when it was recognised that the natural heat of

Chap. II.] of Plants. Dutrochet. 509

organisms was a product of chemical processes induced by
respiration, for this had been regarded since the time of Aris-
totle as more peculiarly an effect of the principle of life. And
now another discovery was made, equally calculated to pro-
mote the reference to mechanical principles of those general
and important phenomena of life which had hitherto been in-
dolently ascribed to the operation of the vital force. It appears
to be a matter of indifference whether Professor Fischer of
Breslau is or is not to be considered as the true discoverer of
endosmose in 1822, for it is certain that it was Dutrochet^
who first studied the subject with exactness, and above all per-
ceived its extraordinary value for the explanation of certain
phenomena in living organisms. He repeatedly called atten-
tion to this value in the years between 1826 and 1837, and
endeavoured to refer a variety of phenomena in vegetation to
this agency. He had first observed the operation of endos-
mose in its mechanical effects in living bodies ; the escape of
the zoospores of an aquatic Fungus and the ejection of the
sperm from the spermathecae of snails first led him to the
hypothesis, that the more concentrated solutions inclosed in
organic membranes exercise an attraction on surrounding
water, which, forcing its way into the inclosed space, is there
able to exert considerable powers of pressure. To Dutrochet

1 Henri Joachim Dutrochet, born in 1776, was a member of a noble family
which belonged to the department of thelndre and lost its property during the
revolution ; he therefore adopted medicine as a profession, and took his
degree at the Faculty of Paris in 1806. He was attached to the armies in
Spain as military surgeon in 1S08 and 1809 ; but he retired as soon as
possible from practice and devoted himself in great seclusion to his physio-
logical pursuits, living for some years in Touraine. He was made cor-
responding member of the Academy in 1S19, and communicated his
discoveries to that body. Becoming an ordinary member in 183 1, he spent
the winter months from that time forward in Paris. He died in 184.7 after
two years' suffering from an injury to the head. Dutrochet was one of the
most successful champions, in animal as well as vegetable physiology, of
the modem ideas which displaced the old vitalistic school of thought after
1820. See the ' Allgemeine Zeitung ' for 1847, P- 7^0.

510 Theory of the Nutrition [Book hi.

must always belong the merit of having brought into notice
this mechanical effect of endosmose and of employing it to
explain a number of vital phenomena. Many things in which
a mechanical explanation had not been hitherto thought of
could now be traced to a mechanical principle, the effects
of which could be exhibited and more accurately studied
by means of artificial apparatus. Dutrochet rightly attached a
special value to the fact, that all states of tension in vegetable
tissue could be at once explained by endosmose and exosmose,
though, as so often happens in such matters, he may have ex-
tended his new principle to cases where it was not applicable,
as we shall see below. His account of the nature of endos-
mose itself must now be considered to be obsolete, nor did
the mathematician Poisson or the physicist Magnus about
1830 succeed in framing a satisfactory theory on the subject.
It was discovered in the course of the succeeding twenty
or thirty years, that the phenomena observed by Dutrochet,
and which he called endosmose and exosmose, were only com-
plicated cases of hydro-diffusion, which with the diffusion of
gas forms an important part of molecular physics. Dutrochet,
like his immediate successors, conducted his investigations
into osmose with animal and vegetable membranes, the latter
being of a complex structure ; with these he always observed
in addition to the endosmotic flow of water into the more
concentrated solution, an escape of the solution itself, and
from this he concluded that there must always be two currents
in opposite directions through the membrane which separates
the two fluids, that, as he expresses it, the endosmose is always
accompanied with exosmose. This error, which was even
developed later into a theory of the endosmotic equivalent, has
had much to do till recently with making it impossible or
difficult to refer certain phenomena of vegetation to the pro-
cesses of hydro-diffusion. To mention only one case, Schlei-
den rightly observed that if endosmose, as Dutrochet under-
stood it, is the sole cause why water is absorbed by the roots,

Chap. II.] of Plants. Dutrochet. 511

there must also be a corresponding exosmose at the roots ;
and this, which was called root-discharge, Macaire Prinsep
thought he had actually discovered, and even Liebig firmly
believed in its existence till a recent period, although the
researches of Wiegman and Polstorft' (1842) and later more
careful investigations showed, that there was no noticeable
discharge by exosmose to answer to the great quantity of
water with substances in solution in it which is taken up by
the roots. Again, Dutrochet's theory of endosmose did not
fully explain the way in which the several substances which
feed the plant find their way into and are disseminated in
it. But notwithstanding these and other defects it deserved
the greatest consideration, because it gave the first impulse
to the further development of the theory of diffusion, and
contained a mechanical principle which might serve to explain
very various phenomena in vegetation as yet unexplained.
Dutrochet hastened to apply it to this purpose, where it was at
all possible to do so, and chiefly in his treatise on the ascend-
ing and descending sap ('Memoires,' 1837, i. p. 365), which
was superior to anything which had been written on the move-
ment of the sap in plants in its clear conception of the question
and in perspicuity of treatment. It should be especially men-
tioned that Dutrochet formed a true estimate of the functions
of the leaves as regards both the ascending and descending
sap, and to some extent pointed out the fault which lies at the
bottom of the earlier experiments with coloured fluids. After
communicating a number of good observations on the paths of
the ascending and descending sap, and noticing particularly
that in the vine the vessels of the wood serve for the movement
of the sap only in spring, when vines bleed, but that they are
air-passages in summer, when transpiration causes the most
copious flow of water in the wood, he proceeds to consider the
forces which effect the movement of the ascending sap in the
wood both in spring and summer. He first of all judiciously
distinguishes two things which had been before always mixed

51 a Theory of the Nutrition [Book hi.

up together, the weeping of severed root-stocks and the rise of the
sap in the wood in transpiring plants. The first is caused, he
thinks, by impulsion, the other by attraction; we should now say,
that in weeping root-stocks the water is pressed upwards, in trans-
piring plants drawn up. He then refers the phenomenon of im-
pulsion to endosmose in the roots, and without going much into
detail as regards the anatomical conditions, he compares a
weeping root-stock to his own endosmometer, in the tube
of which the fluid that has been sucked in rises by endosmose
and even flows over ; it is true that no very thorough under-
standing of the matter was gained in this way, but at any
rate the principle which was to explain it was indicated.
He then endeavours to explain the movement of the water
which ascends in the wood of transpiring plants by the action
of endosmose from cell to cell. In this he failed entirely,
as was afterwards perceived ; but he succeeded in showing
that all the mechanical explanations that had been previously
attempted were incorrect, and the whole treatise, though
unsatisfactory in its main result, contains a great number of
ingenious experiments and acute remarks.

With the exception of Theodore de Saussure, who occupied
himself exclusively with chemical questions in physiology,
Dutrochet was the only vegetable physiologist in the period
between 1820 and 1840 who studied all its more important
questions thoroughly and experimentally; his treatise on the
respiration of plants, which has been already mentioned, is
excellent in itself, and was of the greatest importance at the
time it appeared, because it brought the chemical processes in
respiration, the entrance and exit of the gases, for the first time
into correct connection with the air-passages in the plant, with
the stomata, the vessels, and the intercellular spaces, and sub-
mitted the composition of the air contained in the cavities of
plants to careful examination. It was the best work on the
respiration of plants in the year 1837 and for a long time after ;
and if Dutrochet made the mistake of regarding the oxygen

Chap, ii.] of Plaiifs. Dutrochet. 513

which is disengaged from the plant itself in the hght as the
chief agent in respiration, and the oxygen directly absorbed
from the atmosphere as only subsidiary to this, he compensated
for it by recognising the importance of the fact, that only cells
which contain chlorophyll decompose carbon dioxide, and still
more by correctly distinguishing between respiration by the
absorption of oxygen and the decomposition of carbonic
dioxide in light ; these two processes were at that time and
afterwards very inappropriately distinguished as the diurnal and
nocturnal respiration of plants, and this misleading expression
maintained itself in spite of Garreau's protest in 185 1 till after
i860, when a modern German physiologist succeeded in
establishing the true distinction between respiration and
assimilation in plants. Another mischievous complication
arose about 1830 connected with the expression, circulation of
the sap ; it was thought that an argument for such a circulation
even in the higher plants was to be found in the ' circulation
of the sap ' (protoplasm) in the cells of the Characeae, which
had been detected by Corti and more exactly described by
Amici ; Dutrochet (Memoires, I. p. 431) exposed this confusion
of ideas, and has the merit of refuting at the same time the
absurd theory of the ' circulation of the vital sap,' for which
Schultz-Schultzenstein had received a prize from the Academy
of Paris.

We shall recur in the next chapter to Dutrochet's minute in-
vestigations into the movements connected with irritability in
plants, which he also endeavoured to refer to endosmotic
changes in the turgidity of the tissues, but he did not do justice
to the anatomical conditions of the problem. And here we
may take occasion to remark, that Dutrochet's works were
often undervalued, especially in Germany, greatly to the
detriment of vegetable physiology. His younger German con-
temporaries, von Mohl and Schleiden, and at a later time
Hofmeister, were right in pointing out what was erroneous
and sometimes arbitrary in his mechanical explanations of

l1

514 Theory of the Nutrition [book hi.

various movements in plants, and it cannot be denied that he
was sometimes led into obscure and doubtful views, as for
instance when without any apparent connection he regarded
the inhalation of oxygen as a mechanical condition of the rising
of the sap and also of heliotropic curvatures, and that his
attempts at explanation were not seldom forced and impro-
bable ; but all this does not prevent it from being true, that an
attentive reader will still gain much instruction from his physio-
logical writings and be excited by them to examine for himself.
Dutrochet was a decidedly able man and an independent
thinker, who it is true was often led astray by his prejudices,
but at the same time manfully protested against the old tradi-
tional way of dealing with physiological ideas, and substituted
careful examination both of his own and others' investigations
for the accumulation and comfortable retailing of isolated ob-
servations which was then the fashion. After de Saussure's
' Recherches chimiques ' Dutrochet's ' Memoires pour servir a
I'histoire anatomique et physiologique des vegetaux et des ani-
maux,' 1837, are without doubt the best production, which
physiological literature has to show in the long period from
1804 to 1840. If later botanists, instead of dwelling on his
faults, had developed with care and judgment all that was
really good in his general view of vegetable physiology, this
branch of botanical science would not have declined as it did
in the interval between 1840 and i860. We shall discover
the greatness of Dutrochet as a vegetable physiologist by com-
paring his work above-mentioned with the best text-books of
the subject of the same time, those of De Candolle, Trevira-
nus, and Meyen ; not one of them comes up to Dutrochet's
Memoires in acuteness or depth.

The three text-books just mentioned contained little or
nothing new either in facts or ideas on the subject of the
nutrition of plants ; all three were rather compilations of what
was already known, and differed from each other only in their
selection of material and in the form which each sought to give

Chap. II.] of Plauts. Dc Caudolle. 515

to the general theory ; but this is a reason why we should take
a nearer look at them, that we may learn how the spirit and
tendencies of the time were reflected in vegetable physiology,
and made themselves felt particularly in the theory of nutrition.
De Candolle's work appeared in French in 1832 in two
volumes, the first only being devoted to the subject of the
nutrition of plants, and in German in 1833 with many valu-
able annotations by the translator Roeper, under the title,
' Pflanzen-physiologie oder Darstellung der Lebenskriifte und
Lebensverrichtungen der Gewachse.' It suffers, in common
with the other two books we have mentioned on the same
subject, and with the earlier works of Du Hamel, Mustel,
and other writers, from a too discursive mode of treatment,
w^hich has the eff"ect of burying the points of fundamental
importance under a huge mass of facts and statements from
other writers. It contains much that might have been
omitted as obsolete, and much empirical material of a purely
chemical nature, which could not at that time be applied to
the purposes of physiology. Nevertheless, it deserved the
great consideration which it enjoyed for a long time, especi-
ally in Germany, for its author had undertaken to treat veget-
able physiology as a separate and peculiar branch of know-
ledge, not ignoring at the same time its connection with and
dependence on physics, chemistry, phytotomy, and biology
proper, and thus to give a full and complete delineation of
vegetable life ; whereas the best works that had been written
since Du Hamel's time, especially on the nutrition of plants,
had proceeded from chemists and physicists or from plant-
growers like Knight and Cotta, who treated the subject in a
one-sided manner, each from his own point of view, and made
no attempt to give a connected account of all the phenomena
of vegetation. For this reason De Candolle's ' Physiologie
vegetale' is the most important performance that appeared
after Du Hamel's ' Physique des Arbres ' ; and if we wish to
know what progress was made in vegetable physiology gener-

L 1 2

5t6 Theory of the Nutrition [Book hi.

rally, and in the doctrine of nutrition particularly, in the period
from 1758 to 1832, we have only to compare the contents of
these two books. That this progress was a considerable one,
appears plainly from a short summary at the end of the first
volume of the general theory of nutrition, as De Candolle him-
self conceived it ; this summary will show us at the same time
that he aimed rather at giving a clear account of the whole of
the internal economy of the plant, than at searching into the
moving forces, the causes and effects. From this he was
necessarily withheld by his assumption of a vital force. He
distinguished four kinds of forces ; the force of attraction which
produces the physical, and that of elective affinity which causes
the chemical phenomena; then the vital force, the original
source of all physiological, and the soul-force, the cause of all
psychical phenomena. Only the first three of these forces
operate in the plant, and though it is necessary to find out what
phenomena in vegetation are due to physical or chemical causes,
yet the main task of the vegetable physiologist is to discern
those which proceed from the vital force, and the chief mark of
such phenomena is that they cease with the death of the plant
(p. 6). Of course therefore all the peculiar phenomena of nutri-
tion, which are manifested only in the living plant, come within
the domain of the vital force. It must be allowed, however, that
De Candolle has made a very moderate use of the vital force,
and confines himself wherever he can to physical and chemical
explanations ; and when he has recourse to the vital force, it is
owing less to the influence of his philosophical point of view
than to the fact that his account is based rather on tradition and
information at second hand than on actual research. It is true
that De Candolle was perhaps better acquainted than any con-
temporary botanist with the physics and chemistry of his day,
and it is part of his great merit that he should have acquired
so much knowledge on these subjects while engrossed in his
splendid labours as a systematist and morphologist ; but he be-
trays, at least in his later years, a want of practice in the study

Chap. II.] of Plants. De Candolle. 517

of physics and a want also of the habit of mind which this
imparts, and which is more important to the physiologist than a
knowledge merely of many facts. But this defect is still more
apparent in Treviranus and Meyen, whose works on physiology
were published soon after that of the great systematist.

