Skip to main content

Full text of "Principles of the anatomy and physiology of the vegetable cell"

See other formats




JUirry Soane./see. 













V- 1 ' 


* . ** 





^ - 




a * 







-v . 


\ \ 


\ c 


•<X lb 


V m 




I*' 4 

';.. <£ 

f / V 


• "V 
1 it- 

; v/ -. ^ / ■-... J 



: h? mo--> 00.- I It 
iff |k& sv -: 



— <z 

: :: : ; 
:: ■: 



. P 

• ■ 



1 - 



» **• 

1 * -■-*,. 






. . . * - * 






.\ ■ ' <- - V ^ '■ V 










..'* : - 





/ 1 ■ 




- 1 



/ '-| - \ - 

/ >:>■ - \ 

-'^ i -■ 

\..\ 1 . 

*i' .-■' 1/ i 


N*. - ■ ■■-..'-■' { ; 

1 • V i ^ 

* v" •. - : i 

< / >- I 

V - 1 J ^ 



. K 

*\**->*- V^+*+ 


'■ AN\-V *■> 


* - 




4 V 

* •■ * 


■■■ :■■ -..■■ 


* ^t- 

^ fc .,t** 

w * * 




.. ~ 







»* * . 





■ .■ . 


■p- • - — -. V/ I 

\ /-•• s --?-^ 


\... / 




j^' ••■'' '/■ ■'■■" \\-~a 

i - ■■■. 

1 J\ V, *# *f *. . »* . 

I ;■■:■■-- 

• •*-■■ ' 7-i 

\ ■ t 

» » . •■-.-■•. 1 

■3: : : ^ 

"-,^- ■ ••-" .. 

"-~.~.^.,, ...... .-,...:.,....., ,,,„,...,_, ..„^.v--° 

— > e 

> ■ 

a * 


A ■ 

* * 

I : 






/ * 


- » * t - - - 


: j 

■' f\ ■ 

.• ■ ■- : 


- 1 







r r * V |*t» *■■■ J 


I 1 : 

^ aaa _ 
v -» * * ♦• „ , 

K.J — --' 

•S-iv' 1 



-■ * 




/.-■" .-■■ 

.-• # ' ' 


,..;, ~*"" 




*. * 






^ » 








-■:■•:■-■::•• •"■ 

i j 


,■ m 


1, * 

■ > 

■ I 

* ! 




■ --:;:---.-■. 

" ." 


1 :-, 

'--V ■■ ^ 



-_ - + 



■ I T* 


I . ■ ... 

;-■ •■'--■.:■- . a 


* * * 


.x rf 

- J 




• . 




* • 

■ 1 


; - 1 ^ 


. . 






■ r- 




"*-•*- ^ » . 

^ _-- 

- J * *' "-*-'-*'*^ t - .. 1 

'- '. - 



- 1 



■ ■• : 




i\\W ■■■■ IV, 

*••*— #••" ■*- ,-_ 

■1 - 



T'ohn 'Ji Voorst. l.Pa ' < " 





* ,.- v 














( With the A uthor's permissio n) 

B Y 

Lecturer on 

ARTHUR HENFREY, F.R.S., F.L.S., etc., 

Botany at St. George's Hospital; Author of Outlines of Anatomical and 
t '/, lysiological Botany ; Rudiments of Botany; etc., etc. 

amitf) an Cllttstutik Pate antf numerous afflfootaute. 








Cambridge University Library, 
permanent tfepo 
Botany Scho 


T. E. Metcalf, Printer, 63 ? Snow Hill 






Mr. Arthur Henfrey having informed me that he 
intends publishing an English translation of the pre- 
sent treatise, I take this opportunity of making known 
to the English reader the purpose I had in view in the 
preparation of the book. The following pages were not 
originally intended to appear as an independent work, 

or to give a summary of the wide 


of the 

Anatomy and Physiology of Plants, but appeared as 

" Cyclopaedia of Physiology" published 



by Dr. Rudolph Wag 

of Gotting 


up to 

furnish students of Animal Physiology 
particularly the Medical Profession, with a review of 
the Anatomical and Physiological conditions of Vege- 
tables (of the Cell), in 


enable them to form 

a definite judgment upon the analogies which might be 

drawn between the structure and vital functions of 

animals and plants. This intention, together with the 

circumstance, that I was compelled to crowd the whole 

exposition into the space of a few sheets, rendered it 

necessary to direct especial attention to the individual 
cell, as 

the fundamental or^an of the Ve 

nism. Since, however, the cell only 

etable Orora 




and physiolo 

independence in the lowest 













and since, in the more highly organized plants 

both the structure and the physiological functions of 

the individual cells becom 




ence upon the other parts of the pi 


r depend - 

of the vegetable 


moreover, since functions then present them 

selves, of which no trace 

plants, it became requisite to take 

be found in the lower 
account of the plants 
of higher rank, and of the various organs which these 

possess. ~~~ 

feet, still 

The treatise, therefore, contains, if an imper- 
in many respects, a more extensive resume of 

Vegetable Physiology, than might be conjectured from 

the title. 

Unhappily, the Physiology of Plants is a science 
which yet lies in its earliest infancy. Few of its dog- 

mas can be 

garded as settled beyond doubt 


step we meet with imperfect observations, and con- 

for exampl 
the doctrin 

with the most contradictory views 

; thus, 

opinions are still quite divided regarding 
of the development of the cell, of the 

origin of the embryo, and of the existence of 

an lm- 


in the higher Crypt 


in these 

and in other cases, the small compass of the present 
treatise forbids a more extensive detail of the researches 

upon which the 

however, that I have succeeded 

opposing views are founded 

I hoi: 

in making clearly pro 

inment, the chief points upon which these contests turn, 
Mid thus, in facilitating the formation of a judgment 


and, I have 

:glected to indicat 

(he literature from which further instruction is to be 



Tubingen, October 19 th 



Introductory Remarks . „ 

I. — The Anatomical Condition of the Cell 

A. Form of Cells 
R Size of the Cell 
C. The Cell-membrane 

a. Physical Properties 

b. Structure 

e. Chemical Conditions 


I). Cells in their Reciprocal 

~ Contents of Cells .... 

a. Primordial Utricle, Protoplasm, and Nucleus 

b. Cell-sap ..... 

c. Granular Structures . 

d. Compounds dissolved in the Cell-sap 
P. Origin of the Cell . 

a. Division of the Cell 

b. Free Cell-formation . 

11. — The Physiological Conditions of the Cell 

A. The Cell as an Organ of Nutrition 

a. Absorption of Watery fluids 

b. Diffusion of the Sap in the Plant 

c. Nutrient Matters . 

cL Elaboration of the Nutriment 

e. Secretions 

f. Evolution of Heat . 

B. The Cell as an Organ of Propagation 

a. The Multiplication of Plants by Division 

b. Propagation by Spores and Seeds 

a. Propagation by Spores . 

* Propagation of Thallophytes 
** Propagation of the Cryptogams 

having Stems and Leave 

b. Propagation by Seeds 


■atf * 

The Pollen 
The Ovule 



%* The Origin of the Embryo 


























1 1 












Figs. 1 — 6, Conferva glomerata. 

1. The growing points of the plant. — a, Terminal cell; b. Kami- 

fication of a cell, beginning ; c, Ramification further advanced, 
with the commencement of the formation of a septum at its 
base ; d, a perfect septum ; e, Prolongation of a branch- cell 
twice the length of the cells in general, with the commence- 
ment of the formation of a septum in the middle. 
Terminal cell grown to the double length, with an imperfect 
septum in the middle. 

3. Constriction of the cell-contents by the half -completed sep- 


4. A half-completed septum, in which a considerable deposition of 


cellulose membrane has already taken place. 

5. A septum in progress of formation after the action of an acid, 

which has caused contraction both of the primordial utricle 
(a) and the cell-contents (&). 

6. Complete septum split into two lamellae by the action of an 


7. The two uppermost cells of a hair from the filament of Trades- 

cantia Sellowii y with nuclei and currents of protoplasm. 








Figs. 8 — 1 1. Formation of the Pollen in Althaea rosea. 

8. Four nuclei in the contents of the parent-cell, with the com- 

mencement of the formation of four septa. The primordial 


utricle and cell-contents contracted from the action of alcohol. 

9. Farther advanced development of the septa of the parent-cell. 

10. The primordial utricle removed from the parent-cell, not yet 

completely divided into four parts. 

1 1 . Completed division of the parent-cell. 


Figs. 12 — 18. Formation oft7ie embryo in Orchis Morio 

(from Hofmeister). 

Fig. 1 2. The ovule, a considerable time before fertilization, a, the outer 

coat ; b, the inner coat ; s, the embryo-sac ; c, the funiculus. 
Three nuclei have been formed in the micropyle end of the 

„ 13. The internal parts of the ovule a short time before fertilization. 

a, inner coat of the ovule ; s, embryo-sac ; b, germinal vesicle, 

„ 14. The ovule at the moment of fertilization, a, b, s, as in the pre- 
ceding figure j p, the pollen-tube ; f, a few cells which have 
made their appearance at the chalazal end of the embryo-sac. 

„ 15. Further development of the impregnated germinal vesicle. It 

contains two nuclei which lead to its division into two cells. 

„ 16. The embryo-sac with a pollen-tube adherent. The germinal 

vesicle is parted into two by division into an upper (a) and 
a lower (b) cell, 

„ 17. The pro-embryo {Vorheim). Its superior portion (a), the sus- 

pensor, has originated through the division of the cell a of 
Fig. 16; its inferior portion, the rudiment of the embryo (b) 











through the division of the cell b of Fig. 16. 




stage of development. 

Figs. 19 — 22. Spores of Prolifera rivularis (from Thuret). 

19. Movin 

20 — 22. Various stages of the germination. 



24. Germination of the same (from Thuret). 





Two cells from the antheridium of Sphagnum, with seminal fila- 
ments (from linger). 

27. An isolated seminal filament (from Unger). 

28. A seminal filament with two cilise treated with iodine. 



29. Seminal filament of Pteris serrulata (from Leszcyc-Suminski). 







If we examine the texture of plants with a powerful microscope, 
we find that it does not consist, as appears to the naked eye or 


forated by a greater or less abundance of cavities, but is composed 
of minute portions, of definite form and organization, separable 
from each other (the elementary organs). 

Observ. Universal as the agreement among phytotomists has been for 
some thirty or forty years on this fundamental proposition of vegetable 

anatomy, it was a long time 

before it acquired general 


The very founders of the anatomy of plants, Leeuwenhoek, Malpighi, and 
Grew, were, indeed, led by their researches to the detection and distinc- 
tion of the elementary organs as organized parts, but the real conditions 
were again misconceived throughout the whole of the eighteenth century 
On the one hand, Ludwig and Bohmer, seeking an analogy with animal 
cellular tissue, described vegetable cellular tissue as a mass of irregular 
fibres and lamellae interwoven together ; on the other hand, C. F. Wolff 
(theoria generationis) described vegetable substance as a homogeneous 
mass hollowed into holes and canals, a view which still found an active 
defender during the first ten years of the present century, in Brisseau de 
Mirbel, and is even now held by him to be the condition in the earliest 
stage of development of vegetable tissue, if not that of the subsequent- 



mists of the present century. 


a completely closed, globular, or elongated vesicle, composed of a 




this remains still closed after its development is completed, it is 
called a cell, cellula ; but if a row of utricles arranged in a line 
become combined, during the course of their development, into a 
tube with an uninterrupted cavity, through the absorption of theii 

the vessel 

„ .. 7 __ — j- ^ 

(spiroid of Link). 

Observ. The tracing back of the whole of the elementary organs to 
the primary form of the utricle, has been accomplished only quite recently. 
The earlier phytotomists, who took the elongated cells for long tubes, 
overlooked their analogy with the short cells, believing that they were 
rather to be compared with the vessels, and they described them as a 
special anatomical system under different denominations (fibres, lympha- 
tic vessels, &c), in which error they were followed even by Treviranus 









(" Physiolog? i. 64), although Sprengel, Rudolphi, Link, and Kieser had 
already recognized that they all were modifications of the cell. Far less 
than this was the true nature of the vessels perceived by the earlier phy- 
totomiste ; and I believe that I was the first to detect their origin from 


De struc- 

Memoirs of the A cad. of Munich 
29). No sharply defined line can be drawn be- 

tween vessels and cells, for reasons which will be hereafter discussed. 
W hether the milk-vessels, which indeed occur only in a comparatively 
small portion of plants, and play a very subordinate part both in ana- 
tomical and physiological relations, originate in an analogous manner from 
rows of cells, or are to be regarded as a system essentially different from 
the rest of the elementary organs, is a question upon which no opinion 
has yet acquired an universal acceptance. linger asserts the former 
("Annuls of the Vienna Museum'; ii. 11) ; but it is more than doubtful 
whether his observations were accurate, and it seems that the milk- vessels 
ought to be regarded as membranous linings of passages which appear be- 
tween the cells. (See an anonymous memoir in the "Botanische Zeitunq," 
1846, 833, entitled " The Milk-vessels : their Origin, &c") 

The basis of the substance of all vegetables consists of the 

cells, since even 


plants all the 

organs are in the youngest condition composed of cells alone, and 
the vessels only appear during the subsequent development. In 
the lower plants (Fungi, Algas, Lichens, Liver-mosses and Mosses) 
all the elementary organs persist in the organization of the cell. 

Observ. The circumstances, that a plant is composed of cells alone, or 
also possesses vessels, have not that importance either in a systematic or a 
physiological point of view which De Candolle attributed to them, when he 
used them for the primary division of the vegetable kingdom, into Cellular 
and Vascular plants, for these conditions do not ran parallel with the total 
organization of plants, since there exist both Cryptogamic and Phanero- 
gamic plants with and without vessels. 



The forms under which cells present themselves are so manifold 
that a special examination of all would occupy a far greater space 
than can be devoted to it in this place ; I therefore confine my- 
selt to a few observations. 

In the first place, in examining the form of the cell, we have to 
take notice that it depends upon two circumstances. On one hand 
the form of the cells is determined, like that of every organic 
body, by its indwelling laws of development ; on the other hand 
the individual cell, in the far greater majority of cases, cannot 
follow those laws uninterruptedly, because it forms part of a com 
pound tissue, and is compelled by its intimate connexion with the 
surrounding elementary organs, to accommodate itself to the space 
thus determined for it, and in consequence of the pressure to 
which it is exposed laterally from the surrounding elementary 


organs, to assume forms which would be foreign to it under con- 
ditions of free, unrestrained development. 

The sphere must be regarded as the fundamental form, in which 
every freely developed cell first appears. Although this form oc- 
curs not unfrequently with great regularity in very young cells, 
this is more rarely the case in full-grown cells. For in most in- 
stances the growth of cells is by no means uniform ; sometimes one 
diameter remains short and the cell assumes the form of a flattened 
ellipsoid ; but far more often one of the diameters becomes more 
or less elongated, and the cell passes into the form of an elon- 
gated ellipsoid, or, by farther extension, into that of a cylinder. 
Roundish forms are found more or less regularly developed in many 
lower Algse, e.g., in Protococcus, in the yeast plant, in completely 
or almost wholly isolated cells of higher plants, as in spores and 
pollen-grains, in the knob-shaped ends of many hairs of plants, &c. 
The cylindrical or attenuated conical forms are likewise frequent in 
the lower orders of the vegetable kingdom, in hairs, and the like. 

The frequently occurring form of the elongated ellipsoid, and 
still more the cylindrical shape, point to the innate tendency of 
the vegetable cell towards an unequal growth, in which an oppo- 

sition manifests itself between the 


axis and the 

transverse axes, between the upper and lower ends, and the 
lateral faces of the cell ; but in many other cases a still greater 
deviation from the primary form is met with, where particu- 
lar points exhibit an isolated growth, giving rise to papillary 
elevations and gradual development of these into cylindrical pro- 
cesses, and thus to a ramification of the cell. The 
phenomenon is very common ; it occurs, for instance, ^%. 1. 
in the formation of the pollen-tubes upon the stigma, 
in the germination of most spores, and in the most 
striking degree in many Algge. In these last the 

ramifications produced at the lower end of the cell 
frequently form a contrast to the upper end 


they fulfil the functions of root fibrils, e. g. } in Botvy- 
dium (fig. 1), in germinating Confervce, &c, while the 

protrusions sprouting out from the upper end form 
the foundation of abundant, often very regular, rami- 
fications of the plant, e. g., in Vaucheria, Bryopsis, 
&c. This phenomenon is seen most distinctly in uni- 
cellular Algae, as in the genera just named; but in 
most cases this process of ramification is combined 
with cell-division, which renders the detection of it 
difficult, and the uni-cellular becomes converted into a 
many-celled plant, e.g. } m Conferva gtomerata (pi. 1, latum. 

figs. 1—6). 

Those cells which have grown together with other cells or witl 


vascular utricles, into a tissue, exhibit much slighter differences 
of form than the freely developed cells. It is true that in this 



. ''i 




■ -/- 



case even a greater complication of form may arise from the 
growing out of particular places through unequal development, 
when one side of a cell lies free upon the external surface of a 

plant or in one of its internal air- 

• i • • • 1 i • i # 

Fig. 2. 


structures, and in the star-shaped 
cells of the air-cavities of the Nym- 
phcecB (fig. 2) ; but in most cases such 
irregular growth of individual cells 
is rendered impossible, simply by 
the mechanical conditions in which 
they are placed. It is a general 

rule, that cells combined into a tis- 
sue are bounded by a number of 

Stellate hair from the leaf-stalk of Nym- plane Surfaces, instead of DOSSeSS- 

ing a rounded external form, since 
that part of a cell by which it is adherent to another cell becomes 
flattened, and only the free parts of the cell-wall can follow the 

original tendency to become rounded. The form of 
such cells depends, therefore, principally upon their 
relative position, and their more or less crowded 
condition ; and the further modification of the form 
depends upon whether the dimensions of the cell in 
different directions are pretty nearly equal, or one 
dimension considerably exceeds the rest. 

Taking into consideration, in the first place, the 

Fig. 3. 




^ i 



the short and the elongated. 

Liber-cell of 
Cocos botryophora 

The short cells, developed pretty uniformly in all 
directions, form the elements of the structure of all 
higher plants, since all their organs are formed, in 
their earliest stages, of these alone, and even in full- 
grown plants the bark and pith of the stem, as well 
as the soft parts of the leaves and the organs of 
fructification in general, are composed of cells of 
this form. During the development of the indivi- 
dual organs, fibrous strings are formed in the 
cellular mass constituting their ground-work, and 
these fibrous strings, which are composed of elon- 
gated cells and usually also of vessels, which lie 
among the elongated cells, receive in this case the 
name of vascular bundles, and taken collectively 
constitute the wood of the plant. The mass com- 
posed of short cells, in which the vascular bundles 
are imbedded, is named, in contradistinction to the 


The elongated cells of the vascular bundles 






(fig. 3) are, as a rule, distinguished from the short parenchymatous 
cells, not only by their elongated, often fibrous shape, but also by 
the two ends being attenuated to points. In this case they are not 
arranged end to end in lines, but their attenuated extremities are 
interposed between the lateral surfaces of the cells situated above 
and below them ; while the parenchyma cells, if, as is usual, they 
are arranged in lines, stand one upon another with flattened ends, 
their cavities being thus separated by partitions directed at right 
angles to their longitudinal axes. Link founded upon this differ- 
ence of the ends the distinction between parenchymatous and pro- 
senchymatous cells, a distinction which is indeed well grounded 
when we compare extreme forms, but which is by no means to be 
carried through, since the most manifold transitions occur from 
parenchymatous cells, with more or less oblique cross-walls, to 
perfect prosenchymatous cells. 

In many Thallophytes, especially in many Fungi fe. <y., Boletus 
igniasrius) and Lichens (e. (/., in Evernia), isolated portions of 

the substance are found of fibre-shaped, frequently irregularly 
interwoven cells (irregular cellular tissue of Kieser). Gradual 
transitions also occur from this form of cell to the form of the 
parenchymatous cell. 

The form of the parenchymatous cells is most intimately con- 
nected with their relative position. 

The simplest condition is afforded by such cells as lie one above 
another in a simple row, as the cells of the Confervce (pi. 1, fig. 1), 
articulated hairs, &c. Here the cells become flattened on the sur- 
faces of contact, while the side-walls retain their natural curvature. 
Accordingly as these possess a cylindrical curvature, or one more 

approximating to a globe, does the entire cellular filament obtain 

a cylindrical or beaded shape. 

When parenclrymatous cells lie side by side in a p- a 
simple layer, as is the case in the leaves of most Mosses 
and Jungermanniw, and in the epidermis of the higher 
plants, their lateral surfaces, by which they are cohe- 
rent together, become flattened; while the lower and 
upper free sides are either more or less convex, coni- 
eally elongated (fig. 4), or quite flattened like the rest, ceiisofthe 
Taken as a whole, such cells exhibit the form of many- epi pJm o°f the 
angled plates or prisms, the shapes of which again pre- Bmn ia^ s bar ' 
sent modifications, accordingly as the growth of the 
cells in the direction of the surface, which they combine to form, 
is uniform or irregular. The lateral faces of tabular cells are 
usually perfectly fiat. Yet it sometimes happens, for instance in 
the anthers of Chara, and in the epidermal cells of many leaves 
(fig. 5), that the side-walls are curved into waving lines, or zig- 
zagged in sharp angles. 

It is not so easy to define the form of the parenchymatous cells 
"when they are collected together in masses (fig. 6), as is the rule 








m tlie internal substance of organs, for instance in pith, in bark 
&c for here every cell 1S surrounded on all sides by other cells' 
and exhibits as many flattened surfaces as there are cells standing 
in connexion with it. Kieser (« Chnmdz. der Anatomie dm ~ " g 

zen, 8 


necessarily be that of a rhombic dodecahedron under such circum- 
stances since this form encloses the greatest space within the 
smallest amount of limits, and that their form is usually that of a 
rnombric dodecahedron elongated in a perpendicular direction, be- 
S be P? m 37. form 0f . the ^getable cell is not the sphere but 
I tn S S( K • 1S i P l° P ° Sltl0n ma ^ be Emitted theoretically, but 

JwW VT m a ^° Ur t0 S6ek acfcua11 ^ to observe the form of 
the rhombic dodecahedron m a cell in nature, since the contigu- 
ous cells are always far too unequal in size for them to become 

Fir/. 5. 

Fig. 6 

Epidermis of the lower face of the leaf of 

Hell&borus foetidus. 

Parenchymatous cells from the bark of 

Ewphorb ia cm iciriensis. 

moulded into regular mathematical forms by their reciprocal pres- 
sure So that in cross sections of a parenchymatous tissue the cells 
are found certainly of many-angled but of irregular forms ; and 
the faces of transverse slices of the individual cells have a very vari- 
able number of sides (usually from five to eight). It is therefore 
more suitable to call such cells polyhedral instead of dodecahedral 
On the more or less crowded arrangement of the cells it depends 
whether the plane surfaces of these meet at acute angles (fig. 7) . 
or whether, when the cells are more loosely aggregated, the^sur- 
faces of contact are but small (fig. 6), and large portions of the 
cell- walls between them remain unconnected with the neighbour- 
In the latter case, the free portions of the cells retain 
their natural rounded form. In particular cases, however the 
portion of the cell-wall immediately surrounding a plane surface 
in contact with another cell, grows out in a tubular form, so that 

mg cells. 




when several such processes are formed, the cell acquires a star-like 



When in such cases the cells are arranged in one 

plane, as occurs in the cross- walls of the air-canals of many water- 
plants, all the rays of the star lie in one plane (figs. 8, 9) ; when, on 
the other hand, the cells are heaped together in masses, as in the 
pith ofJuncus ejfusus, the rays project from all sides of the cell. 

Fig. 7. 

Fig. 8. 

Stellate cellular tissue from the leaf-stalk 

of Musa. 

Fig. 9 

Cells of the pith of 
A canthus mollis. 

Partition bounding 1 an air-canal in the 
leaf-stalk of Sag ittaria sagittifolia. 

Fig. 1 0. 

Far more frequent than such re- 
gularly branched cells, are those 
of a roundish form, exhibiting a 
shorter projection at one or more 
points, and so having a moder- 
ately irregular form ; the paren- 
chyma of the lower side of the 
leaves of most plants is com- 
posed of such cells (fig. 10). 

Observ. Some phytotomists have 
distinguished a greater number of 
tissues according to the forms of the cells, applying particular names to 

Parenchymatous cells from the leaf o 

Orchis mascula. 




















The arrangement of Hayne, which did not attract the least notice, I may 
pass over here. Meyen distinguished : 1, Merenchyma — tissue composed 
of spherical cells, the cells only partially in contact ; 2, Parenchyma ; 3, 
Prosenchyma — this name was applied by Meyen to the woody tissue of the 
Coniferse ; 4, Pleurenchyma, which was the name by which he distin- 
guished the prosenchyma of all other plants. The division of merenchyma 
from parenchyma v/as superfluous, and cannot be carried out, because there 
are so many transitional forms ; the alteration of the established term 
prosenchyma into pleurenchyma was altogether inconvenient, and was not 
adopted. But the wilderness of botanical terminology would have been 
increased beyond all reasonable measure by Morren, had not his subdivi- 
sions been passed over unregarded ; for he divided the parenchyma alone 
into no less than eight tissues, which he named, merenchyma, conenchyma, 
ovenchyma, atractenchyma, cylindrenchyma, colpenchyma, cladenchyma\ 
and prismenchyma. All such far-fetched subdivisions of the cellular 
tissue are wholly valueless, because no exact connexion exists between 
form and function, and frequently enough the same organ is formed of 
cells differing considerably in form, — in two closely allied plants. 


^ Important as the accurate determination of the size of the indi- 
vidual elementary organ is, in many special researches, particularly 
those relating to the history of development, yet in general the 
knowledge of the size of cells is of very subordinate value ; and 
this the more that not only do the cells of the same organ exhibit 
extraordinarily great variations in respect to their size, but the 
contiguous cells of one and the same organ not unfrequently differ 
considerably from each other. Pollen grains afford a very striking 
example of the former ; their dimensions are tolerably constant in 
each species of plant ; but their diameter varies from 1-3 00th of a 
line in Myosotis to 1-1 5th of aline and more in Cucurbita, Stre- 
litzia, &c. The cells of a single organ often differ to the extent of 
some being twice or thrice as large as others. 

The diameter of the cells of parenchyma may be stated at a 



cular cases (e. g., in the spores of many Fungi, in the yeast cells) it 
falls to less than l-500th, and in other instances it rises, e. g., in 
succulent parts, in the pith of the elder, &c, to 1-1 0th of a line and 

so that in such cases the individual cells are actually visible 


to the naked eye, which is not generally the case. 

The dimensions of many elongated cells form a striking contrast 
with this small magnitude of the majority of parenchymatous cells 
since while the transverse diameter of the former is usually consi- 
derably smaller than the diameter of the parenchymatous cells 
the longitudinal extension is very remarkable. In regard to the 
majority of elongated cells, especially the prosenchymatous cells of 
the wood and bast or liber of most plants, we should be very much 



deceived if we deduced from the fibrous structure of these organs 
•Teat length of the constituent cells ; yet, on the other hand, 


cases do occur when particular cells exhibit an astonishing length. 
The prosenchymatous cells of wood generally exhibit only a length 

of l-3rd to one line, exceeding this last dimension but seldom; 
as a rule, the bast cells attain about the same length ; yet in some 
cases they occur of far more considerable length, for I found them 
1-6 to 2*6 lines long in a Palm (a species of Astrocaryum). 
The bast cells of flax and hemp are considerably longer, but diffi- 
pull, fn TYip.fl.Rnre. sincie it is often impossible to ascertain the com- 

mencement and termination of a cell. Many 


simple cells also exhibit a very considerable length, especially 
cotton, the longest fibres of which do not, however, exceed one to 
two inches. Among the cells of the higher plants the pollen grains 
are the most striking for their great longitudinal growth, the fili- 
form prolongation penetrating into the style attaining in long- 

longifiora, Cactus grandiflorus, &c, a 

length of three inches and more. 

The most 


of large cells are found in the 

Bryopsis, and especially in Cham, in the larger species of which 




a. Physical Properties. 

In most cases the membrane of cells possess a considerable de- 
gree of stiffness and solidity. But in this respect extreme dif- 
ferences occur between the cells of different plants and of their 
different organs ; and, moreover, this condition may exhibit ex- 
treme variations at different periods of the growth of the same 



plants, for example of most Algse, Fungi, Lichens, and the cells 
of fleshy leaves and fruits are very soft ; while the cells of many 
woods, e. g., in Palms and Tree Ferns, and those of the albumen 
of many fruits, exhibit a bony hardness ; and finally, the cells of the 




operation become more or less softened and swollen up. The latter 
phenomenon occurs in a higher degree the younger and softer the 
cell is ; whether, however, as Schleiden states, the membranes of 



The swelling up occurs strongly in many thick-walled 

• -1 T • i • T - « ^ „ * .J • 

as m 

cells which in a dry condition have a horny consistence, 
Lichens, Fucoidese, and in certain gelatinously soft cells (the so- 
called collenchyma cells) lying beneath the epidermis of herbace- 
ous plants. In the short parenchymatous cells no great difference 




appears to occur m the strength of the expansion in the different 
directions ; but m the elongated cells of the bast and wood, the 
swelling up resulting from moistening takes place principally in 
the direction of the breadth, and only in a very small degree in 
the longitudinal direction. 

The cell-membrane of young cells is completely colourless and 
transparent ; in full-grown cells it is frequently imbued with yel- 
low, red, or brown colouring matters, whereby in manv cases the 
transparency is importantly interfered with. This alteration is 
very striding m the change of the sap-wood into heart-wood, for 
in many trees, e.g., m the ebony and yew, the white is converted 
into a more or less dark colour, without the cell-membrane in- 
creasing in thickness, while at the same time it acquires a far more 

considerable solidity and independence of the influence of mois- 

Observe. It is difficult to conceive how some phytotomists (Link "Ele- 
ment. PUl. Botr 1824, p. 366 ; Meyen, "Physiol." i. 30) came to the opinion 
that cells contract m the direction of their length when moistened, and 
again expand when dried, since, on the contrary, all cells expand in every 
direction when moistened. In the elongated cells of the wood the con- 
traction by drying in the direction of the length is, of course, but small, 
yet it occurs constantly. In wood of Dicotyledons the longitudinal con- 
traction from the wet to the perfectly air-dried condition amounts to only 
-07 'A to 0-4 per cent., while the contraction in the direction of the breadth 
is as much as 4 to 9 per cent. According to Schleiden's experiments, the 
bast-cells of flax expand only about 0-0005 to 0-0006 ; but he considers 
it possible that there was an important error here (Beitrage, i. 69). Ac- 
cording to the researches of Ernest Meyer, the Manilla hemp (Phor- 
mtum ?) expands, when wetted, about l-50th of its length, while the 
increase of breadth amounts to 1 -5th. 

h. Structure. 


examining a 

Fig. 11. 

Fig. I 

transverse section of a thick walled cell, e. g., 

of wood-cells of Cle- 
matis Vitalba, the 
bast -cells of Palms, 
(fig. 11), or the thick 
walled pith - cells of 
Hoya carnosa, 
12) we find bystrong- 

Ml MB* 

Trans verse section through 
the liber-cells ofCocos bo- 

cavity of the cell 


ly magnifying, that 
the cell-membrane is 


xrans verse section through a thick 
walled cell of the pith of Horn 

composed of numer- 
ous super -incumbent 
layers concentrical- 



-by the action of a mineral acid of proper 





% 1 3 

degree of concentration the membrane is caused to swell up, its 
lamellar structure becomes very much more distinct, and a great 
number (often fifty) of separate layers may be detected. By this 
means the lamellar structure may be demonstrated even in those 
cases in which the unaltered membrane appeared completely homo- 
geneous ; for instance, in the horny cells of the albumen of Phy- 
telephas. Usually the wall of the cell is of equal thickness on 
all sides ; in this case the layers run uninterruptedly round the 
cavity and form perfect cells encased one within another. In 
many cases (e. g., very frequently in the epidermis-cells 
and in the brown cells which 
surround the vascular bundles 
of the Ferns) the different sides 
of the cell possess, on the con- 
trary, a very different thick- 
ness ; in this case the layers of 
the thicker portion of the wall 
are not continued over the thin 
sides, but are bevelled gradu- 
ally off. 

This condition alone allows 
us to conclude with great pro- 

Fig. 13. 

that the 



the cell-membrane in thickness 
does not depend upon the thin 
membrane of the young cell it- 
self growin 

Cells of tlie Epidermis of the stem of Viscum album. 

thicker by the absorption of new cellulose, but that 
it arises from a periodical depositionof new membranes upon the 
already completely developed wall. 



nd more accurate knowledge of this process are only obtained 
through the circumstances next to be mentioned. 

The wall of young cells having yet very thin membranes, ap- 
pears perfectly smooth and uniform ; but if the tissue of the same 
organ is examined at a later period, the walls of its cells are found 
to have become thickened ; these walls are almost without excep- 
tion found to be covered with a greater or smaller number of pore- 
like points or slits, which are distinguished by the name of dots 
(tiipfel or pits). A more minute examination of the cross-section of 
the cells (figs. 11, 12) reveals that these spots are formed by canals 
which open freely into the cavity of the cell, but are closed externally 
by the outermost thin membrane of the cell. When all these cir- 
cumstances are taken together, it becomes most indubitably evi- 
dent, that the primary membrane of the cell is completely closed 
and not possessed of visible pores ; that the subsequent deposits, 
on the contrary, have the form of perforated membranes, and 
that the deposition of these secondary membranes takes place in 
the direction from without inwards upon the inside of the primary 



w - 






It is now no longer worth while to give an historical review 

of the opinions that had been expressed as to the structure of the cell- 
wall and of the spots, before the appearance of my essay " On the Pores of 
Vegetable Cellular Tissue/' in 1828. But it is necessary to advert to the 
objections which have recently been advanced by Harting and Mulder 
against my doctrine of the structure of cells, and of the gradual and 
successive deposition of the secondary layers from without inwards. 

(See Harting " Mik? 

H. v. Mold 






Bot. Zeitung, 1847, 337. — Mulder "Physiological 

\Bot. Zeitung, 

Chemistry:' — Mohl "On the Growth of ? 

1846, 337.) I believe I may safely leave unnoticed the objections ad- 
vanced by Hartig. A ^Vm^ Br_^_. 7 7 t -, ^/* _.._a 



Mulder and Hartin 

Pflanzenzelle. " ) 


cal grounds, and seek to demonstrate that the cell-membrane increases in 
thickness in the direction from within outwards by the deposition of 
layers upon the outside of the original membrane, which process of growth 
is followed, in some cases, by a deposition in the interior of the cavity of 
the cell, while in particular instances (in the cells of horny albumen) the 
membrane itself grows thicker by the interpenetration of foreign matter. 
In the first place, my opponents deny that the thin membranes of the 
young cell are imperforate, and that only the subsequently internally 
deposited layers are porous, since they, on the contrary, believe, that they 
found the membrane of young cells to be perforated like a sieve, while a 
perfectly closed membrane is deposited subsequently on the outside of 
these closed cells. It is, of course, not for me to decide who observed most 
correctly, I or Harting ; but I must stand by the facts I have stated, and 
do not believe that Harting would have been deceived in the manner he 
has, if, instead of selecting only cells having small pits for his observa- 
tions, he had extended his researches also to cells with large pits, between 
which the secondary membranes appear in the form of narrow fibres ; and 
had properly regarded the analogy which exists between the structure of 
the vascular utricles and cells. 

view of the external growth in his micrometrical measurements of young 
and of thickened cells (Linncea, 1846, 552), by which he arrived at the 
conclusion that the cavity of the wood-cells expands during the increase 
of thickness of a shoot, in exactly the same proportion as the unlignified 
cells, whence he argued that the thickening of their walls is to be ascribed 
to a deposition taking place upon the outside of their primary membrane. 
On the other hand, I consider that I have demonstrated by my measure- 
ments ("Bot. Zeitung" 1846, 358) that exactly the contrary occurs, and 
that the thickening of the walls is combined with a narrowing of the 
cavity of the cell. — Mulder and I 

from the chemical reaction of the cell- wall (which will be spoken of here- 
after). The membrane of young cells is coloured blue by the action of 

Harting finds a second reason for his 



t// x o «/ — T p 

and the outermost membrane a brown, colour, altogether withstanding the 
solvent power of sulphuric acid, which is not the case with the interme- 
diate and inner layers. From this my opponents draw the conclusion 







F m 

that the membrane of the young cell and likewise the inmost layers of 
full grown cells are composed of cellulose, the intermediate and outermost 

layers, on the con- 
trary, of other com- 
pounds, which are 
subsequently form- 
ed and deposited on 
the outside of the cel- 
lulose membrane. 
Against this I have 
shewn (^Botanische 

Zeitunf 1847 ,497) 
that the chemical 
researches by which 
their deductions are 
supported, were im- 
perfect ; that the 

Fig. 14. 

Fig. 15. 

Cells of the albumen of Sagus tcedigera. 

outermost layers of cell-membrane are composed in like manner of cellu- 
lose, but are infiltrated with foreign compounds, which prevent the re- 
action of iodine and sulphuric acid ; that the date of origin of a layer 
must not be deduced from the elic- 

it 16. 

mical reaction, since both the inner 
and outer layers may undergo a che- 
mical metamorphosis, which does not 
stand in any connexion with the time 
of its origin ; and that therefore ana- 
tomical grounds alone can serve for 
the decision of the order in which dif- 


ferent layers have been developed. — 
Lastly, in reference to the statement 
that the thick walled cells of the 
albumen of Phytelephas, Iris, &c. 
(figs. 14, 15), and the so-called col- 
lenchyma cells (fig. 16) possess uni- 
form, and not lamellated, walls, and 

that consequently their primary mem- I 

brane itself has increased in thickness ; Ceils from the leafstalk of Nymphcea alba. 
this assertion depend s simply upon im- 
perfect investigation. If the authors had treated these cells with sulphuric 
acid of the proper degree of concentration, they would have found the 
lamellation. — In short, the researches which I was caused to undertake 
by the objections of Harting and Mulder, served only to strengthen the 
grounds on which I had built my theory of the growth of cell-membranes. 

The secondary cell-membranes deserve a separate mention. Taken 
altogether, it is seldom that they appear to the eye, as the primary 
membrane does, in the form of an uniform smooth pellicle, as it 
were a hardened mucilage, for example in the Confervce and in 
many hairs. Whether in such a case they are really devoid of 
special structure, is doubtful, for such cells, when drawn out 
lengthways, sometimes tear in an oblique direction, so that they 






may be more or less perfectly drawn out into a spirally wound 
band. This phenomenon, together with the visible conditions of 
structure, to be spoken of directly, appear to me to indicate that 
the secondary celt-membranes, without being composed of actual 
primitive fibres (which cannot in any way be demonstrated), pos- 
sess indeed a fibrous structure, since their molecules are connected 

** •*«.•>■ • J _ .__ _1 





tion. ("See "On the Structure of 
" Vermischte Schriften") 

Next to these cells, appearing perfectly homogeneous to the eye, 
come such as exhibit a very fine spiral streaking of their mem- 
brane, as is the case in the cells of many woods, e. g., in Pinus syl~ 
vestris, and in a very striking degree in the bast-tubes of the Apo- 

cynese and Asclepiadese, e.g., in Vinca 
Fig. 17. (fig. 17), Nerlum, Ceropegia, and Hoya. 

Although in many of these cases also the 
membrane has the aspect of being com- 
posed of separate fibres lying very close 
together, yet this appears actually not 
to be the fact, but the streaking to be 
dependant upon the unequal thickness 
or density of the different parts of a 
a piece of the same, connected membrane. In favour of this 
more highly magnified. ^ ^ p ar ti C ular, the circumstance, that 

in the bast-fibres of the Apocynese, the spiral is wound 
sometimes to the right, sometimes to the left, m the 
superincumbent layers of the same membrane ; the ap- 
parent fibres, therefore, then cross, a condition of which 
I know no example in the actual division of the se- 
condare membrane into fibres. 



f ** % < Vt i £%* ft J fft * fi/T/i 

f /. % . , i * - * y / 1 - ■ > •> c % tf/> 
y § i * * 4 * i * i % * > • j * j * f * f ■ > 


In other cases occur, instead of the streaks, perfect 
slits running in a spiral direction, by which the second- 
ary layers become divided into broader or narrower 
a. Liber-ceii of bands (fibres), running parallel with each other. The 
vinca major, direction of the spiral in which the fibres run is, as a 
rule, the same in all the -cells of a tissue ; therefore the fibres of 
two' contiguous cells cross upon their two coherent walls. In the 
overwhelming majority of cases the fibres are wound to the right 
(in a botanical sense, i. e., therefore in the manner of a left-handed 
screw). Instances of the contrary do certainly occur, sometimes 
merely as isolated cases in particular elementary organs, some- 
times regularly in particular specimens of a plant. Such spiral 
fibres occur in rarer cases in the common parenchymatous cells of 
the stem and leaf-stalk ; for example, to a very remarkable extent 

--:-- -* t»t j.1. „ i~ ™ n^Tr Orchidese ; on the otner 

Nepenthes, m m 

hand they are more frequently confined to special organs, tor in- 
stance to the elaters of the HepaticsB, the cells of the sporangium 
in Eauisetum (fig. 18), a portion of the cells of the leaf and the 





cells of the cortical layer in Sphagnum, the hairs in the Cactacea3, 
particular layers of the seed-coat in Casnarina, Salvia, many Po- 
lemoniaceaB, &c., and in many plants to the anther-cells. Parti- 
cular organs composed of such fibrous cells, not unfre- 
quently possess a spongy, soft consistence, e. g., the Fig. 18. 
outer rind of the root of many tropical Qrchidacese and 
Aroidese, the sepals 

verticillatum. the 

chrys Morisoni, G. 
(Ethusa Gvnawium 

The annular fibre (fig. 19) which runs in a trans- 
verse direction on the cell-wall, crossing the longitu- 
dinal axis of the cell at right angles, is to be regarded 


It not un- 

Cell from the 
sporangium of 

Equisetum ar- 

frequently occurs alternating with the spiral fibres in 
the same cells as the latter, e. g., in the cells of many 
anthers, in the sporangium of the Jungermannise, and 
in the leaves of Sphagnum. It may be regarded as a 
middle form between the right and left wound spiral 

The reticulated structure of the secondary mem- 
branes occurs infinitely more frequently than the regu- 
lar spiral formation, and scarcely a plant can be found, 
from the Mosses upward, in which this structure cannot be more 
or less clearly distinguished in the majority of its cells. Some- 
times, but in comparatively rare cases, the secondary membranes 
of the reticulated cell resembles those of the spiral- 
fibrous cell, in that they are likewise divided b}^ closely Fig. 19. 
adjacent pits into narrow fibres, which fibres, however, 
do not run in a spiral direction, but are connected into 
a more or less regular net, with narrower or wider, 
roundish or angular meshes, e. g., in the cells of the 
wing of the seed in Swietenia, of the pericarp of Pi- 
cridium tingitanum, P. vulgar e, in the seed- coat of 
Gucurbita Pepo, of the parenchyma of the leaf of Sanse- 
viera guineensis (fig. 20), in isolated cells of the pith 
of Rubus odoratus, Erythrina Gorallodendron. But 
in the great majority of cases the secondary membrane 
is perforated by comparatively small orifices at few 
points only, and therefore does not appear under the 
form of a net-work of narrow fibres, but as a connected 
membrane nerforated like a sieve,. 


l.t , 





r *»•»-, m 




II T '1 

I * 4 1 ■ . x 4 t 


>. M| 

l' V ''\\ 



Since this is the 

usual condition, which occurs in almost all cells 


cite examples ; yet 

Cells from the 
[See sporangium of 


it may be permitted to name some particularly charac- 
teristic cases, the investigation of which prepares the way to a com- 
prehension of less distinct structures, e.g., the parenchymatous cells 
of the leaf-stalk of Cycas revoluta, the thick walled pith-cells of 


(fig. 12), the cells which form the stony concre- 





t i 





tions in the flesh of pears and quinces, the horny albumen of Pky- 
telephas, of many Palms (fig. 14), and of the Rubiacese. These 
smaller orifices in the secondary membrane are denominated pits, 
the cells themselves pitted cells. The numerous transitions from 

this form of cell into the form of those hav- 
ing a net-work of narrow fibres, and from 
these into the spiral-fibrous cells, furnish 
the evidence that the fibres are not, as 
earlier phytotomists believed, to be consi- 
dered as a peculiarly organized elemen- 
tary portion, but that they are nothing 
else but narrow sections of the secondary 

Fig. 20. 



exists a distinction in form, but none in 

essential nature. 

The distribution of the pits upon the 
cell is usually altogether irregular, espe- 
cially upon the horizontal transverse walls 
of the parenchymatous cells. On the other 
hand, it is common, and especially in elon- 
gated cells, for the pits upon the lateral 
walls of the cells so far to exhibit regu- 
larity in their position, that they stand more or less exactly in the 
direction of a spiral, and are frequently drawn out lengthways in 

this direction (fig. 21), so that they appear as short 
Fig. 21. s iits. Sometimes also a certain rule may_ be met 

with in reference to the places on which pits exist 
or are deficient. Thus in the wood-cells of most 
Conifera? they are found on the side-walls, turned 
towards the medullarv ravs ; thus in loosely con- 

Cells of the leaf of Sanseviera 



nected parenchymatous cells they not unfrequently 
occur on the flattened parts of the walls by which 
the cells are coherent together, while they are ab- 
sent from the surfaces which bound the inter-cel- 
lular passages, as occurs frequently in the cortical 
cells of Dicotyledons ; or, if they occur on the inter- 
cellular passages, they differ in size and form from 
those situated on the side-walls of the cells, e. g., 
in Cycas, in the wings of the seeds of Swietenia. 
The pits are moreover usually wanting to the 
outer walls of the epidermal cells, but they may also occur here ; 
as, for example, on the leaves of Cycac. 

The pits of one cell are most intimately connected m regard to 
form and position with those of the contiguous cell ; an d it is a 
general law, that when two pitted cells are coherent together, the 
pits of the two cells lie exactly opposite to each other ; so that in 
very thick walled cells the cavities of the two cells are ou ly sepa- 

Wood-cell of Ginkgo 




rated from each other, in the canals of the pits, by the primary- 
walls, which form a very thin partition (figs. 11, 14, 15). This 
dependence of the structure of one cell upon that of its neighbours, 
becomes the more prominent the more the reticulated formation 
prevails in the secondary membranes, and it disappears in propor- 
tion as the spiral structure becomes more distinctly evident. 
Therefore where the pits are scattered irregularly they correspond 
accurately in form and position ; where they are arranged in a 
spiral direction, and present the appearance of short elliptical slits, 
they correspond in position but no longer in form, since being situ- 
ated obliquely in the opposite direction, they cross and only cor- 
respond at their central portion (fig. 21). Finally, when the pits 
are extended into long spiral slits, surrounding the cell, the rela- 
tion to the contiguous cells has altogether disappeared. 

In thick walled cells the pits usually form cylindrical canals, 
which, however, frequently open into the cavity of the cell by a 
funnel-shaped opening at their inner extremity; and sometimes 
the outer blind end is somewhat enlarged. Not unfrequently two 
or more pit-canals unite into one common passage, opening into 
the cavity of the cell (fig. 12). 

In many cases the primary walls of two contiguous cells sepa- 
rate from each other at the spots where the pits lie and leave a 
lenticular cavity between them, which has a rather larger circum- 
ference than the 
pit itself (fig. 22) 
and then ap- 
pears like a ring 
surrounding the 

pit (fig. 23). I am 
only acquainted 
with this struc- 

Fig. 22. 




i^tf. 23. 



Transverse section through a 
pit (a) of Pinus Pinea. 

The pit of Pinus Pinea seen 
in face; a, canal of the pit; b, 

gated cells ; it is 
most distinct in 
the wood - cells 
of the Coniferse 
and - 

but it occurs in 
the wood -cells 

of many Dicotyledonous trees. These cavities are not yet existent 
in very young cells, but they are found before the deposition of 
the secondary membranes, and the formation of pits arising out of 
this. Schleiden's assertion that these cavities arise from the secre- 
tion of a bubble of air between the previously blended cell- walls is 
incorrect ; they are filled with sap in the young condition of the cells. 
In isolated, but very rare, cases, the primary membrane whicl 
is stretched across the pits as a partition, becomes absorbed after 
the completion of the development, whereby the pitted cells be- 



■* - 





come converted into porous cells. This occurs most remarkably 
in certain Mosses, especially in the fibrous cells of Sphagnum, 


&cf (See " A natomical researches on 
±hn p^/v.^/110 /7^77..q nf Sr)haanum" in 


Fig. 24. 

*&e Porous Cells of 




294; also 

Porous cells of the leaf of 7Kcra- 

7mm alaucum. 


nomenon is very rare in the Phanero- 
<- amia ; I found it decidedly in fibrous- 
cells, e. g., in the rind of the root of 
Epidendrum elongatum, in the seed- 
coat of Martynia, &c, &c. Whether 
it occurs normally in the wood-cells 
x vivu* oo kj xtft^ <— ~, is yet a matter of doubt to me. 
In the generality of cases, all the layers deposited on the inside 
of the primary membrane agree completely in their form, so that 
there is no reason why we should adopt a further division of the 
layers than that into primary and secondary membrane. But m 
particular cases, the secondary membrane consists of two layers of 
strikino-ly different structure, so that it becomes necessary to dis- 
tinguish between primary, secondary, and tertiary membranes. 

To what extent such a distinction into secondary and tertiary 
membrane exists, cannot be stated in the present state of our 

" e, confine myself to the mention of 
: existence of the tertiary membrane 
rtnintv. To these belong the wood 



may be demonstrated with certainty, 
cells of Taxus and Torreya, the pri] 
branes of which are formed exactly as m the wood-cells of Finus 
but their cavity is lined with an inner membrane, which is covered 
with a fibre-like thickening running in regular spiral lines (fig. 25). 

The same structure is repeated in the wood- 
Fig. 25. . cells of certain Dicotyledonous trees, e. g., in 

Viburnum Lantana. 

The contrast between the secondary and ter- 
tiary membranes is most striking in cells which 
occur in the coats of the seeds of very various 
plants, and in which one of the inner mem- 
branes is split into spiral fibres; while the 
other consists of homogeneous layers, which 
when wetted with water swell up so strongly 
that they burst the primary membrane. This 
property is generally found in the secondary 
layers while the tertiary membrane appears 
as a spiral fibre, e.g., in the outer cells of the seed-coat of Gollomia 
and other Polemoniacese, of the pericarp of Sdtwi, m the hairs of 
the fruit of Senecio vulgaris, &c ; in other cases the secondary 
membrane is formed of spiral fibres, and the tertiary layers con- 

Wood-cells of Taxus 



sist of the substance capable of swelling up, e. g., in the hairs of 
the seed of Ruellia strepitans. 

Observ. 1. Hartig, who first discovered that the tertiary membrane in 
Taxus possessed the form of a connected pellicle and was not composed of 
fibres, propounded the doctrine ("Beitrage zur Entwlehlungsgesch. derPflcm- 
zen? 1843) : that such an inner coat, which he called the jitychode, occurred 
in all cells. He thought that this membrane was distinguishable from 
the intermediate layer (his Astathe) by definite chemical characters, since 
it was not coloured blue by iodine and sulphuric acid, like the latter, and 
agreed in this character with the outermost coat of the cell (which he 
called the Eustathe), Hartig considered this inner layer as the oldest, the 
outermost the youngest, of the cell-membranes. The whole of this doc- 
trine depends upon very imperfect observations. The tertiary membrane 
of Taxus is composed of cellulose, it is therefore a true cell-membrane ; but 
Hartig seems, in many other cases, to have taken the primordial utricle 
(subsequently to be described) for a layer of cell-membrane, and thus to 
have classed together structures which have nothing at all in common. 

Observ. 2. It may not be out of place, after this exposition of the struc- 
ture of the secondary membranes, to cast a glance at the structure of the 
vascular utricle, since the different modifications of the structure of the 
cell-wall are met with again in the vessels, and, indeed, in many cases dis- 
played much more distinctly than in the cells, so that these conditions 
were observed in the vessels long before they were known in the cells, 
albeit much that was incorrect was stated of them. The vessels were 
divided according to the modifications of the structure of their secondary 
layers, into spiral, annular, reticulated, dotted vessels, &c. 

The most widely distributed form is the spiral vessel, for this occurs in 

all plants which 
Fig. 27. Fig. 28. Fig. 29. p 0Sgess vessels ; and 

particularly, in most 
organs the first ves- 
sels which 

Fig. 26. 





— rzrz™snoiiii ess fe 




— — rv::;jnininw!! 



Spiral vessel of Impa- 
tiens parviflora. 







belong to this form, 
so that they are met 
with in the hind- 
most parts next the 
pith, of the vascu- 
lar bundles of the 




dary membrane of 

these vessels is di- 
vided into one or 

Spiral vessels of Sambucus 


more (in M 
many as 20) paral- 
lel spiral fibres, 
which as a rule ter- 
minate in an annu- 
lar fibre at the upper 
and lower ends of 
the vascular utricle. 

If the vessel is developed in an organ which has already completed 






c 2 






longitudinal growth, the turns of the spiral fibre lie close together (fig. 
27) ; but if the organ undergoes elongation after the completion of the 
development of the vessel, the turns of the fibre are drawn far apart (figs. 
28, 29), by the stretching which the vessel suffers ; consequently, very 
loosely wound spiral vessels are usually found in the posterior first-formed 
portion of the vascular bundle, nearest to the pith, while those lying nearest 

the bark have close convolutions. 

The annular vessels (fig. 30) form a slight modification of the spiral 
vessels, for in many cases a series of vascular utricles containing spiral 


Fig. 30. 



^ "I" "" ri1 ! H|^„ 







^. *•<•«" — — ***#J 



»■"• i 


* #*;;tii ti 



■ »Ti 


*■**. *** **. 



!!i ,l! 

fibres are regularly found followed in the same vessel 
by a series of utricles which contain annular fibres, or 
spiral fibres and annular fibres alternate without any 
definite rule, often in the same vessel. 

The reticulated vessels occur in manifold modifications, 
in particular among the vascular Crypt ogamia, and in 
the outer youngest parts of the vascular bundles of the 
Monocotyledons. In these occurs a dependence of the 
form and distribution of the pits upon the formation of 
the adjacent parts, similar to that which we have found 
in the pitted cells. When several vessels lie immedi- 
ately upon one another, the walls by which they are 

fcher (fi 


31, a) are covered with trans- 

coherent toge 

verse pits, separated by narrow fibres, and these pits 
occupy the whole breadth of such a side-wall, but are 
not continued over the angles at which the several 
lateral faces of the vessel meet. 

To this form is applied 

stem esS of a° GoOTd tlie term scalariform ducts. But if the wall of such a 

containing- both ' vessel is in contact with cells by a large or small surface 

rmgs and^a spiral ^ ^ ^ its pits exMbit the e iii p tical or rounded form 

of the pit of the cells, and are sometimes distributed 
quite irregularly, sometimes arranged in a spiral direction, and the vessel 
retains the name of reticulated. Very frequently the same vessel exhibits 
both these modifications of structure at different points. 

Lastly, the pitted vessels (fig. 32) which occur in the wood of Dico- 
tyledons (with the exception of its 
Fig. 32. oldest parts, in contact with the pith) 

exhibit on those points of their walls 
by which they are in contact with a 
second vessel, a more or less abundant 
quantity of pits surrounded by a line, 

Fig. 31. 



@ /3g) ^ @5 @ @ @ 

@><g> ^Jp> © © © 

f<S) <B> © © © © © <§> 

W- © @ ^ © © @ ©> 
t^v©© © @<i?.©©© 

IC 'H_@ © © © © © © 

while the walls bordering on cells pre- 
sent the form of reticulated vessels, 
i. e., possess pits without a boundary 
line, or are quite devoid of them. In 
some cases, for example in the Lime, a 
tertiary membrane occurs in the pitted 
vessels, which appears in the form of 
fibres running between the pits. 

The septa between the vascular utri- 
cles do not always become perfectly 
absorbed ; but in the reticulated, and especially often in the pitted vessels, 

Reticulated vessel fr om 

a tree Fern. 

Pitted vessel from 
Latirus Sassafras 





secondary layers are deposited in the form of a net-work, or of parallel 
cross fibres on the transverse or oblique partitions of the vascular utricles, 
while the primary membrane is regularly absorbed between, these fibres, 
so that the open communication between the vascular utricles is not 

Observ. 3. In the description of the structure of the cells and vessels, 
I have mentioned the spiral and reticulated course of the fibres as two 
distinct modifications of the structure of the secondary membrane. Since 
transitions between the two structures frequently occur (fig. 33), and 
since when the fibre is reticulated the pits are arranged more or less dis- 
tinctly in spiral lines ; since, moreover, the pits scattered over an uniform 
membrane frequently have a longish form, and their long diameter like- 
wise situated in an oblique spiral direction, the thought readily presents 
itself that spiral structures form the basis of secondary membranes of all 
cells and vessels, and that the other forms owe their origin to subsequent 
transformation of the spiral cell and spiral vessel. The view has been 

expressed by most phytotomists in reference to the 

Fig. 33. 

■*«»* * * ■ 

* * ■ ■ i * - 1 

vessels ; but the conceptions that have been formed 
of the processes occurring in this metamorphosis 
were for the most part of rather a rough character. 
Thus the notion was extensively embraced, that the 
spiral fibre could not follow the expansion which 
the vessel underwent during its growth, and tore up 
into fragments, which again united into rings, and 
thus brought about the formation of annular vessels. 
Completely as this idea, which was a contradiction 
to all observation, had been refuted by Molden- 
hawer, it remained a standing article in all 

totomical writings up to " Meyeri 


Reticulated vessel from the 

leaf-stalk of Rheum 


Schleiden (" On the Spiral Structures in the Vege- 
table Cell" Flora, 1839) sought to explain the origin 
of the annular vessels from the spiral vessels in a 
manner less easy to refute, assuming that in each 
case two turns of a spiral fibre grew together into a 
ring, while the rest of the fibre, running between 
these rings was subsequently dissolved. My own 


rf the 

to declare most decidedly against this explanation, since they demonstrated 
the rings to be primaeval, original structures, from their very first appear- 
ance, and the seeming transitional stages from spiral vessels into annular 

vessels to be permanent intermediate forms between the two kinds of 

The idea that the reticulated vessels are produced from spiral vessels 
has been more extensively defended, and especially lately by Schleiden 

and Unger (Linncea, 1841, 394 J 

Nothing appeared simpler than the 
assumption that cross fibres were formed between the convolutions of the 
spiral fibre, and that the spiral was thus converted into a reticulated 
vessel. But two circumstances lead me to reject this notion most de- 
cidedly. In the first place, observation of the vessels in which the second- 
ary layers have just begun to be formed, gives evidence that the delicate 


: » 








fibres first deposited are already connected into a net-work, as is especially 
seen in the examination of the young roots of the Palms. On the other 
hand, this conception of the transition of a spiral vessel into a reticulated 
vessel is incompatible with the mechanical condition of the fibre. When 
swo spiral vessels lie upon one another their fibres must cross, since in the 
majority of cases the fibres of the two vessels run in the same direction 
(homodromous) ; but we find that when two reticulated vessels lie against 
one another, the fibres in the two vessels are placed transversely, and cor- 
respond accurately together in position ; which could only result from 
the fibres of the two vascular utricles losing their original spiral direc- 
tions, and one being pressed down to the right, the other to the left, until 
their situations should exactly correspond. Who will believe in such a 
motion of fibres, which are not free but adherent to the vascular utricles, 
themselves coherent together? and who has seen anything of the kind? 
A process of this kind might be held to be possible so long as we were 
ignorant of the true structure of the vessel, and believed that the fibre 
lay free in the cavity of the vessel, an error which formerly prevailed ex- 
tensively, and which one would not have expected to have still met with 
in a writing of Schleiclen's (" Beitrdge? i. 188). And if the incredible 
statement, that the fibre performed such a journey over one side of the 
vessel, were actually assumed to be true, how should the prolongations of 
it over the other sides of the vessel behave 1 Would these tear away or 

be pulled backwards and forwards, to restore by their more oblique posi- 
tion what was lost in their spiral course over the other side ? Instead of 
the confusion which must necessarily arise from this, we meet with the 
most beautiful order. If the lateral walls of the vessel are in contact 
with cells, we find its pits corresponding with those of the cells ; if one 
part of a vessel is connected with another vessel we meet with horizontal, 
slit-like pits. Thus we see clearly that one elementary organ influences 
the organization of an adjacent one in a definite manner, but we are no- 
where able to observe, that an organ already developed to a certain extent 
allows its already organized parts to perform movements in order to place 
themselves opposite the parts of the neighbouring organs. Since none of 
these matters can be seen, the processes are referred back by Schleiden to 
a time at which the observation is impossible. Thus he says (" Griindz. 
tier wiss. Botanik" i. 228^), it seems to him very probable that the spiral is 
in existence long before it is visible under our optical instruments, since it 
is composed at first of a substance which does not differ optically from the 
cell- wall and cell-contents ; hence, many forms might be referred to the 
spiral only at that epoch, if we assume that the intermediate stages were 
run through before the structure was yet visible. I readily allow the 
author to speculate as to the course of fibres which cannot be seen, but I 
must be excused from following him into this region. Valentin, indeed, who 
originated the theory of the expansion of the spiral fibres in all directions 
(" Rep. f. Anat. crndPhys? i. 88), believed that this could be demonstrated 
by observed facts, for he stated that he had found the secondary mem- 
brane making its first appearance in the form of a granular substance, the 
granules of which at first exhibited no definite order, but were subse- 
quently arranged into spirals, and became connected into the spiral lines 
which might be distinguished on the completely formed membrane ; a 
view which has not acquired confirmation from any subsequent obser\ 

r er 







It is scarcely worth mentioning that, Meyen (" ' Physiologie" i. 45) 
set up tlie theory that not only the secondary layers, but also the primary 
membrane was composed of distinct spiral fibres grown together. He 
was led to this opinion principally by the cells containing a very fine 
spiral fibre, of a Stelis gathered by him in Manilla, the structure of which 
he completely misapprehended, since he imagined that the fibres formed 
the primary membrane, while they belonged to the secondary. 

In conclusion, it may be remarked that Schleiden's hypothesis (" Bei- 
trdge" i. 187), that in the formation of the secondary layers there exist at 
first, at least, two spiral bands, one corresponding to the ascending current, 
the other to the descending current of the mucilaginous formative sub- 
stance, the two extremities coalescing at the ends of the cell, and that in 
most cases these become blended together at a very early period, is simply 
to be banished into the region of dreams. 

The opinion which formerly prevailed widely, and which Link (" Phil. 

1837, i. 177) still defends, that the pits of the scalariform ducts 
and pitted vessels are the remnants of the fibres of spiral vessels broken 
up into fragments, requires no further refutation. Holes in a membrane 

can scarcely be considered as elevations. 

Observ. 4. In the preceding I have spoken of cells and vessels as clearly 
separated organs, because in most plants the fully-developed cell differs in 
a marked manner from the fully-developed vessel ; but it must not be 
forgotten that transitional structures occur. One form, the porous cells, 
has already been mentioned ; these come near to the vessels in the large 
open pores, by which they communicate with each other, but they are dis- 
tinguished from those by the fact, that they form a parenchymatous tissue 
in the manner of cells, lie upon the surface of 
organs, and, in part, in Sphagnum (fig. 33, B), 
open even to the external air ; while the vascular 
utricles are always combined into tubes, which 
run among the cells in the interior of plants. 
Another intermediate structure occurs in the vas- 
cular Cryptogamia, particularly in the Lycopodia 
and Ferns, as well as in the Coniferse and Cyca- 
dese. In these plants we meet with the peculiar 
condition that the wood is not composed of a 
mixture of elongated cells and vessels, but of ele- 
mentary organs of one kind, which resemble pro- 
senchymatous cells in their form, and vessels in 
the structure of their walls, and give evidence of 
their near relation to the latter, in the fact that 
the prolongations of the vascular bundles of the 
stem entering into the leaves, contain perfectly 
developed vessels ; as also in the fact, that in the 
stems of Coniferse and Cycadese, the innermost 
elementary organs, bordering on the pith are per- 
fect spiral vessels, and that in Ephedra particular 
wood-cells become united into perfect pitted ducts. 

Fig. 33, B. 


-*r. i -•**•- 

* * - * 


Porous cell furnished with 
annular fibres from the leaf of 

Sphagnum cymbifolium. 

Observ. 5. 

Perhaps it is not altogether superfluous, in reference to the 

terminology of the pitted cells and vessels, to remark that since the struc- 
ture of the pits (tibpfel) an 







understood, it is the more general custom to apply the term pit (tupfel) 
to the canals perforating the secondary layers, and closed externally by 
the outer membrane of the utricle, and the term pore to the same canals 
when the primary membrane has been absorbed and the orifices of the 
utricles open freely into each other. Schleiden, on the contrary, uses the 
name of porous instead of pitted (getupfelten) cells, calls the pits pores, 
and the pores holes (locher), because (" Beitrdge? i. 189) according to 
Adelung and Heinsius, the word tilpfel (dot J means a shallow depres- 
sion, or a slightly elevated spot upon a surface. I will not enter into 
any etymological controversy against such authorities, but keep simply 
to my Swabian German, and am consequently of opinion that a panther's 
skin is getupft (spotted or dotted), although its spots are neither depressed 
nor elevated.* 

c. Chemical Conditions. 

The basis of the membranes of all the elementary organs of 
vegetables consists of neutral hydro-carbons ; in -almost all cases, 
and perhaps without exception, of cellulose. 

Cellulose is colourless, insoluble in cold and boiling water, 
alcohol, ether, and dilute acids, almost insoluble in weak alkaline 
solutions, soluble in concentrated sulphuric acid ; it is converted 
into dextrine by dilute sulphuric acid at a boiling heat. When 
imbued with iodine it becomes coloured indigo blue if wetted 
with water, this colour appears more readily under the conj oined 
influence of water, sulphuric acid, and iodine. According to Payen, 

formula of its composition is C12 H 


cell-membrane, since a series of both organic and inorganic com- 
pounds are deposited within it ; in which fact is to be sought the 
explanation of the manifold physical and chemical differences 
which are exhibited by the membranes of the same cell at different 
periods of their age, as well as by the cells of different plants. 

The combination of cell-membrane with inorganic substances is 
a very general condition, for the only examples of exception to 



entered as a substitute for the fixed bases. In all other plants a 
skeleton (the ash), corresponding to the form of the membrane, 
and composed of the alkalies, earths, and metallic oxides which 
had been deposited in it, remains behind after the cell has been 
burnt. The younger an elementary organ is, the more abundant, 
in general, the alkalies appear to be ; the older it is, the more 
exclusively the earths and metallic oxides seem to be combined 

* Some confusion exists also in our English terminology, the terms 
dotted and pitted tissues are indifferently applied to these structures, called 
by the Germans getupfelt. I have used the word pitted throughout this 
translation to express this term, because it indicates the true structure. 

A. H. 


3 el 




with its substance. The higher the degree in which the latter 
occurs, the harder the membrane becomes, as is shewn by the 
relation of the heart- wood to the sap-wood, and in a still greater 
measure in many seed-coats of a bony consistence, e. g., the peri- 
carp of Lithospermum, which contains much lime, the epidermis 
of Equisetum and Calamus, in which a great quantity of silica is 
deposited. However, we are without any accurate knowledge of 
these conditions, in spite of the countless analyses of ashes which 
we possess, for these give the product of ash of the cell-contents 
and cell-membrane together. 

The deposition of organic substances is not less general than 
that of inorganic compounds, at least in particular layers of cell- 
membrane. Among these the nitrogenous compounds are cer- 
tainly the most widely distributed. They do not occur in the 
membranes of cells which are just at the commencement of their 
development, for these are not coloured yellow by tincture of 


not the case. 


instances, and especially in the cells of the wood, to the series of 
proteine compounds, we have evidence (as Mulder pointed out) in 
the violet colour which hydrochloric acid produces after long oper- 
ation, and in the yellow colour which ammonia produces after a 
previous action of nitric acid. The presence of these compounds 
explains how, according to Chevandiers analysis, wood contains 

Fig. 34. 

0*67 to 1*52 per cent, of nitrogen. The 
darker yellow a cell - membrane is co- 



loured by nitrogen, the more firmly it 
withstands the action of sulphuric acid, 
and the more difficult it is to obtain the 
blue colour by the combination of this 
and iodine. In most parenchymatous 
cells, especially in the thin walled, this 
blue colour usually appears so intensely 
that the original yellow tint totally dis- 
appears ; in the thick walled cells, on the 
contrary, especially those of wood, the 
strong yellow colour is not altogether ^^ of ^ hotryophomt 

Overcome, and the COlOUr aSSUmeS a Clirty a, Primitive membrane ; b, secon- 

.•i iji • n n „ „ rt darv, strongly incrusted layers ; cc. 

green tint ; lastly, m Others no blue CO- the rest of the secondary layers. 

lour is produced at all, and the membrane 

offers such resistance, even to concentrated sulphuric acid, that 

it either only swells up slightly or remains quite unaltered, only 




may readily be taken for the primary membrane of the cell ; but 
as a rule it is composed of several super-imposed layers, and fre- 
quently contains the outer ends of the pit canals (fig. 34), whence 


- - - ■ ■ 

M ■ 





it is quite clear that in an anatomical sense it is not a well-defined 
membrane, but that it is composed of the primary membrane, 
and a few layers which belong to the secondary deposits, and 
which have undergone the same chemical changes as the primary 

membrane itself. 

Besides the nitrogenous compounds and the colouring matters 
which are diffused through many cells, especially those of the 
wood, the membranes of a great number of cells also afford a series 
of compounds devoid of nitrogen, which sometimes have a differ- 
ent composition from cellulose, sometimes are isomerous with it. 
Compounds of the first kind in which carbon, and, still more, 
hydrogen, are contained in relatively greater quantity than in 
cellulose, occur in the cell-membranes of fully developed wood, on 
which account all the earlier elementary analyses of wood give a 
false result, since the mixture of different compounds forming the 
cells of the wood was taken for a simple combination (the so- 
called woody fibre). 

While it is beyond doubt that all the compounds differing from 
cellulose in composition, form interstitial deposits in the cell- 
membrane composed of cellulose, entering into it subsequently to 
its first production, it is on the other hand doubtful whether the 
compounds which are composed, like cellulose, of carbon and the 
constituents of water, and which are either isomerous with cellu- 
lose, or differ from it perhaps only in containing a smaller amount 
of water, are to be regarded in like manner as depositions in the 
cellulose, or whether they replace cellulose and form the cell- 


Doubts in 

reference to this point are raised, especially by the cells of many 
of the lower plants, e. g., the cells of many Lichens, as of Oetraria 
islandica, which are partially soluble in hot water, and yield a 

substance similar to starch ; also the cells of many Algae, a&^Sphce- 
rococcus crispus, which yield a mucila _ 

Kutzing ("Phycologia genercdis") assumed that they were com- 
posed of a peculiar compound, named by him phytogelin. In none 
of these cases can we state with any certainty whether, or what 
share, cellulose takes in the formation of these membranes; and as 
little whether or not inorganic compounds, which might modify 
the characters of the cell-membrane by their action, are com- 
bined with it. We labour under the same uncertainty in regard 
to the differences which distinguish young cells from those in older 
conditions. Thus the membrane of the former swells up strongly 
in water, and is not coloured blue by iodine alone (but only by 
iodine and sulphuric acid). We have not at present any definite 
facts to enable us to express a decided opinion whether we are to 
assume that the compound of which the young cell-membrane is 
formed is essentially different from cellulose, and during the pro- 
gressive development of the cell undergoes a chemical metamor- 
phosis, a change of arrangement of its constituents or the like, or 






that this compound is replaced by cellulose, or that both are to b 
regarded as the same compound only distinguishable by slight 
differences in their conditions of aggregation ; or that the differ- 
ences are caused by the interstitial deposition of various foreign 
compounds. The same occurs in reference to the substance of 
those cells which are coloured blue with the same facility as 
starch, by the action of a weak tincture of iodine, but differ from 
starch by their behaviour to warm water, as is the case in the 
horny albumen of many plants, e. g., of Cyclamen, in the cells of 
the embryo of Schotia, &c. (See " On the Blue Colouring of Ve- 
getable Cell-membrane by Iodine/' in my "Vermischt 

Observ. 1. The credit is due to Pay en (" Memoir es sur les developpe- 
raents des vegetaux" 1844) of having demonstrated that the substance of 
all cells, from the highest plants down to the Fungi, when purified from 
foreign deposits, exhibits the same composition, and assumes the blue 
colour of cellulose on treatment with iodine and sulphuric acid. Accord- 
ing to his views the cellulose occurs in a tolerably pure condition in very 
young cells, while the membranes of older cells are combined more or less 
with foreign organic or inorganic compounds (which he called incrusting 
substances), through the presence of which the physical and chemical pro- 
perties of the cell-membrane undergo alterations, 
stances may be more or less completely extracted by treating the cellulose 
tissue with acids, ammonia, alcohol, ether, &c. Thus, according to his 
statement, nitrogenous substances and silica occur in the cuticle, pectate 
and pectinate of lime and of the alkalies in the thick walled epidermal 
cells of the Cactece, inuline in the cells of the Lichens and Algse, and in 
the hard cells of wood capable of being polished three or four compounds, 
designated by Payen lignose, lignone, lignine, and ligninose, substances 
which are richer than cellulose in carbon and hydrogen. 

These incrusting siib- 

Observ. 2. 