De Candolle first brings together all the facts in physiology
which have been discovered from the beginning, not omitting
the chemical researches of more modern times into the sub-
stance of plants, and then gives a general delineation of the
processes of nutrition in the plant : ' The spongioles (an unfor-
tunate invention of his own which has not yet disappeared from
French books, and plays a great part in Liebig's latest work) —
the spongioles of the roots, being actively contractile and aided
by the capillarity and hygroscopic qualities of their tissue, suck
in the water that surrounds them together with the saline organic
or gaseous substances with which it is laden. By the operation
of an activity which is manifested principally in the contractility
of the cells and perhaps also of the vessels, and is maintained
by the hygroscopic character and capillarity of the tissue of the
plant and also by the interspaces produced by exspiration of
the air and by other causes, the water sucked in by the roots
is conducted through the wood and especially in the inter-
cellular passages to the leaf-like parts, being attracted in a
vertical direction by the leaves and in a lateral direction by the
cellular envelope (cortical parenchyma) at every period of the
year, but chiefly in the spring ; a considerable part of it is
exhaled all day long through the stomata into the outer air in
the form of pure water, leaving in the organs in which the
evaporation takes place all the saline, and especially all the
mineral particles which it contained. The crude sap which
reaches the leaf-like parts of the plant there encounters the
sun-hght, and by it the carbonic acid gas held in solution by
the sap, whether derived from the water sucked in by the roots
or from the atmospheric air, or being part of that which the
oxygen of the air produced with the surplus carbon of the plant

5i8 Theory of the Nutrition [Book in.

is decomposed in the day-time ; the carbon is fixed in the plant
and the oxygen discharged as gas into the air. The immediate
result of this operation appears to be the formation of a sub-
stance which in its simplest and most ordinary state is a kind of
gum consisting of one atom of water and one of carbon, and
which may be changed with very little alteration into starch,
sugar, and lignine, the composition of which is almost the same.
The nutrient sap thus produced descends during the night from
the leaves to the roots, by way of the rind and the alburnum in
Exogens, by way of the wood in Endogens. On its way it falls
in with glands or glandular cells, especially in the rind and
near the place where it was first formed ; these fill themselves
with the sap and generate special substances in their interior,
most of which ar6 of no use in the nutrition of the plant, but
are destined either to be discharged into the outer air or to be
conducted to other parts of the tissue. The sap deposits in its
course the food-material, which becoming more or less mixed
up with the ascending crude sap in the wood, or sucked in with
the water which the parenchyma of the rind draws to itself
through the medullary rays, is absorbed by the cells and chiefly
by the roundish or only slightly elongated cells, and is there
further elaborated. This storing up of food-material, which
consists chiefly of gum, starch, sugar, perhaps also lignine, and
sometimes fatty oil, takes place copiously in organs appointed
for the purpose, from which this material is again removed to
serve for the nourishment of other organs. The water, which
rises from the roots to the leaf-like parts of the plant, reaches
them in an almost pure state, if it passes quickly through the
woody parts, the molecules of which are but slightly soluble.
If, on the other hand, the water flows through parts in which
there is much roundish cell-tissue filled with food-material, it
moves more slowly and mixes with this material and dissolves
it ; when it is drawn away from these places by the vital activity
of the growing parts, it reaches them not as pure water but
charged with nutrient substances. The juices of plants appear

Chap, ii.l of Plaiits. Dc Caudollc. 519

to be conveyed chiefly through the intercellular passages. The
vessels probably share in certain cases in these functions, but
serve generally as air-canals. The cells appear to be the really
active organs in nutrition, since decomposition and assimila-
tion of the juices take place in them. Cyclosis ( of Schultze's
vital sap^) is a phenomenon which appears to be closely con-
nected only with the preparation of the milky juices, and to be
caused by the actively contractile nature of the cell-walls or of
the tubes. Woody and other substances are deposited in every
cell in different quantities according to their kinds and the
accompanying circumstances, and clothe their walls ; the
unequal thickness of the layer so deposited appears according
to Hugo von Mohl to have given rise to the supposition of per-
forated cells ; that is, the parts of the cell-wall that remain trans-
parent appear under the microscope as pores. Every cell may
be regarded as a body which prepares juices in its interior ; but
in vascular plants their activity stands in such a connection
with a complex of organs, that a single cell does not represent
the whole organism, as may be said of the cells of certain cellular
plants, which are all like one another. There is no circulation
in plants like the circulation in animals, but there is an alter-
nating ascent and descent of the crude sap and of the formative
sap which is often mixed with it. Both these phenomena depend
perhaps on the contractile power in cells that are still young,
and if so, this power would be the true vital energy in plants.'

What is strange to us in De Candolle's theory of nutrition is
due chiefly to the predominance of the vital force ; yet at the
same time it gives the facts in their general connection, and its
best feature is, that the true function of the leaves, the decom-
position of carbon dioxide in light and the production of
organisable substance, is made the central point of the whole
circle of the processes of nutrition. Very different in this
respect were the views of the two most eminent German

* See above on page 513.

5^0 Theory of the Nutrition [Book hi.

vegetable physiologists at the close of the period before us,
Treviranus and Meyen, though they are not in accord with
one another in their general conception of the subject. It
may be said that all the prejudices and errors, built up on the
foundation of the hypothesis of a vital force during the first
thirty years of the 19th century, culminated in Treviranus;
while others were already setting up the mechanical explana-
tion of the phenomena of vegetation as the one object to be
attained, Treviranus produced once more the whole machinery
of the obsolete doctrine of the vital force, and with such
effect, that his ' Physiologie der Gewachse ' was already obso-
lete when it appeared in 1835. The second volume of
Meyen's ' Neues System der Pflanzenphysiologie ' was a strik-
ing contrast to the work of Treviranus ; Meyen endeavours as
far as possible to trace back the phenomena of vegetation to
mechanical and chemical causes, though he does not often
succeed in bringing anything to light that is new or of lasting
service. He, like Treviranus, was deficient in sound training
in chemistry and physics ; they did not stand in this respect,
as Hales and Malpighi once did, at the highest point of know-
ledge of their time. At the same time there was a great
difference in the way in which each dealt with the writings of
his predecessors ; Treviranus, who had done good service in
former years in phytotomy, was not equal to the task which
he had now undertaken ; his physiological expositions are
marked by feebleness of thought and by an inability to survey
as from a higher ground the connection between the facts ;
he distrusts all that had been done during the previous thirty
years, and almost everywhere appeals to the publications of
the 1 8th century; he lives indeed in the ideas of the past,
without gaining vigour from the forcible reasoning and fresh-
ness of thought of a Malpighi, a Mariotte, or a Hales. Meyen's
treatment of his subject is on the contrary fresh and vigorous ;
he does not disregard the old, but he holds chiefly to the
modern conquests of science ; while Treviranus with singular

Chap. II.] of Plaiits. Tveviraiius and Meyen. 521

ill-luck constantly overlooks what is valuable in itself and
important in its results, Meyen generally picks out the best
things from the books before him ; Treviranus timidly avoids
expressing any view decidedly and maintaining it ; Meyen, amid
the multiplicity of the labours which we have already described,
finds no time to arrange his thoughts, is hasty in judgment
and often contradicts himself. But with all these defects, he
is still the champion of the new tendencies that were being
developed, while Treviranus lives entirely in the past, and
shows no trace of the actively creative spirit which was soon to
burst forth so mightily in every branch of natural science.

If we examine what both these writers have said on the
subject of the nutrition of plants, we shall find that the differ-
ence in their general views in physiology as described above
appears at once in their treatment of the work of suction in
the roots, and of the means by which the sap ascends ; here in
Treviranus the vital force is everything ; it makes the vessels
of the wood conduct the juices from the roots into the leaves,
with other antiquated notions of the kind; Meyen on the
contrary adopts Dutrochet's position, and even rejects De
CandoUe's spongioles. Treviranus knows not what to make of
respiration ; Meyen explains it without hesitation as a function
that answers to respiration in animals, and finds in it the main
cause of the natural heat which Treviranus derives in the old
mystical fashion from the vital force. In one point however
they agree, namely, in a complete misconception of the con-
nection between the decomposition of carbon dioxide in the
leaves and the general nutrition of the plant. It is necessary
to the understanding of the confusion of ideas which had crept
at this time into the doctrine of nutrition, and to a right estimate
of the services of Liebig and Boussingault on this point, that
we should look a little more closely into the chemical part of
the theory of nutrition in Treviranus and Meyen.

Treviranus in the introduction to his book repudiated the
idea of a vital force separable from matter, but he was in fact

522 Theory of the Nutrition [Book hi.

a prisoner within that circle of ideas, and he made a much
freer use of the vital force than De Candolle ; he went even
farther than this, and in his want of chemical experience he
hit upon the grossly materialistic notion of a vital matter
(I. p. 6). This vital matter is a half-fluid substance, which
may be obtained from all bodies that were once alive by
boiling and by decay ; it is formed from other elements, but it
is itself the true elementary matter with which alone physi-
ology has to do ; it is common to the animal and vegetable
kingdom, and is purest when in the form of mucilage, albumen,
and gelatine ; that animals and plants alike consist of this vital
matter explains the circumstance, that plants serve as food for
animals and animals as food for plants. He goes on to show
that a similar unctuous substance, called by chemists extract of
the soil, and considered by many of them to be an important
ingredient in the nutrition of plants, is their true and proper
food. This extract of the soil was therefore the vital matter
which plants take up ; it was natural that Treviranus should no
longer attribute any importance to the decomposition of
carbon dioxide in the leaves, especially as he was unable to
understand the chemical connection of all that Ingen-Houss,
Senebier, and de Saussure had written. He explained the co-
operation of light in the nutrition of plants to be a merely
' formal condition,' and the salts in solution in the water of the
soil were in his opinion stimulants for the use of the extremities
of the roots, which were thus put into a condition of 'vital
turgescence ' ; and as the functions of the leaves, such as
Malpighi and Hales had conjectured, and Ingen-Houss, Sene-
bier, and de Saussure had proved it to be, had no existence for
Treviranus, he made the assimilation of the soil-sap take place
on its way, as it flowed upwards and downwards through the
plant. We see that nothing can be conceived more deplorable
than this theory of nutrition ; it would have been bad at the
end of the 17th century, it is difficult to beUeve that it could
have been published thirty years after de Saussure's work.

Chap. II.] of Plauts. Trevirmiiis and Meycn. 523

There is much in the details of Meyen's views on the
chemical processes in the nutrition of plants that is better than
what we find in Treviranus ; it is a great point that he con-
cluded from earlier experiments, that the salts which find their
way with the water into the roots are not merely ' stimulants '
but food-material, and, as was before said, he explained the
respiration of oxygen by plants correctly in accordance with de
Saussure's observation. But he too stumbled over the assimi-
lation of carbon ; he, like so many before and after him, was
confused by the simple fact, that gaseous matter takes part
both in the nutrition and the respiration of the plant ; and
taking the processes in both cases for processes of respiration,
he considered the absorption of oxygen to be the only im-
portant and intelligible function, and the decomposition of
carbon dioxide in light to be a matter of indifference as
regards the internal economy of the plant. Instead of ascer-
taining by a simple calculation, whether the apparently small
quantity of carbon dioxide in the atmosphere was perhaps
sufficient to supply vegetation with carbon, he simply declared
it to be insufficient, and because plants will not flourish in
barren soil merely by being supplied with water containing
carbon dioxide, he gave up the importance of that gas alto-
gether. He too found the humus-theory, which had been
constructed by the chemists, more convenient for his pur-
pose, and like Treviranus derived the whole of the carbon in
plants from ' extract ' of the soil, without any close attention
to the facts of the case ; he refused to believe that the soil
is rendered not poorer but richer in humus by the plants that
grow on it. It is obvious then that the account given by
Treviranus and Meyen of the chemical processes that take
place in the nutrition of plants, though correct in some of
the details, could afford no true general view of the processes
of nutrition, because it entirely misconceived the cardinal
points in the whole theory, namely the source of the carbon,
and the co-operation of light and of the atmosphere; and

524 Theory of the Nutrition [Book hi.

thus the best results of the observations of Ingen-Houss,
Senebier, and de Saussure were lost upon the German veget-
able physiologists.