Mulder ("Physiological Chem."J 

researches on the chemical conditions of the walls of the elementary 

He also, like Payen, arrived at the result, that the membrane of 


all young organs consists of cellulose in almost a pure condition (the for- 
mula of which he determined as C24, H42, O21) ; but in reference to the 
alterations which the membranes undergo in the course of time, he pro- 
pounded totally different views. He here starts from the fundamental 
doctrine that a given layer of an elementary organ which is not coloured 
blue by iodine and sulphuric acid, does not contain cellulose ; that there- 
fore, when the same layer can be demonstrated to consist of cellulose in 
the earliest periods of the growth of the elementary organ, the cellulose 
must have been displaced by other compounds, or that if this origin from 
a layer of cellulose cannot be demonstrated, it is a later formation, and 
has been composed of other compounds from the first. In this way he 

_ — ^ y 

increases in thickness in three ways : 

elementary VJ . 6WXXO 
1, By the deposition of younger 

layers upon the inside of the membrane ; this occurs in the vessels and in 
a doubtful manner in the thickened pith-cells of Hoy a carnosa. 2, By 
the deposition of layers upon the outside of the elementary organs, which 
occurs generally in cells ; in .parenchymatous cells layers of the same kind 





H= * 



alone are generally deposited ; in wood-cells, on the contrary, first an 
outer coat is formed, and then subsequently intermediate layers of consi- 
derable thickness are formed between this and the inner primary mem- 
brane. 3, The new substances are deposited in the cell-wall of many 
cells (in the horny albumen of Phytelephas, Iris, and the so-called collen- 
chymatous cells), and therefore the wall does not exhibit lamellation. 
The constitution of these different deposits is described as very varied. 
Proteine is shewn to be merely an infiltrated matter, taking no part m 
the formation of the cell-wall, and is wholly wanting, or only just trace- 
able in very young cell-membranes; but it occurs in the intermediate 
substance of all old wood-cells, and most old pith-cells, but not in bark- 
cells or collenchymatous cells. The following compounds are particularly 
noticed as forming definite layers of the elementary organs. Intermediate 
wood-substance (the formula of which is stated at C40, H56, 02e) 3 a com- 
pound which is coloured yellow by iodine and sulphuric acid, swells up in 
weak acid and dissolves in stronger ; it gradually displaces the cellulose 
more or less perfectly in the secondary layer of vessels, forms the ^ outer 
layers of pith-cells and the intermediate of the wood-cells, in which it 
becomes the more intimately combined with the cellulose the further the 
layers lie toward the inside. External wood-substance, which is coloured 
brown by iodine and sulphuric acid, and does not dissolve in the latter ; 
it is stated as probable that this is isomerous with the intermediate wood- 
substance, but (as in the woody matter of the putamen of hard fruits) is 
distinguished from it by containing ulmin. It forms the outer layer of 
wood-cells, scalariform ducts, and pitted vessels. Besides these more 
generally distributed compounds, there occur other peculiar, less exten- 
sively prevalent, compounds not yet fully characterized, one of which 
forms the cuticle ; another the cells of cork ; another the cells of the homy 
albumen of Iris and Alstrwmeria. The following are regarded as incrust- 
ing compounds, penetrating into the substance of the cell-wall : pectose in 
the cells of the collenchyma, of the Apple, &c. ; starch in Getraria islan- 
dica ; vegetable mucilage in Sphcerococcus crispus ; and a peculiar sub- 
stance isomerous with cellulose, in the cells of the albumen of Phytelephas. 
My own investigations ^Investigation of the question ' Does cellulose 
form the basis of all vegetable membranes V " — Botan. Zeit. 1847, 497) com- 
pel me to declare most distinctly against the view of Mulder's, that a 
great proportion of the layers composing the membranes are from the 
first composed of compounds different from cellulose ; and also against 
his opinion as to the relative ages of the layers, deduced from these pro- 
positions (which I have already discussed above under an anatomical point 
of view). I found that the application of iodine and sulphuric acid, in 
which Mulder places such unconditional trust, is a means in the highest 
degree unsafe for deciding whether a membrane contains cellulose or not. 
My researches shewed me that the influence of sulphuric acid was by no 
means necessary for the production of the blue colour in membranes which 
are not strongly incrusted, as in the parenchymatous cells of succulent 
organs, but that iodine and water alone are sufficient ; while in full-grown 
and hardened cells sometimes the primary membrane alone, sometimes 
even a greater or smaller portion of the secondary layers had, through the 
deposition of foreign substances, altogether lost the property of becoming 
blue on the application of sulphuric acid and iodine, although they were 




still composed of cellulose, and iodine alone would very readily produce a 
blue colour in all their membranes after the infiltrated matters had been 
removed. The means I employed to remove the infiltrated substances 
were caustic potash and nitric acid. The first proved to be most effective 
in the cells forming the surfaces of plants (such as epidermal cells, periderm 
and cork) ; a maceration for twenty-four to forty-eight hours in strong so- 
lution of potash, at common temperatures, caused iodine to produce a pure 
blue colour in all these cells. The application of potash is not so effective 
in the cells situated in the interior of the plant, but that of nitric acid 
always answers the purpose completely, either when the preparation is left 
to macerate for a length of time in dilute acid, or is boiled in acid of mo- 
derate strength until the yellow colour which it assumes at first has dis- 
appeared again. After this treatment, the whole of the layers of all 
elementary organs are coloured a beautiful blue by iodine even when they 
offer so great a resistance to the action of sulphuric acid before the treat- 
ment with nitric, as is the case in the outer membrane of wood-cells and 



in Ferns. After these experiments there cannot be any doubt, 
that cellulose forms the basis of all the membranes of the higher plants, 
that the greater or less resistance of many membranes to the combined 
action of iodine and sulphuric acid, is caused by infiltrated foreign com- 
pounds, and that the "substance" of cuticle, of cork, and the "outer and 
middle wood-substance," regarded by Mulder as peculiar compounds, are 
combinations of cellulose with foreign infiltrated deposits. Of what nature 
these deposits are, which interfere with the reaction of cellulose, future 

researches of chemists must decide. 

Observ. 3. Schleiden takes up quite a different point of view. (" On 
Amyloid" Beitrdge, i. 168. "Some remarks on the substance of vege- 
table membranes" Beitrdge i. 172.) Without regarding that the cell- 
walls are not composed of one chemical compound, but that they have 
a series of substances deposited in them, possibly exerting an influence 
upon their properties, — lie considers the differences which are observed 
in the cell-membranes as unconditional proofs of difference in the sub- 
stances of which they are formed, and believes that the compounds dis- 
tinguished by chemists, forming the series of hydrates of carbon, are 
but a very sparing selection from the infinite multiplicity of compounds 
belonging to this series, occurring in plants. According to his views, the 
plant forms a fundamental substance, which remains the same in re- 
ference to its elementary composition, but is capable of infinite modi- 
fications by internal imperceptible changes, and also, in part by the in- 
crease or diminution of chemically combined water : forming a series, the 
adjoining members of which differ imperceptibly to us, sugar being the 
lowest, and the substance of perfectly developed membrane the highest, 
of the members, which become more and more insoluble in water from 
below upward. Three compounds, in particular, of this series, forming 
cell-membranes, are minutely characterized according to their behaviour 
to iodine and water: 1, Cellulose, of which it is stated that it is not 
coloured blue by iodine, when in a pure condition ("Grunclz. der wiss. 
Botanik" 3rd ed., i. 172), which is decidedly untrue. 2, Amyloid, 
Schleiden used this name to signify the substance, announced by himself 

and Vogel, 







: : 



mencea, Mucuna, and Tamarindus, which are readily coloured hlue by 
iodine. According to his account amyloid dissolves in boiling water, and 
its compounds with iodine are dissolved in water with a golden yellow 
colour. The latter is decidedly incorrect, and in regard to the former, 
Schleiden himself says ("Betorage," i. 167), only the intermediate layers 
were dissolved even after twelve hours boiling, and all the cellulose tissue 
remained. 3, Vegetable Jelly;— under this name Schleiden comprised a 


sorin, uerasm, Jreczin, u-eim, <&v.) 

their property of swelling up strongly in water and not becoming coloured 
by iodine. He ascribed to this substance the property of gradually be- 
coming diffused in cold water, and believed many vegetable cells to be 
composed of this substance, transitions from it existing on the one hand 
(through the cells of the Fucacese) into cellulose, and on the other (by 
many kinds of horny albumen) into amyloid. Excepting the statements 
that cellulose is not coloured by iodine, and that there exist cells soluble 
in water, there is no doubt of the correctness of the anatomical founda- 
tions on which this theory rests. But on the other hand, there is just as 
little doubt that the whole of this representation of the infinite multipli- 
city of neutral hydrates of carbon and the distinction between them ac- 
cording to their greater or less expansion in water, and more or less 
facility with which they are coloured by iodine, could only be considered 
as established, when it was proved that the substance of vegetable cells 
possessed this property in its pure condition, and that these differences 
were not caused by foreign deposits. Since not only is this proof wanting, 
but, on the contrary, the most definite evidence exists that the chemical 
and physical properties of vegetable membranes can be modified in the 
greatest degree by infiltrated matters, Schleiden s view is devoid of any 
solid foundation. 




Leaving out of view the lowest plants, and the spores and pol- 
len-grains of the more highly organized, cells do not occur isolated, 
but crown together in great numbers in connected masses ; in 
this 'manner they form the so-called cellular tissue, eontextus 
cellulosus (parenchyma or prosenchyma, according as it is com- 
posed of parenchymatous or prosenchymatous cells). 



between any two cell-cavities must necessarily be composed of a 
double membrane, and this may be readily observed in reference 
to the secondary layers, in all thick walled cells, by means of the 
microscope, for it is clearly seen, that the individual layers of the 
membranes surround the cavities of the cells concentrically, and 
that the secondary layers of the several cells are separated from 
each other by the primary membrane. 

Observ. It is hy no means so simple an affair as it seems at first sight 
to determine the limit between two cells. Formerly, when observers 
were restricted to weaker and less perfect magnifying instruments, the sur- 



face of the cross section of the primary membrane appeared as so narrow 
a line, that it was taken for the boundary line between two neighbouring 
cells, and was drawn as such. Subsequently, when the knowledge of 
cellulose structure had progressed further, the primary membrane was 
distinguished from the secondary layers, and the outermost layer of cell- 
membrane was seen under stronger microscopes to have a clearly visible 
breadth (or thickness), the idea remained of an easily distinguishable 
boundary line between the two coherent cells, and such a line was even 
figured. This, as Hartig correctly observed, was untrue, for our micro- 
scopes do not shew any boundary line between the two coherent primary 
membranes {see figs. 21, 22, 25, 32, 44). When Hartig drew from this 
the general conclusion that no limit exists, and that the outer membrane 
of the two cells is common to both, his induction was too hasty. The 

impossibility of seeing a line of demarcation with our microscopes, war- 
rants, a priori, nothing more than the conjecture that our present instru- 
ments are not yet sufficiently perfect for the purpose. It is self-evident 
under these circumstances that nothing has been accurately made out as 
to the manner in which cells are connected. 

The cells cohering together may be separated, from each other ; 
in very succulent tissues, as in the parenchyma of many juicy 
fruits, a slight pressure suffices for this ; in somewhat firmer tis- 
sues the connexion of the cells may often be so loosened by boil- 
ing in water or by freezing, as to become easily separable ; while 
in very solid tissues a long maceration in water or a short boiling 
in nitric acid is necessary. It might be imagined that the double 
nature of the outer membrane could be readily demonstrated by 
this separation of the cells, but wrongly, for I found that the 
outer membrane, when distinctly perceptible, was not split into 
two layers in such cases, but torn into pieces, some adhering to 
one and some to the other cell, so that the separated cells were 

composed chiefly of secondary layers.* 

It has been remarked already, in the description of the form of 
-cells, that the flat faces of cells meet at sharp angles in compara- 
tively few cases, since the corners and edges are generally rounded 
off. It follows necessarily from this condition, that the cells are 
not, for the most part, coherent together by their whole surfaces, 
but leave empty spaces between them, which run along the edges 
of the cells in the form of triangular canals having no special 
walls of their own, opening into each other at the corners of the 
cells, and so forming a net-work of narrow and wide tubes branch- 
ing throughout the whole plant, to which the name of intercelhi- 
lar passages has been applied (see figs. 6, 7). In living plants they 
are, with few exceptions, filled with air. 





I V 

Schultz has lately made known a process for isolating the conjoined 

n * ' It consists in boiling them for a short time 


cells even of woody tissues. 

with chlorate of potash in nitric acid. 

does not dissolve the outer membranes. 

It is not clear, however, that this 

-A. H. 




Intercellular passages occur mostly between parenchymatous 
cells ; they are frequently absent from prosenchyma, or when pre- 



sent, are, at least, very narrow. 

the surface of the plant, since th~ r . j 

the outermost layer of the plant are, in general, and in all parts 
growing under ground or in water without exception, accurately 
in contact at their angles ; on the other hand, on most organs ex- 
posed to the air, especially on the lower sides of leaves, there 
occur little orifices bounded by crescent-shaped, curved cells, sto- 

mates or stomata 

Fig. 35. 

a free communication between the air 
contained in the intercellular passages 
and the atmosphere. 


cells are, the more do the intercellular 
passages take the form of regular, nar- 
row canals {see fig. 7) ; on the other 
hand, the more globular the shape of 
the cells (fig. 6), and in a still higher 
degree, the more an unequal growth 
has caused them to approach the form 
of the stellate cell (fig. 10), the more 
do the intercellular passages take the 

— . - -m • , • 111 



Epidermis of the lower face of Helle- 
borus foetidus. a, stomate. 

formed of such cells, since the space 
occupied by the intercellular passages 

then becomes more equal to, or in ex- 
treme cases, many times surpasses, that 
filled by the cells. The lower side of leaves and corollas are 
formed of such tissue, moderately spongy, the pith of Juncus 
eifusus gives a very highly developed example. 

In other cases the intercellular passages lying between regular 
polyhedral cells become expanded at particular points into larger 
cavities, or into long canals, which latter are frequently interrupted 
at certain distances by partitions composed of stellate cells. This 

n. . _j. ~v.A in 4-V.^ l^o^ofolV nf rrmmv wa.f.p.r- nun 

.. stem 

marsh-plants, in which the wide 
rated from each only by a sing 
there also exists a roundish 2 


ity (breathing - cavity, Ath- 
Canals and cavities of this 



Limes, Cycadese, and for milk-sap in Rhus. 

In many cases the spaces between the cells are filled up with a 


cells upon the outer surface, and sometimes only imperfectly fills 





Fig. 36. 

the intercellular passages, but usually forms a dense mass in it 
and quite obliterates its cavity. This occurs in remarkable quan- 
tity in the tissue of many Algse 3 especially of the Fucoidese, the 
Nostochinese, in the cortical 
layer of many Lichens, in 
the Albumen of many Legu- 
minosa3, e. g. y Sophora japo- 
nica (fig. 36), Gleditschia, &c. 
It is found in smaller quan- 
tity, and therefore less readily 
perceptible, in the intercellu- 
lar passages of wood, e. g., of 

Pinus (fig. 22) and Bwxus, as 
well as in the intercellular 
substance of bark. The mass 
composing the intercellular 
substance usually resembles 
so much the substance of the 


Transverse section through the albumen of So- 

pJwra japonica ; a, intercellular substance ; b, cavity 
of the cells. 

cell-walls between which it 
lies, that the application of 
re-agents, as of iodine and 
sulphuric acid, does not af- 
ford any certain means of 

accurately distinguishing it from cell-membrane ; in other cases 
the boundary line between them is very sharply defined. 

An analogous secreted layer, appearing in the form of a mem- 
brane, occurs upon the surface of freely exposed cells ; it possesses, 
like the outermost membrane of wood-cells, the property of resist- 
ing obstinately the solvent power of sulphuric acid. To this be- 

long the outer membrane of spores and pollen-grains and the cuticle 
(fig. 37, a), which invests the whole 
of the surface exposed to the air 
of the higher plants, in the form 
of a connected membrane. 

Fig. 37. 


Cells of the epidermis of the leaf of Helle- 

borus fcetidus. a, cuticle. 

Observ. When I propounded the 
theory of the intercellular substance 
("Illustrations and Defence of my 
View of the Structure of Vegetable 
Substance" 1836), this appeared to me 
to possess a far greater importance in 

the vegetable organism, than it proved I 

to have subsequently on more accu- 
rate investigation of this substance itself and more minute research 
into the development of cells. I did not perceive that the intercellular 
substance is a product of the cell, and thought I had discovered in it an 
universally distributed mass, in which the cells are imbedded, and which, 
in many cases, exists before the formation of the cells. The real condition 
is in most cases decidedly the reverse ; but it is not yet, however, clearly 

. : 

i ! 







made out whether or not, in certain cases, for instance in the albumen 
of Schizolobium excdsum {see Schleiden on " Albumen" in the " JSfova 
act. Natur. Curios" xix. p. 11, pi. xliii, fig. 55), cells and intercellular 

substance originate together; but nothing can be decidedly determined 

about this, since we are altogether without observations on the develop- 


In very many cases it is extraordinarily difficult to distinguish the in- 
tercellular substance from the cell-wall. In regard to this, my opinions 

differ in many cases from those of many other ob- 
servers ; for instance, of Schleiden, especially in re- 
lation to the structure of the cells which swell up 
in a jelly-like manner in water (the so-called collen- 
chyma-cells), which occur in the outer layer of the 
rind in many plants ; for example, in Cucurbita 

Fig. 38. 



to the cell-membrane, and are formed of second- 
ary layers deposited in the angles of the cells ; 


according to the opinion I formerly ex- 

Collenchyma-cells from the 
stem of Beta vulgaris. In 

the angles of the cells the 
substance of their membrane 
(a) is very hygroscopic, and 
swells up gelatinously in 

pressed, still defended by Schleiden, the cells possess 
walls of uniform thickness, and the laminated mass 
lying between their angles is to be regarded as in- 
tercellular substance. In such difficult cases it is 
best to allow the cells to swell up in nitric acid, to 
render the stratification of their membrane more dis- 
tinct, and thus to make out the position of the primary membrane (fig. 39). 
Unger (" Botan. Zeitung? 1847, 289) has recently sought to demon- 
strate that the origin of the intercellular substance and of the cells is 

simultaneous. The reasons advanced by him do 
not seem to me convincing. In the present state 
of our knowledge, however, we can say very little 
about this ; the whole theory of the intercellular 
substance requires a thoroughly new investigation. 
The membrane secreted upon the surface of cells 
exhibits most remarkable conditions, since no inter- 
nal organization or composition from different layers 

Fia. 39. 



The point of union of four 
cells of Beta swollen up in 
hydrochloric acid. It shews 
the uniform dense tertiary 
layer (b) ; the gelatinous 
secondary layers (a) ; and 
the primary membrane (c). 

can be detected in it, while it is yet very frequently 
clothed in an extremely complicated manner with 
reticulated projecting ridges, straight or waving 
lines, or granular or spiny proj ections, as is seen in 
the most varied and elegant manner on many 
spores and pollen-grains. Linear projections also 
occur frequently upon the cuticle, and these are by 
no means arranged in correspondence with the sub- 
jacent cells. It is not at present known of what chemical compound 
these membranes are composed : cellulose is not found in them. 

The structure and origin of the cuticle, and the epidermis-cells lying 
beneath it, have been the subjects of manifold discussions. When an 
epidermis, especially one from the upper side of a leathery leaf, is sliced 
transversely, the walls of its cells turned outwards are seen to be much 
thicker than the rest. Iodine and sulphuric acid either colour the whole 
of this outer wall dark yellow, and sulphuric acid does not dissolve it, or, 


the outer wall exhibits these properties down to a certain depth, so that 
a layer (fig. 40, a) is thus formed, which is 
most strikingly distinct from the subja- 
cent cells, and when the latter have been 

Fig. 40. 

dissolved in sulphuric acid, remains behind 
as a continuous and apparently homogen e- 

ous membrane. 

Since Ad. 


^ Ann. des Sc. Nat. Ser." § i, 65) had dis- 
covered that a continuous membrane, not 
composed of cells, called by him cuticula, 


Cells of the epidermis of the upper 
face of the leaf of Hoya carnosa. a, 
the portion of their walls acquiring a 
yellow colour with iodine. 

might be separated by maceration from I 

the outer surface of the epidermis, it ap- 
peared natural to suppose that the layer just spoken of, which is fre- 
quently very thick and is coloured brown by iodine and sulphuric acid, 
was this cuticula, and to ascribe its origin to a secretion upon the outside 
of the epidermis-cells, a process of which Schleiden even gave a detailed 
description (" Grundz. der wiss. Bot." 1st ed. i, 288). This view, however, 
proposed by Treviranus, and defended by Unger, Harting, Mulder, and 
otheis, is in great part wrong. The so-called cuticle consists, with the 

Fig. 41. 

The epidermis of the upper side 
of the leaf of Hoya carnosa treated 
with caustic alkali, a, the cuticle 
separating-; b, the swollen, lami- 
nated euticular layers of the epider- 
mal cells. 

exception of a layer extremely thin in most 
plants (fig. 41, a), of the thickened walls of 
the cells, which are infiltrated with a sub- 
stance coloured brown by iodine, to which 
they owe their power of resisting the action 
of sulphuric acid. When this substance is 
removed by caustic potash, not only is the 
composition out of cell-membranes evident, 
since the separate layers of these become 
visible, but iodine now very readily produces a 
blue colour ^Bot. Zeitung" 1847, 592). This 
composition of the so-called cuticle, of cell- 
membranes, is seen beyond all doubt in the epidermis of an old stem of 
Viscum album (fig. 42) ; the epidermis-cells consist here of two or three 
jenerations enclosed one within 
another, of which all the thick- Fig. 42. 

ened walls on the outer side j 
have become blended together 
into a membrane composing the 
cuticle (H. v. Mohl, " On the 
Epidermis of Viscum album" 

Bot. Zeitung, 1849). I call 
these layers belonging to the 
epidermal cells the euticular 
layers of the epidermis, to dis- 
tinguish them from the mass 
secreted on the outside of the 
cells, the true cuticle, which is 
soluble in caustic potash, in 
most cases forms but a very 

thin coating over the epidermal I 

cells, and only rarely, as in the 

shoots of Ephedra, and the upper surface of the leaves of Cyms, forms 

<" / 

Epidermis of an old stem of Viseum album. 









a, layer of considerable thickness, and in which no cellular has yefc been 

shewn to exist. 



In the present state of our knowledge it is an impossibility to 
give even a tolerably complete description of the contents of cells, 
since of the large number of organic compounds produced by the 
vegetative processes, almost all of which occur in the cells, only a 
very small number can be demonstrated at present in the plant 
itself by means of the microscope, since most of them occur in 
solution in the cell-sap and in too small quantity for them to be 
rendered visible by re-agents. I must, therefore, confine myself to 

the mention of the organized productions found in cells, and the 

universally diffused substances. 


Primordial Utricle, Protoplasm and Nucleus. 

In all young cells, whatever their subsequent contents may be, 
whether they persist in the stage of cells or become changed into 
vascular utricles, a series of formations are met with, which dis- 
appear again more or less perfectly in the subsequent periods of 
life, and which stand in the closest relation to the origin and 
growth of the young cell, but only in particular cases in relation 
to their later functions. 

If a tissue composed of young cells be left some time in alcohol, 

or treated witl 
membrane becomes 




cells, in the form of a closed vesicle, which becomes more or less 
contracted, and consequently removes all the contents of the 
cell, which are enclosed in this vesicle, from the wall of the cell. 
Reasons hereafter to be discussed have led me to call this inner 

cell (fig. 43, a) the primordial 

Fig. 43. 


" Remarks on 



}ell of the leaf of Jungermannia Taylori. a, the 
primordial utricle separated by the action of iodine. 

table Cell" — Bob. Zeitung, 
1844, 273. Transl. in Tay- 
lors Scientific Memoirs, vol. 
iv. p, 91). Iodine colours it 
yellow, and it is therefore 
probably always nitrogen- 
ous. According to Mulder, 
proteine may be detected in 
it in many, but not all, cases, 
by nitric acid. Cellulose 
cannot be found in it, and 
the compound of which it is 
composed is as yet unknown. 

The primordial utricle disappears again with the thickening of 








the walls of the vessels, the cells of the wood, of the pith, of the 
inner part of the petiole, and of thick leaves. It usually adheres 
firmly to the cell-wall, and can be discovered even at first in the 
form of a thin granular coat, coloured yellow by iodine, when the 
cell-wall is dissolved in Sulphuric acid ; in particular cases it ap-* 
peared to me not to be so firmly connected, but to be dissolved 
and to assume before it vanished the form of an irregular net of 
fibre-like streaks. On the other hand, the primordial utricle re- 
tains its complete integrity throughout the whole life of those 
cells which contain chlorophyll, thus especially in the cells of 
leaves, and in those of the fleshy rind of the Caetese, Eupkorbice, 
&c, and in like manner in the cells of many Cellular plants, par- 
ticularly of the Algae. 

Observ. It was natural enough that the primordial utricle should have 
been seen by others before I called attention to its existence as an univer- 
sally prevailing structure; in particular, Kiitzing (Linncea, 1841, 546, 
"Phycologia generalise 38) had discovered it in the Algse, and described it 
as a special coat of the cell under the name of the Amylid-cell He applied 
this unsuitable name under the idea that its substance was changed into 
starch by the action of potash, which is not the case. Karsten had de- 
scribed the same in his "Dissertatio de cella Vitali" but attributed import 
to it quite different from that I have, since he considered it to be a secon- 

dary cell. 


Algse, but taken it not for a membrane, but a layer of mucilage, — a view 
in which Schleiden appears to participate. I must declare against this 
opinion in toto. No fixed limit can, of course, be indicated between a soft 
membrane and a compact layer of mucilage, but a layer 
from which (as will be described more minutely further Fig. U. 

on) folds grow out and cause constriction of the contents 
of the cell, certainly must be regarded as a membrane, 
and not a layer of fluid mucilage. 

In the centre of the young cell (fig. 44), with rare 
exceptions, lies the so-called nucleus cellulce of Rob. 
Brown (" Z ellen-hem ; " "Cytoblast" of Schleiden) ; 
the origin of this will be treated more minutely here- 
after in the description of the origin of cells ; it is 
usually of very considerable size in proportion to 
the magnitude of the young cell, so that in parti- 
cular cases, e. g., in the cells of jointed hairs, it almost 
fills up the cavity. The remainder of the cell is 
more or less densely filled with an opake, viscid 
fluid of a white colour, havin 

granules intermm- 

the stem 

Cell from 

of Orchis mascula, 
with a nucleus. 

gled in it, which fluid I call ^protoplasm ( "On the 

Mo \-ement of Sap in the Interior of the Cell," — Bot 

Zeitung, 1846,73). This fluid is coloured yellow by . 

iodine, coagulated by alcohol and acids, and contains albumen in 

abundance, whence young organs are always very rich in nitrogen. 

















As the cell increases in size, its membrane grows in much greater 
proportion than the nucleus, which certainly frequently enlarges 
■for a certain time, but becomes smaller in proportion to the cell. 
During the growth of the cell irregularly scattered cavities are 
formed in the protoplasm ; these are originally isolated, and very 
frequently present a most deceptive resemblance to cavities of 
delicate-walled cells, subsequently, however, they become blended 
together in many directions ; the protoplasm is then accumulated 
at one side, in the vicinity of the nucleus ; on the other side it 
coats the inside of the primordial utricle, and these two collections 
are connected together by thread-like processes which are some- 
times simple and sometimes branched, so that the nucleus appears 
suspended, as in a spider's web, in the centre of the cell.* An 
internal movement in the protoplasm now begins to be visible. 
Originally no definite arrangement can be perceived in it ; but 
the more the protoplasm changes from the uniform mass which 
it originally formed, into the condition of threads, the more dis- 
tinctly it may be seen that each of these threads represents a 
thinner or thicker stream, which in one thread flows from the 
nucleus to the periphery, turns round there, and flows back again 
in another thread. The thickness, the position, and the number 
of these threads are subject to constant change, which shews, 
beyond a doubt, that the currents move freely through the watery 






In most 


cases the nucleus does not appear to take any part in this move- 
ment ; but the motion may easily be overlooked on account of its 
slowness, since I found in Tradescantia virginica, in which I saw 
the nucleus move slowly up and down, that this only passed over 
the distance of 1 -45,000th of a line in a second, which is naturally 
much too little to allow of the movement being seen directly, 

oifying powers. The 
nucleus retains its central position in many cases even when the 
cell is fully developed, e. g., in Zygnema, but it mostly becomes 
gradually withdrawn towards one side of the wall of the cell, where 
it becomes attached by its viscid investment to the primordial 
utricle, but always forms the centre of the currents of sap. The 
circulation of the protoplasm is very slow ; I determined it in the 
hairs of the filaments of Tradescantia at an average of l-500th of 
a line per second, in the stinging hairs of Urtica haccifera 1 -750th, 
in the hairs of Gucurbita Pepo at 1-1 857th, &c. (" Bot. Zeitung" 


In most cells this phenomenon is transitory, for not only is the 
nucleus itself dissolved in time in the majority of cases, but the 
protoplasm also becomes more and more diminished in quantity, 
or at least frequently appears motionless, as appears in all proba- 


Pl. 1, fig. 7. The end cell of a hair of the filament of Tradescantia 

ff Q 

VI / 

l% % 




bility to be the ease in the cells of many succulent fruits, in which 
the nucleus frequently remains perfect up to the time of the ma- 
turation of the fruit. In one series of cases, however, the circu- 
lation is persistent in the full-grown cell, e. g., in the stinging hairs 
of nettles and Loasce, in the hairs of Cucurbitaceous plants, in the 
hairs of the filaments of Tradescantia, in the hairs of the corolla 



In some plants the protoplasm is 

not distributed in isolated reticularly arranged currents, but flows 
along the cell-wall in a broad stream, returning back upon itself in 
a circular direction at one side of the top of the cell, and flowing 



form of the circulation is displayed very beautifully in the cells of 
the leaves of Vallisneria spiralis, and in the cells of Chara, the 
inside of which is clothed with spirally arranged rows of chloro- 
phyll granules, which the current accurately follows. 

Observ. 1. The wonderful phenomenon of the movement of the proto- 
plasm is usually designated by the most unsuitable name of « rotation of 
the cell-sap." Although described by Corti in 1774, the phenomenon 
was altogether forgotten till discovered a second time by Treviranus in 



1807. For a long time it was supposed to be a peculiarity 

belonging to a few water plants (Chara, Ilydrocharis, Vallisneria, Cau- 
liniaj, until the researches of recent times shewed that it was an univer- 
sal phenomenon. The cause of the motion is altogether unknown ; the 
explanation of Amici, that in Chara the rows of chlorophyll granules which 
clothe the walls of the cells, and which the current of sap follows, exer- 
cise a galvanic action upon the sap, and thus give rise to the motion, can- 
not be considered applicable, since these granules are absent in all other 
plants and even in the roots of Chara. The description of the pheno- 

non in question, by Schultz, furnishes a pattern of imperfect observa- 
tion and unfortunate conclusions ; he regards the currents of protoplasm 
as composed of milk-sap, flowing in a branched vascular system, having 
its origin in the vessels of the milk-sap, and penetrating the walls of the 
cells ("Die Cyclosis des Lebensajtes in der Pflanze," 293). 

Observ. 2. According to Schleiden's statement ("Grundz" i. 211, pi. 1, 
fig. 6), it sometimes happens that a secondary cell-membrane becomes 
deposited over the nucleus as it lies upon the wall of the cell, so that it is 
enclosed in the substance of the cell-membrane and protected from fur- 

The nucleus, like all 


This account is a 

Itogether incorrect. 

ther change. w ...._,. 

the rest of the contents of the cell, lies in the cavity of tne primordial 
utricle, and the cell-membranes are formed over the outside of the latter. 
The conditions which determine the early solution of the nucleus or its 




very soon in vascular utricles and in wood-cells ; it lias likewise very olten 
disappeared from full-grown parenchyma-cells, especially m those of the 
middle layers of the stem, wh ile it is very frequently found quite perfect 
in spores, pollen-grains, in the ceils of j ointed hairs, m the cells of hemes, 
and in the boundary cells of stomates ; the cellular tissue of many Or- 

and Commelynacese is remarkable for the long retention of the 




i ■ 

: i 






• \ 

Observ. 3. It has already been remarked that the cavities in the pro- 
toplasm, filled with watery cell-sap, sometimes deceptively resemble cells. 
This is the case in a much less degree as long as the protoplasm is only 
hollowed into distinct isolated cavities, but the similarity becomes very 
great when the hollows have so increased in number or size, that the layers 
of protoplasm between them have assumed the form of thin partitions. 
In this case the cavities acquire the shape of polyhedral parenchymatous 
cells ; and those lying on the surface of the mass of protoplasm become 
rounded off on their free sides, as cells would in such a case ; in shorfc, the 

resemblance to a delicate-walled cellular tissue could not be greater. 


if we reflect that the protoplasm is a viscid fluid, which, as its delicate 
currents shew most distinctly, does not mix with the watery cell-sap, 
this appearance becomes comprehensible enough^ the protoplasm bears 
the same relation to the cell-sap as a frothing fluid does to the air con- 
tained in its bubbles. The unceasing flow and continued transformation 
of the mass of the protoplasm, furnish most distinct proof that we have 
to do with a fluid, and not with an organized structure. We must keep 
in view this condition of the protoplasm of the young cells, if we would 
avoid being deceived by the forms which it frequently presents in full- 
grown cells, especially in those of succulent fruits, e. g., of Grapes. In 
these it forms not only, in part, a connected frothing mass, but a portion 
of it occurs in isolated globular masses, which usually contain in their 
interior one or more cavities filled with cell-sap, and consequently possess 
the form of vesicles. These are met with in every gradation of size, from 
scarcely perceptible vesicles to bodies like cells, some l-100th of an inch 
in diameter. No more movement in the substance of the protoplasm can 
be detected in these cases ; on the contrary, the walls of these vesicles 
exhibit a tolerable degree of firmness, so that the comparison of them 
with cell-like structures is not at all far-fetched. Nevertheless, such a com- 
parison seems to me out of place ; since none of our means, — for instance, 
application of the compressor, or treatment of iodine, — will enable us to 
discover on these vesicles a membrane which would form a contrast with 
the contents. Under these circumstances, I can only regard as a mistake 

Karsteu's view (" Creation" Die Urzeugung. 

u C ontribxitions to 

yf Cell-life 

Bot. Zeitung, 1848, 457; 

Bot. Zeit. 1848, 361), 

according to which these utricles are the rudiments of cells. 

b. Cell-sap. 

In full-grown cells the protoplasm, usually forms but a very 

subordinate part, as to mass, of the contents of the cell; while the 

watery cell-sap, which at first appeared only in isolated cavities, 

formed by degrees in the protoplasm, fills the whole cavity of the 

The quantity of it is subject to variation, according as the 

plant has absorbed or evaporated more water ; the decrease, how- 

ever, cannot descend below a certain limit in the cells of most 

organs of the higher plants, without destroying the life of the 
cell . 

Although the cell-sap always contains in solution a series of 
organic and inorganic compounds, as a general rule it appears to 
the eye like pure water, since it is but rarely that colouring mat- 






ters (usually red or blue) are dissolved in it ; and still more 
rarely is the quantity of the uncoloured substances, such as gum, 

Teat as to increase in a striking manner its 

dissolved in it, so 
power of refracting light. 

In many, yet comparatively rare, cases, the cell-sap of particular 
cells becomes wholly displaced by compounds which the cell itself 
prepares, e. g. y etherial oils. 

Observ. Among the organs of the higher plants, ripe seeds alone hear 
to be perfectly dried without being killed ; the older wood of trees may 
also lose a great quantity of its sap without death ; the limit to which this 
is possible is as yet unknown. The rest of the organs, particularly the 
leaves, do not bear any considerable loss of water. It is different in many 
lower plants, especially the Mosses, Lichens, and many Algse, e. g. y in 
JSfostoCy which may be completely dried up without injury. 


c. Granular structures. 

In the majority of parenchymatous cells, organic structures — 
usually of granular form — are met with, at all events at certain 
periods of the life, swimming in the cell-sap or slightly adherent 
to the walls. Two of these, the chlorophyll granules and starch 
are very generally diffused. 

Clilorovhvll (leaf-ereenY on the nresence of whi(?h 

depends the green colour of plants, never occurs 

Fig. 45. 

dissolved in the sap, but always in the form of a 
softish mass of definite or indefinite shape ; many 

phytotomists have asserted the existence of a green- 

coloured cell-sap, but I have never been able to 
find it. 

Amorphous chlorophyll forming patches or threads 
which adheres to the cell-wall and the granules con- 
tained in the cell, is of comparatively rare occur- 
rence, yet it occurs here and there in the Phane- 
rogamia, in the same cells with the chlorophyll 


defined form. In certain Algse it presents itself in 
the form of flat bands, in Conferva zonata, Dra- 
pamalclia plumosa, &c, in each cell as a trans- 
verse annular band ; in Zygnema (fig. 45), in the 
form of a spirally wound band ; in Mougeotia, in 
the form of a flat or curved plate lying in the in- 
terior of the cell, &c. In the great majority of 
plants, however (see fig. 10), it possesses the form 
of globules, which sometimes lie upon the wall of 
the cell (where they are usually irregularly scat- 
tered, but in Char a arranged in rows), sometimes swim in the 
cell-sap, and sometimes surround the nucleus. 

But a very small portion both of the band-shaped masses in 












colouring matter ; so that in pieces of plants from which the 
colour has been extracted by alcohol, they are found little altered 
in size, as softish masses which are coloured yellow by iodine, 
therefore contain nitrogen. Whether this is ^ simply albumen, as 
Treviranus states, remains to be proved ; but it is probable that it 

is a proteine compound. 

Even in the matter extracted by ether, the true green colouring 
substance forms but an extremely small portion, according to 



mass of that which is soluble m 


tiJLCCljU XXXCLDO \JX UXXCtPU VV JULJ-V^XA akj KJ^J-i^.^a.vy J-*.* ^vo.^.wj- w^^u*.^*,*^ ^^ w t *^-c*.. j_ aav^ 

chemical composition of chlorophyll is not yet made out with cer- 
tainty ; Mulder's analysis gave Ci 8 Hi 8 N 2 3 , but requires repeti- 

From his researches it would appear tliat chlorophyll is 



that uncoloured chlorophyll exists in all parts of the plant, 
capable of conversion into green by free oxygen ; a conjecture, 
however, against which speaks the circumstance that neither the 
expressed sap, nor any tissue whatever of plants, acquires a green 
colour by exposure to the influence of the air. 

Starch granules are very frequently enclosed in the chlorophyll 




strips of Zygnema, but in an extraordinary number of cases in 
the chlorophyll granules of the most varied plants, and especially 
distinctly in those of Char a. Sometimes only one starch granule 
exists in the chlorophyll grain, sometimes several, but usually not 
more than three or four ; in Anthoceros alone I found from 50 to 

100 starch granules in each of them. These starch granules are 

usually of very small size ; the longest I determined at 1-S00th of 
a line, the smallest, acquiring a distinct blue colour with iodine, 
l-2000th of a line, and it still remains uncertain whether or not 
still smaller granules, which occur in many cases in chlorophyll, 
consist also of starch. The history of the development of chloro- 
phyll is still involved in obscurity. So far as I have traced the 
matter, it stands in the closest connexion with protoplasm at its 
first appearance in uncoloured organs which have been developed 
in the dark, when the formation of chlorophyll is brought about 
in these by the influence of light ; for on the first appearance of 

the „ 

assume a greenish tint, exhibiting the form of granular patches of 

mucilage having no definite outline. Subsequently, the starch 

granules, where such occur in the cells, e. g., in the potato, or any 

young leaves, become clothed by a more or less thick coat of 

chlorophyll presenting a distinct boundary line ; while in other 

cells chlorophyll granules are met with which contain no starch. 

In other cases in which the very young organs contain no starch, 





franules of 





it appear at a later period in the perfect chlorophyll globules, and 
increase in size with the age of the plant. Thus it seems to me 
that starch does not stand in any causal and necessary connexion 
with chlorophyll, but that the proteine substance combined with 
chlorophyll sometimes assumes the definite form of 


bands, &c., and sometimes, when starch granules are present, be- 

comes deposited on these as upon a nucleus. 

Observ. The relation of chlorophyll to starch is viewed in an essen- 
tially different way by Mulder, who rests upon my description of the 
former. He assumes that the chlorophyll granules are always produced 
from starch granules, since the latter become partly or wholly converted 
into the wax connected with the green colouring matter, and in so doing 
either assume the form of globules or become blended together, and pro- 
duce amorphous chlorophyll. This transformation of starch into "wax 
must be accompanied by an abundant evolution of oxygen gas ; and 
Mulder therefore believes that plants do not exhale this gas because they 
are green, but while they are becoming green. I cannot accept this 
theory on account of anatomical reasons, for in many young organs we 
find chlorophyll but not starch, which should precede it, and in the Con- 
fervas particularly, in which the chlorophyll occurs in the form of bands 

and plates, as in Zygnema, &c, these structures never consist of a sub- 
stance having any resemblance to starch, hut, on the contrary, the starch 

granules occurring in this chlorophyll increases in size with the age of the 

Observ. 2. I have described the chlorophyll granules as a softish, homo- 
geneous substance, and not as utricular structures, such as they were 
formerly stated to be by Sprengel, Meyen, Agardh, Turpin, and others, 
for I never could succeed in discovering upon them an enveloping- mem- 

brane distinct from the contents. Their utricular nature has, however, 
been defended in recent times by Nageli. {"Zeitschr. f. vriss. Botcm" 
iii. 110); according to his statements, a whitish membrane and green 
contents may be clearly distinguished in the large chlorophyll granules of 
the Algse, Charge, and Mosses. Also Goppert and Colin ("Bot. Zeit" 
1849, 665) say that in Nitella they saw the chlorophyll granules ex- 
pand by absorption of water into vesicles composed of a thin translucent 
membrane, which finally burst. I am not in a position at the present 
moment to test these statements respecting the chlorophyll granules of 
Nitella; but I have formerly frequently examined them and detected the 
occurrence of starch granules in the chlorophyll, but could never find a 
membrane upon the latter. Nageli believes, moreover, not only that he 
has seen a membrane in many cases, but that he has found proof of a 
complete analogy of these vesicles, with cells, in the phenomena of their 
vegetation. In this he is not warranted by a single fact ; for that the 

chlorophyll granules may grow, and during growth alter in form, is no 

proof at all of the cellular nature, any more than is the circumstance that 
their number may be multiplied by division as in Nitella. 



might occur in globules devoid of a membrane ; but that it depends on 
the formation of secondary vesicles inside the chlorophyll vesicles, is an 
hypothesis devoid of all foundation. 

Observ, 3. We know very little as yet of the anatomical conditions of 







the other colouring matters of plants. The reds and blues are usually 
dissolved hi the cell-sap ; in particular the red colouring matter of leaves, 
which acquire this colour in atitumn , that of most flowers and red fruits ; 
and in like manner the blue colouring matter of most blue flowers. Only 
in very rare cases do we find the red and blue colouring matter of flower 
in the form of globules, e. g., the red of Salvia splendens and the blue of 
Strelitzia regince. 


nected with a foreign matter forming the globules, or itself alone consti- 
tutes these is unknown. The yellow colour of leaves which are bleached 
in autumn consists of altered chlorophyll (Xanthophyll) ; in flowers the 
yellow pigment usually occurs in the form of globules ; but in other cases 
diffused uniformly in the cell-sap; in the yellow perigonial leaves of 
Strelitzia it has the form of slender, crescentically curved and irregularly 
wound fibres, which swim in the cell-sap. In the red coloured Algee, the 
chlorophyll seems, at first sight, to be replaced by red colouring matter, 
but according to the researches of Kiitzing (" Phycologia generalis" 21), 
green chlorophyll granules are also present, only their colour is hidden by 
the red colouring matter which accompanies them. 



still mor 

are without it. 

phyll, since perhaps no plants except the Fun 
Whether or not starch occurs in an amorphous condition is sun 
doubtful. Schleiden (" Grundzuge" i. 181) believes that he found 
it in this state in Sarsaparilla, in the rhizome of Garex arena- 

" ~ is. It is likewise 

mm mm 

doubtful if it occurs in a state of solution, for I have repeatedly 
seen the sap of particular cells, particularly of Zygiwma, but 
also of Phanerogamia, e. g., of the Potato, acquires _ a wine-red 
colour with iodine ; but this colour is no certain sign that we 
have to do with starch. 


versally is that of small, colourless, transparent granules, which are 
accumulated in the cells without definite ' 



tVVV-' U.XXA W.XW w ^* - ■%— ^ 

variable number, sometimes swimming freely in the sap, some- 
times slightly adherent to the wall. Their size varies from 
an immeasurably small diameter to a magnitude visible even to 
the naked eye (according to Payen from 2-1000ths of a milli- 
metre in Ghenopodium Quinoa, to 185-1000ths in the Potato) ; 
granules of very different diameter occur together in the same cell, 
but the maximum size of the granules of each plant is tolerably 


Like the size, the form of the granules varies extremely in dif- 
ferent plants, and is sometimes so characteristic, that in many 
instances we can determine with tolerable certainly, by the m icr o- 


the source where a starch has been obtained. Small 


miles are mostly regularly globular ; but the larger lull-grown 


exhibit very 

irregular forms 

m many plants, being 

sometimes elongated into the shape of rods, sometimes flattened, 

sometimes made to 


sometimes made to assume angular ioim uy uiuuua± [ 
and mostly possessing irregular projections. (See the 






by Fritzsche in " Poggend. Ann." part 32 ; of Payen in "Mem 

n /r. ~„ 7 ^~ 7~^ 7 _-_#_ .7 ._ T7" . .. i. _ J.> T r» rN i t • t • t • 


and of Schleiden in his 

" Grundziige.") 

The starch granules of different shape agree in the 
circumstance that they are not composed of one uni- Fi 9- 46 - 
form mass, but of super-imposed layers of varying 
density, whence they derive a pretty appearance with 

polarized light, each granule exhibiting a coloured 
cross. These layers are usually much thicker on one 
side of the granule than on the other (fig. 46), so that 
the organic centre is far removed from the middle 
point, and often closely approximated to the surface. 
In fresh granules there is no cavity in the centre, but sta J^ f^o 8 of 
one is readily produced by dessication and by the 
contraction this produces of the internal softer substances. This 
process may be traced very beautifully under the microscope, by 
removing a part of the water, by strong alcohol, from fresh starch 
granules taken from the Potato. In this case a little globular 
cavity is first formed, and then radiating fissures soon run out in 
all directions, traversing the layers of the granule at right angles. 


softer, and 

more swollen up by water than the outer. But the firmness is 
still so great that the starch granules may be broken up into 
angular pieces by pressure. Cold water does not exert any sol- 
vent power over them, even when the granules are cut into thin 
slices, so as to allow the water to come immediately in contact 
with their inner layers. In boiling water they swell very much, 
even a hundred times their original volume, without actual solu- 
tion. The same effect is produced by the action of strong acids 
and caustic alkalies. When iodine and water act simultaneously 
either in the swollen or unswollen granules, these are coloured, 
according to the amount of iodine they absorb, wine-red, indigo- 
blue, and up to the deepest black blue, without undergoing any 
alteration, for when the iodine is removed again by alcohol, they 
again possess their original properties. 

In all vegetable cells starch is a transitory product, destined to 
be re-dissolved at a later period, and applied to various purposes 
of nutrition. Thus the starch disappears from the albumen of the 
seeds of Palms about the period of maturation, and in its place 
appears a fixed oil, for which it undoubtedly furnishes the mate- 
rial ; thus it disappears in the elaters of the Liverworts when the 
spiral fibre is developed in them; and it vanishes during the ger- 
mination of seeds and bulbs, serving for the nutriment of the 
young plants, &c. It is unknown at present in what way the 
solution of the starch granules takes place in these cases ; when 
artificially converted into dextrine and sugar, by diastase or sul- 
phuric acid, a swelling up of the granules precedes its transforma- 
tion ; but this does not happen in the living plant, for the sub- 





sta,nce of the granule remains solid, and is corroded and dissolved 
layer by layer from without inwards. 

Observ. 1 . 


the development of starch granules. That they are origmally small and 
roundish, is decided, and the laminated structure proves that the increase 
of size does not depend on the expansion m all directions of the original 
granule, but on gradual deposition of layers produced ^^ively. As to 
the order of the succession nothing is known. n ™ OTr m 


softest and richest in water, that the innermost layer * the >J**g*> 
when we follow this hypothesis we must naturally assume that «-mi,lta- 

neouslv with the deposition of each new layer, or rather of a new central 
nucleus which is by subsequent growth to be converted into a layer, 
all the old layers expand, and exhibit an increase of thickness, the more 
irregular the older they grow, since the eccentricity of the organic centre 
increases with the size of the granule. Or we may conclude, on the con- 
trarv with Fritzsche and Schleiden, from the young starcn granules being- 
globular, and the innermost layers of full-grown «^^Jg™% 
a globular form, while the outer layers exhibit an irregular thickness on 
their different sides,-further from two starch granules lying ^e by de, 
being sometimes enclosed in a common external layer— that the outer- 

he youngest. * , x , 

uoserv * Most recent researches upon starch indicate that all the 
lavers of ' the granules are composed of one and the same substance and 
that there is no enveloping membrane contrasting with the contents. 
But the latter is likewise asserted in many hands Several German phy- 

most layer is the youngest. 
Observ. 2. 


totomistJS, especiauy ojjxou.gcx, i^u ^^-j -~^~ ^ 

tures occurring in cells as vesicles and as the rudimem of cehs but 

Turpin ( 

Mem. du M<< 

("J^sJle dela CMmie organique") were the authors who especially deve- 
loped and disseminated this theory. Turpin regarded the granular struc- 
tures which occur in cells (therefore starch and chlorophyll m particular), 
comprehended by him under the general name of globuhne, as i vesicles 
wlnl sprouted from the cell-walls, were attached by an umbilicus (for 
which be took the hilum of starch granules), and grew into cells by subse- 
quent enlargement. These views obtained greater diffusion m regard to the 
starch granule through Kaspail, and much credit was given to his state- 
ment that it was composed of an outer membrane resisting the action of 
water and inner contents soluble in water and consisting of gum. All 
to has been, very properly, long since forgotten, for all these statements 
re t upon the most wretched observations j but the utricular nature of 
the starch grain has been again defended recently by mgeh(«Zetischr. 
fwiss BoC hi., 117, Bay Society's Bublications, 1849, p 183). Accord- 

IX him, the'starch g/ain consists of ^^^J^rTTU 
concentric layers are deposited on the inside of the membrane, as in 
Wfrm g cells, thus the cavity of the vesicle is reduced to the sma lest 
possible size, being, however, always filled with fluid. Evidence for these 
statements is sought for in vain, even in the plants named by Nageh, m 
which he affirms that he found the outer membrane tolerably thick and 
uncolourable by iodine; wholly derived from his imagination is the fur- 
ther statement that the granules rendered angular by mutual pressure 






originate together inside a chlorophyll granule; for granules of this kind 
are met with in subterraneous parts, in which no trace of chlorophyll occurs, 
as in the rhizome of Gloriosa superba. 

In many plants the starch is replaced by inuline, in many 
parts, especially in the roots ; e. g., in the tubers of the Dahlias, 
oiHelianthus annuus, &c. Since we possess no re-agent for it 
this substance still escapes from microscopic investigation, even 
if Schleiden's statement, that it occurs in the form of small Gra- 
nules^ is well founded. Thus nothing is known respecting 3 its 
diffusion in the Vegetable Kingdom. 



by iodine, this was the case with an inuline prepared from Taraxacum 
by Mulder, which I had an opportunity of examining. Other inuline, 
which Prof. Chr. Gmelin prepared for me from the Dahlia, was not colour- 
ed m the least by iodine, even when I added tincture of iodine to the hot 
solution, before the inuline was precipitated from ifc. 

d. Compounds dissolved in the cell-sap. 


Certain compounds, most closely allied to starch and inuline, 
escape from microscopic observation almost under all circum- 
stances, notwithstanding their wide distribution in the Vegetable 
Kingdom, because they are dissolved in the cell-sap, and there are 
no means of detecting small quantities of them ; these are dextrine, 
gum, and sugar. 

Dextrine seems to occur in all organs which are the seat of an 
active process of nutrition, but can only be discovered in the ex- 
pressed saps, not by microscopic observation. 

Other kinds of gum, gum arabic, cherry-gum, tragacanth, the 
mucilage of the seeds of Quinces, of Linseed, &c, playing a compara- 
tively subordinate part, being diffused through but a small part 
of the Vegetable Kingdom, are mostly to be considered as secre- 
tion in the^ plants in which they do occur, and frequently are only 
met with in isolated parenchymatous cells, as in Cactus, or in 
the cells of particular organs, such as the seed-coats, or in cavities 

and canals which lie between the cells, as in the CycadeEe. Wh 

such kinds of gum completely fill the cells or canals in which 
they occur, they may be detected by the dense, slimy mass which 
they form with water, or by the coagulation caused by alcohol ; 
in many cases, for instance in the cells of the seed-coat of Gydonia, 
it is doubtful whether the gum is to be regarded as a substance 
secreted in the cavity of the cell or as forming secondary layers in 
it. In any case the substance of which many cell-membranes 
swelling up strongly in water are composed, such as the secondary 
layers of the cells of the seed coat of Collomia and of the pericarp 
of Salvia, seems to be closely allied to these kinds of gum. So 
long as these mucilaginous substances remain so loosely charac- 








terized by chemists, and no re-agents for them have been made 
out, vegetable anatomists are not in a position to make out their 
distribution in the Vegetable Kingdom, or their importance to 

the plant. 

Sugar is very widely distributed, especially cane-sugar, since it 
not only replaces starch in many plants at the time just preced- 
ing flowering, as in the Sugar-cane, the Beet, &c, but still more 
frequently precedes the deposition of starch in an organ, and is 
also formed at the solution of the starch as in trees in Spring, in 
germinating seeds, &c. Neither Cane nor any other sugars (grape- 
sugar, fruit-sugar, mannite, &c.) are objects for microscopic obser- 
vation, since they are dissolved in the cell-sap, and we are without 
re-agents for them. 

Although occurring in a fluid form, the fixed oils are readily 
detected by their refusal to mix with water, and by their strong 


power, when they occur in abundance, 


— ~& 

do principally in the seeds of many plants, more rarely in the 
coats of the fruit (in Olives, many Palms, &c), still more rarely in 

the organs of vegetation (tubers of Gyperus esculentus). 


when they exist only in smaller quantities, as is the case in a great 
number of plants, they escape observation by the microscope, since 

they are not then separated as cl early visible drops floating in th 
cell-sap, but are combined with the proteine substances. The 
essential oils, when produced in large quantity, usually com- 
pletely fill isolated ceils, or groups of cells and cavities which lie 
between cells, and then are easily discovered ; on the other hand, 
in very many cases they seem to exist in such small quantities, 
that they are wholly dissolved in the cell -sap ; at all events they 
cannot be visibly demonstrated in the greater number of petals. 

All plants prepare a more or less abundant quantity of organic 
acids (oxalic, malic, citric, tartaric acid, &c), which are found only 
in exceptional cases in a free condition, usually combining with 
bases into acid-salts dissolved in the cell-sap ; and many of the 
inorganic acids, which the plants receive from without, remain 
undecomposed. The greater part of these salts, especially those of 
the alkaline bases, escape microscopic examination by their solu- 
tion in the cell-sap ; but there is scarcely one of the higher plants 
in which some organ or other does not secrete in the cavities of its 

cells insoluble salts of the earths with organic or inorganic acids, 
in the form of crystals. This usually takes place in cells which 
contain no granular organic structures; but crystals, and chloro- 
phyll granules, and the like, do not necessarily exclude one 
another. In particular cells situated at the ^ upper sides of the 
leaves of many Urticacese, e. g., in Morns, Ficus elastica, &c, is 
found what appears to be a peculiar organic structure (a coni- 
cal projecting process of the internal wall of the cell, formed 
of cellulose), upon which crystals are agglomerated as upon a 




Crystals occur sometimes singly in a cell, or in numbers irregu- 

larly scattered, combined into star-shaped 
groups, or laid side by side in the form of 
a bundle. Th6 last condition (fig. 47) is 
the most frequent, for there can scarcely 
exist a plant in which have not been 
found in some organs, for instance the 
anther, or in the bark, such bundles of 
very fine, needle-like four-sided crystals, 
terminating at each end in four-sided py- 
ramids (De Candolle's " Raphides"). The 
composition of these needle-like crystals 

is variously given ; according to Pay en 

Fig. 47. 


and Schmidt, they are composed of oxa- 
late of lime ; according to Buchner and 
Trinchinetti of phosphate of lime ; ac- 
cording tO NeeS VOn Esenbeck Of a double Needle-shaped crystals, from the 

salt of lime and magnesia with phosphoric ^fc^ 
acid. In very many plants, e. g., very 

beautifully in the Rhubarb-root, occur four-sided rather obtusely 
pointed prisms of oxalate of lime ; and moreover very frequently 
mulberry-like agglomerations of rhombohedrons, which are com- 
posed of carbonate of lime, more rarely of tartrate of lime (in old 
Cactese), and sulphate of lime (in the Musacese). (See " Unger 
on " The Formation of Crystals in Vegetable Cells" in the "Ann. 
of the Vienna M us." Th. ii. — Payen " Memoir es sur les Developpe- 
ment des Vegetaux" — Schmidt "Sketch of a General Method of In- 
vestigating the juices and excretions of the Animal Organism") 




It is an universal law in the development of cells that the 
contents are formed before the cell-membrane, and that the orga- 
nization of the nitrogenous structures precedes that of the mem- 
brane composed of cellulose. In plants, the formation of cells 
occurs only in the cavity of older cells, and not between or upon 

The formation of the cells takes place in two different ways : 
1, through division of older cells; 2, through the formation of 
secondary cells (tochter-zellen) lying free in the cavity of a cell. 


Observ. It would be superfluous to give an account of the older 
theories of cell-formation which had existed up to the appearance of my 
dissertation on the multiplication of vegetable cells by division, in the 
year 1835, since none of them were based on any secure foundation. 
Actual origination of cells had been observed only in pollen-grains and 
spores, but the connexion of the formation of these with cell-formation in 
general was altogether overlooked, and the emptiest conjectures had been 
ventured as to the origin of cells from chlorophyll and starch-granules, 







1 \ 



from the globules of the milk-sap, from cavities appearing in a homo- 



to solve the problem of cell-formation by careful observation of the deve- 
lopment of Marchantia, but he did not succeed in finding out the mode 
of development of the single cell; he believed that he discovered three 
modes of formation of cells : a, between other cells (developpement inter-u- 
triculaire) ; 6, on the surface of other cells (devel. super-utriculaire) ; c, in 
the cavity of other cells (devel. intra-utricidaire). But all more recent 
observations speak decidedly against the existence of the first two modes 
of development described by Mirbel. It is true that Kiitzing (" Phyco- 
logia generalise 64) has assumed the formation of cells in the intercel- 
lular substance, and, in like manner, Unger (" Grundz. der Anatomie? 45) 
attributes this process to the Phanerogamia. Neither of them, however, 
have any adequate evidence for the support of their views. In the dis- 
sertation just spoken of, I sought to demonstrate in the Cryptogamic 
water-plants, that the earlier notion of the necessity of cells originatin 


under the form of very small vesicles was false, and that division of the 
cells takes place by the formation of partitions, which cut off the contents 
of the parent-cells into separate portions ; but it was not until I had 
discovered the primordial utricle that I was able to trace accurately the 
processes in the formation of this septum. (See the revised edition of this 
paper in my u Vermischt. SehrifC 1845.) Before this had happened 
Schleiden ( "Beitrage ztir Phytogenesis, 
in "Taylor's Scientific Memoirs," vol. ii.) had discovered the free cell-for- 
mation, and declared it to be the sole mode of formation of cells, whereby 
the whole theory of the development of cells was pushed into a false direc- 
tion, from which it has been chiefly brought back into the right path by 

Unger and Nageli, who demonstrated the great prevalence of the process 
of cell-division. 

" in "Midler 

a. Division of the Cell. 


undergone by the primordial utricle of the dividing cell, in conse- 
quence of which partitions are developed, growing gradually 
inwards from the periphery of the cell, and dividing the cavity of 
the cell into two or more separate compartments. This process 
is preceded in almost all cases by a formation of as many nuclei as 
there are to be compartments in the mother-cell ; in rare cases this 
process does not occur, and the changes of the cell-contents are 


mordial utricle. 

I investigated the 






exhibits growth and cell-multiplication at two places, 
cipal trunk of it consists of a row of cylindrical cells of pretty 

(a) becomes elongated 
(fig. 2), and then divided in the 


twice the length of a cell 

middle (fig. 2 a), by a cross-partition, into two cells of the usual 
length, of which the lower remains unaltered, while the upper 
undergoes the same changes as the previous terminal cell, &c. 



While the filament is becoming longer in this way, the membranes 
of many of the older cells of the filament become protruded out 

sideways at the upper end (fig. 1, h), the process growing gra- 

dually into a cylindrical branch (fig. 1, c) as large as a cell, which 
then becomes shut off at the base from the stem-cell, by a parti- 
tion (fig. 1, d) ; then it presents the same elongation and the 

same division in the middle (fig. 1, e) as the end cell of the stem 
exhibits, thus producing a branch, which is capable of ramify in 

again in like manner. 

So that consequently, there are never any small cells, which 
would be required to grow, formed in these plants, but every cell 
possesses from the first very nearly the dimensions to which it is 
subsequently fixed, only a slight growth in width occurring in it. 

The process of the formation of the septum is as follows : the 

cells are lined by a primordial utricle, on the inside of which 

6), which by the 
of the plant, such as 


lies a layer of chlorophyll granules (pi. 
action of substances injurious to the life 

figs. 5 

alcohol, acids, &c, are separated from the primordial utricle (fig. 
5 a), while this also under the same circumstances becomes de- 
tached from the cell- wall. At the place where the partition is to 

be formed, an annular fold grows inwards, gradually contracting 

and parting off more completely the chlorophyll layer, which is 
detached from the primordial utricle for some distance (fi 

During this time a cellulose membrane is deposited all over the 
outside of the primordial utricle (figs. 3, 4) ; so far as this lies be- 
tween the outer surface of the primordial utricle and the inner 
surface of the dividing cell, it constitutes the youngest and inner- 
most of the secondary membranes of the latter ; but at the point 
at which the primordial utricle forms the fold just described this 
cellulose layer is continued into the duplicature of the fold, and 
thus forms an annular, thin, imperfect septum composed of two 
layers. This annular fold, and the cellulose membrane lying in 
it, contract more and more upon the central orifice until this dis- 
appears, the chlorophyll layer and the primordial utricle are cut 
off into two portions, and the cellulose membrane presents itself 
as a perfect partition (fig. 6). Thus, without important disturb- 
ance of the contents of the mother-cell, two secondary cells are 
formed in it, which receive within them the whole contents, and 


contact with the 

membrane of the parent-cell serve as layers of thickening to it, 
while where the secondary cells touch they appear as a partition 
of the parent-cell. 

Observ. 1. I have given a somewhat detailed account of these pro- 
cesses, because I believe that I have traced them more minutely than 
others have done. 

ZeitschrifC i. 98) thinks that my description 
the parting off of the cell-contents by a fold growing inwards in the 
I, is incorrect j he denies to the primordial utricle the characters of a 


cell , 

meiuDrane, and contends that it is a layer of mucilage, not sharply de- 

e 2 







fined internally, and to the interior of which the chlorophyll granules 
adhere ; he further assumes of the chlorophyll mass, that it is not sepa- 
rated gradually from without inward, into two parts, hut at once across 
the whole cavity, and at this point the mass of mucilage at the same 
time, and suddenly, forms a double layer as a cross wall, which secretes 
the true cell-membrane. These statements do not all agree with nature ; 
the formation of the septum is gradual, the time required for its forma- 

;orcling to Mitscherlich (" Monatsber. d. Ahacl zu Berlin" 

—5 hours, 

A T ov. 1847) to 4- 

Observ. 2. The division of cells without previous formation of a nucleus 
appears to occur only in cellular plants and especially in the Algee. It 
has been observed by JSTageli in Oscillatorise, Nostochinese and Diatomese. 
It has been extended to the Phanerogamia by Unger, who thought he 
saw nuclei first appear in already formed cells in many cases, a state- 
ment which certainly depends on error of observation. 



(See " Folke, Physiol. Studien. 


ft ; Rail 


Desmidiece," 5.) In these unicellular Algse the cell consists of two 
symmetrical halves, the boundary between which is sometimes 
indicated only by a line (e. g., in Glosterium) , and sometimes lies 
hidden in an often very considerable constriction (e. g., Euastrum 
Cosmarium). When the cell divides, these two halves of the cell 
separate from each other, while a new portion is developed be- 
tween _ them, consisting of a very delicate pellicle forming a con- 
tinuation of the cell-membrane, and this new portion becomino- 
divided into two parts in the middle by a septum, the original 
cell is separated into two, each of which is composed of half of 
the original full-grown cell, and one of the very small rudiments of 
a second half. This second half grows until it equals the older 
half in size and shape, whereupon the subdivision begins again. 
It is doubtful whether, as Ralfs assumes, the same process occurs 



In all cases of the division of cells in plants having a stem and 
leaf, and likewise in many cases among the Thallophytes, the 
formation of the septa is preceded by the development of as many 
nuclei as there are subdivisions formed in the cell. The mode of 
origin of these nuclei is two-fold : either they are formed anew 
or an existing nucleus separates, by division, into several. ' 

When nuclei are formed anew in a cell, masses of protoplasm 
not sharply denned outside and increasing in density inwards, be- 
come accumulated at the points where the nuclei are to appear. 
Later on, especially by treating with iodine, we may observe in 
the middle of each of these masses a globular body formed of 
mucilaginous granular substance, more hom ogenous and frequently 
far more transparent than the surrounding protoplasm, often 
clearly denned externally, and almost without exception contain- 

. • 



ing one or more sharply circumscribed round granules (the nucle- 
oli, KernkorperchenJ ; the large round bodies are called the nuclei 

(zellen-hern) or cytoblasts. The nuclei are usually smaller at 
their first appearance than they are afterwards, so that their 
rowtli is unmistakable. The surface of perfect nuclei appears 
smooth and clearly defined, but it cannot be decided with cer- 
tainty whether we ought to distinguish an enveloping membrane 
and contents distinct from this, or to ascribe the membranous as- 
pect of the outer layer to a somewhat greater density ; the nucleoli 
always appear solid at first ; they often become hollowed out into 
vesicles subsequently. The substances both of the nucleus and 
of the nucleolus are coloured yellow by iodine. 


Observ. Opinions differ very much as to the mode in which the nucleus 
is formed from the granular protoplasm. Schleiden was the first to dis- 
cover the import of the nucleus and to trace its development. Accord- 
ing to his views (" Grundziige" 3 ed. i, 208) they originate by the formation 
of large granules in the protoplasm (afterwards the nucleoli) and other 
granules becoming heaped up around these, and the whole becoming 
more or less blended together and united into the nucleus. According to 
JSTageli's views (" Zeitschrift. f. wiss. Bot. III. 100, Ray Society's Publica- 
tions" 1849, p. 166), the nucleus is not formed by the union of a consider- 
able mass at once, but appears first as a very minute structure, for the 
rudiments of the nuclear body may be distinguished while they are yet 
little larger than the globules of the protoplasm. He also assumes that 
the nucleolus is formed first, and then a layer of protoplasm is deposited 
around it, which again becomes enclosed in a gelatinous membrane not 
coloured by iodine ; Hofmeister (" Entwich. d. Pollens? in "Bot. Zeit" 1848. 
"Die Enstehung des Embryo" 1849, 62) declares distinctly against both 
these opinions. According to his researches, the formation of the nucleus 
is not preceded by the origin of nucleoli, but the nucleus presents itself 
first under the form of a globular drop of a mucilaginous fluid, which be- 
comes coated by a membrane over its outer surface. In many cases no 
trace of a nucleolus can be seen in the nucleus at first, and one or more 
(up to twenty) are subsequently formed in it, while in other cases one 
or more granules of a more solid substance swim in the fluid of the nucleus 
from the very first, but not all of these are necessarily developed into 
nucleoli, for only some of them can increase considerably in size and ac- 
quire a membranous coat, the others becoming dissolved. Leaving out of 
the question the membrane of the nucleus and of the nucleoli, the exist- 
ence of which I never could satisfy myself, this latter view appears to me 
the more correct ; that of Nageli decidedly wrong. 

The second mode of origin of a nucleus, by division of a nucleus 
already existing in the parent-cell, seems to be much rarer than 
the new production of them, for as yet it has been observed only 
in few cases, in the parent-cells of the spores of Anthoceros, in the 
formation of the stomates, in the hairs of the filaments of Tra- 
descantia, &c, by myself, Nageli, and Hofmeister ; but it is pos- 
sible that this process prevails very widely, since, as the preceding 
statements shew, we know very little yet respecting the origin of 











nuclei. N. 

sion, tne membrane of the nucleus forming a partition, and the 
two portions separating in the form of two distinct cells. I was 
quite as unable to see such a membranous septum and a mem- 
brane on nuclei generally, and the division appeared to me to take 
place by gradual constriction. According to Hofmeister's descrip- 
tion (" Enstehung des Embryo," 7) the membrane of the nucleus 
dissolves, but its substance remains in the midst of the cell ; a 
mass of granular mucilage accumulates around it; this parts, 
without being invested by a membrane, into two massp.s and 

(tochter-lceme ) 


It is still an unsolved question how often the process of divi- 
sion of the nuclei can be repeated, whether it continues indefi- 
nitely, or whether after one or more divisions it becomes extinct, and 
the formation of a new nucleus becomes necessary. In the spores 
of Anthoceros I found a second division, for in the parent-cell of 
these a mass was formed, which first parted into two subdivisions 


same in the development of pollen-grains (" Zur Entwickelunqs- 
gesch d. Pollens."— Bot Zeit, 1850, 225). In these cases, there- 
lore, a twofold division occurred. But, according to Wimmel, 
the case is different in the formation of the parent-cell itself, for 
when one of these cells is about to divide, a new nucleus is formed 
in it, which becomes divided and gives rise to the development of 
two secondary cells. When one of these secondary cells is ^fco be 
divided again, its nucleus takes no part in it but becomes absorbed, 
a new nucleus being formed which divides, &c, so that here each 
nucleus is capable only of one division. 

The number of nuclei that are formed in a cell varies very 
much ; in most cases there are two, as in the formation of paren- 
chymatous cells in the bark and the pith, in the formation of 
wood-cells in the cambium ; but in elongated cells, particularly 
in hairs which become articulated, half a dozen or more nuclei are 
often found lying in a row. In like manner varies the proportion 
of the size of the nucleus to the cavity of the cell ; in the paren- 
chymatous cells of wood, in the cells of bark, and of the suberous 
' of the Dicotyledons, I found the nucleus relatively very 

small ; but in the hairs, in the cells of very small organs still con- 
tained within the bud, as in the young leaves, in the cells of the 
apex of the root, in which organs the cells, divide while they 
are still very small, the nuclei occupy a very considerable portion 
of the cavity of the cell. 

The formation of nuclei is soon followed by that of septa be- 
tween every two of the former, which is effected by the primor- 
dial utricle becoming folded inwards in the same manner as de- 

a partition is formed 



scribed above 


reaching to the centre of the cell, and by the deposition of cellulose 



membranes on the outside of the primordial utricles during this 
process, which membranes form secondary layers to the parent- 
cell where in contact with its walls, and laminae of a partition 
dividing the parent-cell where in contact at the point of junction 
of the two secondary cells. The number and direction of then- 
septa depend altogether on the number and position of the nuclei, 
since each of these becomes the centre of a secondary cell. The 
secondary cells accurately fill the cavity of the parent-cell, so that 
there is no trace of inter-cellular passages running between them, 
and the entire contents of the parent-cell are taken into the cavi- 
ties of the secondary cells. 

Since the membrane of the secondary cells deposited during 
the formation of the partition is immeasurably thin, while the 
membrane of the parent-cell usually possesses, before the division, 
a perceptible, often considerable, thickness, we naturally find, on 
examining a cellular tissue shortly after the division of the cells 
(fig. 48), a very considerable difference in the thickness of the dif- 


Fig. 48. 

External layers of the rind of Cerens peruvianus.—a, cells of the rind with contracted primor- 
dial utricles contracted, in part containing newly-formed septa (e). a Cork-cells ; &, the outer layers of 
the rind-cells, newly-formed by the division of the latter ; c, cells of the epidermis ; d, cuticle. 

ferent sides of the cells composing it, for some of the walls consist 
of the blended membranes of the secondary cells, others of these 

of the narent-cells. This condition is in 


a high degree striking in the investigation of many organs in 
which the development has just begun, e. g., in the formation of a 
periderm in the outer cells of the bark, where most of the newly- 
formed and thin septa run parallel with the epidermis ; in cam- 


■ ■ I 






bium, where the septa lie parallel with the bark; in jointed hairs, 

&c. When 

, . j ~~— ^^xxa^au ixu ±±x\j±^ } ui uulu very nt/iie 

growth, this condition of the thickness of the walls is permanent 
ana it is possible, when the membranes of the secondary cells 
have been thickened by the deposition of layers, to distinguish 
tneir membranes clearly, in their whole course, from the mem- 
brane o± the parent-cell, e.g., in the pith of Taxodium distichum. 
Un the other hand, when, as is usually the case, the secondary 
cells increase much in size after their production, this condition is 



naturally share in the expansion of the secondary cells, and be- 
come thinner m proportion to this expansion ; in consequence of 


sion of the secondary cells is repeated. 

It has already been observed that the secondary cells completely 
fall the cavity of the parent-cell at their first origin. Thus no 
traces of intercellular passages can be found in tissues in the first 
stages oi their development. The passages are formed subsequently 
by the separation of the cell-membranes at the angles of the cells 

and are not, as is usually represented, the remains of free open 
spaces between globular cells which have been compressed together 

in consequence of growth. 

In like manner the stomatal pores 

are produced by the separation of two cells formed by the divi- 
sion of a parent-cell. 

Observ That the formation of cells in all the organs of plants (ex- 
cepting the cells originating in the embryo-sac) depends upon the division 
ol older cells, an opinion which could not, for a long time past, be op- 
posed by any careful observer, unless he were misled by preconceived 
notions. Even Meyen (« Physiologies ii. 334) declares this process of cell- 
lormation to be very general; but linger (« Linnma? 1841, 402; " Bot 
Zed., 1844, 489), who subsequently applied to this process the term me- 
rismatic cell-formation; andNageli (« Zeitschr. f wiss. Bot.," iii. 49 1846) 
who used the expression parietal cell-formation, more especially asserted 
the general occurrence of this process of formation ; the former declaring 

to be the usual mode, the latter ascribing to it the production of all vege- 
tative cells. & 

But circumstances occurring in the division of the cells were inter- 
preted in a different way from what I have done. Meyen assumed that 
the cell-membrane itself became folded inwards, and in this way formed the 
partition, which is decidedly incorrect. Unger thought the septum to be 
originally simple, splitting afterwards into two lamella ; Nageli denied 
that the septum is formed gradually from without inwards, assuming that 
the membrane of the secondary cell is formed simultaneously all round its 
cavity, whence it would of course result, that the septum composed of the 
membranes of two contiguous secondary cells would be formed at once 
across through the cavity of the parent-cell. 

In reference to this latter point, I, of course, readily admit that one 
seldom succeeds m observing the gradual development of the septum in 


- - : * ^ •*. _ ■ ■ 




consequence of the folding in ward of the primordial utricle, but in par- 
ticular cases I have seen this process most distinctly. The description 
given above rests chiefly on observations which I instituted upon the 
parent-cells of pollen-grains, and in the cells which separate from each 
other in the pore-cells of stomates. Mirbel (" Eecherches sur le Marchan- 
tia") detected, in 1833, that the parent-cells of the pollen-grains divide 
by septa which grow from without inward ; but the correctness of this 
statement was denied by Nageli (" Entwickelungsgesch. d. Pollens" 1849), 
who asserted that secondary cells (which he called special parent-cells) 
were formed in the interior of the parent-cells, and that the seeming septa 
were nothing else than the coherent walls of these cells, which were not 
formed in the direction from without inwards, but simultaneously all over 
the contents, — a view which was shared also by Hofmeister (" Entw. d. 
Pollens" — Bot. Zeit. 1848, 654). That these representations are incorrect, 
and that the septa grow from without inwards {see pL 1, fig. 8 — 11, 
which represent different stages of development of the parent-cells of the 
pollen-grain of Althoea rosea), was already stated by Unger (" Ueb meris- 
matisch. Zellenbildung bei der Entwick der PollenJcorper" — " Bericht. der 
Ver. der Naiurforsch. zu Gratz"), and no doubt remained in my mind, 
since I succeeded in bursting parent-cells of pollen-grains, the septa of 
which were but half-formed, and pressing free the primordial utricle (pi. 1 , 
fig. 10), which was half constricted by folds passing inwards, into four 
globular subdivisions connected together into a common cavity in the 

Lave elsewhere (" Verm. Sehrift." 252) sought to demonstrate 



of secondary cells in the parent-cell, with an intercellular space running 
between them, as Nageli states. The observations of Henfrey (" Annals 
of Nat History" vol. xviii, 364) are in exact accordance with mine. Of 
course one does not succeed in the vast majority of cases of the examina- 
tion of a tissue where the cells are in course of development, in observing 
the gradual growth of the septa from without inwards, and when I as- 
sume that this process occurs universally, I certainly rest upon the analogy 
to the few cases in which I have traced their gradual development ; but 
it seems to me more logically correct to lay the main stress upon a few 
accurately investigated cases, than to disregard such observations, and to 
use as the basis of the theory of the development of cells, the imperfect, 
though numerous, observations in which the gradual growing in of the 
septum was not seen, but the mode in which it really was formed was not 
perceived at all. 

6. Free Cell-formation. 


In free cell-formation, the cell-membrane is developed over the 
surface of a mass of nitrogenous substance swimming in a fluid 
which contains formative matter, without the co-operation of a 
parent-cell. In the regular course of vegetation this process of 
cell-formation occurs only In the interior of cells ; it may occur 
independently of the life of the parent plant in the creation of 
parasitic Fungi, Yeast cells, &c, both in the decomposing fluid of 
cells and in the excreted or expressed juices. In normal free cell- 
formation the secondary cells usually possess but a very small size 









in comparison with the parent-cell, and stand in no connexion, or 
at least, not a necessary one, with the walls of the latter. 