6. Settlement of the question of the food-material
of plants. 1 840-1 860.

We have noticed in the previous section the rise of views
during the period between 1830 and 1840 which were calculated
to make the hypothesis of a vital force appear superfluous, at
least as an explanation of certain important phenomena in
vegetation ; such were the referring the natural heat of plants
to chemical processes, and the movement of the sap to osmose ;
in the domain of chemistry also, in which Berzelius had in the
year 1827 made the distinction between organic and inorganic
matter to consist in the fact, that the former is produced under
the influence of the vital force, the opinion was openly expressed
that such an intrusion of the vital principle could not be
allowed, since organic compounds had been repeatedly pro-
duced from inorganic substances by artificial means, and
therefore without its aid. The general tendency of scientific
thought was now in fact unfavourable to the nature-philosophy
of former days ; it inclined to free itself from the obscurity
that attended the idea of a vital force, and to assert the belief,
that chemical and physical laws prevail alike outside and inside
all organisms; this idea became an axiom with the more
eminent representatives of natural science after 1840, and if
not always expressed in words, was made the basis of all their
attempts to explain physiological phenomena.

Thus a freer course began to open for the intellectual
movement of the time even before the year 1840, and strict
inductive research, and above all the establishment of facts
and closer reasoning were now demanded in the question of
the nutrition of plants, as they were also in the domain of
morphology and phytotomy. But in dealing with the theory

Chap. II.] of Plants. Liehig. 525

of nutrition, the first thing required was not the discovery of
new facts so much as the forming a correct appreciation of the
discoveries of Ingen-Houss, Senebier, and de Saussure, and
clearing away the misconceptions that had gathered round
them. The chief modern representatives of vegetable physio-
logy, De Candolle, Treviranus, and Meyen, had increased the
difficulty of the task by neglecting to keep the several questions
of their science, the chemical especially and the mechanical,
sufficiently distinct from one another. The question, what are
the materials which as a rule compose the food of plants,
though one of the first and most immediate importance, had
been very imperfectly investigated, while attention had been
diverted to a confused mass of comparatively unimportant
matters, and the solution of that question had been rendered
impossible for the time by the humus-theory, an invention of
chemists and agriculturists, which Treviranus and others had
fitted so readily into the doctrine of a vital force. To Liebig
belongs the merit of removing these difficulties and all the
superfluous matter which had gradually gathered round the
subject, and of setting forth distinctly the points which had to
be considered ; this was all that was required to ensure a satis-
factory solution of the problem, for former observations had
supplied an abundance of empirical material. But some points
of minuter detail were brought out in the course of his
investigations which required new and comprehensive experi-
ments, and for these a most capable and successful observer
was found between 1840 and 1850 in the person of Boussingault.
But before we go on to give a fuller account of the work
of Liebig and Boussingault, we may mention a circumstance
which serves to indicate the character of the revolution in
scientific opinion before and after 1840. An anonymous
' Friend of science ' had put a prize at the disposal of the
Academy of Gottingen for an answer to the questions, ' whether
the inorganic elements, which are found in the ashes of plants,
are found in the plants themselves, in cases where they are not

526 Theory of the Nutrition [Book hi.

supplied to them from without ; and whether these elements
are such essential constituents of the vegetable organism, as
to be required for its full development.' The first question
appears in the present day absurd, since it implies the possi-
bility of elementary matter coming into being, and of certain
special elements coming into being in the plants themselves,
an idea however not unfamiliar to the nature-philosophy and
the vital force school. It was easy for Wiegman and Polstorff,
the authors of the essay that gained the prize (1842), men of
the new school, to answer the first question in the negative,
and indeed their answer to the second question involved a
negative answer to the first. The investigations made by
Wiegman and Polstorff in connection with the subject of the
second question were conducted in a thoroughly intelligent
manner, though they set out from the hypothesis that a certain
quantity of compounds of humic acid, as it was called, must
be present in the food-mixtures. Their experiments, better
adapted to the purpose than any previous ones, showed con-
vincingly that it is necessary to the normal nutrition of the
plant that it should take up the constituents of the ash ; the
observers also took into consideration a number of other
questions connected with nutrition, in which however we
may already see the influence of Liebig's book which had
come out during their investigations.

This work was the one entitled ' Die organische chemie in
ihrer Anwendung auf Agricultur und Physiologic,' which
appeared first in 1840 and was afterwards repeatedly reprinted
and enlarged. The name of the author, the first chemist of
Germany, raised an expectation that the questions respecting
nutrition would be dealt with otherwise than they had hitherto
been, and this expectation was more than fulfilled by the
novelty and boldness with which Liebig cleared up the most
important points of the theory, seized upon all that was
essential and fundamental, and disregarded the unimportant
matter which had before only served to confuse the question.

Chap. II.] of Plaufs. Licbig. 527

Moreover, he was able to rest on long-accepted facts in just
those points which were the most important, and on these he
had only to throw the light of his chemical knowledge to
dispel the previous darkness. In accordance with his main
purpose, which was to apply organic chemistry and vegetable
physiology to the service of agriculture, Liebig directed the
severity of his criticism first of all against the humus-theory
constructed by chemists and agriculturists and thoughtlessly
adopted by various physiologists ; this was the first thing that
must be got rid of, if the question was to be answered, of what
substances does the food of plants consist, for the humus-
theory was at once incorrect, and the product of a want of
reflection which overlooked facts which lay before men's eyes.
Liebig showed that what was known as humus is not diminished
but constantly increased by vegetation, that the quantity in
existence would not suffice for any length of time for the
support of a vigorous vegetation, and that it is not taken up
by plants. This once established, and Liebig's calculations
left no doubt on the point, there remained one source only for
the carbon of the plant, namely, the carbon dioxide of the
atmosphere, with regard to which it was shown by a very
simple calculation resting on eudiometric results that its
quantity is sufficient to supply the vegetation of the whole
earth for countless generations. It is true that Liebig in his
zeal went much too far, when he found something contradictory
in the true respiration of plants, because it is connected with
the elimination of carbon dioxide, and simply denied its reality.
On the other hand the theoretical significance of the fact
established by de Saussure, that the elements of water are
assimilated at the same time as the carbon, was now for the
first time clearly explained. Liebig was better able to realise
the importance of this fact for the theory of nutrition than
de Saussure had been. But these weighty points were not the
ones which attracted most attention with the adherents and
opponents of Liebig ; the practical tendency of his book made

528 Theory of the Nutrition [Book hi.

the discussion, to which it gave rise especially among chemists
and agriculturists, turn rather on the question of the source
of the nitrogen in the substance of plants. The humus-theory
had made the nitrogen like the carbon enter the plant in the
form of organic compounds. De Saussure in his great work of
1804 had named ammonia as a compound of nitrogen which
might be taken into consideration with others, but he arrived
at no definite conclusion. Liebig, from different points of
view and in reliance on his own investigations into the nature
of nitrogen and its compounds, arrived at the result, that
ammonia must ultimately be the sole source of the nitrogen in
the plant, and that the ammonia in the atmosphere and in the
soil is quite sufficient to supply vegetation with the requisite
amount of nitrogen just as the carbon dioxide of the atmosphere
is the sole source of the carbon of the plant ; and so he con-
cluded that ' carbon dioxide, ammonia, and water contain in
their elements the requisites for the production of all the
substances that are in animals and plants during their life-time.
Carbon dioxide, ammonia, and water are the ultimate products
of the chemical process of their putrefaction and decay.'

Liebig was less happy, at least as regards his mode of treat-
ing the subject, in his remarks on the necessity and specific
importance of the constituents of the ash to the nutrition of
plants. Instead of insisting on an experimental answer to the
question, what constituents of the ash are absolutely indispens-
able to the health of one or all plants, he lost himself in
ingenious chemical theories, intended to show the operation of
inorganic bases in fixing vegetable acids, the extent to which
different bases can replace each other, and similar matters.

It is not requisite for our purpose to follow Liebig in his
applications of his theoretical remarks to agriculture, still less
to occupy ourselves with the sensation and the discussions
which his work excited among practical and theoretical
farmers and agricultural chemists. The scientific value of
Liebig's considerations on the nutrition of plants stood out in

Chap. II.] of Plants. Liebig. 529

a purer and more definite form for the vegetable physiologists,
who turned their attention chiefly to the points mentioned
above. It is true that Liebig's work encountered lively opposi-
tion from these men also, and the two foremost representatives
of vegetable physiology at that time, Schleiden and von Mohl,
criticised it unsparingly ; this was due partly to the deductive
method adopted by Liebig, to which botanists were un-
accustomed in physiological questions, and partly to the
derogatory expressions in which he indulged against the
vegetable physiologists, whom he held responsible with the
botanists generally for all the absurdities connected with the
humus-theory. Von Mohl asked, and justly, whether de Saussure,
Davy, Carl Sprengel, Berzelius and Mulder, the real founders
of the theory, were botanists. But it was unnecessary for
von Mohl, Schleiden and others to feel touched by Liebig's
reproach, at least so far as it was addressed to professed
physiologists, for they were no more physiologists than Davy,
Berzelius or Mulder. Professed vegetable physioligists, official
public representatives of vegetable physiology there were none,
and then as now every one who occupied himself occasionally
with questions of the kind was called a vegetable physiologist.
In this way the contest became a dispute about words, and
Liebig, von Mohl and Schleiden lost an excellent opportunity
for influencing public opinion in favour of the idea, that it was
high time to establish public official representatives of so
important a branch of science, who should devote themselves
entirely to it; how could it be expected that Professors of
botany, who were required by the government and the public
to work for the advancement of systematic botany, phytotomy,
and medical botany, to give instruction in these subjects, and
to devote a large portion of their time to the management of
botanic gardens, should do much to promote the study of
vegetable physiology, which demands very considerable
acquaintance also with physics and chemistry? and where
were the laboratories and the instruments for the serious

M m

530 Theory of the Nutrition [Book hi.

prosecution of this branch of science ? But these questions
were not raised, and the old state of things remained for the
time unchanged.

As regards the scientific questions at issue between Liebig
and von Mohl, Schleiden, and various agricultural chemists, the
contest was chiefly about matters of secondary importance, and
among these might be included the objection that Liebig
knew scarcely anything of the anatomy of the plant. The
main point was, that he had corrected mistaken views as to
the way in which plants are fed, had refuted gross errors, had
shown what was fundamental and essential and what was
unimportant. Everything that was written on the ""subject
after 1840 shows that he did all this completely; the publica-
tions called forth by the controversy on his book occupied in
the main the ground which Liebig had cleared. Now every
body knew all at once what was meant by the decompositon
of carbon dioxide in the green parts of plants, that the
constituents of the ash are not mere seasoning to the vegetation,
and the like ; firm ground had been won for all, a number of
scientific truths had become common property for ever ; this
did not of course make it less meritorious in others, to test the
rest of Liebig's theories, or even to correct his great mistake
about the respiration of plants, as was done emphatically by
von Mohl.

It would not be consistent with the design of this work to go
into all the details of the discussion excited by the appearance
of Liebig's book, into questions for instance respecting the first
products of assimilation in plants, and their further transforma-
tions by metabolism. Whether the primary use of the basic
mineral constituents is merely to fix the vegetable acids, whether
these acids are the first products of assimilation, or whether
carbo-hydrates are the immediate result of that process,
and similar questions, were for some time only matter of
conjecture, deduction and combination, unsupported by certain
observation obtained by suitable methods ; it was not till after

Chap. II.] of Plants, Boussingault. 531

1S60 that new paths were struck out on these subjects, and
important results achieved. More important at the time for
the advance of the science was the further examination of
the question respecting the source of the nitrogen which
plants assimilate; it was the more necessary that this point
should be finally settled, because Liebig's deductions still
gave room for many doubts, and the first of vegetable
physiologists, de Saussure, in his later days made the mistake
of coming forward in opposition to Liebig as a defender of the
humus-theory, maintaining (1842) that ammonia or the nitrates
are not themselves the food-material of plants, but only serve
to dissolve the humus. Others also found it difficult to give
up entirely the old and favourite doctrine of the humus ;
though von Mohl and others acknowledged that the carbon of
plants is mainly derived from the atmosphere, yet they thought
themselves obliged to assign to the humus, on account of the
nitrogen which it contains, a very important share in promoting
vegetation. Under these circumstances it was extremely
fortunate for physiology that Boussingault took up the ques-
tion. He had occupied himself before the appearance of Liebig's
book with experimental and analytical investigations into
germination and vegetation, and specially into the source of
nitrogen in plants. His experiments in vegetation in 1837
and 1838 produced no very decisive results; but he continued
' them for some time longer, improving his methods of observa-
tion from year to year ; and between the years 1851 and 1855
he succeeded in establishing with all certainty as the result of
many repeated trials, that plants are not capable of assimilating
the free nitrogen of the atmosphere, but that a normal and
vigorous vegetation is produced, when they are supplied with
nitrogen from the nitrates in the soil. It appeared also that
plants will flourish in a soil from which all trace of organic
substance has been removed by heat, if a nitrate is added to
the constituents of the ash ; this proves at the same time that
the whole of the carbon in such plants is derived from the

M m 2

53^ Theory of the Nutrition [Book hi.

carbon dioxide of the atmosphere without the co-operation of
the humus, and that consequently the favourable effect of a
soil rich in humus on vegetation must be due to other causes
than those which were assumed by the humus-theory. We
cannot describe the further services rendered by Boussingault
to the theory of nutrition, for this would take us too much into
technical details, and the best and most important of his
results were first given to the world after i860, and do not fall
therefore within the limits of this history. But it should
be mentioned that Boussingault must be considered the
founder of modern methods of conducting experiments in
vegetation. Liebig had before spoken in terms of sufficient
severity of the miserable way in which experiments on the sub-
ject of the nutrition of plants were managed after de Saussure's
time till later than 1830, but he did not himself introduce better
methods ; this was reserved for Boussingault. One instance
may be given ; those who desired to decide the question of
the humus by experiment, such as Hartig in conjunction with
Liebig and others, generally adopted the plan of supplying
plants with compounds of humus-acid, and seeing what
would be the result. Boussingault did as Columbus with the
egg ; he simply made plants supply themselves with food in a
soil artificially deprived of all trace of humus and containing a
mixture of food-material, in order to prove beyond question
that they do not need humus.