In the Phanerogamia, free cell-formation occurs only in the 
embryo-sac, in which both the rudiment of the embryo (the em- 
bryonal vesicle) and the cells of the endosperm originate in this 
way ; inthe Cryptogamia it occurs only in the formation of spores 
in the Lichens, and some of the Algae and Fungi. 
t The formation of free cells is usually preceded by the produc- 
tion of nuclei. _ In this case more or less abundant accumulation 
of protoplasm in the parent-cell forms the first sign of the second- 
ary cells. This sometimes fills up the cavity of the parent- cell, 
e. g., in the parent-cells of the spores of the Lichens, Pezizce, &c, 
sometimes it occurs in relatively small quantity under the form 
of cloudy masses not sharply defined, and of currents, as is usual 
in the embryo-sac (pi. 1, fig. 12, s). In this protoplasm are formed 
isolated points of concentration in the form of more or less trans- 
parent nuclei, around which accumulates a variable portion of the 
surrounding protoplasm, originally exhibiting no decided outline, 
subsequently clearly defined by the formation of a primordial 
utricle over the surface, which is rapidly followed by the produc- 
tion of a cellulose membrane enclosing the whole nitrogenous 
contents (pi. 1, figs. 13, b ; 14, 6). 

Observ. To Schleiden belongs the merit of discovering free cell-formation 
and the dependance in which the origin of a cell stands to the formation 
of a nucleus ; but he was led by this discovery to the misconception that 
this was the only mode of formation of the cell occurring in nature. In 
accordance with this hypothesis, the cells which were formed in other cells 
would always be much smaller than the parent-cells, and would gradually 
expand until they filled up the cavity of the parent-cells, and their walls 

into contact. But as the whole process could not take place in 



nules, or the like, without the displacement of these structures, and yet in 


present after the division, Schleiden invented an hypothesis to explain the 
circumstance, namely, that these structures in the cavity of the parent- 
cell were dissolved outside the secondary cell, and formed a-new inside it. 
But as nothing of this process can be observed in nature, it alone suffices 
to refute the doctrine of the universality of free cell-formation. Even 
when quite recently, in consequence of Nageli's observations, Schleiden 
("Grundz" 3rd ed. i. 213) can no longer deny that a division of cells does 
occur, still he is far from acknowledging the universal diffusion of this 
process, since he only refers to the older notion, retracted by Nageli 
himself, that this mode of formation occurs in the Phanerogamia or in 
the special parent-cells of the pollen-grains, and altogether ignores the 
fact that JSTageli and others have shewn this to be the mode of formation 
of all cells except those originating in the embryo-sac ; consequently, 
Schleiden still ascribes to free cell-formation an influence on the develop- 
ment of the plant which by no means belongs to it. When he states 
that the cells are developed in this way in the embryonal vesicle, this is 



decidedly false, for all recent observation s agree in shewing that the em- 
bryo originates from the germinal vesicle by cell-division ; not less incor- 
rect is it, that free cell-formation may be traced in j ointed hairs, and j ust 
as little does it accord with the mode of formation of other plants that, as 
is stated {"Grundz? i. 211), cells are formed in cells, and the parent-cells 
absorbed, in the points of the roots and shoots of the stem of Gypripe- 
dium. The entire representation proves that Schleiden has never once 

observed the division of a cell. 


The first account given by Schleiden (" Beitr. zur Phytogenesis 
Archiv" 1848) of the process of cell-formation, was faulty in many re- 
spects. He altogether overlooked the important circumstance that the 
nitrogenous substances were the originators of the formation of the 
nuclei and the cell, for he believed the granules of protoplasm, which 
he denominated mucilage (schleim), to be identical with the granules of 
gum, and thought that the protoplasm might be replaced by starch, and 
go through similar metamorphoses ; for he expressly mentions that starch, 
or the gramilar mucilage replacing it, is present in the pollen-tubes, but 
those substances are soon dissolved or change into sugar or gum. In the 
formation of a nucleus those little mucilaginous granules were produced 
in the protoplasm, then a few larger granules, and soon afterwards the 
nuclei shewed themselves. "When a cell was formed, it had at first the 
form of a segment of a sphere, the plane side formed by the cytoblast, the 
convex side by the cell-membrane. Originally the cell-membrane was 
soluble in water, but it soon expanded more and more, and acquired 
greater consistence ; and its walls, with the exception of the cytoblast, 
which always formed part of the wall, were composed of gelatine. The cell 
now soon became so large that the cytoblast appeared only as a little body 
enclosed in the lateral wall. . The cytoblast might go through the whole 
vital process with a cell, if it were not dissolved and absorbed in cells des- 
tined to higher development, either in its place or after it has been cast 
off like an useless member, in the cavity of the cell.— The whole of this 
account of the relation of the nucleus to the cell-membrane is incorrect. 
The nucleus is not connected with the cell-membrane' under any circum- 
stances, for it is enclosed, with all the rest of the contents of the cell, in 
the primordial utricle. Its position in the newly originating cell is, as 
appears to me, always central, and its form mostly globular ; it does cer- 
tainly often lie upon the wall of the cell subsequently, and becomes flat- 
tened. The distinction which Niigeli tries to carry out between central 
and parietal nuclei is not founded in nature. 

In Schleid en's more recent writings the above views are partially modi- 
fied. It has been recognized that the supposed gum is a nitrogenous 
substance, but the name mucilage {schleim) has been retained ; and it is 
stated of the young cell, that in many cases, after one side of it had become 
elevated like a vesicle from the surface of the nucleus, a second layer is 
deposited upon the free side of the latter, protecting it from solution ; the 
special statement that all cells are formed in this way is more and more 
extended to all organs of plants, even to the cambium-layer of the Dico- 
tyledons (" Anatomic der Gacteen? 35). 

Although, it is a rule, which has no exception in the normal 
development of the cells of all the higher plants, that nuclei make 
their appearance in the nitrogenous substances which give rise to 









the formation of a free cell, yet this is not a necessary condition, 
for it appears that every globular mass wholly or partly composed 
of proteine compounds is capable of undertaking the function of 
a nucleus, clothing itself with a membrane, and thus producing a 
cell. This state of things is of very frequent occurrence in the 
formation of the spores of the Algae, where the whole contents of 
an entire cell, e. </., in Vaucheria, of two copulated cells, e. g., in 
Zygnema, become balled together into a globular mass, and coated 
by a membrane. But it is not always such large masses, com- 
posed of starch and chlorophyll granules and protoplasm, which 
give rise to the formation of a spore ; in very many cases smaller 
globular masses of the green contents, produced by the union of a 
a few chlorophyll granules, and undoubtedly also single granules 
of chlorophyll, may assume this function whence Kutzing called 
the granules lying in the cells of Algse — gonidia. This occurs in 
the most striking manner in Hydrodictyon, in every cell of which 
the sporidia produced from chlorophyll granules arrange them- 
selves in a net-work over the whole of the inner surface of the 
parent-cell, become converted into cells which grow together at 
their angles, and thus collectively form a new plant. 

Pollen-grains and the spores of the higher Cryptogamia exhibit 
a peculiar mode of formation which connects the division of cells 
with free cell-formation. After the development of four nuclei, 
produced by the division of a single nucleus, accompanied simul- 
taneously by the absorption of that nucleus which had given origin 
to the parent-cell, the latter becomes divided into four compart- 
ments (Nageli's special parent-cells) by the folding inward of its 
primordial utricle and the gradual formation of septa (which are 
four or six in number, according to the relative position of the 
nuclei, or, it is first divided into two segments, which are again 
divided into two chambers (Nageli's special parent-cells of the 
second degree). These secondary cells are adherent to the wall of 
the parent-cell wherever in contact with it, therefore up to this 
epoch only the common process of cell-division occurs (pi. 1, fia S 
8, 9, 11). But the contents of each one of these four subdivisions 
now become clothed by a new membrane (the inner pollen or spore- 
coat), which, although in accurate apposition with the membrane of 
the cell in the cavity of which it lies, does not adhere to it, and 
subsequently secretes the outer pollen- or spore-coat. The forma- 
tion of this inner pollen-cell only resembles free cell-formation in 
the circumstance that its membrane is produced in the cavity of 
another cell, around a primordial utricle which contains a nucleus 
without adhering to the parent-cell and forming one of its secon- 
dary layers ; it is distil) guished from free cell-formation by the 
fact that the nucleus and the primordial utricle around which the 
new cell-coat is produced, belonged previously to the parent-cell, 
and had caused the origin of this itself, and had not been newly- 
formed for the secondary cell. 





Even as in anatomical respects tine cell appears, on the one hand 
as an independent organism, self-contained, and following its own 
proper laws of formation in its development, and again, on the 
other hand, in the great majority of plants, does not appear iso- 

lated, but forming part of a greater whole, with which it is not 

merely mechanically connected, but by the influence of which its 


its pits, &c, are dependant on the condition of the neighbourin_ 
ce ll Sj — s0) in like manner, is the physiological activity of the cell, 
on one hand independent of, and on the other dependant on, and 
ruled by, the vital 'activity of the entire plant. 

The vital functions of plants are separable into two great 
classes, into those of nutrition and those of propagation. Both 
are committed to the cells. The share which the individual cell 
takes in one or both of these functions varies extremely according 
to the degree of elevation of the organization of the plant. 

In the lowest plants, whether, as in Protococcus, they consist 
of a single cell, or as in the Confervas of rows of cells united into 
a thread, each cell is capable of an independent existence. It ab- 
sorbs fluid from the surrounding medium, respires, assimilates the 
absorbed substances, &c. ; in short, the simple vesicle suffices for 
the accomplishment of all the various functions which must co- 
operate in the nutritive processes of the plant. The more highly 
organized a plant is, the more these various functions are com- 
mitted to particular organs, the offices of which in this way be- 
come special and one-sided, thus being reduced to a dependence 
on the functions of the other organs. The function of absorption 
is committed to the root ; that of breathing and the elaboration of 
the absorbed substances to the cells of the leaf, &c. "With the 
combination of many cells into a whole, leading a common life, 
comes the necessity of a passage of the sap from one organ to 
another, a circulation of the fluids, which the simply formed plant 
can wholly dispense with. This movement of the sap is in great 

part committed to particular cells, which take but a subordinate 
part in the real business of nutrition. 

Analogous to the more independent condition of the cell as an 
organ of nutrition, in proportion as the organization of a plant is 
simpler, the greater is its activity as an organ of propagation. In 
the lowest plants the same cell is an organ of vegetation in the 
earlier period, and an organ of fructification in the later period of 
its life, germinal granules f keim-korner ) being formed in its in- 
terior. In the higher plants, on the contrary, these two functions 
are committed to different cells, in which case, at first, as in the 

1 t 










Lichens, all the organs of fructification are alike, while in the more 
highly developed plants a contrast between these appears, a male 
and female sex, the conjunction of which is necessary for the origin 
of a new plant. 

Thus, the more complicated the structure of the entire plant 
becomes, the more manifold the vital phenomena of the whok 

display themselves, the more do we see the functions of the fun- 

damental organs of the vegetabl 

become restricted to an activity 
continually becoming more special. The question here presents 
itself : In what connexion does the more manifold or more special 
activity of the cells stand with their organization ? To tins ques- 
tion we have no answer. The organization of cells, the substances 
of which their membranes are composed, are so uniform through- 
out the whole vegetable kingdom, and all the organs of the par- 
ticular plant, that as yet the connexion which must exist between 
the form and organization, and the function of the cell, is alto- 
gether unknown. 

The function of nutrition and that of propagation form a strik- 
ing contrast in all the cases in which the propagation is by spores 
and seeds, since the reproduction in these, through the germination 
of an organ furnishing a new plant, always causes the death of 
the organ of propagation, and in many cases of the whole plant. 
But there is another kind of multiplication ; the propagation by 
buds, which depends on the common laws of growth, and hasffcs 

This mode of increase is 


ans of vegetation. 

Leaving out of view 

based on the peculiar growth of the plant. 

the simplest forms of the vegetable ldngdom, the plant does not 
consist of a fixed number of organs, developed together and at- 
taining the full-growth at the same time, so as to form a com- 
pleted whole, and to suffer a common death ; but the organs of 
the plant are developed successively in an unlimited series ; every 
fresh shoot has the strength of youth, and is capable, under fa- 
vourable circumstances, of entering on an independent life sepa- 
rately from the other parts, and of growing into a new plant. 
When even all the parts of a plant do lead a common life, they 
do not collectively form one individual, but separate individuals 
growing out of each other, and blended together in. consequence 
of their growth. It depends on the degree of organization of a 
plant what part we are to regard as a special individual. When 
an uni-cellular plant divides into two cells we must regard each 
cell as an individual, e. g., in the Diatomege ; in the Thallophy tes, 
for instance in the Lichens, each lobe of the thallus can carry on 
an independent life when separated from the rest of the plant ; in 
the higher plants each branch forms a repetition of the stem which 
grew from the seed, and a ramified plant is looked upon as a col- 
lection of as many individuals as there are branches upon it. In 
this manner a branched plant (when not exhausted by the pro- 
duction of seed) is ever young in its fresh shoots, although one 




part after another grows old and dies ; new, active individuals 
sprout annually from the old ones, and there is no natural termi- 
nation to the life of the whole. At the same time, the possibility 
is given for a plant, in consequence of this unceasing production 
of shoots, to become separated into an unlimited number of dis- 
tinct plants, in a natural way by spontaneous, or by artificial, divi- 
sion. From this peculiarity of the unlimited growth of a shoot 
has the German language derived the expressive terms gewdchs 

(a vegetable, from wachsen to grow). 

Observ. The peculiarity of their organization, and the unlimited power 
of growth of plants, offer many difficulties to the definition of the dura- 
tion of plants, and have given rise to many incorrect theories. Every 
individual cell, and every individual organ has a determinate end to its 
life, but the entire plant has not, since the individual shoots run through 
their periods of development quite independently, and only share in the 
weakness of age of the older organs when these are no longer able to 
convey to the young shoots the needful amount of nourishment, in which 

he latter do not die from deficiency of vital energy, but are starved. 
It therefore depends wholly upon the mode of growth of a plant whether 
this occurs or not. When a plant possesses a thallus spreading horizon- 

case t 




tally by the 

into a larger ^circle, after the old parts in the centre have been long de- 
cayed, as is seen in old specimens of crustaceous Lichens, in the fairy 

aused by Pungi, &c. In like manner when a higher plant has a 
creeping stem, and possesses the power of sending out lateral roots near 
the vegetating points, and in this way conveys nourishment directly to 
the young terminal shoots, the latter are wholly independent of the death 
of the older parts of the stem and of the primary roots, and there exists 
no internal cause for death in such a plant. It is truly a different plant 
every new year and vegetates in a new place, but there is no definite 
boundary between it and its predecessors ; such a plant is like a wave 
rolling over the surface of a sheet of water, it is every moment another, 

and yet always the same. 
Grasses, Rushes, &c, have • vegetated in this manner upon peat bogs and 
similar localities perhaps for thousands of years. Plants with upright 
stems are placed in much more unfavourable circumstances. It has been 
declared of these also, and particularly of the Dicotyledonous trees (De 
Candolle, " Physiologie Vegetate" ii. 984), that they have no internal cause 
for death, but I believe incorrectly. Examples of very old trees, such as 
De Candolle collected (e. g., Taxus 3000, Adansonia 5000, Taxodium 
6000 years old, &c), only prove, naturally, that death occurs at a very 
late period in many plants placed in favourable circumstances, but not 
that it does not necessarily happen. To me there appears to exist in all 
trees, whether they belong to the Dicotyledons, or, like the Palms, to the 
Monocotyledons, an internal cause which must produce death in time — 
namely, the increasing difficulty of conveying the necessary quantity of 
nourishment to the vegetating point, resulting from the elongation of the 
trunk from year to year. Even when the force which carries the sap up 
suffices to raise it to 200 feet or more (many Palms, as Ceroxylon andicola, 

' ~ -180 feet 

Areca oleracea, attain a height of 150 

some Conifers, e. g., 






Finns Lambertii, Abies Douglasii, of more than 200 feet), yet a maximum 
is reached there, and the terminal shoot is less perfectly nourished every 
succeeding year, becomes stunted more and more, and the tree at length 


Thousands of experiments have shewn that the young shoots of old 
trees, when used as grafts, slips, &c, furnish as strong plants as the shoots 
of young trees; even in the Palms (Phoenix dactylifera) experiment has 
shewn that the apex of the stem, when its vegetation begins to slacken 
in an old tree, grows again into a strong tree when cut off and planted in 
the earth. Not one single experiment speaks in favour of the opinion 
promulgated by Knight, that all parts of a tree have a common end to 
their life, and that the different trees which have been raised from one 
and the same tree by grafts, decay about the same time as the parent 
plant. A whole series of cultivated plants (I will only mention the 
Vine, the Hop, the Italian Poplar, and the Weeping Willow) are propa- 
gated by division, without any decreased power of vegetation ever beino- 
seen. Nothing was in greater contradiction to the laws of vegetable life 
than the frequently expressed opinion, that the Potato disease of recent 
years was to be ascribed to a degeneration of the Potato plant, arising 
from the unceasing propagation by tubers. 

If we are surprised at the intensity of the vegetative force of 
individual plants, in consequence of which it re-appears with new, 
unweakened energy in every bud, so must we marvel at the force 
committed to so simple an organ as a cell is, if we reflect what 
an influence it exerts upon the total economy of nature, as one of 
the grandest of phenomena. The plant lives almost solely upon 
inorganic substances ; its cells are chemical laboratories in which 
these are combined into organic compounds. The plant prepares 
in this way. not only the nutriment required for its own develop- 
ment, but also the food on which the entire animal kingdom de- 
pends. But plants not only nourish animals, they maintain the 
air in a lit state for their respiration, since their breathing process 
removes carbonic acid from the atmosphere and replaces it by 
oxygen gas. 

In all these functions the plant is throughly dependant upon 
the outer world ; its food is brought to it without its own co-opera- 
tion, by water and air ; its respiration takes place without activity 

of its own, through a penetration of its substance by gases with 

which it is in contact, in consequence of a physical law ; not even 
does its internal circulation of juices depend on a mechanical 
activity of a circulating system ; thus every necessity for motion 
is removed. It is true we here and there meet with movements 
in this or that organ, but these, occurring isolated in the vege- 
table kingdom, are also altogether of subordinate kind in the 
individual plant. They also are committed to the cells. 

E ■ 



through, cells. 



In all plants the fluid nutriment is taken up by absorption 

As the cell-membrane has no orifices, only such 
matters as are actually dissolved, can be absorbed into the cell with 
the water which penetrates the cell-membrane ; in like manner, 
in all the higher plants, a mechanical penetration of solid sub- 
stances, even when suspended in water in the finest state of divi- 
sion, between the cells into the interior of the plant, is impossible, 
since the cells which form the surface of the plant are accurately 
fitted together, leaving no orifices between, except the stomates, 
which never occur upon roots or parts growing under water. 

Gaseous fluids, by which the cell- walls are also readily penetrable, 
may in like manner be taken up by the cells situated at the sur- 
face ; but they can moreover penetrate between the cells, into the 
interior of plants, through the stomates. 

Observ. The Thallophytes possess no proper organ of absorption, but 
the whole of their surface is adapted for it, and when, as in many Algse and 
Lichens, they have root-like processes, these are only organs of attachment 
and not special organs of absorption. In many Fungi and Lichens the sub- 
stance of the thallus is composed of such loosely connected cells, that fluids 
which come in contact with them penetrate between the cells into the sub- 
stance of the thallus, so that the absorption is not confined to the superfi- 

eial cells here. 


agents of the absorption of water. 

figure as an absorbing organ, their freely penetrable leaves being the chief 

In the higher plants absorption, is com- 
mitted to the root alone, since the epidermis of the leaves and the periderm 
of the other parts are much too difficult of penetration by water, to be 
capable of taking up a sufficient quantity of it. This obstruction occurs 
e^en in the root except at the young parts situated near the points. Con- 

sequently, if a plant be placed in water in. such a manner that its younger 
roots are curved up above the surface, it dries up, while it keeps fresh 
when only the younger roots (not however the extreme points, known by 
the name of spongioles, alone) are immersed in water. The parts, how- 
ever, the leaves particularly, protected against the entrance of fluid water, 
are readily penetrable by watery vapour, and plants can in this way appro- 
priate water from very moist air, as is clear from the increase of weight of 
entire plants or cut twigs ; this explains the great use of dew to the vege- 
tation of dry, hot regions. 

It has long been decided, that solid substances, insoluble in water, no 
matter how finely they are powdered, e. g. } the charcoal of gunpowder, can- 
not pass into plants ; but this may be doubtful of the colouring matter of 
Phytolacca, of decoction of log- wood, of infusion of saffron, &c, since many 
observers, e. g., Be Candolle, have seen such colouring matters pass into 
living plants. But all accurate observations indicate that this does not 
happen in uninjured roots, but only occurs when the coloured fluid comes 
in contact with wounds of the plants. 








Since the discovery of endosmose, most vegetable physiologists 
have assumed it as an axiom that the absorption by cells depends 
wholly and solely upon the laws of endosmose, none of the pecu- 

liar forces of the living cell co-operating. All the conditions 

to bring about strong endosmose do really exist in the living 
vegetable cell, namely,, a membrane freely penetrable by watery 
fluids ; on the one side of this the cell-sap which contains proteine 
substances, dextrine, sugar, &c, in solution, on the other side the 
water occurring in nature, in the state of an extremely diluted 
saline solution. This renders it readily explicable how cells which 
are laid in water swell up rapidly, in many cases, if they contain 
a concentrated protoplasm and have not firm walls (e. g., many 
pollen-grains), the powerful absorption of water causing them to 
burst; and how, on the other hand, if they are laid in a strong 
solution of sugar, gum, &c., they become emptied and collapse. 
Under these circumstances, the assumption that the absorption of 
the cells will be regulated by the laws of endosmose, is fully justi- 
fied, yet special proofs of this can only be partially advanced, be- 
cause on one side the phenomena of absorption are too little known 
in many respects, and on the other side the theory of endosmose 
is not yet perfect enough to allow of our making out in all cases 
the share it has in any given phenomenon. 

According to the researches of Th. de Saussure (" Recherch. 
chim. sur la Veget" 274), healthy and diseased roots behave very 
differently in reference to absorption, the latter taking up the 
substances dissolved in the water in far greater quantity than the 
healthy roots ; the action of a poisonous substance (sulphate of 
copper) had the same result as disease of the roots, for it was not 
only taken up in relatively very much greater quantity, but also 
caused the absorption of other substances v, hich were placed with 
it for absorption by the roots, in larger proportion than occurred 
in healthy roots. This condition alone would excite great doubts 
of the opinion of many physiologists, e. g., of Treviranus, that the 
absorption is an expression of vital force, since it involves the 
contradiction that weakening and destruction of life are combined 
with an exaltation of an activity dependant on it ; while it would 
not be at all striking for changes to occur in a diseased or dead 

cell, which would cause an alteration in the physical character of the 
cell and of the phenomena standing in connexion with it. If the 
roots are healthy, they take up different substances in very dif- 
ferent quantity from solutions of like degree of concentration 
(Saussure experimented with solutions containing twelve grains 
of foreign matter in forty cubic inches of water), and they separate 
the fluid into a dilute solution which they absorb, and a more 
concentrated which they leave behind. 

Ohserv. The distinctions which occur in solutions of different sub- 
►stances, are very considerable. Saussure in each case allowed half the 

. - 



solution to be absorbed, therefore fifty parts of the dissolved substance 
should have been absorbed, instead of which Polygonum 
absorbed of, — 


Chloride of Potassum 

Sodium . 

Nitrate of Lime . . 
Sulphate of Lime 
Chloride of Ammonium 

Acetate of Lime . . 

Sulphate of Copper . 






14*7 parts 













Saussure tried to explain these differences in the absorption from phy- 
sical differences in the solutions, especially by the assumption that the 
quantity of substance absorbed, depended on the greater or less degree of 
viscidity which it imparted to the water by its solution. He regarded, 
namely, the cell-membrane as a very fine filter, through which not only 
would a denser solution penetrate more slowly, but which was also ca- 
pable of separating the solution into a more concentrated and a more 
diluted one. This explanation is certainly not sufficient, since we have 
no proof that the finest filter can effect such a separation of a fluid ; and 
secondly, Trinchinetti found that the quantity of substances taken up by 
roots did not run parallel with the viscidity of their solutions. But there 
is nothing in the result of these experiments which would be in opposi- 
tion to the laws of endosmose, in particular the separation into a thinner 
and a denser fluid stand in agreement with these, since many observations 
(of Jerichau, Briicke) have shewn, that in endosmose the fluid does not 
necessarily penetrate the septum in toto, but that in many cases a dilute 
fluid or merely water goes through. We are certainly not in a condition 
to state at present how one salt passes over in this, another in that, quan- 
tity ; to do this it would be necessary to know the contents of the vege- 
table cells and the relation in which they stand to the cell-membrane and 
to the different solutions ; but no contradiction exists between the phe- 
nomena referred to and endosmose. Formerly it might have been con- 
cluded from the different behaviour of diseased and healthy roots, that 
absorption was not a true physical process, but that the force of the living 
plant was to be considered in reference to it ; but not to speak of the 
above-noticed contradiction that a vital act would be exalted in a dead 
cell, there occur in the disease and death of a cell, two alterations which 
cannot be without influence on the endosmose. In the first place the 
living cell exhibits a certain tension, which is lost in the dead cell ; in the 
second place the primordial utricle is very readily detached from the 
inside of the cell-wall in diseased or dead cells ; these two circumstances 
place the cell-wall in a condition essentially different from the normal 
one, and we may readily conceive that the endosmotic force of the cell- 
wall becomes essentially different, and that the dead cell-membrane is 
penetrated much more easily and quickly than the wall of the living cell. 
There are frequent opportunities of observing the more easy penetration 
of a diseased or dead cell, in microscopic investigations where tincture of 


F 2 


>i> ■* 


: ■ 






lie near together, some healthy, others diseased, the latter are very much 
more quickly penetrated by the tincture of iodine. 

An important question in absorption is this : are the different 
substances absorbed by different plants in equal relative quan- 
tity, or does one plant take up one substance, another a second 

in greater abundance? Saussure, who thought the latter condi- 

tion not improbable, could not find any confirmation of it in 
his experiments, for the variations which he found in the absorp- 
tion of different substances by different plants, were not more con- 
siderable than the variations which occurred in different experi- 
ments with the same plant. Trinchinetti ( Sulla facolta assorhente 



pose one another, whereby he shewed that certainly one plant ab- 
sorbed one, another plant the other salt, in preference, from a mix- 
ture of nitrate of potass and common salt. Thus Mercurialis annua 
and Chenopodium viride absorbed much nitre and little salt, 
while Satureia hortensis and Solanum Lycospersicum took up 
much salt and little nitre, and from a mixture of sal-ammoniac 
and salt Mercurialis absorbed more sal-ammoniac, while Vicia 

Fa' a -took more salt. 

If, however, as there is every appearance, the result obtained by 
Trinchinetti be correct, we can by no means deduce from it the con- 
clusion that the plant possesses the power of absorbing substances 

useful to it and excluding those which are injurious, for experi- 

ence has amply demonstrated that it does not possess this latter 
power, that it can even, as Saussure's experiments with sulphate 


which it applies to its nutrition, and we must assume that the 
cause of the differences in question is to be sought in the physical 
and chemical peculiarities of the particular substances, and their 
relation to the cell-membrane and the cell-contents. 

Observ. It is a known fact that different species of plants which grow 
side by side in the same soil, to the roots of which the same nutriment is 
conveyed, shew by analysis of their ashes a very different composition of 
fixed constituents derived from the soil. This circumstance may be ex- 
plained in two ways; either through the assumption that different species 
of plants take up different constituents in unequal quantity from the 
same solution, for which the experiments of Trinchinetti above-mentioned 
furnish positive evidence, or through the hypothesis defended by Liebig, 
that different plants take up equally, like a sponge, all that is dissolved in 
water, but again reject all superfluous or injurious substances. The first 
must be regarded as by far the more probable in the present state of our 
knowledge, since the* second hypothesis, which is based upon Macaire- 
Princep's experiments, presently to be mentioned, that substances unfit 
for the plant can be again excreted by the roots, has not been confirmed 
by later researches. It is certainly not to be denied that plants possess 
in the fall of the leaves a means of removing a part of the substances 








taken up by their roots, but this means can only act in perennial plants, 

and not in annuals. • 

Since the roots undoubtedly possess the power of separating a saline 
solution into a dilute and a concentrated, and absorbing the thinner ; and 
since, according to Trinchinetti's experiments, certain plants absorb par- 
ticular salts only in very small quantity, the question arises whether^ in 
particular cases, the plants are in a condition to take up from a solution 
water alone, with the total exclusion of the dissolved substance. We 
have no definite experience on this point, but such a thing is not impro- 
bable. I may mention here that formation of Fungi has been observed 
even in arsenical solutions, for arsenic is a substance so hostile to vege- 
table life, that it can scarcely be supposed that any plant could maintain 
its existence when it contained arsenic in its sap. It was also observed 
by Yogel (Erdman and Marchand. " Journ." Bd. 25, 209), that Cereus 
variabilis had taken up no copper after having been watered for ten 
weeks with solution of sulphate of copper, that the copper penetrated 
just as little into the leaves of Stratiotes aloides, and that Char a vulgaris 
vegetated for three weeks in a solution of sulphate of copper without 
taking up this metal. 

If the experiments mentioned in the fore^ 
plained in every single detail through the laws of end osmose, _ yet 
there is a great probability that this will be possible in time. 
We must not forget, in considering this absorption, that in the 


These can 

laws of endosmose cannot display themselves clearly, 
only be seen undisturbed where no other force is acting upon the 
two fluids separated by a partition. But only the comparatively 
few plants growing totally under water occur in this condition, 

while the physical conditions in which the great maj ority of plants 


their phenomena depending upon endosmose. Since the leaves 

have a large surface with a comparatively small mass, and are 
provided with numerous stomates on the under side, they are 
fitted to evaporate a great quantity of water. This does occur 
in a surprising degree when external circumstances do not repress 
the formation of vapour; thus, for example, in Hales' experi- 
ments, a sun-flower 3^ feet high lost on an average a pound and 


from which Hales 

reckoned that in comparison of the surfaces, the evaporation. 
was some three times as strong in this plant as in man, and in 
comparison of volume seventeen times as strong. So consider- 
able a loss of water cannot remain without re-action upon the 
absorption of the root-cells. For since the sap in the cells of the 
leaves becomes so much more concentrated through the loss of 
water, their power of inducing endosmose will increase in propor- 
tion, they replace the water taken from them, from the cells of the 
stem, and so this action is continued through the whole tissue of 
the plant down to the roots, which strive to absorb water from 









without, in the same proportion as it is evaporate 
leaves. A proof that the evaporation of the leaf actually in- 
creases the absorption, is again furnished by the experiments of 
Hales, according to which the quantity of water that a shoot ab- 
sorbs is in direct proportion to the number of its leaves, and the 
quantity of water absorbed sinks to one half when half the leaves 
are cut off the shoot ; the experience also speaks in favour of it, 
that during winter the root of a plant standing in the open air, 
for instance, a vine or a hazel bush, begins to absorb if one of its 
shoots is introduced into a hot-house, and the unfolding of its 
leaves caused by the action of heat. Liebig (" Researches on the 




is exerted by evaporation at one point even in apparatus artifi- 
cially contrived, and which, when it is assisted by the pressure of 
the atmosphere, is capable of causing the fluid to flow through 
the membrane against the laws of endosmose. In plants, this in- 
fluence not only suffices to increase the absorption, and cause it 
to commence under circumstances in which it did not otherwise 
occur, but is even powerful enough in plants which have been 

poisoned, to carry the poisoned fluid in great abundance upward 

through the already dead lower part of the plant. 

Ohserv. I here refer to experiments which I have made both on Firs 
and Dicotyledonous trees in regard to the absorption of pyrolignite of 
iron, the diffusion of which through the plant is readily perceived by the 
dark colour. Young trees sawn off and placed with the cut surface in 
the fluid, became filled with it, when they had white wood like the Birch, 
in all their parts from below upwards, and continued to convey the fluid 
upwards in this way through the lower part of the stem, after all their 
cells were saturated with it and their cell-membranes were infiltrated 
with it through their entire thickness : under which circumstances we can 
certainly not imagine them to have retained a remnant of vitality. 


Diffusion of 

The mode in which the fluid taken up by the cells situated at 
the surface of the rind of the root becomes diffused in the plant, 
is a subject which lies in far deeper obscurity than the absorption 
of the cells in contact with watery nutriment. In the lower 
plants which are composed of single cells, as Protococcus, there 
can be no movement of the sap, and even in such as are com- 
posed of simple rows of cells, like the Confervas, each cell seems 
to elaborate independently the nutriment it takes up. In the 
Lichens we have already an indication in the different structure, 
and especially in the green colour of the internal layer, that here, 
where indeed no distinct organs exist, the different layers of the 
thallus are endowed with unlike physiological functions ; we can 
scarcely imagine this without an exchange of the juices of the 







different layers, without a movement of the sap ; but we are 
wholly ignorant of all that relates to this. The case is different 
with the Phanerogamia, in which the different processes connected 
with the nutrition are committed to different organs ; > here we at 
least know somewhat more accurately the course which the sap 
describes, at all events in the Dicotyledons, _ . 

A few simple experiments leave no doubt about tins. _ 
watery fluids are, as we have seen, absorbed by the cells lying at 
the surface of the rind of the root, they flow no further, however 
in the rind, but pass into the wood, even in the small roots and 
ascend in this through the stem and branches. The proof ol this 
is furnished by two facts : if the bark of a plant, best ot a tree, 
is cut through in a ring down to the wood, there is no interrup- 
tion of the flow of sap to parts situated above the wound ; but it 
the wood is cut through, the greatest care being taken to avoid 
injuring the bark, that portion of the plant above the wound 
dries u? at once. From the wood of the stem and branches the 
sap flows onwards into the leaves, and in these into their paren- 
chymatous tissues, as is proved by the powerful expiration of 
water vapour from them. Before the sap has reached the leaves 
it is incapable of being applied to the nutrition ; consequently, 
the vegetation of a plant comes to a stand still when it is de- 
prived °of its leaves. The sap ascending from the root to the 

prived of its leave 

leaves is thence termed the crude sap. It undergoes a chemical 
change in the leaves, rendering it fit to be applied to the nutrition 
of the plant. To this end the sap flows backwards from the 
leaves through the bark, to the lower parts, as the following cir- 
cumstances testify. If the bark is cut off the stem m a ring, 
the growth of that portion of the plant below the wound stands 
as it were still, the stem becomes no thicker, in the Potato plant 
no tubers are produced, &c. ; 'but on the other hand, the growth 
above the wound is increased beyond the usual measure very 

n • i i ..J? J „,„„ J^^U n ^ mnro frnif, i« nprfficted. these 


ripen sooner, &c. The deposition of starch which occurs in the 
cells of the medullary rays in Autumn, goes to prove that the 
portion of assimilated sap which is not used for nutrition on the 
way to the root, runs back to the wood through these horizontal 
medullary rays, and thus the sap describes a kind of circle, not, 
indeed, in determinate vessels, but in a definite path leading 
through the different parts of the plant. 

Observ. It is difficult to conceive how in recent times the results of 
these experiments (for the details of which reference should he made espe- 
cially to Duhamel's -Physique des arbres" and Cottas N aturbeobach- 

tungenub. d. Bewegung des Softes?) could have been questioned , and the 
existence of the descending current of sap in the hark demed. Certainly 

exigence oi tut; utusueiiuiiig tuuv>u« — — r % * 

it is no improvement on the theory cast aside, when the increased growth 
above the annular wound is explained by artificial interruption of the 
upward current of crude sap, in consequence of which the sap contained 







and potential for development (Schleiden, " Grundz, 




of its accustomed food, this explanation may he received as satisfactory. 

Mulder also (" Physiolog. Chem") denies that there exists a downward 
current of the sap, although he does not call in question the fact that the 
nutrient matters formed in the leaves do descend. That is to say, he 
assumes that the substances which the sap carries upwards are exchanged, 
according to the laws of endosmose acting in the ascending sap, with 
those substances which are elaborated in the leaves. If this were the case, 
the latter nutrient matters must descend in the same course and through 
the very cells in which the sap ascends, i. e., through the wood; the above- 
mentioned experiments demonstrate that they certainly do not, but 
remain in the upper parts of the plant when this path is freely open to 

The different layers of the wood do not convey the sap in equal 
quantity ; the outermost, youngest layers, and in stems not more 
than two years old also the medullary sheath, principally preside 
over the conveyance of the sap. The older a tree becomes, and 
the harder the wood it possesses, the less share do the older layers 
take in the conveyance of sap ; hence, trees with hard wood, like 
the Oak, where the sap wood exists in a circle round the stem, dry 
rapidly ; while in trees with soft wood, like the Birch, the central 
layers of wood still carry sap, even in thick trunks. 

When the' question arises as to which elementary 01 
sap ascends in, and by what force it is lifted upwards, we arrive 
at a region wherein all is still obscure, but in which so many the 
more hypotheses have been ventured. 

In the first place, two views stand diametrically opposed to each 
other ; according to one, the conveyance of the sap is committed to 
the vessels ; according to the other, these carry air, and the sap 
flows in the cellular tissue. The adherents of the first opinion (to 

Malpighi, Duhamel, Treviranus, Link) chiefly de- 
pended upoiTthe circumstance that when cut plants were placed 
in coloured fluids, these became diffused through all parts of the 
vascular system, a conclusion which, while referring to processes 

healthy plants, takes its stand on plants placed 

is now not considered 
valid by any one. In like manner, no great weight can be laid 
upon the phenomenon of the sap flowing from the cut vessels when 
trees such as the Birch, Maple, Vine, &c, are wounded in Spring ; 
since these plants are in such different conditions before the un- 
folding of their leaves and in later periods of their vegetation, that 

occurring m 

in . most unnatural circumstances, and 



sible. More 



rkundc" i ; 116), according to which, plants 
winch have been watered for some days with a solution of ferro 




cyanide of potassium, and afterwards with a solution of sulphate of 
iron, had prussian blue precipitated in the vessels and not in the 


periment mu 

be acknowledged as a conclusive evidence for the conveyance of 
the sa,p by the vessels, but although these experiments were con- 
firmed by Rominger (" Bot. Zeit" 1843, 177), and also have been 
made repeatedly bv myself with the same results in many other 

"—Bot Zeit 


Hoffman ("ub. de Organe d. Saftbewegung 
mt Memoirs, Series 2, Vol. L), they furnisl 

cally opposite results, without our being able at present to deter- 


may have depended on accidental injuries in the plaut where the 
saline solutions penetrated into the vessels. 

The defenders of the idea that the vessels carry air, as the chief 
of whom in recent times Schleiden is to be named (" Grundz," 
2nd ed. II. 505), stand simply upon microscopic investigations, 
since in these air is always found in the vessels. This statement, 
special exceptions excluded, is undoubtedly correct. 

In the first place, in regard to these exceptions, our woody 


plants furnish them during the time preceding the unfolding of 
the leaves in Spring. During the winter a portion of the cells of 
the wood are filled with sap, the vascular system with air. Dur- 
ing the rising temperature of Spring the cells become gradually 
fuller and fuller of sap, and this subsequently enters the vessels 
also ; now the sap flows freely from wounds in the wood, which is 
not the case so long as this is contained in the cells alone ; after- 
wards, when the unfolding of the leaves increases very much the 
evaporation of the plant, the wood is again partially emptied of 
its sap, and air re-enters more particularly into the vessels. This 
condition of a special fulness of sap, in which the vessels also con- 

vey it, 

ing plants, especially in Phytocrene and certain species of Gjssus 
(see Gaudichaud, " Observ. sur I' Ascension de la seve dans uns 
Liane;" — Ann. des. sc. not. 2nd ser. VI. 138 — Poiteau, "Sur la 
Liane des Voyagturs" — Ann. des. sc. nut VII. 233). The sap is 
exposed to a more or less considerable pressure in the vessels, so 
that it mostly flows with force out of a wound ; the force with 
which this takes place was first determined by Hales, in his cele- 
brated experiments on the Vine, which afterwards were fully con- 
firmed by other experiments, more particularly by those of Brticke 
(" Pogg Ann." 1844, No. 10). Hales found that the presence of 
the sap flowing out under favourable circumstances balanced a 
column of mercury twenty-six inches high. In the observations 
made by Gaudichaud on Cissus hydrophora, and by Poiteau on an 
unknown Cissus, the sap did not flow free from either the upper or 
lower piece of the cut stem, but only out of pieces of stem which 
were separated completely from, the parent plants, so as to present 
two open ends ; here evidently the vessels were not over-filled 

! - 


„ I **\ v/*«**< 











with sap, and this was retained in the cut plant by the pressure 

of the atmosphere. 

If we take into consideration that the vessels, save in the said 
exceptions, convey air, that in the Vine and other woody plants, 
"before the "bleeding begins, the cells are filled with sap, which is 

only afterwards taken up by the vessels, that after the unfolding of 
the leaves and the great evaporation resulting from this, the ves- 
sels are again emptied of sap, we cannot doubt that the cellular 
tissue of the plant is the primary and principal system to which 
the conveyance of the sap is committed, and that the vessels take 
part in the function only under special circumstances, when the 
plant is temporarily overfilled with sap, or in some very succulent 
plants perhaps throughout the whole period of vegetation. 

All parts of the plant do not play an equally active part in 
the conveyance of the sap, for many experiments go to shew that 

the organs situated at the two ends of the plant are especially 
active at least in the ascent of the sap, the root fibres on the 
one hand driving sap upwards, and on the other hand the leaves 

attracting it. 

That the ascent of the sap in Spring, before the unfolding of 
the leaves, is chiefly caused by the roots driving the sap up- 
wards, might be partly deduced from the fact, that the force with 
which the sap flows from a wound in the stem of the Vine, is de- 
pendant on the temperature in which its roots are placed (Dassen, 
"Froriep's Neuen Notizen," b. 39, p. 129), partly also from the 
fact that the sap does not flow merely from the cut stem of a 
bleeding Vine, but the same phenomenon is displayed in the roots 

But that in many leafy 

plants, in which the attraction of the sap by the leaves is active 
as a second cause of the motion of the sap, the impulse exercised 





according to which, in 

Nymphcea alha and other plants, the leaves dry up, when they, 
or the stems to which they belong, are placed with their cut sur- 
faces in water, but they remain fresh, under similar surround- 
ing conditions, when the fibrils of the roots are uninjured. Yet 
that the leaves, even when only a comparatively small number 
of them are left at the top of a plant, are in a condition to lift 
fluids to a very considerable height in the stem, independently of 
the influence of the root, follows from the experiments made by 
Boucherie ("Compt. rendus" 1840, ii. 894) upon trees, in which a 
solution of pyrolignite of iron was applied to the lower ends of the 

sawn-off stems. 

Observations on bleeding woody plants, especially on the Vine, 

prove that the activity of the roots is capable of causing the sap 

not only to ascend in the cells of the stem, but also to enter into 

the vessels. In like manner the activity of the leaves causes 


; ' 



fluids, in which the open orifices of a cut stem dip, to ascend in 

_ seems very easy to give an explanation of the 

ascent of the* sap, both before the opening of the buds at the re- 
commencement of vegetation, as well as during the period in 

its vessels. 

At first sight it 

which the plants are clothed with leaves. During the period of 
the rest of vegetation, the cells of a perennial plant are filled with 
a o-reat quantity of organic compounds, under the form of proteine 
to and more particularly of starch, which 


mi lm*i" stipes SU^til* 

latter is converted into sugar at the* re-commencement of vegeta- 

In consequence of this, the cell-sap becomes capable of 


than that the cells of the roots should absorb the water which 
exists around them, and that the sap diluted by this should 
be taken up by the cells above, and so be carried gradually up- 
wards from one cell to another, whence the notion that endosmose 



But on closer examination 

the matter appears less simple than it seemed at the first glance. 
The organic compounds, especially the starch, are not, for the 
most part, contained in the elongated cells of the wood, in which 
the sap ascends, but more particularly in the cells of the me- 
dullary rays and in those of the rind of the root, while in those 

Monocotyledons, , - ... -. — -„ , v - 

gum starch, &o, before the time of flowering, these substances 
are deposited in the parenchymatous cells of the stem. Thus the 
substances which cause the setting up of the endosmose, occur in 
cells which do not preside over the conveyance of the sap, while 
in the elongated cells of the wood, substances which would cause 
endosmose exist only in inconsiderable quantity, and in the ves- 

sels not at all. H 

wood -cells and 

vessels, and how is its motion imparted to it ? I consider these 
questions as unsolved at present. # 

Briicke (1. c. 204) has indeed promised to demonstrate that this 
process depends on the laws of endosmose, that the parenchyma- 
tous cells first become densely filled with water by the help of the 
soluble and expansible substances contained within them, and 
then since they continually attract water, pour out that which 
they cannot make room for in their cavities, with a portion of the 
soluble substances, as sap, into the neighbouring vessels; but 
Briicke has not yet furnished the demonstration of this. But 
even if we would assume such an excretion from the cells causing 
the endosmose, to be founded on the laws of that phenomenon, it 
still would remain unexplained why this emptying of the paren- 
chymatous cells does not take place by the most direct path, into 
the intercellular passages running between them, but into the 

wood-cells and vessels. 

The influence which the leaves exert upon the ascent of the sap, 

1 - 


■ s 






\ I 


^^ - * -VH, 


l ali 

■ I 



is connected with the strong evaporation ; this not only causes the 
sap within them to become more concentrated and thus more 
capable of attracting to itself, through endosmose, the sap con- 
tained in the cells of the stem (a property which the sap contained 

A A H • ™f "^ 

in the leaves acquires the more since its organic, especially gummy, 

compounds are formed out of inorganic substances), but, as Liebig 
has shewn, the evaporation from the superficial cells causes the 
flow of sap towards them by itself, and independently of the en- 
dosmose they exert. The ascent of the sap through the cells of 
the stem to the leaves is indeed explicable in this way; but in 
what way does the activity of the leaves cause fluids in which 
the open ends of the vessels of a cut stem dip, to be absorbed by 
the vessels and conveyed upwards in them? That endosmose has 
no share in this is self-evident, for all the conditions to induce it are 





ing to his view, the air contained in the vessels is absorbed by the 
sap of the cells in the different parts of the plant, and used for 
the chemical transformation of their contents, consequently a fluid 
which is in contact with the open mouths of vessels must be 
driven into them by the pressure of the atmosphere. Were this 
correct, a shoot of which the end was cut off and its vessels there- 
by opened at their upper extremities, or a tree from which many 
branches have been cut off, so that the vessels are in communica- 
tion with the external air in many places, could not absorb fluid 

into these vessels. 

But in the ascent of the sap there occurs another phenomenon, 
which cannot be explained by the endosmose exercised by the 
cells; namely, the endeavour of the plant to carry up the sap 
more especially in a perpendicular direction. It is a well-known 
phenomenon that the biid which stands upon the end of a shoot 
receives the most sap ; that it grows out into a stronger shoot than 
those situated lower down ; that of two shoots of which one is 
brought into a vertical position, the other bent sideways or down- 
wards, the growth of the former is favoured, and that of the other 
interfered with. The endosmotic force of its cells cannot be altered 
by this change of position, and yet the strength of the current of 
sap going to the shoot is altered. 

All these explanations of the movement of the sap bear reference 
only to its ascent, not one of them applies at all to the descent 
of the elaborated nutrient sap. If the bark and the cambium 
layer attract the nutrient matter from the leaves because their 
cells contain a more concentrated sap than the cells of the leaves, 
it is not evident why they cannot draw the sap directly from the 
root and the wood, instead of by the long circuit through the 
leaves, and why the bark is wholly incapable of carrying sap up- 

Gathering; all these circumstances together it seems to me to 






follow from them, that the discovery of endosmose has not solved 
the problem which lies in the movement of the sap of plants, 
that in all probability it really does play an important, perhaps 
the principal, part in the absorption and carrying onward of the 
sap ; but that as yet we have no definite experiments to enable 
us to determine accurately the share in the phenomenon which 
is to be ascribed to this force, and that a series of phenomena 
exist which are at all events at present inexplicable by endosmose. 


c. Nutrient Matters. 

The question, what substances serve for the food of plants, 

includes a two-fold one : 

What elementarv materials are made 

use of by the plant in the formation of its substance ? and 2, 
What are the combinations in which those elementary materials 

are taken up by plants? 

The number of elementary substances which occur in plants 
constantly, and, therefore, must be looked upon as necessary con- 



is very inconsiderable, viz.: 1, Oxygen; 2, Carbon; 
an . a, TSHfrnn-ATi ■ fi Rnlnhnr: 6. PhosDhorus; 7, Chlorine; 

8', Iodine°; 9,' Bromine ; 10, Fluorine ; 11, Potassium ; 12, Sodium; 
13 Calcium; 14, Magnesium; 15, Aluminium; 16, Silicium ; ^ 





Observ. These eighteen elements are not all combined in any one plant, 
for not only can one be substituted for another, which is chemically nearly 
allied, e. g., potassium for sodium, magnesium for calcium, <fec, but also 
particular of them, such as iodine and bromine occur only in certain 
plants, of which they certainly appear to be necessary constituents. Under 
these circumstances, these eighteen elementary substances are not all of 
equal importance ; we must evidently lay the greatest weight upon those 
which occur in all plants, since these are to be regarded as the absolutely 
necessary constituents. In this respect the first four mentioned stand 
highest, since the principal mass of vegetable substance is composed of 
them, the first three furnish the material for the formation of cell-mem- 
brane, and nitrogen is a principal constituent of the proteine substances ; 
sulphur and phosphorus, although contained in inconsiderable quantity in 
plants, play a most important part, since they in like manner appear to be 
necessary constituents for the formation of particular proteine compounds. 
It is different with the radicles of the alkalies and earths, for not only 
may one basic body be replaced by another in many cases, but even a sub- 
stitution of ammonia for a fixed base is perhaps often possible. At all 
events, the latter appears to have been the case in certain Mould * ungi 
in which Mulder found no fixed basic substance; but yet in any case this 
condition must be regarded as a great exception, since alkalies and earuhs, 
and indeed particular earths, are necessary to the well-being of all other 
plants. The universally distributed chlorine is a necessary constituent of 
certain plants, while iodine and bromine play m general a very sub- 
ordinate part. Siliciu m, iron, and manganese are very generally diffused, 
but in respect to their importance to the life of plants very little is known. 







J . 



■ *1 f 





The questions, whether plants must take up from without the element- 
ary substances which analysis discovers in them, or whether they have the 
power of transforming the elements one into another, to live upon pure 
water, &c, are no longer worth discussion in these clays. Whether it be 
thought probable or not, that the elements of modern chemistry are actu- 
ally elementary substances, it has been placed beyond doubt from baus- 
snre's researches onwards through all accurate subsequent observations, 
that no other substances occur in plants besides those which they take up 


Bestandth. d. Pfl< 

Of all the elementary substances which enter into plants, 
oxygen is the only one that is taken up in a pure condition; 
plants can only appropriate the others out of chemical compounds, 
which they for the most part decompose. Her- **■ ™<*> *"«« 

once arises 

the question, whether the elementary substances when they are 




inorganic compounds? On no question of vegetable physiology 
has to active a strife existed as on this, especially since Liebig 
(" Chemistry applied to Agriculture and Physiology ) appeared 
as a defender of one of the extreme answers to it. 



is "beyond any doubt, that plants, if not as a whole, yet in an 
overwhelming majority, possess the power of forming organic out 

of inorganic substances, and that 


substances mostly 

play the principal part in the nutrition. This is evident, both 
from observations made on a large scale in free nature, and m 
small artificial experiments. It is a perfectly universal expe- 
rience, repeated in the same manner in the primeval forests oi 
the tropics on the peat bogs, meadows, and heaths of temperate 
regions; and on the rocky soil of the Alps that where the vege- 
tation is left to itself upon a particular soil, and its products are 
not removed from the ground, masses of decaying organic sub- 
stances are formed, in consequence of the death of the plants, accu- 

year to year, which can of course only be the case 
wuuu „ u xmua eneration of plants producing a greater quantity 
of organic substances than it consumes. In a similar way, when 
an estate is cultivated on proper principles, a certain amount ol 
organic substance is taken away, in the form, of gram, cattle &c 

?■*» _ .— i i i___.J__.J_~ _L I -. _--. -. -. 4- 

through each 

having its origin in the 

the necessity of adding organic 

plants grown upon the estate, without 

matters from elsewhere, and 

without diminishing the fruitfulness of the soil 

The experiments of Saussure also, which are above all to be de- 
pended on in questions relating to the nutrition of plants, shewed 
that plants which he grew with water, ma closed space, m an 
atmosphere rich in carbonic acid, increased their organic substance. 
He calculated in a manner which does not indeed admit of exact- 
ness, but still of an approximation to the true condition, that a 



plant which stands in a fruitful garden soil, cannot owe more 
than l-20th of its weight to the absorption of organic subs 
stances ("Recherchea," 268). An abundance of experiments which 
have been made by the greatest variety of observers, have 
shewn that plants grown in sand which has been heated to red- 




flowers and fruit. It is not requisite to demonstrate 
minutely how these circumstances shew the total error of the 
view, supported, indeed, less by vegetable physiologists than by 
aoriculturists and foresters, that plants subsist solely on the 



nuclermg remains oi loruuei pianus <*uu. <*uuu«uo. 

But on the other hand, it is not yet proved, 1 , that all plants 
possess the power of living upon inorganic substances, and % 
that the inorganic substances are the sole food of plants j that 
the organic substances of humous only furnish a contribution to 
the food of plants, in so far as they are separated into inorganic 
substances by decomposition. This theory which, set up by 
Ingenhouss, has found its most active supporter of late years in 
Liebig, must in its one-sidedness be rejected m just the same 

way as the opposite. 

In the first place, it is opposed by the no small number ol para- ' 
sitic plants, which are capable of using for food the sap of living 
plants and indeed, in very many cases, only the sap of a particular 
one or at all events of very nearly allied plants. A very large 
portion of the parasites (the Loranthacese) agree with common 
plants fully in their habit, colour, &c, another portion consist, on 
the contrary, of leafless plants not of a green colour, which bear 
the same relation to the plants which feed them, as the flowers 
and fruit of other plants do to their vegetative organs. 

In the second place, there exists a very large number of plants, 


want of the green colour, in part possess the usual aspect, and 
which derive their nourishment only from vegetable or animal 
substances in a state of decomposition. To these belong, besides 
the numerous class of the Fungi, many Orchidese, bog-plants, &c. 

Thirdly the majority of other plants exhibit a stunted growth 
when raised in soil totally deprived of organic substances. In 
this respect, however, as the experience of agriculturists and 
foresters has proved, different plants manifest extraordinarily 
different necessities. While one plant, such as the fir, buck- 
wheat, Spergula, Sarothamus, Erica, &c, nourish m a soil which 
contains only traces of organic substances, others, like the Cereals, 
require for their vigorous growth, a more or less abundant admix- 
ture of mouldering substances with the earth. 

These circumstances indicate that different plants have a dif- 
ferent behaviour in regard to their nutrition; that in some 
the power of living upon inorganic substances prevails, while 







others require a mixed food, and, finally, to the parasites are 
assigned solely the still undecomposed saps elaborated by other 


Observ. From such experiments made in the rough., of course no 
accurate scientific result can be deduced, these can^be derived only from 
experiments carefully made tipon a small scale. 


without experiments on a small scale of this sort, but unfortunately 
most of them have been made in a manner which renders them incapa- 

To these belong all earlier attempts 

ble of furnishing any useful result. 

to grow plants with" distilled water, or water containing carbonic acid, in 
sand, pieces of marble, &c, in which plants of course would not flourish, 
but from which no conclusion can be drawn, since not merely the organic 
matters, but all the earths, salts, &c, which they required, were with- 
drawn from the plants. In order that these experiments should furnish 
any certain result, they would require to be made in such a way, that the 
same species of plant would be grown in a soil which contained organic 
substances, and in artificial mixtures which contained all the inorganic 
constituents of the fertile soil, without the admixture of any organic 
constituents. In respect to this, Wiegmann, at my suggestion, made 
experiments ("Bob Zett.? 1843, 801), according to which, plants raised in 
soil devoid of humous grew very poorly and mostly soon died. Mulder 
made a larger series of analogous experiments (" Phys, Chem"), which like- 
wise lead to the belief in the use of the organic substances contained in 
arable soil as well as of the humic acid and ulmate of ammonia arti- 
ficially added to it. _ 

Even if these experiments were still far from having decided the ques- 
tion of the necessity of organic food in a definitive manner, the results are 
so very concordant with those of experience on a large scale, that there 
can be no doubt of their general correctness, the more, that these expe- 
riments made on the smallest scale, obtain a confirmation through the 
extraordinary small results which manuring with Liebig's solely inorganic 
manures has everywhere had, when comparative experiments have been 
made. Instead of reforming agriculture by his manures, Liebig has 
caused them to demonstrate the incorrectness of his theory of the nutri- 
tion of vegetables. . , . 

Yet the humous substances m vegetable mould, do not derive their im- 
portance to plants from an immediate applicability as food, but exercise 
their great influence on plants principally through their relations with 
the alkalies and earths, and especially with ammonia. I shall take the 
liberty of giving some of the principal results of Mulder's researches, 
since these* open out a series of new points of view, which promise to 
become of the greatest importance to the theory of vegetable nutrition. 
According to these investigations, the substances beginning to undergo 
decomposition in the earth are gradually converted into a series of 
chemical compounds, first into ulmine, then into ulmic acid, humin, 
humic acid, geic acid, apocrenic, and finally into crenic acid. With the 
exception of the first and third, these compounds play the part of acids, 
and combine in the soil with its alkalies and earths. These acids, con- 
taining no nitrogen, possess a particularly strong affinity for ammonia, 
which is always met with, more or less abundantly, m combination with 
them. The compounds of these acids with alkalies are readily soluble 

: ?r * 




in water, those with earths and metallic oxides h tie 01 -not a ^1 sa 
On the other hand, their compounds with the f^J^ ( ^^ 
readily form double salts with the earths and ^ ^e&^ 
»n\A iq nenta-basic, crenic tetra-basic) ; the alkalies are tnereiore nou 
only a mCs ordering these acids /readily soluble, but they assist m 
conveying the earths into plants by absorption. _ flnn(1 _._. 

Afomina plays a special part in reference to crenic and apocrenic 
acids since it forms perfectly insoluble compounds with them m which 
the acids are preserved from decomposition, and cannot be washed away 
bv water yetVey are not thereby completely withheld from plants 
dncTtitese impounds are capable of decomposition by ammonia which 
is thus a means of conveying these compounds mto plants very gradually, 

^Z" Srt 1 above described relation of the humous acids 
to ammo™! is, since their great affinity for it places them ma condition 
to attract this body, so important to vegetation, from the an and .from 
the animal substances decomposing in the soil and prepares them Jor 
absorption by the roots, yet they aco^ire s ill ^ "^STa^T 

absorption oy one ruuu&, j*™ *>^j — ~l ~ „,™+^n™iQ rlppnm- 

the fact that, according to Mulder's researches the ^*™^™ H J F 
position of the humous substances » connected ™^ * ^£ ti ™ 
ammonia since the oxygen of the air is used for the foghei oxidation 
of the ^ rest of their substance. The evidence that nitrogen » also ^con- 

vey^to plants ZtUs^j, lies in an experiment of Mulders («P%* 
Chemisfrln according to which, young Bean-plants which were raised 
STtZ^e freeW ammonil, in ulmic acid prepared ^jm^gr 
free from ammonia, and in wood-coal, with water fre > from ammoma 
yielded, on analysis, twice or thrice as much nitrogen as the seeds Horn 

"SS SioTtf humous substances, in water are absorbed by the 
roots as such, and not the products of their decomposition, it would cer- 
tafoly be difficult to prove, since these substances cannot be demons«ed 
to exist as such in the plant, but undergo a transformation directly they 
are absorbed. But in spite of the opposite results obtained by Hartig 
(Liebig's "Agricultural Chemistry," 1 ed.) and linger ( Mora 1844 
241), after Saussure's experiments (Liebig^ nnal » xln. 275), Johns* 
("Mitth d (Econ. Ge 'sells, zu Petersburg? 2 heft 162, extracted mWolils 
"ChZ Forschungenr 202), and Trinchinetti's ( « Su Ifacolta assorbente 
dellaradici " 55), the assumption of such absorption is the less unsafe, that 
f hi been long demonstrated, that roots have the power of absorbing 
^v^e^teble substances, e. g, tannic acid, narcotic extracts, &c. 
(See Mulder, « Phys. Chem.") 

The inorganic compounds which are taken up by plants as food 
and which furnish them with the four principal elementary bodies 
whlh They"e for their formation, are water, carbomc ae* 

and ammonia. already been discussed, 

As the absorption of watery fluids has aneauy 
I now turn to the consideration of carbonic acid. This it is well 
known exists universally diffused in atmospheric air and m water 
Shnple experiments prove that plants do not absorb the carbomc 
^dissolved in water, with the latter, by means of their roots, 

\ X 


*. - - 




but that their green-coloured organs, consequently their leaves in 
particular, possess in a high degree, so long as they are exposed to 
light the facultv of absorbing carbonic acid from the medium, be 
it air or water, in which they are placed, and of secreting oxygen 
gas in its place. 


cially to the admirable experiments of Saussure, which have been 
fully confirmed by later ones of Grischow, Boussingault, and 
others. The phenomena may be summed up m the following 

statements. . „ 

When green-coloured plants are exposed to the influence ot sun- 
light under water containing carbonic acid, they exhale oxygen 

' This exhalation of oxygen does not take place m boiled 

When plants are exposed to the influence of sunlight in atmos- 
pheric air to which carbonic acid (up to 1-1 2th of its volume) has 
been added, they remove the carbonic acid and exhale oxygen in 
its place. This absorption of carbonic acid takes place very soon. 
Boussingault (" Economic ruralc," i. 66) placed a shoot of a Vine 
bearing twenty leaves in a glass globe, and while the sun shone 
upon the apparatus, drew through it in an hour fifteen litres ot 
atmospheric air which contained ,0004 to ,00045 of carbonic acid, 
and at the exit of the air from the globe, the carbonic acid was 

to ,0001 or ,0002. According to Chevandier s calcu- 
lations, the trees of a forest, durin ." " ' ' 
which they bear leaves, withdraw from the column of air standing 
above the forest l-9th of its contents of carbonic acid. 



When a leafy shoot with its lower end cupping m waw* w«- 
tainino- carbonic acid, is enclosed in a glass globe, its leaves exhale 
more oxygen than when its lower end is dipped m common water. 
A leafy shoot still connected with a tree, enclosed in a glass globe, 
increases the oxygen gas in the globe. Therefore m both cases 
the carbonic acid carried up with the ascending sap into the leaves 
is retained by the latter, and oxygen gas given off in proportion 

The exhaled carbonic acid is not contained in the plant in the 
form of gas, before its separation, for plants which contain no air, 
like Gonfervce, or leaves from which the air has been exhausted 
bv the air-pump, exhale oxygen in like manner. Pieces of torn 
leaves possess this function as well as entire leaves ; leaves, on the 
contrary, which have had their organization destroyed by pres- 
sure give off no carbonic acid, neither does the epidermis of the 
leaf.' The quantity of oxygen gas which leaves give off depends 
upon their superficial extent and not on their mass. 

The secretion of oxygen varies much m abundance under lllu- 

— - ■ "■ - 1 x "um. According to 


the researches of Draper 

the organization of plants 









SwSZ act's 'adding tTthe intensity of its &*^J™£ 
the chemical and heating rays of the spectrum are without effect. 

Observ. The amount of oxygen given off is determined by tiemoM 
of carbonic acid furnished to the plant ; the volume of the gas given off 
from the plant also corresponds to the carbonic acid taken up by it, but 
thTgas exhaled does not consist of oxygen alone, a more or less consi- 
derable quantity of nitrogen being intermingled with it Draper (I. c. 
180) obtained the following results : 





Pinus Tceda. 


16, 16 

27, 16 
22, 33 

Poa annua. 



8. 34 
13, 84 


22, 10 

When the experiments are made by exposing plants to the sun under 
spring-water, a part of the nitrogen is doubtless derived from the water 

rwell as another part from the *™^£^^«^^ 
plant; but these circumstances do not explain the exhalation ol mtro e 
comnletelv for according to Draper's experiments, it takes place wUen 
XCtotellv deprived off air by the air-pump are experimented on m 
w/ater cotS/ no nitrogen, and the quantity of nitrogen exhaled in- 
closes in proportion to the amount of oxygen during the experiment, 
wMe the rewse must occur if this intermixture depended on a diffusion 
^^Stweaa the oxygen exhaled by the I^^£*£ 
contabied in the water and in the plant. Draper draws from his expen 
ments the conclusion that the exhalation of nitrogen » J>~^ l* e ™ 

of a ferment in the decomposition of the carbonic acid. 

from the results of Saussure's experiments, since m particukr «pen 
ments the exhalation of nitrogen was so consid erabfo, th^td mta^ 
nous contents of the plant did not suffice for it he there 
we could scarcely assume otherwise than that the nrtrog ^^ 

from the air contained m the water and the plant. ^ 

— — j 


required. _ n ^voren eras given off by the plant is 

The reason that the quantity* af oxyge ^ f j^J of ^ 

™^tialto^o«b<^^_^^^.^ ft of . Blan t. enters into 

unequal to the carbonic acia ^ ^ ^ of the plantj enters into 

SSLS S^^XSJKi^ in it. Many phenomena 


g 2 









traversed by wide air passages, are exposed to light under water, the 
oxygen does not flow from the surface of the leaves, but from the cut 
surfaces. It is therefore evident that the gas has to overcome a certain 
resistance to penetrate the epidermis, and we may fairly conclude that 
in many uninjured leaves, a portion of the oxygen excreted m the green 
substances is carried by the intercellular passages and vessels into the 
stem and roots of the plant, and consequently arrives at parts not green 
which as will appear presently absorb oxygen ; consequently a portion oi 
the oxygen must be deficient, on the determination of the amount formed. 
Tor this process speaks Dutrochet's observation (« M emoir " i. 340), that m 
tfmnphcea lutea the air contained in the interior of the plant contains 
less oxygen the further from the leaves it is taken ; in the roots, eight per 
cent. : in the stem, sixteen per cent. ; in the leaves, eighteen per cent. In 
accordance with this, stands the fact, that the vessels of the stem of the 
gourd contain 27 -9 to 29-8 per cent, of oxygen by day (Bischoff "de vera 
vas. spir. nature? 83), while by night no oxygen but much carbonic 
acid is formed in them (Focke, " de respirat. veget.," 21). ? 

It may be mentioned as a curiosity, that, according to Schultz s state- 
ments ("Die Entdeckung der wahren Pjlanzennahrung"), the whole theory, 
that plants exhale oxygen in place of the carbonic acid taken up, rests 
upon an error, for the green parts of plants do indeed decompose vegeta- 
ble acids, and salts of these acids, under the influence of light, but carbonic 
acid forms an exception to this. Wonderful to relate, hydro-chloric 
acid, which contains no oxygen, is named among the acids yielding most 
of it. It is unnecessary to remark that the repetition of the experi- 
ments by Boussingault, Grisebach, and Grischow, fully sustain the experi- 
mental skill of a Saussure against that of the Berlin physiologist. 


The absorption of carbonic acid, and exhalation of oxygen by 
the green parts of plants, under the influence of light, are but a 
part of the complicated relations in which plants stand to atmo- 
spheric air In order to form a conception of these, we must at 
the same time investigate the behaviour of the green parts in 
darkness, and of organs not of a green colour. 

the chief guide here. . . 

As soon as green-coloured parts are withdrawn trom the in- 
fluence of light, their action upon the surrounding air is converted 
into the opposite, they now absorb oxygen, and exhale carbonic 

' " The amount of oxygen taken up varies m the leaves oi 

Saussure is again 


different plants : within twenty-four hours, from half to 



leaves. The volume of the carbonic 

acid exhaled, is somewhat smaller than the quantity of oxygen 
taken up; when the leaves are again brought to the light, they 
again exhale the oxygen which had disappeared 

All parts not coloured green (Fungi, roots, stems, flowers, &c), 
whether exposed to light or not, take up oxygen and exhale 

carbonic acid. . . 

It is usual to apply to thi s absorption and exhalation ot parti- 





cular kinds of gas, the term respiration. Many 1»™j^"^ 
the term as inapt, because plants have no orp n ^X Xt 
and the like. Let us not contest words, but encmir em what 
relation these processes stand to each other and to the life ol the 

^Hants, from what has been said have a doub ^f'f^^ 
consuming carbonic acid and exhaling oxygen by day m the green 
coloured oW and one connected with a consumption of oxygen 
and a formation of carbonic acid in the green organs by night, and 

in those not green by day and night. w wW 

The question, which of these processes predominates, whether 
on the whole, the plant consumes or forms a greater quantity of 
carbonic acid, whether consequently the respiration of plants is 
on the whole a deoxidating or an oxidating process, is again tuily 
cleared up by Saussure s experiments. 

the air 

is found unaltered in volume and composition after ^an equal num- 
ber of days and nights ; thus the plant has formed just as much 
carbonic acid by night as it has consumed in the day Bu il 
carbonic acid is added to the atmospheric air m which the plant 
ve-etates, or the plant is caused to absorb water containing car- 
bonic acid, it exhales oxygen into the surrounding air. 

There can be no doubt that plants m open air are m the same 
position as those in the last experiment, A very considerable 
r ... <* -1 • „„:a ;* /»^r.f v hpiiiP* added to trie 



XT'e^^ S^^^ *5 this.constant addition of 
carbonic acid above the usual amount, is again removed from the 
air by plants and replaced by oxygen. Consequently, plants do 
not purify the air by increasing the proportion of oxygen m it (it 
we do not take into account that carbonic acid which is not formed 
at the expense of oxygen of the air, such as that derived from vol- 
canic sources), but by the removal of the carbonic acid constantly 
flowing into the atmosphere, formed at the expense of atmosphenc 

° X lf o^'der to become acquainted with the influence which these 
two kinds of respiration exercise upon the vital operations of 
plants, we must investigate the phenomena that present them- 
selves when one or other of these breathing processes is inter- 

rU When plants are prevented, by keeping them from the light 
from absorbing carbonic acid and exhaling oxygen, then: nutntaoa 
suffers and thSy become etiolated. They do continue ^ fonn «ew 
shoots at the expense of the nutriment contained m their older 
parts ; these are even larger than those developed under the m- 


nuenee 01 ngnx, out, weais. <*^ w *r> —- 

do not become green, the normal qualities of the saps are not pro- 
duced, bitter, milky plants remain sweet, &c. Some plants will 






i A: 









exist for months in this sickly condition, but they cannot bear it 


On the other hand, when the respiration connected, with the 

consumption of carbonic acid is stimulated by affording to the 
plant, while exposed to light, an unusual quantity of carbonic acid, 
its nutrition is rendered more active. Even when nothing but 
■ water and carbonic acid are given, they are able to increase their 
organic substance, and the weight of this increase amounts to 
something like double that of the carbon which is contained in 
the absorbed carbonic acid. 

Observ. In an experiment of Saussure's, little plants of Tinea appro- 
priated 217 milligrammes of carbon from the carbonic acid absorbed, and 
their organic substance was increased about 531 milligrammes; two 
plants oi Mentha sativa consumed 159 milligrammes of carbon and in- 
creased in weight about 318 milligrammes ("BecJierches" 226). 

When the respiration of plants connected with absorption of oxy- 
gen and formation of carbonic acid, is interrupted by placing the 
entire plant in air containing no oxygen, for example m nitrogen, 
or by placing the plants under the air-pump, all their functions 
at once become paralyzed. The unfolding of the leaves and buds 
is checked and they rot, the leaves no longer turn towards the light ; 
they no longer exhibit the alternate movements of waking and 
sleeping; sensitive leaves lose their irritability (Dutrochet, "Me- 
moires," i, 361, 483) ; even single organs cut off from air decay while 
the rest live on : for instance, roots which are covered too deeply 
with earth. Plants die particularly soon when kept in air devoid of 
oxygen, in the dark ; for example, a Cactus— a plant generally so 
obstinately retentive of vitality— died in five days (Saussure, I. c. 
87). Plants bear being placed in such an atmosphere better when 
they are exposed to the alternations of day and night, since they 
exhale a small quantity of oxygen from their own substance by 
day, and from this form carbonic acid at night, which is again 
consumed by day. Plants are capable of holding out in this way 
a long time, although certainly in a very miserable way and with- 
out manifesting growth ; but if the small quantity of oxygen 
which they form is removed by sulphur and iron filings, or the 


a second time, and die. 

It is clear, from the precedin 


that the respiration of 

green coloured parts during the action of light is related to the 
nutrient processes of the plant, since these become abnormal when 
the function is interrupted, but yet the plant can maintain its 
existence a long time under these conditions. But that which 
occurs in common to all parts, and which consists of absorption of 
oxygen and exhalation of carbonic acid, stands in immediate rela- 
tion to the life of the plant. If the chemical process, which goes 
on unceasingly in all the organs of plants, through the action ol 







^^^yonj^^^^^^ff^ { ^ 

just like an 

animal, becomes asphyxiated, 

an animai, wwmc» aoj^j-— "•<--» - . ,,. 

amcKJV If we wish to speak of a respiration in plant* this 
o^ge^consnming breathing deserves the name far more than 


oxygen-consuming oreaumig u^iv^ -w ™~~ 

ras is a true vital air to plants. 



■moles- o^rvo'Pii p*as IS a uue vilcli <*jljl uv ^/^xx W . — -- 

rfS. pUnt towards the atmosphere becomes the more corus- 
cated, that it does not merely absorb oxygen from wrthouV lake 
the animal, but also a part of that prepared in its own green 

voserv. Liebig must shut his eyes to facts lying open before Hm, when 
he pers 1 ("Agricultural Chemistry; 6th ed.) that the region co^mn- 
ing P oxygen dofs not exist, that the absorption of v^***^* £ 
do° Wiethe life of plants, but is a process of ^ZnTc^olld 
dead wood as in the living plant, and that the exhalations carbomc 

stands in no connexion with the * b !°^ ™£^1 by the roots, 
bonic acid simply rises in the stem with the watei token, up oy 
as in a cotton wick, and so passes out into the «•«•- 


Although the 

Altiiougn tne great diffusion of water and carbonic acid l dm** 
eve7vwhere give full opportunity to plants, of appropriating the 
t^Slelement^of their Lbstance (carbon hydrogen, and 
oxwenl they have not always the opportunity of absorbing tne 
2S of nitrogen requisite for a vigorous development, whence 
tTe imp'ortntV^ winch nitrogenous f^^^\^Z- 

itip- The nitrogen of the air is a perfectly mdiffeient body to 
vfrds pLte Iven Saussure indicated that plants can only take 
up nitrogen in the form of solutions of organic substa *ces or ot 
ammonia; the latter has been especially ^^X^£l 
and his was the merit of demonstrating by ex penment that ammo 
niacal vapours exist in atmospheric air and that «™ m °™^ 
in all ram and e^^J^^^^^***^ 



attention do uie picocnv^ ^ ^~~~~ — - 
ascending sap of the Maple, Birch, &c. 

SS^ of ammonia from th< , soil —^m tote 
vated plants, only because rt is desired to stomal** ttiem 
production of a great mass of the constituents of blood, ■ a qui 
uifferent questiol In the first place, ™ -penment has she™ 

that plants are capable of .f§W£** SSy, it is even 
niacal vapours contained in the ^W^tnonia«I Mlts which 

doubtful whether tto • the w i* »•»» Bouchardat ("iic- 

plants in watery solutions -poisonous to *-££**•. 