In Germany also Prince Salm-Horstmar made similar experi-
ments to those of Boussingault ; he occupied himself chiefly in
determining the relative importance of the acids and bases of
the ash in the nutrition of plants, whether any and which of
them are indispensable ; these are questions which approached
their solution only after i860, and some are not yet decided.

The establishment of the facts, that plants containing chloro-
phyll derive the whole of their carbon from the carbon dioxide
of the atmosphere, and that the latter is also the original source
of the carbon in plants and animals which do not contain

Chap. II.] of Plants. Boussingault. ^'^'^

chlorophyll ; further that the nitrogen which plants assimilate
is derived from ammoniacal salts or nitrates, and that the
alkalies, alkaline earths in the form of sulphates and phosphates,
are indispensable ingredients in the food of plants, must be
considered to be the great results of the labour bestowed on
the theory of nutrition in the period from 1 840 to 1 860, while
the way was also prepared for many points, which were after-
wards of the first importance in the enquiry.

On the other hand the advance made in the theory of the
movement of the sap from the time of Dutrochet till nearly
i860 was so small as to be scarcely worth mentioning j yet it
was an advance, that the physiological value of the doctrine of
endosmose was more and more highly estimated, and that more
solid proofs of the theory itself and a more exact acquaintance
with osmotic processes were making it possible to explain more
of the details of the movement of material in the plant, though
the whole question was far from being finally settled. One
discovery must be specially mentioned, the establishment by
Hofmeister in 1857 of the fact, that the phenomenon observed
for centuries in the grape-vine and other trees, and more
recently in Agave and in many tropical climbing plants, known
by the name of bleeding or weeping and supposed to be con-
fined to certain periods of vegetation, not only occurs in all
plants with true woody cells, but may be produced in them at all
times by suitable means. The knowledge of this fact was an
aid to the investigation of the cause of the weeping.

The theory of the descending sap was in the least advanced
condition during this period ; appeal was still made to experi-
ments of the kind which Malpighi, Du Hamel, and Cotta had
made, and which in reality show nothing more than that in
dicotyledonous woody plants a food elaborated in the leaves
is carried downwards through the cortex. As soon as it was
understood, that all organic substance originates in the leaves,
a fact which no one could doubt after 1840, no experiment
was required to prove that the formative matter necessary for

534 Theory of the Nutrition of Plants.

the growth of the roots, buds, and fruit, must be conducted to
those parts from the leaves. It could no longer be a question
whether such a movement of assimilated material takes
place ; it remained only to consider what are the conducting
tissues, and what is the nature of the substances which are
produced in the leaves and conducted to the rest of the organs.
Both questions in accordance with the organisation of the
plant could be properly answered only by microchemical
methods, and these were not adopted and further developed till
after 1857. We have already said that nothing certain was
known even as late as i860 about the chemical combinations
formed by assimilation in the leaves ; De Candolle supposed
that the primary formative sap was a gum-like substance, from
which the rest of the various vegetable substances were secreted
in the different tissues. Theodor Hartig, who had done good
service between 1850 and i860 by his investigations into the
starch in the wood of trees and into proteid in seeds, by the dis-
covery of sieve-tubes, by observations on the amount of water
in woods at different times of the year, and by other contribu-
tions to botanical science, also occupied himself with the
subject of the descending sap, which he conceived of as a
formless primary mucilage, from which, as from De CandoUe's
gum, the various substances in the plant were deposited as it
travelled through the plant. He says (' Botanische Zeitung ' for
1858, p. 341), 'The crude sap is changed in the leaves into
primitive formative sap,' and 'the formation of solid reserve-
material (from this) involves the elimination of large quantities
of watery fluid.' The occasional remarks of vegetable physio-
logists of all sorts between 1840 and i860 prove, that similar
ideas respecting the formation of a primary mucilage of this
kind in the leaves were generally entertained.

CHAPTER III.

History of the Doctrine of the Movements of
Plants (Phytodynamics).

It will scarcely be doubted at the present day, that the
mechanical laws of growth, of geotropic and heliotropic curva-
tures, of the various kinds of periodic movements, of the
twining of tendrils and climbing plants, and of movements
dependent on irritation, may be referred to a common prin-
ciple, and that in all these movements besides the elasticity of
the cell-walls the still unknown qualities of the protoplasm play
the most important part, and that consequently the ' streamings '
of the protoplasm, the movements of swarm-spores and similar
occurrences must be ranked with these phytodynamical phe-
nomena. From this point of view phytodynamics would
appear to be one of the most important foundations of veget-
able physiology. The recognition of this fact is however of
very recent date, and to imagine that such a conception of the
movements of plants was present to the minds of the early
physiologists would be to attribute to the past ideas to which
it was entirely a stranger. These movements were scarcely
noticed even as curiosities in former ages, and it was not till
the end of the i yth century that some attention began to be
paid to them ; and very slow progress was made at a later time '
in disentanghng the relations which come under consideration
and which are some of them very complicated, in determining
the dependence of the phenomena on external influences, and
explaining to some extent their mechanical conditions.

Single movements of parts of plants are noticed in a cursory
manner by some early writers. Varro was the first who men-

536 History of the Doctrine of [Book hi.

tioned the heliotropic movements of the stalks of many flowers,
which he says were for that reason called heliotropic flowers ;
in the following century Pliny says that the leaves of clover close
when bad weather is approaching; Albertus Magnus in the
13th century, Valerius Cordus and Garcias del Huerto in the
1 6th, thought the daily periodical movements of the pinnate
leaves of some Leguminosae worth recording; Cesalpino
noticed the movements of tendrils and climbing plants, and
was surprised to see that the latter to some extent seek for
their supports. These were every-day phenomena, but the
striking sensitiveness of the leaves of Mimosa pudica intro-
duced from America could not fail to attract attention, and so
we find an essay on the causes of it in Robert Hooke's ' Micro-
graphia' of 1667. The irritability of the stamens of Centaurea
had been already mentioned by Borelli in 1653.

I. We meet with the first speculations on the subject at
the end of the 1 7th century. Ray in his ' Historia Plantarum '
(1693) commences his general considerations on the nature
of the plant with a succinct account of phytodynamical
phenomena, and introduces the whole by a sentence of
Jung : ' Planta est corpus vivens non sentiens,' etc. Though
Ray, like Cesalpino, seems to believe in the Aristotelian
soul of plants, yet he does on the whole endeavour to
explain the movements which he describes by physical and
mechanical laws ; he thinks that the irritability of Mimosa
in particular is not due to sensation, but to known physical
causes ; the movement of the leaf when it is touched is caused
by a contraction, which again is due to a withering or relaxation
■ of its parts. He endeavours to apply the knowledge of his
time to the explanation of the mechanical process : leaves, he
says, remain tense only because the loss by evaporation is kept
constantly supplied by the water that flows to them from the
stem ; if then in consequence of a touch the sap-passages of
the leaves are pressed together, the supply of water is not suffi-
cient to prevent their becoming relaxed. Ray mixes up together

chaV. III.] the Movements of Plants. 5;^^

the movements from irritability and the daily periodical move-
ments, as was done till recent times ; the latter, he says, occur
not only in the leaves of Leguminosae, but in almost all similar
pinnate leaves, and with these periodical movements of leaves
he places also the periodical opening and closing of the flowers
of Calendula, Cichorium, Convolvulus, and others. That these
last movements are due to changes of temperature appeared to
him to be proved by an experiment of Jacob Cornutus on
flowers of Anemone, which, when cut off" and placed in a well-
closed box in a warm place, opened at an unusual time if the
flower stalk only was dipped in warm water. This fact, after-
wards forgotten and discovered again a few years ago, of the
dependence of the movements of flowers on changes of temper-
ature, was applied by Ray to explain the periodical movements
of leaves, which, to use his own expression, fold themselves
together as the cold of night draws on, and open again with the
day, and as he thought that these movements are of the same
kind as the movements of irritability in Mimoseae, he tries
to explain how cooling has the same effect as a touch. It was
natural in the existing state of science to assume that changes
of temperature were the first causes of various movements, for
a thrust was at that time almost the only recognised cause of
motion. Hence Ray explained the movements of growing
stems which are now called heliotropic by a difference of tem-
perature on the opposite sides. A certain Dr. Sharroc had
observed the stem of a plant on which he was experimenting
grow towards that part of a window, where the air found free
entrance through an opening; from this circumstance, and
from the rapid elongation of the stems of plants growing under
cover, which he ascribed to the higher temperature, Ray con-
cluded that cold air hinders the growth of the side of a stem
on which it falls, and that this side must become concave.
Thus Ray used the etiolation of plants grown under cover
to explain their heliotropic curvatures, as De Candolle did one
hundred and forty years later, only with this difference, that he

538 History of the Doctrine of [book hi.

described the rapidity with which forced plants shoot up to the
higher temperature, De CandoUe to want of Hght. On the
other hand Ray knew perfectly well that the green colour of
leaves is not produced by the access of air but by the light, for,
as he says, plants become green under glass, and not under an
opaque cover ; and if they become less green under glass than
in the open air, this is because the glass absorbs certain rays of
light and reflects others. Ray however, like almost all later
observers till quite recent times, did not keep the elongation
and bleaching of etiolated plants sufficiently distinct ; his
account of this phenomenon is spoilt by the presence of much
that is obscure.

It has been justly observed by other writers on botanical
subjects that no notice is usually taken of one of the most
remarkable of the phenomena of which we are here speaking,
because, being a matter of every-day occurrence, it is simply
accepted as something obviously in accordance with the nature
of things ; this is the fact, that the main stems of plants grow
vertically upwards and their main roots downwards. To the
French academician Dodart, whom we have already encoun-
tered in the history of the theory of nutrition, is due the great
merit of being the first to find this apparently simple pheno-
menon really very remarkable; he convinced himself by experi-
ments on germinating plants, that these vertical positions are
caused by curvatures, and endeavoured to discover the physical
reason why the main roots if placed in an abnormal position
escape from it by curving in the downward direction, and the
main stems in the upward direction, till they both reach the
vertical line. It was a matter of minor importance that his
mechanical explanation, which supposed that the fibres of the
roots contract on the moister side and those of the stem on the
same side lengthen, was quite unsatisfactory ; it was much more
important that these remarkable phenomena were made the
subject of scientific enquiry, and we find that various observers
soon after directed their attention to them, and exercised their

Chap. III.] the Movemeuts of Plants. 539

acuteness in attempts at explaining them ; to these attempts we
shall return in a future page.

A still more universal phenomenon than the vertical growth
of stems and roots is the growth of plants generally, and it
required as much or even more of the spirit of enquiry to pro-
pose the question, whether this growth can be explained by
mechanical laws, and what that explanation is. Mariotte
touched on this question in 1679, but only incidentally, and
supposed that the stretching of the pith, which meant at that
time the whole of the parenchymatous tissue, was the cause of
the growth of the parts of plants. This idea might have had
its origin in the Aristotelian notion that the pith is the seat of
the vegetable soul, but Mariotte endeavoured to give physical
reasons for it. Hales in his 'Statical Essays ' of 1727 went
much more minutely into the question of the growth of plants.
Following the train of thought in his doctrine of the nutrition
of plants, he introduces his observations on their growth with
the remark, that plants consist of sulphur, volatile salts, earth,
water, and air, the first four of which attract one another, and
therefore form the solid, inert part of the substance of plants ;
the air behaves in a similar manner as long as it is kept by the
other substances in a solid condition ; but as soon as it is set
at liberty it is capable of expansion. On this power of expan-
sion in the air, by which the juices of plants are quickened and
strengthened, he builds his mechanical theory of growth, accord-
ing to which the plastic parts of the plant assume a state of
tension, and as the air enters into combination with other sub-
stances and so becomes fixed, warmth and movement are
excited, and these make the particles of sap assume by degrees
a form and shape. These principles supplied his starting-point.
To get a clearer idea of the way in which the growth of the parts
of plants proceeds, he made equi-distant punctures in young
stalks and leaves, and found that the intervals between them
increased by growth more in the younger intervening parts
than in the older. In the course of these observations he is

540 History of the Doctrine of [Book hi,

particularly struck by the great longitudinal extension which
accompanies growth, because, as he says, the vessels still con-
tinue hollow, as a glass tube when drawn out to its utmost
extent retains its canal. He finds Borelli's idea confirmed, that
the young shoot grows by the extension in length of the
moisture in the spongy pith ; and he endeavours to explain the
fact that the growing shoot does not extend equally in the
transverse direction, and so become spherically rounded off" like
an apple, from the nature of the structure of the cell-tissue.
That the air enclosed in the tissue and the sap with it presses
into the shoot with sufficient force to produce so great an exten-
sion, he thinks is proved by his experiments, which show him
the great force with which the water rises in the bleeding vine,
and forces itself into swelling peas ; it is known, he says, that
water acts with great force when it is heated in a vessel, for
water can be driven into the air by heat ; the sap in plants is
composed of water, air, and other active ingredients, and makes
its way with great force into the tubes and cells, when it is
heated by the sun.

2. The course of the i8th century gradually increased the
number of the phytodynamical phenomena, to which physiolo-
gists paid more or less attention, and repeated attempts were
made to explain them on mechanical principles. These
attempts were for the most part unsatisfactory, because move-
ments distinct in kind from one another were mixed up
together, their dependence on external influences was not
distinctly perceived, and the knowledge of the anatomical
structure of the parts which exhibited the movements was,
owing to the decline of phytotomy, extremely imperfect.
Moisture and warmth played the chief part in these explana-
tions, but their mode of operation was expressed in the most
general terms ; the mechanical processes in plants were des-
cribed much in the way in which a person with very indefinite
ideas as to the nature of steam and the construction of the
inside of a steam-engine might speak of its movements. The

Chap. III.] the Movements of Plants. 541

majority of writers, in accordance with the tendencies of the
age, professed their desire to refer the phenomena of life in
plants not to an unknown principle called the soul, but to
mechanical and physical causes ; but they did not apply their
minds to the examination of these phenomena with that stren-
uous effort, which in this subject especially could alone lead to
a complete and satisfactory explanation of them.

Linnaeus studied the periodical movements of flowers in
1 75 1 and those of leaves in 1755, but a mechanical explanation
of them was not to be expected from him ; he contented him-
self with pointing out the external conditions of these phe-
nomena in many species, with classifying them, and giving the
periodical movements a new name by calling the positions
assumed by night the sleep of plants ; nor did he use the word
at all in a metaphorical sense, for he saw in this sleep of
plants a phenomenon entirely analogous to sleep in animals.
That the sleep-movements were not capricious but due to
external influences was with him a necessary consequence from
the nature and idea of the plant, which was that of a living and
growing being, only without sensation. But it should be men-
tioned that he stated correctly that the movements connected
with the sleep of plants are not caused by changes of tempera-
ture, or not by these only, but by change of light, since they
take place in the uniform temperature of a conservatory.

Linnaeus' account of these kinds of movement was only
formal, it is true, but still it was well-arranged and clear ; the
treatment of the same and other movements by his contem-
porary Bonnet was quite the reverse. It is scarcely possible to
imagine anything more shapeless, such an utter confusion of
things entirely different from one another, as is to be found in
Bonnet's experiments and reflections on the various movements
of leaves and stems in his work on the function of leaves, pub-
lished in 1754; geotropic and hehotropic curvatures, nutations
and periodic movements, are all run one into another ; a
person who understands something of the subject may find

542 History of the Doctrine of [Book hi.

here and there single things in his experiments that may be
turned to account, but he was himself unable to make any use
of them. He set out with a preconception which prevented him
from the first from understanding what his experiments showed
him ; it was his object to prove from a multitude of instances,
that stalks and leaves so curve, twist and turn in all cases, that
the under sides of the leaves are directed towards the ground,
in order that they may be able to suck up the dew, which
according to his theory is the chief nutriment of plants and
rises from the ground. It is no great merit in him, that amid
all this confusion a correct observation here and there forced
itself upon him, as for instance that organs, chiefly such as are
young and ductile, if they are put out of their natural position,
endeavour to recover it by bending and twisting. On the
other hand his conclusions with regard to the mechanical
causes of these movements are utterly inane ; the least skill in
judging of the results of his experiments must have led him to
very different ideas ; warmth and moisture, he says, appear to
be the natural causes of movement, but warmth is more
effective than moisture, and the warmth of the sun more
effective than that of the air. This explanation is unsuitable to
just those cases which he chiefly studied, the geotropic and
heliotropic curvatures. In one point only he arrived ultimately
at a right judgment, namely that the great lengthening of the
stem, the small size attained by the leaves and the want of
colour in plants grown under cover, are caused by partial or
entire absence of light ; Ray however had shown this before as
regards the colour.

Though Du Hamel, like many later writers, treated Bonnet's
investigations, uncritical as they were and without plan, with
great respect, he gave himself a much better account of the
various movements of plants. In the sixth chapter of the
fourth book of his 'Physique des arbres,' 1758, he discussed
all the phenomena of the kind that were known to him under
the title : ' On the direction of stem and roots, and on the

Chap. III.] tlu Movcments of Plants. 543

nutation of the parts of plants.' Under the head of upright or
oblique direction of the stem and roots, he speaks of geotropic,
heliotropic, and some other curvatures ; then follows a chapter
on etiolation, and under the title, ' Movements of plants, which
approximate to some extent to the voluntary movements of
animals,' he enquires into the periodical and sensitive move-
ments of the leaves of Mimosa ; he winds up with a short
account of Linnaeus' flower-clock, and of the hygroscopic
movements of the valves of fruits. The movements of tendrils
and climbing stems, of which Du Hamel seems to have known
little, are not mentioned in this connection ; but they are
noticed in a former chapter with hairs, thorns and similar
things, — a plan which Cesalpino also adopted. If this way of
dealing with the different movements of plants is to be taken
as a classification of them, it was a very unsatisfactory one ; for
it separates like things, and brings together things unlike ; still
it is an improvement on Bonnet's arrangement, while the
author gives us also some new and valuable observations. He
may claim to be the first who made heliotropic curvature
depend on light, and it is a significant fact that he got this
conclusion from Bonnet's experiments. After examining, like
Hales, into the distribution of growth in shoots, and discover-
ing that this ceases with the commencement of lignification, he
proposed to himself the question : at what spots does the
lengthening of the roots take place, and he found from suitable
experiments that every root-fibre grows only at its terminal por-
tion, which is a few lines in length, and that no other part of it
increases in length. In the chapter on the direction of the
parts of plants he examines the explanations which had been
given of heliotropic curvatures. Astruc and De la Hire had
supposed the weight of the descending sap to be the cause of
the downward curvature of the roots, and the lighter vapours
which ascend in the tissue to be the cause of the upward cur-
vature of the stem ; Bazin on the contrary attributed the geo-
tropism of the roots to the moisture in the earth. Du Hamel

544 History of the Doctrine of [book hi.

undertook to determine whether the moisture, the low tempera-
ture, or the absence of Hght in the earth made the roots curve
downwards, and he was obliged by the result of his experiments
to deny that they do. But he was unfortunate in his own
explanation of the movements which we should now call geo-
tropic, heliotropic and periodic, for he came to the conclusion
that the ' direction of the vapours ' inside the vessels of the
plant and round about the plant has more to do with pro-
ducing these movements than any other causes, and that if
warmth and light appear to influence them, it is perhaps only
because they produce vapours or communicate a definite move-
ment to them. As regards the movements of the leaves of
Mimosa, Du Hamel repeated the experiment made by Mairan
in 1729, in which the periodic movement continued even in
constant darkness ; he found that this was so, and concluded
that the periodic movements of Mimosa do not essentially
depend on temperature and changes of light ; Hill had de-
termined in 1757 that the alternation of day and night was the
cause of the movements connected with the sleep of plants,
because he found that darkness artificially produced in the day-
time made the plants assume the nocturnal position ; but Zinn
in 1759 came to the same conclusion as Mairan and Du
Hamel. It was not till long after that the question was to
some extent cleared up by Dutrochet. Du Hamel thought it
necessary to give a formal refutation of the opinion expressed
by Tournefort, that the movements of plants are produced by
muscles, and to show that Tournefort's vegetable muscles are
hygroscopic fibres.

We have to mention in conclusion, that Du Hamel was the
first who observed that the two branches of a vine-tendril twine
in opposite directions round a support that happens to be
between them ; he also appears to have been the first who
compared the irritability of the stamens of Opuntia and Ber-
beris with that of Mimosa-leaves ; the stamens of Berberis
were afterwards examined by Covolo in 1764, by Koelreuter

Chap. III.] the Movemeuts of Plants. 545

1788, by Smith in 1790, and by others, but without leading to
any discoveries respecting the nature of the irritabiUty. Dal
Covolo's famous essay on the stamens of the Cynareae (1764)
produced no absolutely final result, but it contained some par-
ticulars which threw light on the mechanical laws of these
movements of irritabihty. Koelreuter, who studied these
objects in 1766, thought less of discovering a mechanical ex-
planation of them, than of finding arguments in the irritability
of the stamens for the necessity of insects to pollination. An
entirely new kind of movement was discovered by Corti in 1772
in the cells of Chara, which is now known as the circulation of the
protoplasm ; this form of movement in plants appeared at first
to bear no resemblance whatever to the phytodynamic pro-
cesses then known, and it was not brought into connection
with them till a long time after ; on the contrary an erroneous
idea soon began to prevail, that it was a real rotation of the
sap, as understood by the early physiologists ; this idea held
its ground till far into the 19th century, and being combined
with mistaken notions respecting the movements of latex, was
developed by Schultz-Schultzenstein into the doctrine of the
circulation of the vital sap. For a time indeed Corti's dis-
covery was forgotten, and had to be reproduced by Treviranus
in 181 1. A somewhat similar fortune attended the discovery
of the movement of the Oscillatorieae by Adanson in 1767,
which misled Vaucher into pronouncing them to be animals.

3. Imperfect as were the theoretical efforts of the i8th cen-
tury in this branch of botanical study, yet they aimed at tracing
the various movements back to the play of physical forces.
But in the closing years of the century another order of ideas,
injurious to the healthy progress of science, made its appearance
in this, as in other parts of botany and zoology. Even the
majority of those who had no sympathy with the nature-philoso-
phy and its phraseology, believed that there was in organised
bodies something of a special and peculiar nature ; because the
attempts made to explain the phenomena of life by mechanical

N n

546 History of the Doctrine of [book hi.

laws were on the whole unsatisfactory, all such explanations
were looked upon as impossible and even absurd, while it was
forgotten that the vital force, which was to explain everything,
was a mere word for everything that could not be explained in
the life of organisms. This vital force was personified, and
seemed to assume a really tangible form in the movements of
plants. But the moment that a phenomenon was handed over
to this force, all further investigation was abandoned ; the idea
with regard to phytodynamical phenomena especially was that
of the peasant, who could only explain the movement of the
locomotive by supposing that there was a horse shut up in it.
Moreover the knowledge of the inner structure of plants was at
its lowest point at the end of the i8th century ; the spiral
threads which could be unwound were the only structural
element whose form was to some extent understood, and their
hygroscopic movements were supposed to be due to a combina-
tion of the pulsations of the vital force with the spiral tendency
of the plant. At the same time whole bundles of vessels were
taken for spiral fibres, or were supposed to consist of them, and
these were thought to be vegetable muscles, which contract
under the influence of various kinds of irritation, and so cause
the movements in the organs of plants ; but it was forgotten
that in the organs which exhibit the most striking movements,
such as sensitive leaves and leaves that suffer periodical
changes of position, these ' muscles ' occupy a central position
which unfits them for the function ascribed to them. It would
be unprofitable and wearisome to give many examples of what
is here stated, though many might easily be collected ; it will
suffice to quote some sentences only from Link's ' Grundlehren
der Anatomic und Physiologic' of 1807 ; they are particularly
instructive, because Link declared against the nature-philosophy
and professed to be on the side of inductive science. Under
the head of movements of plants, he discussed geotropic curva-
tures and other movements in the superficial manner of the
time and only to come to the conclusion, that the direction of

Chap. III.] the Movemcnts of Plants. 547

growth of stems and roots is caused by a polarity of a definite
kind in every plant, from which we may argue, he says, ' to higher
connections of our planet in the world of space.' He says again,
' that it is natural to conjecture that light is the cause of the
sleep of plants,' and then gives the contradictory statements of
Hill, Zinn, and De Candolle, all jumbled together into an inex-
tricable tangle in a fashion which sets all maxims of reasonable
discussion at defiance. He then puts aside all attempts at
mechanical explanation with the remark, that plants observe
their regular times of sleep even when kept in the dark and at
a low temperature, for this evident habituation is one of the
most important marks of vitality. He is led to similar results by
Desfontaine's observation, that a Mimosa, exposed to the shak-
ing of a wheeled vehicle, closes at first but then opens again.
Speaking of the rapid oscillations of the leaves of Hedysarum
gyrans and similar movements, he rejects Percival's idea of a
will in plants, but says that the attempts to derive them from
mechanical or chemical causes has only led to solemn trifling.