1000 or 1500 




rience that ammoniacal salts mixed with the soil, greatly further 
the growth, of plants. These different results render it in the 

highest degree probable that the ammoniacal salts enter into com- 
binations with the constituents of the soil, which exercise a dif- 
ferent action upon the plants, from that of the pure salts. In this 
respect the investigations of Mulder upon the humous substances 
are of the highest value. According to these, carbonate of ammonia 
cannot exist for any time as such in humous, but is decomposed by 
the organic acids of the soil; since therefore compounds of ammonia 
with sulphuric and hydrochloric acids, &c, must be converted by 
the carbonate of lime in the soil into carbonate of ammonia, there 
exists the highest probability, that plants always receive ammonia 
in combination with the organic acids of the soil, which would 
explain the difference between the poisonous action of pure ammo- 
niacal salts and their favourable influence when mingled with the 
soil. Moreover, it is not by any means proved that the air con- 
tains enough ammonia for us to regard it as anything like a suffi- 

cient source of nitrogen to plants, while Mulder's experiments 

point to a production of it in the soil ; in any case the amount 

contained in the soil is very considerable, according to Krocker 

(Berzelius, " Jahreshericht" xxvi. 265) it amounts to 40.45 
pounds in a layer ten inches deep extending over a hectare in 

sandy soil, 20314 in argillaceous soil. From these circumstances 
as well as from the experiments of Boussingault and Mulder, it in 
any case follows, that the roots and not the leaves take up the 
substances which furnish plants with nitrogen, while, on the con- 
trary, the leaves play the especially active part in the absorption 
of carbonic acid, 

d. Elaboration of the Nutriment. 

"We know scarcely anything of the chemical processes in the 
interior of plants, on which depend the assimilation of the nutrient 

matter taken 


and the gradual conversion of this into the 

In considering the 

various compounds which the plant contains. 

nutritive processes of plants, two circumstances first strike us. 

1, The uncommonly great agreement of all plants in respect to the 

production of a series of neutral hydrates of carbon, which furnish 
the material for the solid parts of plants, as also in respect to the 
formation of proteine-substances which play an active part in the 
process of development of the cell ; 2, an infinite variety of chemi- 
cal compounds, which are deposited in the different organs of 
particular groups of plants, in spite of the uniform structure 
and the agreement in the nutrient process, so far as relates to 

The chemists of our days, especially Mulder, have sought to 
make comprehensible the formation of such a surprising abundance 
of products by bodies so simply and uniformly organized as plants 









_« Since the plant is a complex of closed vesicles filled with 
fluid, the contents of which stand in reciprocal connexion by en- 
dosmose, this structure alone affords the possibility of the forma- 
tion of the most varied chemical compounds. Even if we would 
suppose a plant to contain a fluid of the same composition in 
all its cells, this equilibrium could not last a moment ; for on the 
one side the sap in the cells of one organ would acquire more con- 
sistence through evaporation, and thereby call into existence an 
opposition toward the other cells, while in the cells of another 
organ endosmose might cause the absorption of a thinner fluid, 
and thus give rise to a flowing of the sap from this organ to the 
former,— which would at once cause a multiformity of the compo- 
sition spreading throughout all the organs. When we take into 
consideration, that on one side ammonia with organic compounds 
are taken up by the cells, while on the other side carbonic acid is 

decomposed, its carbon appropriated, and its oxygen given out 
moreover that the cell-walls act by contact upon the contents of 
th<- cells and that this action again differs according to the differ- 
ent cheniical qualities of the cell-wall and contents,— it becomes 
explicable how the most manifold transformations of cell-contents 
and the formation of abundance of products come to pass in the 

Vegetable Kingdom, the only limitation that exists being the fact 
that the elementary substances do not combine together under all 


This is all correct enough, but it does not advance us one step 
in the knowledge of the processes of vegetable nutrition. When 
we place the contents of all the vessels in a chemical laboratory 
in a condition of reciprocal connexion, we certainly expect that 
an innumerable series of chemical processes will result, but what 
they will be we know not, unless we know what the contents of 
each vessel consist of, and in what order and under what circum- 
stances the contents of one come into operation upon the contents 
of another. It is of this that we are ignorant in plants, and so 
long as it remains uninvestigated, we can only set up more or 

less probable conjectures. 

These circumstances will be my apology for treating this sub- 
ject as briefly as possible. < . 

One of the most general phenomena, since it occurs m all 
^.reen-coloured plants, is, as we have seen, the absorption of car- 
bonic acid, and the exhalation of oxygen gas. The experiments 
of Saussure demonstrate that this process stands in most inti- 
mate connexion with the formation of organic substances; no- 
thing seemed easier than to explain this process. The neutral 
compounds of the plant (sugar, gum, starch, inulme and cellulose) 
are composed of carbon and the elements of water; it was only 
requisite to assume that the carbonic acid was decomposed in the 
leaves, its oxygen given out as gas, its carbon combined with 
water,' which is° never wanting in the plant, and the entire pro- 





cess was elucidated in the simplest way. This theory conse- 
quently met with universal acceptation, and in all books the 
decomposition of carbonic acid, taking place in the leaves, is 
spoken of as a settled fact, but we are without one proof that 
such is actually the state of the case. Liebig remarked, that it 
was far more probable that it was not the difficultly decomposable 
carbonic acid, but the readily decomposable water which was 
separated into its elements, and its oxygen given off, while its 
hydrogen entered into combination with the carbonic acid. 
The result was of course the same. There is no means of testing 
the correctness of either of these theories. But it is possible that 
they are equally false, that the carbonic acid does not enter into 
combination with the hydrogen of the water, but with another 
substance contained in the plant, and that oxygen becomes free 
by the decomposition of an organic substance previously formed. 
The latter is the opinion of Mulder, who assumes that the plant 
does not decompose carbonic acid because it is green, but while it 

is becoming green ; new chlorophyll is constantly forming under 

the influence of light, with this originate the wax and starch 
associated with it, and an excretion of oxygen is necessarily con- 
nected with this ; and this oxygen goes off partly in the form of 
gas, and in part oxidizes the colourless chlorophyll, and converts 

it into green. On the other hand, Draper, on account of the ex- 
halation of nitrogen which he regards as necessary, assumes that 
chlorophyll acts the part of a ferment in the process of decompo- 
sition of carbonic acid, and in this itself suffers a decomposition, 
in consequence of which nitrogen is set free. Thus, at the very 
first step of the nutrition of vegetables, which was supposed to be 
the most thoroughly investigated, opinions become divergent ; 

The only cer- 

each has a certain probability, not on 

U lb 



tainty is, that carbon and water remain within the plant, and are 
applied to the formation of its organized substance. 

On the question of the combinations into which the absorbed 
nutriment first enters, the views of chemists stand in no better 

Saussure's experiments shewed that plants to which 
carbonic acid and water were afforded, acquired increase of 
weight equal to about twice the weight of carbon taken up. 
It may be considered probable, as Davy assumed, that the car- 
bon absorbed enters at once into a neutral combination with the 
elements of water ; in all probability this compound is soluble in 
water; since, therefore, dextrine is found in all green coloured 
organs, it is not unlikely that this, or in other cases, sugar is the 
form under which the said inorganic substances combine into 
organic substance. 

But another probability is opposed to this notion, that the con- 
stituents of water and carbon enter at once into a neutral com- 

bination. AH plants contain, besides 


neutral substances, 

organic acids, in which the oxygen bears a greater proportion to 

* *• 




the hydrogen than in water. Among these acids, oxalic is one 

of the most widely diffused, — scarcely a plant being without it. 
This acid stands very close to carbonic acid, since — supposing it 
anhydrous — it contains no hydrogen, and differs only from car- 
bonic acid, by containing less oxygen. It may, with Liebig 
("AgricuU. Ohem." 6th ed.), be considered very probable, that the 
deoxidizing process connected with the respiration of the green 
organs, does not convert the carbonic acid and water at once 
into neutral compounds, but first only a partial separation of 
oxygen takes place, and the carbonic acid is changed into organic 
acids, first of all into oxalic, the hydrate of which, by separation 
of o-reater amounts of oxygen gas, can be transformed into malic, 

citric, and other acids. It may be assumed of all these acids 
that they are capable of conversion into sugar, starch, &c, by the 
addition of hydrogen. If this conception is adopted, the con- 
stant occurrence of vegetable acids appears a necessity for the 
nutritive processes of plants; and it will explain why plants will 
not flourish when they do not take up a certain quantity of basic 
substances, to combine into salts with these acids. On the con- 
version of an acid into a neutral substance, the base becomes 
free again, can unite with a new portion of acid, and so in the 
course of time, a comparatively small quantity of base may 
bring about the formation of a very great quantity of neutral 


Observ. This notion of the importance of acids in the vegetable eco- 
nomy, has something very attractive about it, since it appears to solve a 
series of questions, but on closer examination a number of doubts present 
themselves. On the one side, the assumption that the acids are formed 
by a decomposition of carbonic acid, appears in any case too general, 
since in many plants with fleshy leaves, an acid is formed every night 
(thus at a time when no carbonic acid is decomposed), which acid is again 
decomposed by day. Here the acid is doubtless formed through oxida- 
tion of a neutral compound. On the other hand, that theory does not 
perfectly explain the case of the basic substances. If these had no other 
destination in the plant than the purpose of fixing free acids, it would 
be all one to plants whatever base was absorbed from without ; any one 
could be substituted for any other. This is certainly, in some degree, 
the case with regard to bases which are very closely chemically allied, 
like potash and soda, or lime and magnesia, but this substitution is only 
compatible to a certain extent with the healthy growth of the plant. 
Particular plants require particular bases, lime, potash, &c, and die when 
they do not find them in the soil. Therefore, the specific properties of 
the bases stand in a definite relation to the nutritive processes of plants, 
albeit, the grounds of this relation are still unexplained. If, moreover, 
the acids form these transitional stages between carbonic acid and the 
neutral compounds, it is remarkable that so many plants produce an 
acid, and especially carbonic acid, in far greater quantity than is neces- 

sary for this purpose, depositing it, in combination with lime, in an in- 
soluble condition, crystallized in the cells, and yet do not subsequently 








\ ■ 






re-dissolve these crystals. It is true that nutritive substances (starch, 
fixed oils, &c.) are frequently produced in greater abundance than the 
requirements of the moment demand, and are deposited in the cells of 
particular organs, but these deposits are only temporary accumulations of 
food to be made use of subsequently; those deposits of insoluble salts 
appear much more likely to be intended to remove from the circuit of 
active juices, compounds which are superfluous to the plant 

Again, this theory does not explain the exchange of different bases 
at different periods of the age of the same organ. From the analyses 
of Saussure was derived the general rule, that young organs are espe- 
cially rich in soluble alkaline salts, older plants in earthy salts and 


A second doctrine propounded by Liebig, is connected most closely 

with this opinion as to the office of the alkalies to neutralize the organic 
acids, namely, the notion that for every species of plant, the amount of 
oxv°*en of the carbonic acid contained in its ash, in the combustion of 
salts originating from vegetable acids, is constant, no matter what soil 
the plant may grow upon ("Agricull Ckem" 6th ed.). For Liebig assumes 
that a plant forms no more of the acids which it produces, than is 
directly requisite for its vital operations, and that these therefore take 
just so much alkali as will fix these determinate quantities of acid. But 
weighty objections may be opposed to this doctrine. I have already ob- 
served that many plants do not produce the organic acids in that quan- 
tity which they would require were these converted into neutral com- 
pounds, but in very considerable superabundance, as for example, all 
specimens of Cactus unceasingly deposit extraordinarily large masses of 
tartrate or oxalate of lime in their cells, as insoluble crystals ; the oxalic 
acid of these crystals is wholly withdrawn from the nutrient ^ operations, 
yet elementary analysis would make its lime appear to exist in the state 
of carbonate, while at the same time, no conclusion could be drawn from 
its quantity, as to the amount of acid necessary in the nutrient processes 

of these plants. 

carbonic salts, are not combined with organic acid in the living plant, 
but in many plants crystals of carbonate of lime occur ; carbonic salts are 
deposited in the substance of many cell-membranes, and all cell-mem- 
branes are combined with alkalies and earths ; consequently, we cannot 
draw from the analysis of ashes, as Liebig assumed, a proof of that law, 
and this is the less possible since, moreover, the fixed alkalies may be 
replaced by ammonia. 

Whatever may be the character of the chemical action to which 
neutral compounds owe their origin, it is at all events, beyond 
doubt that they are produced by a deoxidizing process takin 


place under the influence of light. The effect of the deoxidation 
extends still further, for there can scarcely be a plant which does 
not contain compounds in which the oxygen is not contained in 

smaller quantity, in proportion to hydrogen, than in water, even 

To this class belong chlorophyll 

if it be not altogether wanting. 

and the wax connected with it, the incrusting substances of the 
wood-cells, the fixed and essential oils, resin caoutchouc, &c. 
With the exception of the fixed oils, which doubtless originate 








from starch, we are ignorant 

from what other compounds all 

these constituents are derived ; yet there can be no question that 
their hydrogen is originally obtained from water, and that their 
origin is connected with a separation of oxygen. It is remark- 
able of many of them, especially in the formation of essential oils, 
how much their production is favoured by the action of strong 

The compounds containing nitrogen stand in opposition to those 
devoid of it. Though in quantity they may stand tar behind the 
latter, their importance in the vital phenomena of plants is not 
less ; nitrogenous substances, as we have seen, line the cell as the 
primordial utricle, and consequently the contents of the cells are 
ordered under their immediate influence : thev originate the de- 

velopment of new cells, and set in action the decomposition of 
carbonic acid. Doubtless these constitute but a few fragments of 
the great part which these substances play in the living plant ; for 
many chemical processes, such as fermentation, the formation of 
hydrocyanic acid and amygdalin , the conversion of starch through 
diastase, &c, indicate that the first impulse to the transformation 
of all vegetable compounds, is principally given by the proteme 
substances. The great importance which these substances have m 
the vital economy of plants, is also denoted by their anatomical 
conditions, since they are contained in great abundance in all 
organs destined to further development, and which are endowed 
with more important physiological activity ; e. g., in the points of 
roots in leaf and flower-buds, pollen-grains, the embryo-sac of 
the ovule, and in seeds; while in old organs, principally employed 
in conveying the sap, they occur in far inferior quantity. 

It is as good as certain, from what has been stated above, that 
ammonia in combination with organic substances furnishes the 
nitrogen requisite for the formation of the proteine substances. 
In what organs and under what conditions these compounds are 
formed we know not. Mulder ("Phys. Chem." ) is of opinion that 
they are formed at once in the points of the roots, and are dif- 
fused from here over the rest of the plant. But a determined fact 
may be opposed to this view, namely, the occurrence of salts of 
ammonia in ascending crude sap, which rather indicates that the 
formation of nitrogenous compounds takes place chiefly, if not en- 
tirely, in the leaves. 

Of the formation of the other nitrogenous compounds of plants, 
such as the vegetable alkalies, indigo, &c, and of their import to 
the plant, we know simply nothing ; I therefore consider it super- 
fluous to make any further observations on them here. 

e. Secretions. 

In the consideration of the nutrient process of plants, the ques- 
tion presses itself upon us, whether, in the series of true formations 
which the mutual action of the substances contained m the plant 





■ l 



V ^*fc 


I II' 









t . 




nutrition an* growth of the plant are found, or other compounds 
arise at the same time, which are of no further importance in 
the functions of the living plant, and must be removed from the 
cells carrying on the vital functions of the plant. This question 
cannot be answered with certainty so long, on the one hand, as 
the nutritive process is so imperfectly known, that in regard 



ever explanatory of the details; and so long, on the other hand, 
as we are unacquainted from physiological causes with the import 


but yet not universally diffused throughout the Vegetable King- 
dom ; e. g., of the essential oils, resin, the milk-saps, the vegetable 
alkaloids, &o., which substances are usually denominated secretions. 
A large portion of these substances, in particular the essential oils, 
the alkaloids, the majority of the milky juices, are in the highest 
degree poisonous both to the plants which prepare them,^ and to 
others when they are caused to absorb them. These secretions are 
commonly separated from the other matters within the plant, being 
either, as is frequently the case with the essential oils, enclosed in 
special cells, or contained in canals which run between the cells, 
as is often the case with essential oils and resin, and universally 
with the milky juices. In the majority of plants containing milky 
juices, these canals are lined with a special membrane, and are 


canals destitute of proper membranes, running between the cells, 
since true milk-sap is found in the latter in many plants, as in 

Observ. Although the theory of the milk-sap is but distantly related 
to the subject of the present treatise, the cell, yet I cannot avoid touch- 
in <* here upon the views propounded by Schultz, since if they were con- 
firmed, they would effect a complete metamorphosis of the theory of the 
nutrition of plants. Schultz has striven, for a long series of years, in many 
essays (especially in "Die Natur der lebenden Pflanze" 1823-28 ; "Sur la 
Circulation et sur les vaisseaux laticiferes dans les Plantes" 1839 ; "Die 
Cy close des Lebenssaftes" 1841), to demonstrate a complete analogy be- 
tween the milk-sap and the blood of animals. According to him, the milk- 
sap is organized, and consists of a plasma becoming coagulated out of the 
plant, and of globules which correspond to the lymph and blood corpuscles. 
On the coagulation of the milk-sap, an elastic coagulum, like the fibrine of 
the blood, is said to separate, which is composed of caoutchouc, pure or 
minded with wax and gum, enclosing the globules of fatty or waxy mat- 

ter, the larger of which are 

clothed with a membrane. In addition 

to caoutchouc, the plasma contains sugar, albumen, gum, and salts, in 


In all this account of the analogous organization of the milk-sap and 

the blood, there is not a word of truth. The caoutchouc, as I have de- 
monstrated by the simplest experiments (" On the milk-sap and its motion." 






Bot Zeit. 1843, 563) is not dissolved in the plasma, but forms tlie glo- 
bules, which are destitute of enveloping membrane and of any organization 
whatsoever ; the fluid part of the sap contains no caoutchouc, and does 
not coagulate, but dries in the air into a brittle crust, composed of gum, 
which may be re-dissolved in water, whereby the original character of the 
milk-sap is restored. Therefore the comparison of the milk-sap with the 
blood, in regard to its organization, is in every respect a mistaken one. 

According to Schultz, the milk-sap exhibits a double motion, an inter- 
nal one and a circulation. The internal motion, observed both in freshly 
effused milk-sap and in that still contained in the vessels, depends on the 
molecules of the sap (by which name the globules appear to be meant), 
sometimes joining together, and sometimes separating. The same process 
goes on upon the walls of the vessels, and it is most distinctly noticed 
that the said union and separation takes place, in the same way, between 
the molecules of the sap and those of the walls of the vessels, as between 
the molecules themselves, and in fact the attraction and repulsion of the 
portions of the sap take place in a definite direction, so as to communicate 
a progressive movement to the whole mass of sap. . 

It is impossible to make worse observations, and to interpret what is 
seen more incorrectly, than Schultz has done in regard to the internal move- 
ment of the milk-sap. If the globules are small, as is usual, they exhibit 
the molecular motion of Brown, and, indeed, after having been dried up 
and re-dissolved in water, just as well as when fresh; if larger, as in the 
milk-sap of Sambucus Ebulus, and Musa, there is no molecular motion. 

All the rest is pure fable. 

The flowing movement is, according to Schultz's statements, completely 
independent of external influences, and goes on in the same way in per- 
fectly uninjured plants as in detached organs and in separate layers cut 
off the plant, which would prove that it is not caused by mechanical 
effusion of part of the sap from the walls of the vessels. It is stated that 
it may often be observed in detached slices, that the sap flows onwards in 
a wounded vessel into f the uninjured part of it, while it flows out from 
other wounds which lie in the direction of the current. Since therefore 
the sap flows in one portion of the vessels from the leaves to the root, and 
in another portion in the reverse direction, a kind of circulation is pro- 
duced (called by Schultz Cyclosis), which, however, does not run through 
a definite and perfectly circular path, but parts into numerous circular 
courses, returning into themselves, in the manifold ramifications and 
anastomoses of the vessels. 

That the sap must be in motion in an injured plant, is self-evident, for 
it is well known that it flows with force out of wounds in a lacerated 
milk-vessel : which is caused, not by contraction of the vessel, but by the 
pressure of the cells surrounding it, since the phenomenon presents itself 
in plants wherein the canals of the milk-sap do not possess any proper 
wall. To make out the behaviour of the milk-sap in the vessels, the ex- 
periments must necessarily be made on uninjured plants. From my own 
observations, — I, like Amici and Treviranus, — must deny its movement in 
the uninjured plant. A leaf of Chelidonium is sufficiently transparent 
when it is laid beneath the microscope with its lower surface upwards, 
and covered with a drop of oil and a glass plate, to allow of the appear- 
ances in the milk-vessels being seen. If we examine in this way a leaf of 






I J 






an uninjured plant growing in its pot, or even » j^^^^J? 
the cut surface of the petiole, to prevent ^^*X^ 

which at first is disturbed ^.^^^^Toi £&£££ 
which it is exposed in spreading it out upon tlie sta^e £ 

sun Lit was thrown upon a part of the leaf on one side of the field of 
vlion thTsap was set in motion, and the current was reversed when the 
Swa, thrown upon the opposite side. These experiments place it 
Itonrdonbtto me/that the Gliosis has no existence ^and^at the mov - 
Jvi- of +b* san is produced by mechanical causes. Ine turtner piooi pi 
SSo* founTby Schultz in tie currents of the protoplasm contained m 
£ Is wTch he assumes to be the same mi k-sap «*^ ft m J*^ 
cations of the milk-vessels penetrating the cell walls, needs no * ord of 

Semite" derives from the pretended organization and movement of the 
bcnultz aeiivcb uu _ i ^ t m p i ants as 

S + Tdefinrbe relation to the rest of their organization and systematic 
without a de ^™ d asgerts the contra ry, since he declares that he 
Cfound tttS - the majority of the families investigated by 
has found tne rese arches are altogether unworthy of trust, for 

he minxes ogeTr the most different things. In the second place, the 
he mingles to et ^ - t unsuita ble m the stated purpose, 

composition of the m ilk sap is <1 [h ^ fibrine of fche blood . 

Schultz compares the ^^^V^t beca use the caoutchouc is 
The comparison ^^s shewn f 7^!"^ buV Lvmg that out of the 
not dissolved in ^..^^^^ Sorties of caoutchouc are such, 

Z^Z^T^s ctld t named less fitted for the peculiar 
that no coBStonent p ^ ^ indicatlon of posslbl iity 

^TTt^XeTmeUrnov^o^ within the plant. TMrdly, the com- 
thatit is capable « i exceeding ly in different plants, and ^re- 

position of tb e ^ »P 7* . although 'niost milk-saps agree in being 
q uently m ^^ e «!SSXacriliniIk. B ap of Euphorbia eancien- 

P -°TT; tbe tild iuice If E. balsamifera; beside the narcotic juice of 
sis stands the mia .J ulce °* ,. , -^ . beside the narcotic of Zocfcjca 
Popowr, the acrid jincaof «^^ ies of Lactuca; heside the 

^tn^ -«, the harmless juice of 






A . innocua. These obj ections are met, it is true, by Schultz with the asser- 
tion that the milk-saps of Euphorbia, &c., are not poisonous, but that the 
poisonous matter comes from reservoirs of secretion wounded at the same 
time as the milk-vessels ; this, however, is a complete flight of imaoina- 
tion, for wh ich not the shadow of a proof exists. & 

So the whole of Schultz's theory of the milk-sap is a tissue of the most 
unfounded hypotheses, offering the most glaring contradiction to positive 

Though the physiological import of the secreted fluids preserved 
in the interior of plants is uncertain, there is no doubt that the 
purpose of those secretions which occur upon the surface of plants 
might be more readily made out, if the fluids were excreted in suf- 
ficient quantity to be collected. Whether such excretions occur, is 
still unknown. Here, of course, we can merely have to do with 
those secretions which have a more general diffusion, since local 
exudations, which only occur in particular plants, like the acids in 

the gummy secretions of 

, v ~— ■ 3 special purposes. 

Such a secretion has been attributed by many to the root 




mutata humorum 
Ludgf. Batav. 1789.— Up 

number of authors have cited under this head a treatise by 
Brugmans, "De Lolio ejusdemque varia specie;" but this essay 
seems to have no existence), who thought he discovered that cer- 
tain plants do not flourish in the vicinity of certain others, e. g 
A vena near Garduus arvensis, wheat near Erigeron acre, flax' 
near Euphorbia Peplus and Scabiosa arvensis, &c. He ascribed 
this to the excretion of a watery fluid from the roots of the 
weeds, having the power of corroding the roots of the cultivated 
plants. These excretions were considered by others, for example 
by Plenk ("Physiolog." 43), Humboldt ("Aphorism, a. d. chemisch 

ub. Bewegung d. 

PJianzen." 116), Cotta ("Naturl 

~M "■" " ^-^ •+* w ^^ V m 

Softs" 49), as evacuation of excrements, and the utility oFfallows 
was deduced from the hypothesis that the excrements must be 
allowed to decompose in the soil before other plants could flourish 
in it. But this excretion from the roots was denied by others e. a. 

no very great value was at- 

tached to it The attention of physiologists was drawn again to 

in it. 



Macaire Prinsep instituting, at De Candoll 


which appeared to give positive results. Macaire found, namely 
that plants which had their roots carefully dug up and placed in 
water, gave out into this, chiefly during the night, organic mat- 
ters, which differed according to the kind of plant, being opium- 

L™ ^ L actucew and the Poppy, acrid from Euphorbia, 

At the same time, he be- 



lieved that he found acetate of lead taken up by the plant, again 
excreted in this way, further, that in water whereinto these 

o^/Ox ti- 













K «. 




tions had passed, plants of the same species would not nourish, 


From these 

experiments, De Candolle drew the conclusion that these excre- 
tions were to be compared with the urinary excretions of ani- 
mals, and exnlained from the doctrine, that no organized being 
could use its own excrement for food, the fact of experience that 
cultivated plants, the Cerealia for example, would not nourish for 
any long uninterrupted period upon the same soil. 

The repetition of these experiments by others, left no doubt 
that Macaire had not gone to work with the requisite circumspec- 



torn, lxxii. p. 32) shewed that milk-sap was effused into water from 
the roots of plants of Lactuca which had been dug out of earth 
J1 in consequence of laceration, partly in consequence of 



and Papaver, had grown, some of them for a series ol years, was 


it and these he attributed to the decomposition of the rootlets. 
The experiments of Walser ("Unters. ub. d. Wurzelausscheiclun- 
qen," Dissert. Tubingen, 1838) likewise gave a completely negative 
result, as did also Boussingault's ("Ann. d. Ghvm. et d. Fkys. 1841, 
torn i 217) Moreover that the noxious salts absorbed are not 
excreted by uninjured roots, but only extracted by the water from 
iniured roots, was shewn by the experiments of TT — * ""» 





on Xem^a, and Braconnot demonstrated that Macaire had made 
a clumsy mistake in his experiments, to prove the excretion ot 
an absorbed salt of lead, since he overlooked that the close 
bundles of roots carried the solution of the lead salt over, into the 
vessel of water into which another portion of the roots of the 
same plant dipped, by capillary attraction. 

Under these circumstances, we must regard the secretion ot an 
excrementitious fluid by the roots as not proven. At the same 
time, it is certainly no evidence that the roots do not excrete at 
all I lay no weight upon the reason mentioned by bcnleicieu , 
that the endosmose of the roots must be accompanied by an 
exosmose, for it is too hazardous to deduce the existence ot a 
second phenomenon from one of which so little is known m regard 
to the forces active in it, as is the case of the absorption ot the 




chemical influence upon organic substances placed m contact with 
their roots. Trinchinetti ("sullfac. absorb dradici. 57) observed, 
that a decoction of humus underwent foetid putrefaction when 
left to itself, but this did not take place when the roots of living 
plants were placed in it. In many cases it is observed that the 
roots exercise a solvent action upon solid organic substances; thus 



Gazzen saw this in Clover ; Trinchinetti saw a root of Nepeta 
Catarm grow through the midst of a peach-stone, and the roots 
of Viscum penetrate into the periderm and bark of a tree. 
There can be no doubt, that these effects are produced by a sub- 
stance excreted from the roots. Of what kind this is, we know 
not; yetBecquerel (Guillemin, " Arehiv. de Botanique," i. 398) has 
given an indication in this direction, since he found that roots ex- 
creted a free acid (probably acetic acid), or a substance which was 
converted into an acid in air. This circumstance reminds us that 
Lichens which live upon limestone dissolve the latter, and form 
their fruit in excavations of it, which can only be through secre- 
tion of a free acid. Whether the above-mentioned effects are to 
be ascribed to the free acid excreted by roots, or to the secretion 
of other compounds is not made out. According to Becquerel's 
researches, this excretion of a free acid occurs not only from the 
roots, but from the other parts of plants— the bulbs, tubers, buds, 
and leaves. Becquerel brings it into connection with the evapo- 
ration o£ acetic acid in human perspiration ; if this analogy were 
recognized and the secretion thus interpreted as a true excretion, 
there would still be no inconsistency in imagining it to exercise a 
function, contributing towards the accomplishment of the pur- 
poses of the living plant, even in its excreted condition. 



Observ. Moldenbawer (" Beifirage z. Anatomie d. Pftanzen," 320) ex- 
pressed the opinion that the organic substances used by plants for their 
nutrition, underwent a chemical decomposition by a fluid secreted from 
the roots, and were thus prepared for assimilation. This theory has 
been revived, in recent times, by Schultz (" Die Entdeckung der wahren 
Pfianzennahrunf). He believes that he found living plants (roots as 
well as leaves) decompose solutions of the most varied organic substances 
with evolution of oxygen, before they absorbed them ; thus humous- 
extract becomes acid, milk-sap decomposed, and cane-sugar converted 
into starch-gum. From this he concluded that plants act on the assimi- 
lated compounds in a manner analogous to that of the intestinal canal of 
animals upon their food. How much of truth or error there exists on 
this matter must be decided by future researches of chemists. 

While some discover a removal of excrements in the secretion 
of a watery fluid by the roots, others ascribe the same purpose to 
an aqueous secretion through the leaves. Isolated observations 
had long ago indicated that water is excreted, durino- the nio-ht 
and morning, in the form of drops of liquid, if not from all yet 
irom a great many leaves, since the drops of water which are 
formed at the points and serrations of leaves; owe their origin to a 
secretion, and not to the dew. This subject was especially fol- 

lowed out by Trinchinetti ( 

* J? J.TL * Til 1 J) T • . . it \ 


undescribed f, 

Literal blatt zurLinncea, xi. 66) ; he found little 

glands (which he called glandulce periphyllw) at the spots where 
the excretion took place ; the fluid secreted from these, thouo-h it 


• ■ 


ii 2 







appeared at first like pure, water, contained organic substances, 
and passed into foetid decomposition. Similar observations were 
made by Rainer Graf (" Flora," 1840, 433). 

While this excretion of water occurs only in very small amount 
in most plants, many of the family of the Aroidese, especially Galla 
oethiopica (Gartner, " Beibldtter zur Flora," 1842, 1), Arum Golo- 
casia (Schmidt, in Linncea, vi. 65), evacuate water in larger quan- 
tity from the points of their leaves, so that it flows off m _ drops ; 
this occurs in the most striking degree in a plant described as 

destillatorum (" Ann. of Nat Hist" sec. ser. i. 188), 
in which each leaf — it is true, of colossal size 


o-ave off about half 

a pint every night. The water flows here (as in Arum Colocasia) 
from an orifice in the neighbourhood of the point . of the leaf, upon 
the upper surface, in which terminates a canal running along the 
border of the leaf, while smaller canals, running along the prin- 
cipal nerves, open into this. 

The water secreted, in all these cases, contains but an extremely 

small quantity of organic substance in solution. 

It is probable that the secretion of water in the pitchers of 

- ~ * '-■ ■ n ild be reckoned with 

;' Ann. of Nat Hist 

sec. ser. iv. 1 28), the'fluid secreted by Nepenthes contains only 

27 0,92 per cent, of solid matter, consisting of citric and malic 

the above. 


acids, chlorine, potash, soda, lime, and magnesia. 


rately how far this secretion of drops of fluid water is (as accord- 
ing to Trinchinetti) for the purpose of evacuating substances, 
which, if they remained in the plant, would exercise an injurious 
influence upon its health; yet this hypothesis hardly appears 
probable, when we take into account the extraordinarily small 
quantity of organic compounds removed in this way, together 
with the circumstance that they bear none of the characters of a 
substance%eginning to suffer decomposition. 

The same holds good, also, in regard to the water excreted 
from the leaves in the form of vapour. This likewise contains, as 
the observations of Senebier and Treviranus shewed, an ex- 
tremely small quantity of organic matter, but is nevertheless 
capable of putrefaction. Experiments which were m ade by Bonnet, 
Duhamel, and Treviranus (" Phys." i. 494), to hinder the evapora- 
tion, \>y smearing the leaves with oil and other substances, shewed 
that the leaves died. This result may, however, be just as well 
attributed to a positive injurious effect of the oil, in withholding 
sir as to a suppression of the evacuation of injurious matter. 
Manifold experience puts it beyond doubt that repression of the 
evaporation from the leaves by unfavourable conditions of weather, 
produces disease, often connected with the formation of Fungi, but 
this result may be caused quite as much by a disturbance of the 
normal nutrient processes of the plant connected with the evapora- 





tion of a large amount of aqueous vapour, as by the retention of an 
organic substance which should have been excreted by the leaves. 

f. £1 volution of heat 

With the nutritive processes of plants is connected their power 
of producing heat. That plants possess this power may be de- 
monstrated by simple observations, but these require great ac- 
curacy and certain rules of precaution, to avoid arriving at false 
conclusions ; for in determining the proper heat of plants, not 
only does the mostly very small amount of heat which is capable 
of raising the temperature of the plant a little above that of the 

air, render great caution necessary in making the experiments, 

but, under common circumstances, so much heat becomes latent, 
through the active excretion of aqueous vapours from the leaves, 
that the temperature of the plant, in spite of the latter producing 
heat, sinks below the temperature of the surrounding air. There- 
fore to arrive at accurate results, it is not merely necessary to use 

a very sensitive thermometric apparatus, but also to cut off the 
refrigeration by evaporation. 

That seeds when germinating, as they lie heaped in large masses, 
evolve a considerable degree of heat, is a fact long known from 
the malting of grain, but the cause of it was incorrectly sought 

for in a process of fermentation. 



demonstrated that such is not the case, but that the evolution of 
heat is connected with the process of germination. Seeds of very 

^ . of Hemp, 
Clover, Spergula, Brassica, &c.) made to germinate in quantities 
of about a pound, became heated, at a temperature of the air of 

different chemical composition (of different grains, 


66°. to 59—120° Fahr. 

It was likewise shewn by Goppert, that full-grown plants, also, 
such as Oats, Maize, Cyperus esculentus, Hyoscyamus, Sedum 
acre, &c, laid together in heaps, and covered with bad conductors 
of heat, cause a thermometer placed among them to rise about 


7° (Spergula as much as 22°) above the temperature of the 
air. Dutrochet succeeded, with the help of Becquerers thermo- 
electric needle, in demonstrating an evolution of heat in plants 

J .1 •__ __ _ 1 . fee A 7 t >> -l r\ c\r\ • * u»\ -i .t . , ± _ _ 

standing alone (" Ann. d. sc. nat 

77) ; but here the cold of 

evaporation must be cut off by placing the plant in an atmosphere 
completely saturated with water. Under these circumstances, the 
temperature of all vegetating parts, the roots, the leaves, the 
young juicy shoots (but not those of hard wood), were elevated 
from about one l-6th to 1-1 2th of a degree. The evolution of 
heat exhibited a daily maximum and minimum; the latt__ 
curred about midnight, the former about noon, yet not at the 
same hour in different plants, for the time varied from 10 ajvi. 
to 2 P.M. * 

er oc- 



■ ■ i 










Observ. The earlier experiments to determine the temperature of 
plants, by sinking thermometers in holes bored in the trunks of trees, 
were completely incapable of giving a decisive answer to the question 
whether plants evolve a proper heat, since a number of circumstances, 
the effect of which cannot be taken into account, are influential upon the 
temperature of the tree, namely, the direct warming action of the rays 
of the sun, the cooling influence of evaporation, the sometimes warm- 
sometimes cooling communication of the temperature of the soil, 
through the medium of the ascending sap, which exercises an influence 
according to the time of year, and the difference of depth to which the 
roots penetrate, not to be accurately determined in isolated cases. Under 
these circumstances, it is readily explicable that the experiments made by 
different observers do not agree. While Nau found that the mean tem- 
perature of the tree agreed with the mean temperature of the air, 
Schubler found the tree 1^° to 2|° colder than the air in summer, and 
in spring, on the contrary (March, May), about 
While in the experiments of Schubler, made on pretty thick trees, the 
temperature of the latter never attained the extreme of the temperature 
of the atmosphere, Eeaumur saw slender trees heated 18° to 29° above 
the temperature of the air, in the sun. Under these circumstances, the 
slight evolution of heat of single plants must vanish without leaving a 
trace, in the considerable, and, in some cases, discordant variations of 
temperature, dependent on external influences. 

A very great evolution of beat occurs in the blossom of the 

14° to 

3° warmer. 


rum maculatum 

and, according to Dutrochet's researches (" Comptes rendus" 1839, 
695), rises to 25° — 27° above the temperature of the air. But this 
phenomenon is seen i** far higher degree in Golocasia odora, in 
which plant it has been investigated by Brongniart (" Nnw A ™™- 
d. Museum" iii.), Vrolik and Vriese (" Ann.des Sc, 

Nat" sec. ser. 




1 838). These last ob- 

servers found the maximum of heat 129°, when the temperature of 
the air was 79°. The seat of the strongest evolution of heat 
alters during the time of flowering ; namely, after the spathe has 
opened, the anthers manifest the greatest heat ; they begin to 
cool down with the emission of the pollen, after which the upper 
part of the spadix, covered with abortive stamens, grows warm. 

Similar observations — not, however, made with the thermo- 
meter, and therefore not fitted to give an accurate determination 
of the heat given off by flowers — have been made on J 
italicum, A. Dracunculus, Caladium viviparum, G. pinnati- 
fidum, and Galla cethiopica, by Saussure, Goppert, Schultz, Tre- 

viranus, Gartner, and others. > 

The evolution of heat in. the blossom of the Aroidese exhibits a 
daily maximum and minimum, which, howe^ er, it is remarkable, 
that different observers found to occur at different times of the 
day; thus, in A. maculatum, the maximum occurred in the 
mornino- (Dutrochet), whilst Senebier found it occur after six 


; ; 




o'clock in the evening ; in Colocasia odora, Brongniart found the 

maximum at 5 A.M ; Vrolik and Vriese, as well as Van Beek 
and Bergsma, about 3 p.m. ; and Hasskarl, in Java, at 6 A.M. 
(" Tidschr. v. naturl. Gesch." vii. Istterkund Berigt. 26) ; as also 
Hubert found, probably in the same plant, the greatest heat after 
sunrise, in Madagascar. 