It is plain that men who could print such remarks as these
and still worse than these, could not possibly effect anything
in the province of botany which we are considering. The
broad and shallow stream of such opinions as these flowed on
till later even than 1830, but it ran dry at last when its supplies
were cut off by the effect of new discoveries, and scientific
investigation again gained the upper hand. Some calmer
thinkers, who could not rest content with empty words, had
meanwhile been pursuing the path trodden by Ray, Dodart,
Hales, and Du Hamel, and by experiment and earnest reflec-
tion had brought new facts to light, which were at least calcu-
lated to pave the way for the mechanical explanation of phyto-
dynamical phenomena. Senebier in his ' Physiologic vegetale '
(1700) had described some minute researches which he had
made into the subject of etiolation ; and though he made the
great mistake of attributing the want of colour in the leaves
and the excessive elongation of the stems to the decom-

N n 2

548 History of the Doctrine of [book hi.

position of carbon dioxide which does not take place in the
dark, yet he gave an example of genuine scientific investiga-
tion and again expressed its true spirit, when he said that the
Linnaean phrase, ' the sleep of plants,' was unsuitable, because
the sleeping leaves are not relaxed, but continue as stiff as in
the day-time. De CandoUe also, like Senebier, experimented
in 1806 on the influence of light on vegetation, and succeeded
in proving that the daily period of leaves may be reversed by
artificial illumination ; he was, as we have said above, an
adherent of the theory of a vital force, but only made use of
it when physical explanations failed him. The same year,
(1806) is the date of a brilliant discovery, which was extremely
inconvenient to the thorough-going adherents of the nature-
philosophy and the vital force, and did much to bring the
scientific study of the movements of plants back to the right
path. Andrew Knight^ showed by experiment that the ver-
tical growth of stems and primary roots is due to gravitation ;
he attached germinating plants to a rapidly revolving wheel,
and thus exposed them to the centrifugal force, either alone
or combined with gravitation ; the radicles, which normally
follow gravitation, here took the direction of the centrifugal force,
while the stems assumed the opposite direction. The next ques-
tion was, why gravitation makes the roots and stems take exactly
opposite directions, why, that is, in a plant placed in a hori-
zontal direction, the root-end curves downwards and the stem
upwards. Knight supposed that the root, being of a semi-
fluid consistence, is bent downwards by its own weight, while
the nutrient sap in the stem moves to the underside and causes
stronger growth there, until by means of the curvature so pro-
duced the stem assumes the upright position. Here too, as in
Dodart's case, it was no great misfortune that the explanation
proved afterwards to be insufficient ; it served at the time to

^ Thomas Andrew Knight, President of the Horticultural Society, was
bom at Wormsley Grange, near Hereford, in 1758, and died in London in
J838.

Chap. III.] the Movemeuts of Plants. 549

explain as much as was then known of the matter. The spirit
of true scientific research displayed in Knight's explanation of
geotropism was expressed in many other contributions which he
made to vegetable physiology ; two only must be mentioned
here. He showed in 1811 that under suitable conditions roots
are diverted from the vertical direction by moist earth, an obser-
vation which was confirmed by Johnson in 1828 and afterwards
forgotten. More attention was excited by his discovery in
181 2, that the tendrils of Vitis and Ampelopsis are negatively
heliotropical, that is, that they turn away from the source of
light. A few other cases of this kind of heliotropism have
since been discovered, and they are highly interesting, because
they teach that there is the same opposition in the relations of
plants to light as in their relations to gravitation. Knight
possessed some of the direct and bold reasoning power of his
countryman Hales ; he defied the vital force, and was always
ready with a mechanical explanation, if it was at all possible to
find one. Thus he explained the twining of tendrils by sup-
posing that the pressure of the support drives the juices to the
opposite side, which consequently grows more vigorously and
causes the curvature, which makes the tendril wind round the
support. This theory was at all events better than the one
which von Mohl sought to put in its place in 1827, and no better
one was suggested till very recently. Much the same may be
said of Knight's explanation of geotropic curvatures ; it is true
that Johnson showed in 1828 that the ends of roots as they
curve downwards set in motion a heavier weight than them-
selves, and therefore do not simply sink down, and Pinot in
1829, that they force their way even into quicksilver, and that
consequently Knight's theory, at least as regards the roots, is
unsatisfactory ; but no better theory has yet been found, and
his view also of the progress in the upward curvature of the
stem has not given place to any one that can be said to be
more generally accepted.

It was the commonly received opinion till after 1820 that the

SS'^ History of the Doctrine of [Book hi,

movements of the parts of plants are produced by the spiral
vessels, or, which meant the same thing in those days, by the
vascular bundles. It was an important event therefore when
Dutrochet proved in 1822, that the movements of the leaves
of Mimosa were due to the alternate expansion of the antago-
nistic masses of parenchyma in the pulvinus or cushion of suc-
culent tissue found at the articulation, and that the central
vascular bundle follows passively their curvatures. Lindsay
had indeed arrived at the same conclusion from similar experi-
ments as early as 1790, but his unprinted essay on the subject
was first produced by Burnett and Mayo in 1827. Meanwhile
Dutrochet had also found that light influences the movements
of the leaves in different ways ; alternation of light and dark-
ness excites them to motion, while leaves which have become
rigid in continued darkness are restored by light to their normal
condition of sensitiveness.

Much attention was bestowed in the period between 1820
and 1830 on various questions connected with the movements
of the organs of plants. In 1826 the faculty of medicine in
Tiibingen offered a prize for an essay on the peculiar nature
of tendrils and climbing plants, which was intended to bring
into discussion all the points which required to be cleared up
before a more thorough understanding of the whole subject
could be obtained. The two essays which gained the prize
were published in 1827. One was by Palm, the other by von
Mohl, both of very different value. Palm's essay is a good
and careful college-exercise ; but there is nothing of this char-
acter in von Mohl's. The skill of the composition, the exact
knowledge of the literature of the subject, the wealth of per-
sonal experience, the searching criticism, the prominence given
to all that is fundamental and important, the feeling of cer-
tainty and superiority which the book inspires, all unite to
make the reader forget that it is not the work of a mature and
professed naturalist, but of a student of two-and-twenty years of
age. This academical prize-essay on the structure and twining

Chap. III.] the Movemeuts of Plants. 551

of tendrils and climbing-plants was one of von Mohl's best works,
and altogether the best that appeared on the subject before
Darwin wrote upon it in 1865 ; at the same time it must
be said that von Mohl did not explain the exact mechanical
processes in the tissues, for he assumed a sensitiveness in both
cases which causes the winding round the support, and thought
that this sensitiveness must be conceived of ' dynamically ' and
not ' mechanically.' Nevertheless von Mohl conducted his in-
vestigation up to this point according to strict rules of induc-
tive science, and studied the facts which were capable of being
established by observation and experiment with an exactness
such as had not yet been applied to any case of movement in
plants. It was a genuine production of its author, strictly
inductive up to the point at which deduction became neces-
sary. Von Mohl pointed out in it essential differences in the be-
haviour of tendrils and climbing plants, and the corresponding
distinction between the organs which have to be considered in
each case, and he made the important discovery that contact
with the support acts as a stimulus on the tendril, though he
was wrong in supposing that the climbing stem also is similarly
affected. He at once assented to Dutrochet's new view, that
it is not the vascular bundles but the layers of parenchyma
which produce the movements. He distinctly rejected the
notion constantly repeated, though with some hesitation, since
the time of Cesalpino, that tendrils and climbing-plants ' seem
to seek for ' their supports, as also the idea which many had
adopted without reflection from Grew, that the varying direc-
tion of a climbing-stem is due to the varying influence of the
course of the sun and moon, and showed that the movements
of nutation in the stem are sufficient to -explain the apparent
seeking for the support ; it is true that he did not fully explain
the corresponding phenomena in tendrils, but he saw enough
to set aside the old ideas. We must not here go further into
his many, and for the most part excellent, observations ; some
of course had afterwards to be corrected, but the important

553 History of the Doctrine of [Book hi.

point was, that his full investigation of the subject showed how
such phenomena must be studied, if we are to arrive at a
strictly mechanical explanation of them.

If von Mohl had attempted to give a mechanical explanation
of the processes in the tissue of twining organs he must neces-
sarily have failed from ignorance of the agency of diffusion,
which must certainly be taken into consideration. This agency
was not discovered by Dutrochet till the year (1826) in which
von Mohl undertook his investigation, and some time elapsed
before it was sufficiently understood to be successfully applied
to the explanation of phenomena in vegetation. Dutrochet
did indeed attempt so to apply his theory in 1828, and showed
that changes in the turgidity of tissue are produced by endos-
mose and exosmose, and consequently that a new mechanical
method of explanation had been discovered for processes
which had been usually referred to a supposed vital principle ;
but in his later and more detailed researches into geotropism,
heliotropism, periodical movements and movements of irrita-
bility, which he collected together in his ' Memoires ' of 1837,
he fell into two different mistakes : he assumed conditions of
size and stratification in cells which do not actually exist, for
the purpose of explaining very various kinds of curvature by
endosmose, and he was not satisfied with endosmose in the
parenchyma ; he postulated changes in the vascular bundles
also, which were supposed to be produced by the influence of
the oxygen in a way which he did not explain. Thus there
were blots in his explanation of separate processes, and his
mechanical theories remained unsatisfactory ; but it is worthy
of recognition and was most important for the development of
phytodynamics, that he was thoroughly in earnest in his pur-
pose of explaining every movement in plants by mechanical
laws. Even the opponents of such explanations were obliged
to go deeply into mechanical relations in order to refute him,
and no one could any longer be imposed upon by the simple
assertion that all depends on the vital force ; so devoted

Chap. III.] the Movemeuts of Plants. S5?>

a partisan of vital force as Treviranus had to deal with endos-
mose as an established principle. Moreover Dutrochet's
copious investigations presented such an abundance of in-
teresting observations, delicate combinations, and suggestive
considerations, that the study of them is still instructive and
indeed indispensable to any one who is occupied with such
researches. Comparison of his papers in the ' Memoires ' of
1837 with what was before known on the mechanical laws
of the movements of plants leaves us in no doubt that
energetic mental effort had taken the place of the old com-
placent absence of thought.

Still no single movement had as yet been fully explained on
mechanical principles; but by the year 1840 clearer views had
been attained on the whole subject ; the co-operation of ex-
ternal agencies was in substance recognised, and the different
forms of movement were better distinguished, though much
still remained to be done in this direction ; and as regards the
mechanical changes in the tissue of the parts capable of move-
ment, a factor had been given in endosmose which must be
taken into account, though it might be necessary to seek a
different mode of applying it.

4. Before proceeding to give some account of the theoretical
efforts that were made in this subject between 1840 and i860,
it should be mentioned that new cases of movement in plants
had been discovered. Dutrochet observed that the stem in
the embryo of Viscum is negatively heliotropic, and had care-
fully studied its behaviour ; he opposed the old notion that the
geotropic downward curvature is peculiar to main roots, and
that that is the reason why they are in ' polar ' opposition
to the stem, by pointing to the shoots of the rhizomes of Sagit-
taria, Sparganium, Typha, and other plants, which at least
when young curve downwards with some force ; and on ex-
tending Knight's experiment with a rotating wheel he found
that the leaves also exhibit a peculiar geotropism. These
observations and some new examples of periodical movement

554 History of the Doctrine of [Book hi.

and movements of irritability were connected without difficulty
with the forms of movement that had been long known in the
vegetable kingdom, and contributed to correct the views that
had been entertained respecting them. But this was not the
case for a time with two phenomena which also fall within the
province of phytodynamics, namely normal growth and the
movements of the protoplasm, which exhibit the two opposite
extremes, so to speak, of the facts connected with movement.
Various measurements had been made of the growth of plants
since the beginning of the century, and attempts had been
made to establish its dependence on light and heat, but with-
out any great success. Treviranus had rediscovered the move-
ments of the protoplasm in 1 8 1 1 in Nitella. Similar move-
ments were repeatedly pointed out by Amici, Meyen, and
Schleiden in the cells of higher plants, but they were taken for
streamings of the cell-sap ; it was still unknown that all these
were movements of the same organised substance, which moves
independently in water in the form of swarmspores. These
phenomena, especially the movements of swarmspores, were
noticed and studied separately between 1830 and 1840, but no
one thought of bringing both these movements and the me-
chanical laws of normal growth into connection with the
phenomena which had usually been treated together under the
head of movements in the vegetable kingdom. De Candolle
and Meyen did not mention them in this connection in their
'Compendia' of 1835 ^"d 1839; Meyen on the contrary
discussed the ' circulation of the cell-juice ' with nutrition, and
the movement of swarmspores with the propagation of Algae.
The two writers just named, like Du Hamel before them,
divided into two main groups the movements in the vegetable
kingdom which had been long known and were usually put
together, and treated of geotropic and heliotropic curvatures
and the movements of tendrils and climbing plants under the
head of direction of plants, and the periodical movements and
movements connected with irritability under that of move-

Chap. TIT.] the Moveiueitts of Plants. S5S

ments, though they gave no reasons for this classification ; it
rested evidently on an indistinct feeling outrunning clear per-
ception— that in the one they were dealing with growing parts
of plants, in the other with parts which had ceased to grow,
Dutrochet made no such distinction, but he was the only one
among the chief representatives of vegetable physiology be-
tween 1830 and 1840 who had thoroughly adopted the mecha-
nical view of phytodynamical phenomena. We have said that
Treviranus was a warm adherent of the theory of vital force.
De Candolle and Meyen, it is true, endeavoured to explain
each separate movement if possible by mechanical laws, but
in their more general speculations they readily lapsed into
antiquated views ; thus De Candolle speaks of the sensitive-
ness of Mimosa as a case of extreme ' excitability,' and Roeper,
in accordance with his other views, translated De Candolle's
expression, autonomous movements, by the term ' voluntary '
movements. The movements he is speaking of are those of
Hedysarum gyrans, and Meyen also terms them ' voluntary '
movements, and ranks them with those of Oscillatoria. That
he was influenced in this by a dim reminiscence of the old
vegetable soul is shown by the heading, ' Of movements and
sensation in plants,' placed over the section of his work in
which the expression occurs ; and in the last chapter of this
section, he attributes some kind of sensation to plants on
account of the evident marks of design in their movements,
though he veils his meaning in obscure and tortuous
phrases.

5. The mists of the nature-philosophy and the vital force
disappeared from the phytodynamical province of botanical
science after the year 1840. The methodical research of in-
ductive science, which had still to contend with them up to
that time, was once more acknowledged as the supreme guide
and ruler. A few stray dissentients were still to be found, but
the general voice was against them. There was an eager
desire for exact investigation of the facts, in order to lay a

S5^ History of the Doctrine of [book hi.

firmer foundation for future theory. But no conclusive results,
no such entirely new points of view were gained before i860,
as were established during the same time in phytotomy, mor-
phology, and systematic botany. To these subjects the most
eminent enquirers applied their best powers almost exclusively,
while phytodynamics vanished from the field of view of the
generality of botanists, and no one made them the object of
the comprehensive, intense, and effectual study, which Dutro-
chet had previously devoted to them. At the same time his
example was not without a powerful effect. The working of
endosmose was further investigated and treated as a part of
molecular physics. Greater freedom was thus gained in the
mechanical treatment of phytodynamical questions, and a firmer
basis secured by aid of the advances which were being at the
same time made in phytotomy. But with the exception of
Briicke's essay on Mimosa (1848), the works produced during
this period were chiefly devoted to the critical examination of
the writings of previous observers, and whatever appeared that
was new and positive remained incomplete till after the date at
Avhich this history ends. Under these circumstances we must
be content to indicate briefly the more important of the new
discoveries and of the efforts made at this time to advance the
theory of the subject.

Several observers occupied themselves soon after 1840 with
the influence of light on the growing parts of plants. Payer
maintained in 1843 that the radicles of various Phanerogams
turn from the light, and a controversy arose between him and
Dutrochet on the point, in which Durand took part in ,1845,
but no definite conclusion was arrived at even as regards the
certainty of the fact. The beautiful discovery of Schmitz in 1843,
that the Rhizomorphs grow more slowly in the light than in the
dark, and are at the same time negatively heliotropic, might
have proved much more important ; but the theoretical value
of this fact has till quite recently been entirely misconstrued.
Sebastian Poggioli had discovered in 181 7 that highly refringent

Chap. III.] the Movements of Plants. 557

rays of light were more heliotropically active, and the fact was
confirmed by Payer in 1842; but Dutrochet in 1843 maintained,
and incorrectly, that it is the brightness of the light, and not
its refrangibility, which is the determining factor. Zantedeschi
found in 1843 that red, orange, and yellow light are heliotro-
pically inactive. Gardner on the contrary in 1844, and
Guillemain in 1857, came with the help of the spectrum
to the conclusion that all its rays are heliotropically active, and
the question long remained hampered by these contradictory
statements, till it was taken up again in 1864. This was
a similar case to that of the question of the effect of varie-
gated light on the elimination of oxygen and the formation of
chlorophyll. Daubeny had given attention to the subject in
1836 and inclined to the view, that it was the brightness of the
light rather than its refrangibility which was the important
point ; and Draper's observation, made with the spectrum in
1844, that the elimination of oxygen reaches its maximum in
yellow light and decreases on each side of it, was generally
understood as though it was a question only of the brightness
of the light. It is only within recent times that this view has
been abandoned, and in the same way all the investigations
which have just been mentioned were not settled till after
i86o, and were scarcely turned to any theoretical account.

The bright point in the history of phytodynamics at this time
is Briicke's treatise in 1848 on the movements of the leaves in
Mimosa, not only on account of the very important results which
it records, but still more for the exactness of its method which
has made it a model of research in these subjects. He first
established the essential difference between the periodical
nocturnal position of the leaves of Mimosa and the position
which they assume when irritated, and showed that the former
is connected with an increase in turgidity, the latter with
relaxation ; he showed further that if the upper half of the
organ is removed, the periodical movements and the irrita-
bihty both continue. Of great importance to the theory was

S5^ History of the Doctrine of [Book hi.

the clear account given of the tension which is produced
between the vascular bundle and the turgescent layer of
parenchyma, and the reference of the periodic movements
and of those of irritation to the movements of water in the
antagonistic masses of parenchyma. The details were still
imperfect, but one great advantage was secured, namely, the
doing away with the mysticism associated with the idea of
irritability, from which even von Mohl was not entirely free.

A full enquiry into the downward curvature of roots, pub-
lished by Wigand in 1854, deserves mention, because it threw
some light on the theory of the strictly mechanical questions
connected with a subject which had been for some time ne-
glected, and because, while containing other instructive matter,
it refuted the theory, founded on endosmose and on the struc-
ture of tissue, which had been suggested by Dutrochet and
adopted by von Mohl, since it showed that one-celled organs
also exhibit geotropic curvatures. The great theoretical im-
portance of the fact that all the various phytodynamical phe-
nomena, with the exception of movements of irritability, are
manifested in one-celled organs, was not fully understood till
after i860.

It has been already observed, that no theoretical result was
obtained from the discovery of circulation in cells made by Corti
in 1772, and repeated byTreviranus in 181 1. The same may
also be really said of the later observations of Araici, Meyen,
and Schleiden, which went to show that such movements occur
very generally in vegetable cells. In like manner the move-
ments of swarm-spores, of which a considerable number of
instances had been observed before 1840, were rather the
subject of astonishment than of scientific consideration. The^
could not in fact find their place in the general system until
Nageli and von Mohl discovered in 1846, that it is in the pro-
toplasm that the so-called movement of the cell-sap takes place,
and Alexander Braun made it known in 1848 that the swarm-
spores are naked masses of protoplasm, and indeed true

Chap. III.] tlic Movements of Plants. 559

vegetable cells. A new substratum for the movements in
plants, and one of the simplest kind, was thus obtained ; and
.Nageli attempted in 1849 a mechanical explanation of the
movements of swarm-spores, while in 1859 De Bary exhibited
in the Myxomycetes most instructive examples of such move-
ments. If Nageli failed in his attempt, yet it seemed possible
that the protoplasm had an important share in the production
of all phytodynamic phenomena, and the idea appeared
capable of a very wide application when Unger pointed out
in 1855 the resemblance between vegetable and animal pro-
toplasm. It is true that not one of these later observations
led to any conclusive results till after i860 ; but that the whole
subject of phytodynamics had made considerable advance as
early as 1850 is apparent from the account given of it by
von Mohl in his 'Vegetabilische Zelle' of 185 1, and by Unger
in his ' Lehrbuch der Anatomie und Physiologic der Pflanzen '
of 1855. Von Mohl chiefly exposes the unsatisfactory nature of
the attempts that had been made to explain the phenomena ;
Unger, on the other hand, shows how much that is funda-
mentally important had been already established.

The mechanics of growth had not been included by former
writers among the phenomena of phytodynamics, nor was it so
included by either Unger or von Mohl. It seemed to be sup-
posed that there was a fundamental difference between growth
and other movements in the vegetable kingdom, and this idea
was entertained even in the most recent times. From the time
of Mariotte and Hales no one had made the mechanical laws
of growth the subject of special investigation or theoretical
consideration ; yet some observations had been made on the
formal relations of growth and its dependence on external
influences. Ohlert (1837) was the first after Du Hamel who
studied the distribution of growth in the root ; Cotta in 1806,
Chr. F. Meyer in 1808, Cassini in 182 1, Steinheil and others
made measurements in connection with the same question in
the stem, but only with the result of showing that the distribu-

560 History of the Doctrine oj [Book hi.

tion of growth at the internodes may vary very greatly, and
even Miinter's measurements in growing internodes in 1841
and 1843, and Grisebach's in 1843 led to no appreciable
result, because the observers neglected to apply the figures ob-
tained to the theory of the subject. It seemed to be generally
supposed that it was enough simply to write down the measure-
ments in figures, and that a theoretical result would spring
into being of itself; on the contrary the real scientific work
begins after the figures are obtained. The same cause pre-
vented the observations which have yet to be mentioned from
producing real fruit. The influence of the variability of the
temperature of the air \ and of the alternation of daylight and
darkness on the longitudinal growth of internodes and leaves
after they have emerged from the bud-condition, had often been
investigated; Christian Jacob Trew published in 1727 long-
continued daily measurements on the flowering stem of Agave
Americana in conjunction with observations on temperature
and weather ; a hundred years later similar observations were
made by Ernst Meyer in 1827, by Mulder in 1829, and by Van
der Hopp and De Vriese in 1847 and 1848; but Harting in
1842 and Caspary in 1856 were the first who went at all deeply
into the questions involved. These observations, some of
which were carefully made, led to no further result than the dis-
covery of the fact, which Miinter indicated and Harting applied
to theoretical purposes but which no one else thought worthy
of attention, namely that the rate of growth increases at first
and independently of external causes, till it reaches a maximum,
and then decreases till at length it comes to an end ; they did
not even establish a really practical method of observation.
Scarcely two observers arrived at the same result, because the
questions respecting the relations of growth in length to tem-
perature and light had not been clearly and distinctly put. Com-
munications were published in the periodicals, which simply

^ See ' Arbeiten des botanischen Institutes in Wiirzburg,' vol. i. p. 99.

Chap. III.] the Movemcfits of Plants. 561

tabled long-continued measurements of the longitudinal growth
of parts of plants, and gave an idea of constant irregularity of
growth, without suggesting any explanation of the causes which
produced it ; so indistinct were the ideas of observers on these
subjects even after 1850, that the majority of them proposed to
themselves the question, what difference there is between
growth by day and by night ; it did not occur to them that day
and night are not simple forces of nature, but different and
very variable complications of external conditions of growth,
such as temperature, light and moisture, and that such a mode
of putting the question could not possibly lead to the discovery
of the relations established by law, so long as the several
factors were unknown which are included in the conceptions of
day and night. Harting's essay of 1842 is superior to those
above mentioned, inasmuch as he distinctly endeavoured to
obtain from his measurements some definite propositions that
might be applied to the theory of the subject, and especially to
give a mathematical expression to the dependence of growth
on temperature, but his success in this particular point was not
great. The idea, that there must be a simple arithmetical
relation to be discovered between growth and temperature,
had been suggested by Adanson in the previous century, and
it found many supporters in the period between 1840 and
i860: but it should be observed that the term growth was
used in a loose and popular sense to sum up all the phenomena
of vegetation in one expression. Adanson had supposed that
the time occupied in the unfolding of the bud was determined
by the sum of the degrees of the mean daily temperature,
reckoned from the beginning of the year ; Senebier, and at
a later time De Candolle, declared against the existence of
any such relation, but a similar idea was not only very
generally entertained after 1 840, but it even came to be treated
as a probable natural law. Boussingault had pointed out that
in the case of cultivated plants in Europe and America, if the
whole period of vegetation expressed in days is multiplied by

o o

5<52 History of the Doctrine of [Book hi.

the mean temperature of the same period, the products do not
deviate widely from one another in the same species. It was
thereupon assumed that these deviations are due to incorrect
observation, and that such a constant product of the period of
vegetation and the mean temperature will be found in every
species. This product then received the unmeaning appella-
tion of the sum of the temperature. If such a relation between
vegetation and temperature really exists, it would necessarily
follow that other things, such as light, moisture, the soil, &c.,
have no influence at all on the period of vegetation, not to
speak of those internal causes which help to complicate the
simplest processes of growth. It is unnecessary to expose in
this place the absurdities involved in this idea of the sum of
the temperature ; the needful remarks will be found in the
'Jahrbucher fiir wissenschaftliche Botanik' of i860, i. p. 370.
It is a remarkable fact however that such monstrous reasoning
should have been able to prejudice science in various ways even
later than the year i860. A new science was actually invented
and called Phaenology, which accumulated thousands and thou-
sands of figures, in order to discover the sum of the tempera-
ture for every plant, and as this crude empiricism showed that
the simple multiplication of the period of vegetation by the
temperature gave no constant result, the square of the tempera-
ture was tried and other tricks of arithmetic adopted. Though
Alphonse de CandoUe as early as 1850 expressed well-founded
objections to the whole of this method of treating the subject,
in which the mean temperature played much too important a
part, yet he was so far unable to keep clear of the prevailing
ideas, that he thought he could express the effect of light by an
equivalent number of degrees of temperature, and so save the
supposed law of temperature in vegetation. To this idea may
be traced his work on the geography of plants, published in
two volumes in 1855, which however contains a rich treasure
of personal experience and knowledge of the works of other
writers.

Chap. 111.] the Movemeiits of Plants. ^67,

It appears then that scarcely any point of fundamental
importance in phytodynamics was cleared up before the period
at which this history closes ; it was not till after that date that
these questions began to be studied from new points of view,
and they are at the present time still under discussion.

o o

INDEX.

Adanson, 66, ii6, 545, 561.

Aepinus, 257.

Agardh, 143, 160, 205. 352.

Albertus Magnus, 14.

Aldrovandi, iS.

Alpino, 380.

Alston, 402.

Amici, 223, 284, 371, 432, 434, 558.

Ammann, 39.

Aristotle, 4, 6, 13, 16, 43, 51, 219,

376, 450.
Astruc, 543.

Bachmann, 7, 39, 63, 74-76, S3, loi.
Baisse ^de la Baisse), 483.
Banks, 139.
Bartling, 144, 145.
Batsch, 125, 137, 143,
Bauhin, Kaspar, 5, 6, 8, 12, 13, 17,
19, 24-26, 33, 39,64, 80, 100, 115.
Bazin, 543.
Beale, 472.
Berkeley, 205.
Bemhardi, 109, 225, 256, 263-266,

347-
Bischoff, 161, 198, 207, 438, 439.
Blair, Patrick, 39 r.
Bock, Hieronyraiis, 3, 13, 14, 19,

24, 27, 28.
Boehmer, 2 48, 48 3.
Boerhaave, 78.

Bonnet, 163, 247, 486-4S8, 541.
Borelli, 536.
Bornet, 210, 443.
Boussingault, 373, 449, 531, 561.
Bradley, 391, 406.
Braun, A ,162,165,169,170-181,184,

208, 312, 314, 334, 336, 442, 558.
Bravais, 169.
Brisseau-Mirbel, 198, 224, 226, 250,

256> 259, 261, 262, 272-275, 284,

307- 3", 321.
Brongniart, Adolph, 147, 321, 432,

436-
Brown, Robert, no, 112, 122, 139-

I44> 155, 161, 227, 323, 433. '

Briicke, 339, 556, 557.
Biunfels, 3, 5, 13, 14.
Brunn, 255.
Buffon, 89.

Burckhard, 83, 391, 397.
Burnett, 550,

Calandrini, 486.

Camerarius, Rud. Jak., 60, 77, Si,
87. 361, 376, 385-390-406.

Candolle {see De Candolle\

Caspary, 560.

Cassini, 559.

Cesalpino, Andrea, 5, 7, 9, 12, 17,
18, 23, 37,40, 42-57, 61,63, So,
81, 103,125, 163, 219, 220,450.

Cessati, 213.

Choulant, 19.

Clnsius [see de I'Ecluse).

Cohn, 209, 213, 442.

Comparetti, 249, 263, 282.

Corda, 184, 205.

Cordus, Valerius, 29, 536.

Comutus, Jakob, 537.

Corti, 314, 513, 545, 558.

Cotta, 506, 559.

Covolo, dal, 410, 545.

Cramer, Karl, 203.

Dalechamps, 29, 30.

Darwin, Chas., 11, 12, 49, 53, 152,

169, 180, 183, 351,431.
Daubeny, 557.
De Bary, 210, 213-215, 292, 314,

318, 339> 372,443, 559-
Decaisne, 442.
De Candolle, Alphonse, 562.
De Candolle, Pyrame, 9, 71, 92,

no, 112, 122, 126-139, 307, 484,

51.5, 537.554.555. 561.
De la Baisse, 483.
De Lamarck, 127.
De r;^cluse, 13, 18, 19, 29-31, 55.
De la Hire, 543.
De rObel, 3, 6, 13, 17, 18, 23, 26,

32, 35, 58, 64, 67.

\66

Index.

Desfontaines, 136, 293, 307.

De Vriese, 508, 560.

Dillenius (Dillen), 76, 211, 437.

Dioscorides, 3, 4, 13, 15, 28, 34.

Dippel, 343.

Dodart, 538, 547.

Dodoens (Dodonaeus), 13, 18, 22,

29. 30.
Draper, 557.
Du Hamel du Monceau, 89, 247,

368,488-491, 542-545, 559.
Du Petit-Thouars, 137, 489.
Durand, 556.
Dutrochet, 212, 370, 509-514, 55°,

552, 553-

Ehrenberg, 208, 211, 322, 354, 438.
Eichler, 350.

Endlicher, 9, no, 146, 333.
Erlach, 354.

Fabri, 403.

Fischer, 509.

Fogel, 59.

Frank, 39, 343.

Fries, Elias, 10, 111, 153, 205.

Fuchs, 3, 13, 14, 15, 18, 19, 20, 24.

Fiirnrohr, 192.

Gartner, Karl Friedrich, 370, 421,

427-430.
Gartner, Joseph, 23. no, 122-125,

207,413.
Galen, 3, 15.
Garcias del Huerto, 536.
Gardner, 557.
Gaudichaud, 293.
Geoffrey, 391, 395.
Gesner, Konrad, 18, 20, 29, 379.
Ghini, Luca, 18.

Girou de Bouzareingue, 422, 426.
Giseke, 137.

Gleditsch, 211, 212, 391, 393.
Gleichen-Russworm, 247, 249, 263,

404, 431.
Goeppert, 184, 370, 507.
Goethe, 62, 144, 156-160, 263, 390.
Grew, Nehemiah, 69, 89, 93, 97,

221, 222, 223, 225, 231, 232, 234,
, 239-244, 263, 382-385, 551.
Grischow, 506.
Grisebach, 560.

Guillemain, 557.

Haartman, 400.

Hales, 89, 224, 363, 476-482, 539.

Haller, 66, 89, 404.

Hanstein, Johannes, 203, 343, 348,

350.
Hartig, Theodor, 301, 314, 342, 354,

532, 534.
Harting, 303, 560, 561.
Harvey, 205.
Hassenfratz, 495.
Hebenstreit, 76.
Hedwig, 123, 198, 207, 224, 253-

255, 263, 283, 431, 437, 438.
Henfrey, 312, 335, 440.
Henschel, August, 422, 424, 425.
Herbert, William, 370,420,421,431.
Hermann, 68.
Heucher, 76.
Hill, 76, 544.
Hofmeister, Wilhelm, 11, 118, 167,

170, 184, 199-203, 208, 209, 210,

228, 312, 318, 335, 336, 371, 439,

440.
Hooke, Robert, 221, 223, 229-232,

536.
Homschuch, 206.

Ingen-Houss, 224, 368, 491, 493,

494-497.
Irmisch, 165.

Jessen, 397.

Johnson, 549.

Jungermaun, 39.

Jung (Juugius), 40, 43, 58-63, 64,

73, 80, 1 1 5, 1 55, 2 21 , 381 , 454-456.
Jussieu, Antoine Laurent de, 9, 23,

77, 92, 109, no, 116-122, 125,

155,431-
Jussieu, Bernard de, 9, 41, 109, 115.

Karsten, 313, 320.

Kessler, 19.

Kieser, 160, 283, 320.

Knaut, Christopher, 74, 76.

Knight, Andrew, 421, 431, 506, 548.

Kolliker, 313.

Koelreuter, 89, 122, 123, 247, 406-

414,431,437, 544, 545-
Ktitzing, 205, 206.

Index.

567

Lantzius-Beninga, 198.

Lavoisier, 491, 492, 507.

Leemvenhoek, 223, 244, 245, 259.

Leibnitz, S3, 391, 397.

Leitgeb, 203.

Lesczyc-Suminsky, 43S, 441 .

L'Heritier, 137.

Leveille, 205.

Liebig, 373, 449, 525-531.

Lindley, 9, 147, 148.

Lindsay, 550.

Link, 161, 211, 225, 255-259, 261,

267-270, 310, 505, 546.
Linnaeus, 8-10, 37, 40, 41, 49, 56,

65= 7i> 79-ioS, 113, 118, 397-

402, 431.
Lister, 470.

Lobelius {see de I'ObelV
Logan, James, 391, 392.
Ludwig, 76, 248.

Macaire, Prinsep, 511.

Magnol, 8, 470.

Mairan, 544.

Major, Joiiann Daniel, 456, 460, 469.

Maipighi, 44, 48, 63, 69, 89, 155,
221, 223, 231-239, 241, 262, 363,
366, 367, 381,457-461.

Man, James, 258.

Marcet, 506.

Mariotte, 461-470, 539.

Mattioli, 3, 18, 29.

Mayo, 550.

Medicus, 255, 267.

Menzel, 39.

Mercklin, 441.

Mettenius, 198, 202, 439.

Meyen, 208, 225, 226, 259, 260,
284-292, 305, 310, 322, 333, 351,
508, 514, 523, 554, 555, 558.

Meyer, Chr., 559.

Meyer, Erast, 18, 160, 161, 401, 560.

Micheli, 211, 437.

Mikan, 385.

Milde, 202, 440.

Millardet, 350.

Miller, 391, 392.

Millington, 3S2, 384, 385, 399.

Mirbel {see Bris?eau-Mirbel).

Mohl, Hugo von, 105, 161, 183,
192, 223, 226, 227, 259, 260, 284,
291-311, 31S, 321, 325, 329, 336,

340, 349, 350, 351, 354, 355, 374,

529-532, 550, 551,. "^SS-

Moldenhawer, J. J. P., 225, 257-

261, 276-284.
Morison, 7, 8, 63, 66-68, loi.
Morland, Samuel, 391, 394.
Morren, 208, 322.
Mulder, 303, 529, 560.
Miiller, 343.
Miinter, 560.
Mustel, 266, 267, 490.

Nageli, 11, 63, 118, 16 r, 166, 1S3,
185, 193-197, 208, 226, 227, 297,
302, 312-316, 318, 326-334, 336,
340, 346-356, 438, 558, 559.

Naumann, 169.

Needham, 431.

Nees von Essenbeck, 160, 205, 212,
438.

Nieuwentyt, 472.

Oelhagfn, 39.
Ohlert, 559.
Oken, 161.

Palm, 550.
Payen, 303.
Payer, 191, 556, 557.
Percival, 547.
Perrault, 403, 460, 470.
Persoon, 211.
Plato, II.

Platz, Wilhelm, 483.
Pliny, 3, 13, 15, 34, 37S.
Ploessl, 258.
Poggioli, 556.
Polstorff, 526.
Pontedera, 391, 399, 401.
Priestley, 491-494.
Pringsheim, 203, 209, 210, 213, 318,
372, 442, 443.

Radlkofer, 314, 350, 354, 435-

Ramisch, 422, 426.

Raspail, 320.

Ratzenberger, 19.

Ray, 7, 8, 39, 40, 59, 60, 63, 67, 68-

74,101, 115, 384, 471, 536-53S.
Reichel, Christian, 484.
Rivinus {sec Bachmann).
Roemer, 401.

568

Index.

Roeper, 144, 371, 555.
Rudbeck, 76, 79.

Rudolphi, 211, 256, 258, 267-270.
Ruppius, 76.

Saiut-Hilaire, Auguste de, 149.
Saint-Pierre, 137-
Salm-Horstmar, 532.
Sanio, Karl, 309, 316, 318, 341,

349. 350.
Sarrabat {see de la Baisse).
Saussure, Theodore de, 126, 369,

370, 497-504, 506, 531.
Sbaraglia, 472.
Schacht, Hermann, 280, 283, 302,

305, 318, 337> 338, 341, 343. 345>

348, 434, 435.
Schaeffer, J. C, 211.
Scheffer, 39.
Schellhammer, 74.
Schelver, F. J., 422, 424.
Schimper, C. Friedr., 162-170.
Schimper, W. B., 198.
Schlechtendal, 192.
Schleiden, 63, 161, 179, 183, 188-

193, 226, 297, 302,311, 322,323,

326, 341. 345, 433-436, 529, 558-
Schmidel, 20, 123, 197, 438.
Schmitz, 212, 556.
Schrank, Paula, 255, 425.
Schulz-Schulzenstein, 293, 300, 320,

545-
Schulze, Franz, 284, 318, 373.
Schulze, Max, 314, 339.
Schwann, 313.
Schwendener, 215.
Selligue, 258.
Senebier, 126, 224, 249, 369, 495-

497, 547, 561.
Sharroc, 537.
Smith, 545.

Spallanzani, Lazaro, 422-424.
Sprengel, Konrad, 363,368,414-422.
Sprengel, Kurt, 66, 125, 224, 256,

259, 262, 263, 268, 320, 469.
Steinheil, 559.
Sternberg, 184.
Suminsky {see Lesczye-Suminsky).

Thai (Thalius), 18.

Theophrastus, 3, 4, 13, 15-17, 34,

219, 377-
Thiimmig, 248, 473.
Thnret, 209, 210, 314, 372,442,443.
Tonge, 470.
Toumefort, Pitton de, 7, 8, 39, 63,

76-79, 83, loi, 115, 391,401, 544-
Tragus [see Bock).
Trentepohl, 206, 207.
Treviranus, 19, 161, 256, 261, 267,

270-272, 275, 290, 310, 320, 425,

520-524, 645.
Trew, 560.
Trog, 212.
Tulasne, 213, 435.
Turpin, 320.

Unger, 161, 184, 198, 206, 227, 300,
305, 312, 314, 318, 325-329, 333,
336-340, 346, 375, 438. 559-

Vagetius, 59.

Vaillant, Sebastian, 391, 397, 398.

Valentin, 355, 386, 387, 402.

Van der Hopp, 560.

Van Deyl, 257.

Van Helmont, 455.

Varro, 535.

Vaucher, 126, 207, 372, 438, 545.

Voight, 160.

Volkamer, 39.

Vrolik, 508.

Wallroth, 215.

Walther, Friedrich, 483.

Weickert, 257.

Wiegman, 526.

Wigand, 105, 341, 558.

Wilbrand, 425.

Willoughby, 470.

Wolff, Christian, 221, 247, 402, 403,

472-476.
Wolff, Kaspar Friedr., 44, 155, 190,

249-253, 273, 275, 276, 319, 405.
Woodward, 472.
Wright, 257.
Wydler, 165,

Zaluziansky, 380, 381.
Zantedeschi, 557.
Zinn, 544.

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