In very few cases has evolution of heat been observed in the 
blossoms of other families. Saussure, by means of an air-thermo- 
meter, found the flowers of Gourds 1° to 3°, those of Bignonia 

radicans 1 


and Mulder those of 

of Polyanthes tuberosa |°, 
Cactus grandiflorus 1° — 2° Fahr. warmer than the atmosphere. 

There can be no doubt that the evolution of heat from flowers 
results from the respiratory process connected with the formation 
of a large quantity of carbonic acid. Saussure found that a 
blossom of Arum maculatum consumed in twenty-four hours, 
before its heating, or after it had ceased, five times its own 
volume of oxygen, while a warmer blossom consumed thirty 

times, its spathe five times, the bare portion of its spadix thirty 
times, and the part covered with flowers 132 times its volume of 
oxygen. Vrolik and Vriese (" Ann. d. Sc. Nat sec. ser." xi. 62) 
found the heat of a blossom of Colocasia odora increase about 
9° to 10°, when brought into oxygen gas, while no evolution of 
heat took place at all in carbonic acid. 

In like manner, there can be no doubt that in germinating 
seed, the respiration of which is equally connected with the con- 
sumption of oxygen and the exhalation of carbonic acid, the evo- 
lution of heat stands in connection with the formation of carbonic 
acid ; but whether this source furnishes all the liberated heat, or 
a part of it depends upon the vegetative process of the germina- 

ting seed, cannot be* determined in the present imperfect state of 
our knowledge of the chemical transformations of the substance of 
the seed connected with germination. 

In vegetating organs the source of heat is evidently different. 
It is true, as we have seen, that oxygen is consumed and carbonic 
acid formed by all organs, but since on the whole a greater quan- 
tity of carbonic acid is decomposed in the green- coloured organs, 
than is formed in the remaining parts, more heat must be consumed 
than produced in the respirating process of vegetating organs. 
But evolution of heat must be connected with the nutrient process, 
for the plant forms its organic substance, if not wholly yet in 
part, from gases and liquids. Since then the growth of the plant 
exhibits a daily exaltation, occurring about noon, it is quite in 
accordance that the evolution of heat also should occur in in- 
creased degree at the same time. 
















Multiplication of PI 


to the lower or higher stage of organization of the plants ; for the 
lower it is, the more does the individual cell possess the power of 
independently producing a new vegetable, whether "by simple 
division or by the formation of a bud ; while the higher the or- 
ganizati on of the entire pi ant stands, the more does the _ capability 
of maintaining an independent vitality leave the individual cells 
and become committed to sm aller or larger assemblages of cells, 

which must become developed into an organ of complicated 

structure, before their separation from the parent plant, to ensure 
their growing up into independent plants 

Multiplication of plants by division of every individual cell is 

' '"■ n ' " ----"' A1 - ge. In the 


generality of cases, the dividing cell parts into two, more rarely 
into four cells, in which again the same process of multiplication 
may be repeated. This is of universal occurrence in the uni- 
cellular Algae, e. g., in the Diatomacese, Desmidiacese, &c. ; after 
the division, the newly-formed cells either separate from each 
other or remain joined together in colonies arranged in rows or 
flat layers, more or less firmly connected by a mass of mucilagi- 
nous matter, thus forming a transition towards the plants - — 





example, in the Oscillatoriese ; in the first instance, growth of the 
single individual is the result of the process of division of the 
cells in these plants, but the extraordinary readiness with which 
they break up into separate pieces, or, as in Nostoc, the single 
cellular filaments separate from each other by solution of the 
connecting mucilage, together with the power of the single pieces 
to grow up again into new plants, give great facility to the mul- 
tiplication of 'the individuals by division of their cells. 

The capability of multiplying in this way by unceasing divi- 
sion of the cells, appears to be unlimited in many lower plants, 
such as the Diatomaceae, Oscillatoriea?, &c. ; at all events, any 
other mode of propagation has been either rarely or not at all 
discovered in them ; in other cases, however, and especially in the 
Desmidiacese {see Ealfs' "British Desmicliece," 5) this division is 
confined within definite limits. After a series of divisions have 
taken place, this process ceases, and the formation of spores 




cells the development of single cells or groups of cells into inde- 
pendent plants occurs chiefly in the Lichens, where very frequently 
the layer composed of globular cells breaks up, by the cells fall- 
ing apart into the form of powder {gonidia, lagerkevme), either 



at particular points or all over the thallus, these cells falling upon 
foreign bodies and becoming developed into new plants, if they 
find a favourable station. But this phenomenon is to be regarded 
as more or less a result of disease, for the normal development of 
the thallus is interfered with by it, and if the formation of goni- 



>A -~ — ~ w^-^.K^j.v^v/At^^x^ JLLI. 

proportion to that by spores, the more favourable the station to 

J_ l_ ^ __ _T i /"• i ~\ t i it .- . 



The same 

niese, which frequently break up more or less completely into 


served whether these are capable of further development into new 


plants. But the formation of the 

Marchantia, and Blasia. These structures ._. „ 

hollow receptacles of various form, from a stalked cell, which is 
converted by repeated subdivision into a cellular nodule, which 
becomes detached, readily strikes root, and grows up into a new 

are developed, in 


Mirbel, " Mecherch. s. I Marchantia volvm 

Far more important, or perhaps merely better known, through 
3 masterly researches of W. P. Schimper (" Reck Anatom et 
Morph. s. I. Mousses"), than in the Liverworts, is the part played 
by multiplication through independent growth of single cells in 
the Mosses, for almost every cell of the surface of these plants is 
capable of conversion by repeated division into a cellular nodule 
which grows up into a leafy stem, whence is explained the extra- 
ordinary diffusion of these plants, even of such species as never 
bear fruit in particular localities. Schimper observed this process 
on the rootlets of the Mosses, partly directly, partly after they had 
become converted into a green structure composed of confervoid 
filaments, resembling the proembryo ; he found the same pro- 
embryo-like structure grow out from the leaf-cells of many species, 
(e. g., Orthotrichum. Lyellii), and confirmed what Kutzing had 
already seen, that even the cells of torn leaves will produce simi- 
lar growths under favourable circumstances. In particular cases 


of Mnium palustre, M 


into tuberous structures, spontaneously separating. 

From the fact that the cells of different parts of the ^ VMW 
pable of becoming developed into a bud or a proembryonaT confer- 
void structure producing a bud, it follows that in these plants, not- 
withstanding their already rather complex structure, the subordi- 
nation of the individual cell to the purposes of the whole is still but 
small, and that the individual life even here readily acquires the 
preponderance. But whether in the higher plants the individual 
cell is still capable of coming forth independently in an analao-ous 
manner and giving rise to the formation of a bud by development 










mass in its interior, or whether a complete group 

must co-operate from the very beginning for the formation ol the 

bud, we shall not be able to decide until we shall have traced back 

If, however, 


it should be the case that the formation of a bud starts originally 
from a single cell, this is still incapable, in the higher plants, of 


x 'est of the plant be- 
fore it*has produced a new individual and this has grown up to a 

of nutriment 


by other cells. Therefore in all the w v 

only organs of considerable size, composed of numerous cells and 



of laying down the foundation of a new plant. 

I have explained above, the doctrine that a branched plant is 





Taken strictly, this is not absolutely true, for a perfect plant pos- 
sesses not only an ascending axis, clothed with leaves, but a de- 
scending axis, a root. In many plants (in all leafy Cryptogamia, 
and in the Monocotyledons), even the primary axis is imperfect, 

3ly the ascending portion of it exists, while a primary 

descending axis is wanting, and is replaced by secondary axes 
which shoot out from the lateral surfaces of the stem. The same 
incompleteness exists in every branch, it consists merely of an 
ascending axis, therefore corresponds simply to half a plant, as also 
each ramification of the root represents the corresponding half of 

a complete plant. 

Since, however, the individual parts of a plant very generally 




sustenance is still conveyed to them by the parent plant, until the 

a . . • I II I „ 1 1 — _ 


exists, as a rule, little difficulty in pr 
furnished with all necessary organs, from 

part of a plant, 
axis, since, 




from its lateral surfaces, and thus to become 

more difficult 

dition to sustain itself independently. It is 
a new plant from a detached descending axis, since such a root is 

^A f.n rrmrlnne, a, leaf-bud. from which the future stem has to 

. is much less re 
om an ascending 

a new plant ; in this 



to which 


The readiness with which both descending and ascending axes 
are formed at places where they do not make their appearance in 



the natural course 

of vegetation 

varies extremely in different 

plants, while at the same time we are unable to find a reason for 
this variation in the organization of the particular species of 
plants ; in many species, for instance in the rooting of Cactese, 
Willows, &e., this development takes place so readily, that it can 

be counted on with the greatest certainty, while in others the 

development of the wanting organs, for example, of roots and still 
more of leaf-buds in Finns, never or but very rarely occurs. In 
general the formation of the said organs takes place the more 
readily the richer the detached part is in parenchymatous cellular 
tissue, and the more assimilated nutriment there exists deposited 
in it, at the expense of which it may be sustained until the organ 
necessary to make it a complete plant is formed ; but this rule is 
only valid for the extreme cases, and, mostly, we cannot say 
what is the reason, they are readily or not all inclined to such 

In very many plants, the formation of buds, which grow up 
into distinct plants, is a regular operation, independent of external 
causes. These frequently separate spontaneously from the parent 
in a rather rudimentary condition, and grow into independent 
plants subsequently ; in other cases, such separation occurs after 
the parent plant is dead and decayed, through particular ramifica- 
tions of it remaining alive. 

In the plants having a thallus, we meet with the formation of 
shoots which have not the form of the ordinary branches, but in 
which the formation of the parent plant is repeated. Thus, in 
the Algse, new plants are not unfrequently produced, both from 
the frond and from the disk-like base of this, or out of stolo- 
niferous prolongations of it. In the Liverworts and Mosses it is 
a very general condition for single branches, the so-called innova- 
tions, to repeat the form of the main stem, and when this decays, 
to appear as the stems of new plants. In the higher plants, 
ramifications very frequently occur, deviating in form from the 
ordinary leafy branches, and destined to serve for the multiplica- 
tion of the plant. They present themselves either in abbreviated 
and thickened forms (as bulbs and tubers), in which case they do 
not generally produce roots of their own until detached from the 
parent, or, on the contrary, they exhibit a predominant longitudi- 
nal growth (as runners or stolons above or below the surface of 
the ground), in which case, roots are developed, and they sustain 
themselves independently before their separation from the parent. 
The branches destined to the multiplication sometimes spring 
from the normal place, from the axis of a leaf (e. g., the bulbels 
of L ilium tigrinum) ; sometimes they originate from abnormal 
metamorphoses of flower-buds (the bulbels of the inflorescence, of 
many species of Allium, the tubers of Polygonum viviparum) ; 
sometimes they break out, as the so-called adventitious buds, 
from spots which do not normally bear buds. The latter occurs 





Plums, &c.), as well as on the leaves of many plants (e. g. y As- 

pidium bulbiferum, Malaxis paludosa, and Bryophyllum cali- 


The pollarding of a plant frequently causes the development of 
shoots. The formation of roots generally takes place readily 
when the descending sap is arrested anywhere in its downward 
course by cutting through the bark ; especially when, at the same 

time, light is excluded from 


moist. In this case, the roots break out in most plants from the 
thickening which is formed at the upper border of the wound. 
On the other hand, the plant is caused to form leaf-buds in un- 
usual places when the whole of the leafy part is cut off; for then 
leaf-buds are formed beneath the bark, both on the lower part of 
the stem and on the roots, breaking through the bark, and grow- 
ing up into stems. Most Dicotyledonous trees possess this power 
until they have attained too great an age, but most of the Coni- 
fers are devoid of it. This capability of forming leaf-buds is so 
great in many plants, that every firs 

used for raising new plants from it, — for example, in the horse- 
radish, Madura aurantiaea, &c. 

most difficult to induce the formation of buds on the 


It is 


leaves. Detached leaves have very 
when they are placed in moist earth ; they afford, under such cir- 
cumstances, the peculiar example of a plant which fully exercises 
the functions of nutrition, but is altogether incapable of growth. 
Such rooted leaves sometimes attain an age far exceeding their 
usual period of existence ; thus Knight, for example, saw the 
leaves of Mentha piperita, which he had caused to produce roots, 
maintain themselves fresh for more than a year, and assume 
almost the aspect of evergreen leaves (Knight, " Selection from 
the Physiol. Papers" 270). Growth into a new plant is only 
possible in such a rooted leaf when it developes a leaf-bud ; in 
general, this does not readily happen. There are plants, it is 
true, as already mentioned, on the leaves of which leaf-buds are 
regularly developed ; and a considerable number of plants have 
been noticed, on which buds had formed accidentally, on par- 
ticular leaves, still connected with the plant, e. g. } Drosera, Por- 



the whole, these examples are rare. Buds are most readily formed 
on detached leaves when these have a fleshy consistence ; their 
development has been observed in particular on the bulb scales of 

77T • • J" • 7 • 7*7 7~7~ */7 Ci *n • 




tima, on the leaves of Omithogalum thyrsoides, &c. ; moreover, 
not unfrequently on the leaves of different species of Crassida 
and Aloe. Buds are formed much less readily than on such suc- 
culent leaves, on leathery leaves, — for example, of Citrus, Aucuba, 
ya carnosa, Fieus elastica, Theophrasta, &c, although these 





strike root freely (Se 


>/ Bud-fi 

tion;" Munter, "Observations on special Peculiarities on the 

Mnr7# n-f M^H-AnrlAnn+A^ ~-P D/„..i. 7... T> J » -n . rr .. -_.„ 

537, et seq). 

>/ Multiplication of 

■Bot. Zeit 1845, 

A detached portion of a plant is not, however, merely capable 
of producing the organs wanting to form a perfect plant, but it 
is also in a condition to become blended with another plant and 

_ _ 1 T»r» • ."■■, -mm*-* - _•*• ' 

lead a common life with it, 

on which capability depend the 

numerous garden operations which are known under the not very 
apt name of " ennobling" (veredeln, grafting). The conjunction 

is a 

of young, succulent parts, still in course of development, 
necessary condition of this blending. This con dition is very easily 
fulfilled in Dicotyledonous plants, because there exists between the 
bark and the wood a layer of elementary organs in course of de- 
velopment, the so-called cambium, and thus there is little diffi- 
culty in so uniting the two plants, that this layer, of both parts, 



the vascular bundles lie scattered through the whole stem, and no 
definite cambium layer exists, the conditions are far more unfa- 
vourable. It is true, according to De Candolle's account (" Physiol." 
ii. 787), the gardener Baumann, of Bollwiler, succeeded in graftino- 
Draccena ferrea on Dr. terminalis ; but the graft died after on? 


Nat" Sme 

ser. vi. 131) on the grafting of Grasses, had a more favourable 
result, for he succeeded in grafting even species of different genera, 
e. g., Kice upon Panicum crus galli with success, a result which 
is explained by the fact that, in the Grasses the lower part of the 
internodes enclosed in the leaf-sheath remains for a lono* time 
soft and succulent. A second necessary condition of the blendino 1 

01 growtn, is great similarity oi tne two plants ; they must not 
only be nearly allied botanically, but have a great agreement in 
the composition of the sap. 


Observ. 1 . The possibility of grafting plants upon one another is de- 
termined, in general, by their systematic position, yet many anomalies 
occur. While it is usual that different species of one genus can be grafted 
upon one another, and in many cases it is even possible in species of 
nearly-allied genera, as, for instance, Pears on Quinces, on Crataegus Oxya- 
cantha, or on Amelanchier vulgaris, while Syringa vulgaris at least grows 
to Fraxinus excelsior, to Phillyrea latifolia, Olea europea to Fraxinus (De 
Candolle's "Physiol" ii. 791) and Castanea vesca to Oaks ; yet, on the con- 
trary, in many cases an union, or at least the maintenance for a long 
endurance of the graft, cannot be secured, in spite of far closer botanical 
affinity, e, g., between Chesnuts and Beeches, or Apples and Pears. 

Observ. 2. The propagation by division is in many cases of the highest 
practical value. Although the case occurs here and there, that a parti- 
cular branch of a plant disagrees from the rest of the branches of the speci- 
men in certain small peculiarities of growth, the colour of the leaves the 
doubleness of the flowers, the character of the fruit, &c, possessing the 













properties of a special variety, yet this is an exception to the rule. Every 
part detached from a plant retains this agreement after its separation, and 
thus propagation by division affords the means of multiplying certain 
varieties which could not, or only with uncertainty, be propagated by 
seed. Cases certainly do occur in grafted trees where the composition of 
the sap of the stock exercises a certain influence upon the characters of the 
fruit of the graft, but on the whole, this is an exception. (Gartner has 
given a comparative account of the observations on this subject, in his 
" Experiments and Observ. on Hybridation' — " Versuchen und Beobacht. ilb 
du Bastardbildung" 606.) 

b. Propagation by Spores and Seeds. 


In all vegetables which attain their full normal development, 
the period of vegetation is succeeded by that of fructification, 


executed the vegetative functions, in their subsequent period of 
life become organs of fructification, or ; special organs of fructifica- 
tion become developed. 

Observ. The universality of this proposition is truly only borne out by 
analogy with the majority of plants, for in the present condition of our 
knowledge we cannot determine whether all vegetables fructify. In many 
lower plants we are still unacquainted with any fructification, either be- 
cause they are really deficient in them, as may be possible for instance in 
the Yeast-plant, or that we do not know all the stages of their develop- 
ment. The latter is the case in many lower plants ; the difficulty of study- 
ing them is increased by the fact that a large number of forms have been 
described as peculiar species, especially among the Algse, which are only 
earlier stages of development, and in many cases abnormal examples pro- 
duced by unfavourable external conditions of plants frequently belonging 
to totally different families. 

gan destined for a germ may 





after its separation from the parent plant, under the influence of 
external circumstances favourable to the excitement of vegetation, 
grows up directly into a new plant through expansion of its mem- 
brane and production of new cells in its interior, this is called a 
spore (spora, keimkom). The formation of spores takes place 
without fertilization, and plants which are propagated by spores 
are termed Gryptogamia or Exembryonatce. 

When, on the other hand, the propagative cell (as embryo-sac) 
forms part of a compound organ, and through previous impreg- 
nation, produces in its interior the rudiments of a perfect plant, 
furnished with stem and root (the embryo, hevm), and this becomes 
detached with the enveloping parts formed by the further deve- 

• ■ 



lopment of the ovule, from the parent-plant, these envelopes to- 
gether with the embryo, are collectively termed the seed, and the 
plants which bear seeds, Phanerogamia or Embryonatce. 

Observ. As will appear below, all the plants bearing spores are not 
unisexual, but the impregnation in them stands in a totally different rela- 
tion to the production of the new plant, from what it does in the Phane- 
rogamia. In the latter, the formation of the embryo is the immediate 
result of the impregnation ; when this does not take place, the seed 
cannot germinate. In the Cryptogamia, on the contrary, which have an 
impregnative process, neither the cell which forms the spore, nor the 
spore itself become impregnated, but this is formed and becomes capable 
of germination without a previous impregnation, and impregnating organs 
are found, sooner or later, upon a germ-plant, or pro-embryo, growing from 
the spore, upon the action of which organs depends the development of 
the yet imperfect plant into a complete vegetable. 



of Thallophyt 

* i 

There is considerable variation in the modes of development of 





In the Fungi we are above all struck by the production of an 
enormous number of spores, so that in proportion to the great 


to the large sporangium, the vegetative part of those plants, the 


devoid of any definite outline, exhibits an inconsiderable deve- 


Goniomycetes and Hyph 

mycetes, the formation of the spores, notwithstanding the innu- 



of the fructifying part of the Fungus into its constituent cells, or 
into granules composed of several cells closely connected together ; 
whence Leveille says, correctly, that the Fungus consists, in its 
simplest form, of a simple or cellular filament terminating in a. 
spore. When we come to the Mucorinece, we already 


expands into a vesicular cell, in the cavity of which a mass of 
spores are formed by free cell-formation. A similar origin of the 
spores is met with also in the higher forms of Fungi, in which, 
however, the single cell producing the spores no longer constitutes 
the entire organ of fructification, but large sporangia appear 
under the most varied forms, wherein the parent-cells of the 
spores are collected together in a definite layer, which sometimes 

lines the cavity of the sporangium 










sometimes forms a globular nucleus imbedded in the substance of 
the sporangium, as in the Pyrenomycetes, and sometimes appears 
as a membrane lying free upon the outer surface of the sporan- 
gium^ as in Discomycetes and Hymenomycetes. In the higher 
Fungi, the number of spores formed in a parent-cell is definite, 
and we meet at once here that fixed numerical relation, which 
remains the same in the formation of the spores of the Crypto- 
gamia and of the pollen-grains of the Phanerogamia throughout 
the whole Vegetable Kingdom, according to which, usually four, 
more rarely eight or sixteen, spores or pollen-grains are formed in 
a parent-cell, while the number may also sink on the other side 
to two _ or oue. Among the Fungi, four spores are formed in 
the majority of cases (in the Hymenomycetes), sometimes only 
two or one in a cell ; in a few groups, as in the Tuberacece and 

^ fcetes, the number rises to eight (LeveiHe; "Reck, s. Vhy- 

Ghampign." — Ann. d. sc. nat. sec. ser. viii. 321 ; Corda 



In regard to the form of the parent-cells, two modifications 


fasc i) 


are developed by free cell-formation, after a previous production 
of a nucleus, and then frequently (e. g., PezizaJ each spore again 
divides by a septum into two, sometimes even into more, cells. In 
the Ly coper dacece and Hymenomycetes, on the contrary, four (in 
rare cases only two, or one) protrusions of the wall of the parent- 
cell are formed, each of which becomes the seat of the production 
of a spore. These parent-cells are called basidia. 
t From the small size of the spores of most Fungi, it is not de- 
cided whether the cell-membrane of the spore secretes a special 
layer upon its outer surface in all cases (a kind of cuticle) In a 
great number this may be easily perceived ; like the outer coat of 
pollen-grams, it is frequently covered with reticularly connected 
ridges, little spines, &c. In germination, the coat of the spore ex- 
tends itself into a filament, which in the minute mildew-like Funo-i 
is capable of growing on into a perfect plant. Whether this pro- 
duction of a new Fungus from a single spore occurs also in the 
higher Fungi, or whether the filaments which grow forth from a 
number of spores germinating side by side, must become com- 
bined into a common tissue, has yet to be decided by observation. 
The latter is at all events a common process. (See Ehrenberg's 
"De mycetogenesi, Nov. Act. Nat. Gut." x. p. 1, 161.) 

In the Lichens the fructification of many Fungi {Pezizeee and 
SphcBriacece) is repeated most exactly. In the interior of the 
thallus is formed a gelatinous nucleus of elongated cells, converg- 
ing towards the central point, and embedded in an abundance of 
intercellular substance. A portion of these cells become tubular 
(asm or thecce) and produce the spores. In the naked-fruited 
Lichens the thallus opens above the nucleus, and the latter spreads 






out into a more or less flat disk (the thecal layer) ; in the covered- 
fruited, it remains enclosed in the thallus. In each of the parent- 
cells eight spores are formed by free cell formation, and in very 
many cases these form two, four or a greater number of secondary 
cells m their interior. Very few observations have been made on 
the germination of these spores. According to Holle (" ZurEnt 
wickelungsg. von Borrera ciliaris."— On the development of B 
cilwris, Diss. 1848, Gottingen), the secondary cells break throucj 
the primary spore cell as filaments, and are con- 8 

verted^ into cells outside the spore. ' 
Meyer's account ( tf """ " 

According to 

Fig. 49. 

Nebenstunden mein. Beschaftig 



ung. 175) the outer membrai.. w . ^ nf , vxc m uui) 
torn and when a number of spores germinate side 
by side, the filaments into which they grow out be- 
come blended together, and contribute jointly to the 
formation of a new plant. 

According to the observations of Tulasne (" V In- 
stitute ' No 849), the inner spore-coat, both of simple 
and compound spores, grows out into one or more 
filaments, which soon ramify and acquire septa 
and whose short interlacing branches form little 
cushions upon which little colourless cells accumu- 
late, and m which the green cells forming the rudi- 
ments of the cortical layer of the new plant, make 
tneir appearance. 

We meet with a far greater complication of phe- 
nomena when we look towards the spores of the Alese 
even though here no co-operation of two sexes occurs' 
this latter may indeed seem doubtful in a number 
ol Algse, m which a so-called copulation occurs but 
a more minute examination of this process shews 
that it bears no analogy to sexual reproduction. 
1 his conjugation presents itself most distinctly in the 
so-called Conjugate (the geneva— Zygnema, fig. 49, 
—lyndandea, Mougeotia, Staurocarpus, &c), in 
which it was observed first by Vaucher The fila 
ments of these Confervae lie parallel, side by side 
or bent in a ziz-zag manner towards each other 
and send out from their cell-walls towards the — 
the nearest cell of the neighbouring filament, a blunt branch (a) < 
which grows together with a similar and co^espoiXig Si 
the. other cell coming to meet it, upon which the partition Z the 

Z^T^^TZ^^^ *? «*? -tter of tt 

Two cells of Zyg- 

of conjugating. — 

a, commencement 
of the formation 
of the connecting 
branch ; b, con- 
necting branch ; c, 


cavity of oneof them, orl*" the^nneZT b~£ this^s ™ 

spore (<,). rhe following circumstances tell against this 
being considered as an act of impregnation. T& cltente 
















of the two cells are exactly similar ; sometimes all the cells of 
one filament take away the contents of the cells of the other ; 
sometimes this happens only to a part of the cells, while the rest 
empty themselves into the cells of the second filament ; and some- 
times spores are formed in cells which have not copulated, all 
this taking place without any definite rule. 

Copulation has recently been discovered in many uni-cellular 
Algas, in particular by Morren in Closterium ("Ann. d.Sc. not. sec. 
ser." v. 257), by Kalis, in the Desmidiacese, and by Thwaites ("Arm. 
of Nat Hist" xx. 9, 343) in the Diatomacese. Eemarkable as the 
whole process of copulation is, its product is, in many respects, 
enigmatical in no less degree. In the copulation of uni-cellular 
AlgaB, two new individuals are generally formed ; thus there is no 
increase connected with this mode of propagation, but frequently 
only one new individual is formed, and thus is presented the 
strange phenomenon of a propagation resulting in a diminution 
of the number of individuals, since the copulating individuals die. 
In the Diatomacese, moreover, the individuals produced by copu- 
lation are much larger than their parents. In the majority of 

n ' ' _ * 1 _ ge, particularly in the Desmidiacese and Zygnemece* 
the spore produced from the union of the contents of the two cells 
has not yet been seen to germinate, and it is not improbable that 
it ought to be regarded, not as a spore, but as a sporangium, that 
is to say, as a cell, the contents of which become developed into 
numbers of germs (See Agardh, "Ann.,d,Sc.natsec.Ser"vl 197: 



In by far the greater number of the Algse, the spores are not 

formed by copulation, but in single cells, either, as in the lower 

stative cells towards the close of their existence, 
or in special fructification cells. 

The spores of a very large number of AlgaB, either before their 
exit from the parent-cell, but principally in the period just succeed- 



voluntary motions, and have given origin to the most fabulous 
conceptions concerning the transformation of animals into plants. 
We owe the first extensive and accurate observations on these 
moving spores to the younger Agardh ("Ann. d, Sc. nat, sec. Ser." 

According to his researches, 


Ncstochintw, Oscillaicrice, C<mJ 

Ectocarpcce, TJlvaccce, and Siphoncce. The following is his account 

of their development. 


the cells, the chlorophyll, which in the young cells of these plants 
forms a homogeneous mass, becomes transformed into globules, 
which towards the close of the cell's life assume a spherical shape' 
become detached from the wall of the cells and balled together in 

Erroneous in Sregard to Zynemese, see Vaucher, Mever, and, more 
recently, Pringsheim. Flora. Ails'. 1852.— A. IT. 



a globular lump in the middle. A " swarming " now be ff in* to be 
evident m this mass, the granules become isolated, aid 

i , ,i ., n ~ ? & -— — «. v ^ k;k.k;kji.ii.v j^uictuuu, ana swim 



f^Tw g ™w +1 By degTeeS the ^ be S in t0 ^hdraw towards 

the darkest part of the water, become attached to any solid body 

and begin to ffermina.tA W on o™,™;™ ^ ^ •* 7 __ . , -^ 

germinate, by an expansion 


Agardh observed a transparent process (beak, tfcfoio&Z) a t that 

end of these spores which always went first in the movements 

But the true organ on which this movement depends, is not this 

L, / 8 ? Tl SSC ' Ser - Xlx - 266 )> there exi «t at the brighter 
coloured end of the spore, cilise of various lengths moving rapidly 

Th. ™ \ ^f 0118 .^S the motion of the ^ole spom 
The number of these cihae diners in different genera. Thuret 

found m Conferva glomerate (see tab. 1, 23, 24,) and rivularis, 
7° p clh 7 % on ea <* s P^e, m Ohoetophora elegans four, on the spores 



which represent the spore (19) and its first stages of ' develop^ 

+L™ Q /vp 177 j r- ; 7 °r ico ux juwucwrpus nave two, 

*M Ll %? ^ Mntercmvrpha four cilia. These observations 

obtained full confirmation by others 


Infus. in Algen) 

by Fresenius 

tM i^ ti (re P? ated > Siebold, M*m> d fl a ^. Sme. Ser. 

xn. ii>i; 1 he opinion that these spores possess animal life during 
the period of their movement, and become plants at the moment 
of germination, does not however, depend merely on a confusion 
of their movements w ■ L fLo »«i„«4.™ ±- .. J ■.+ . 7 , uu 



cases each of these spores contains a red spot (according to N&Ji 
a red oil-drop) which was taken for a/eye by Ehrenbero- and 
others Even before Thuret had made know/his observations 
upon the organs of motion of the zoospores, linger ("Die Pilar, ^p 

vm. Moment* der Thier-werdung") had published very minule 
observations upon the formation and motion of the very W 
spores of Vauchema. In Vaucheria, the single granules of chlo 



filament, or of globular protuberances seated upon lateral branches 
alter being separated from the contents of the rest of the fibre 
by a- septum, becomes balled together into one 

which makes its way out by a slit in the cell-membrane and ex- 
hi bits rapid advancing and twistin * TJ • 


_. ^^^ «,^ v cwiuiiig ana twisting 

ail over with countless very short cilise. ™ „ ^ xv u , u . e rorTn _ 

tion of the spore occurs early in the morning, its exit from the 

parent-cell usually takes place about 8 A.M., fid aftefitsnfotion 

i 2 







► . 




decomposition ?) and germination commences by the coat of the 
spore growing out into a filament. 

Observ. — These observations first demonstrated the existence of cilise 
in the Vegetable Kingdom. It may be distinctly seen in Vaucheria 
that they do not belong to the cell-membrane (spore coat), but to a mem- 
brane clothing this. What the corresponding condition is in the zoospores, 
is as yet unexplained, since a membrane enveloping the whole spore has 
not yet been observed in these. Perhaps this may arise solely from the 
small size of the spores and the tenuity of their coating membrane, per- 
haps, however, the coat only exists locally around the beak and the points 
of insertion of the cilise. Mettenius, indeed ("Beitrage zur. Botanik^ i. 34), 
assures us that the cilise are in connexion with the contents of the spores' 
but he has not offered sufficient evidence of this. When we compare these 
motions with the ciliary phenomena of animal cells ,and with the motions 
of the seminal filaments of the higher Cryptogamia, no doubt can remain 
that the movements of the cilise are the cause and not the effect of the 
movement of the spore, as Nageli (''Unicellular Algce," 22) believed; an 
opinion against which V. Siebold has already declared. The action of 
poisonous substances, such as alcohol, opium, and iodine, immediately 
arrests the motion. 

It appears possible for the formation of zoospores to originate 
from one single grannie of chlorophyll, while in other cases, where 
only one or few spores are developed in a cell, (e. g. Braparnal- 
dia, Chcetophora), perhaps larger sections of the mass of chloro- 
phyll, or even the primordial utricle, by becoming constricted into 
separate segments, are the parts concerned in the formation of 
the spores. ^ The actual conversion into a spore is not accurately 
known in its intimate processes, but must consist essentially in 
the formation of a cellulose membrane around the chlorophyll 
granules. It has already been remarked that in Vaucheria the 
whole mass of chlorophyll of a cell becomes coated with a mem- 
brane. Intermediate forms between these two extremes are met 
with, thus Saulier ("Ann. d. Sc. nat Sme. 8er." vii. 157) found 
in the genus Derbesia, very closely allied to Vaucheria, that 
neither the entire mass of chlorophyll collected into one spore, nor 
did its grains remain isolated, but separate groups, each com- 
posed of hundreds of grains of chlorophyll, became gathered up 
into globular masses, acquired a membranous coat and formed a 
short beak and a circle of cilise upon the surface.* linger (" Lin- 
naza." 1843, 129) observed a perfectly analogous formation of 
the spores of A chly u prclifera, which, according to Thuret ("Ann. 


* See further on this subject, Thuret, "Ann. des. Sc. nat. 3 Ser. n torn, 
xiv. and xvi. ; Cohn on Hcematococcus, Nova. Acta. vol. xxii., and on 
Stephanosphcera, "Annals of Nat. Hist." Oct. and Nov. 1852. — A. Braun. 
" Ueb. die Vefjungimg? Leipzig 1851. The active zoospores have no 
cellulose membrane when first set free. — A. H. 




d. Sa 

3ms Serr iii. 274) 

numerous cilisa 

Whether, as Agardh as 

of the lower, and the want of it in those of the higher Alo^ (the 


these plants into two sections, appears very doubtful, for accord- 
ing to Decaisne and Thuret ("Arm. d. Sc. not. Sme Ser." iii. 10) 

not only do the spores of the Fucacese present the same coat 
covered with short cilise as those of Vaucheria, which, however 
either from the size or some other cause are motionless, but there 


enclosed in special cells, sometimes on the same plants that produce 
the spores, sometimes on distinct specimens. The said observers 
indeed^ have not recognized them as spores, but interpreted them 
as seminal filaments, but they have not the least resemblance to 
these, while they agree with the zoospores in form and in the pre- 
sence of a red point, the so-called eye. It is trulv a remarkable 
circumstan ce that one plant should bear two kinds of spores, dif- 
ferently formed, but the same occurs again as an universal rule in 
the Geramiem and Floridece, for these plants bear not only the 
generally recognized spores, and gemmae testifying their nature 
as such by generation, which originate, like pollen-grains, in a 
parent-cell dividing into four chambers (the so-called ' Mra- 
spores), but other spores also, which are not produced in fours in 
a parent-cell, and are contained in variable numbers in fructifica- 
tions of the most diverse shapes (capsula, glomeruli, favella, &c.) 
The spores of this second kind germinate, as "Agardh has shewn 
like the tetraspores, their membrane extending itself on one side 
into a root-like prolongation, on the other into a filament which 
divides into cells, and grows up into a plant. 

Decaisne and Thuret observed a most peculiar circumstance in 
the spores of many Fucoidese; namely, the spores had not com- 
pleted their development at the time of their maturation and de- 
tachment from the parent plant, for, after this, commenced a divi- 
sion into the proper germinating spores (in Fucus serratus and 
vesiculosus into eight, in F. nodosus into four, in F. canalicu- 
latus into two secondary spores). 

Martins thought he had found, in the spores of Fucus, that the 
separate spores did not grow up into new plants, but as in the 
Fungi, a number of germinating spores became conjoined to form 

one common plant. 


Decaisne, and Thuret. The spores of the Fucoidese germinate like 
those o£ all other Algae, by expansion of their internal coat on one 
side, into a root-like fibre, on the other into a filament which 
becomes subdivided into cells. 

yf the Cryptogams having Stem 


(with the exception of the Charas, to be mentioned presently) all 






attempts to discover male organs has proved the more vain the 
further the investigation of these plants has advanced, in the more 
highly organised families of Cryptogamia, on the contrary, in which 
there exists separation of the organs of vegetation into stem and 
leaf, the last few years have seen the discovery of convincing 
proofs of the existence of two sexes. 

In the last century, when Hedwig in particular devoted himself 
to the investigation of the Cryptogamia, the idea that two sexes 
must exist in all Cryptogamous plants, was quite predominant ; 
and thus, often enough without a trace of consideration, the most 
diverse parts were, from mere opinion, separated as male organs. 
This brought the whole effort to discover impregnating organs 
into discredit, and the opinion that all the Cryptogamia were de- 
void of male organs, and developed their spores without previous 
impregnation, became more and more diffused. It is true that 
organs had been discovered in certain Cryptogamous families, espe- 
cially the Charas and Mosses, which from the time of their appear- 
ance, from their position, &c, stood in evident relation to the fruit; 
but since no positive influence could be proved to be exerted by 
them upon the young sporangia, their function as anthers was 
denied ; although it was at the same time admitted they had a 
certain analogy with them, whence they were, indeed, called an- 
theridia. In more recent times, two circumstances seemed chiefly 
to strengthen the earlier doubt which had been entertained as to 
the function of the antheridia. My own researches, namely, 
shewed that the spores of the higher Cryptogamia do not, as had 
been previously supposed, exhibit a resemblance in respect to their 
development and structure, to the seeds of the Phanerogamia, but 
that the most perfect agreement exists between them and the 
pollen-grams of the Phanerogamia. From this it necessarily yet 
strangely, appeared that organs of perfectly like structure fulfilled 
the function of germs in one part of the Vegetable Kingdom and 
in the other part constituted the male, impregnating organs ; but, 
little as the formation of a pollen-grain depends upon an impregna^ 
tion, no one circumstance shewed itself in the development of the 
spore, at all more resulting from the co-operation of an impreg- 
nating organ. Still more doubtful did the theory of the impreg- 
nation of the Cryptogamia necessarily become, when Nageli made 
the discovery, in the Ferns, of antheridia in many respects resem- 
bling those of the Mosses, which were not formed upon the full- 
grown plant at the same time as the rudiments of the sporangia, 
but occurred upon the germ-plant (pro-embryo), while the perfect 
plant was devoid of them. 

Under these circumstances, Schleiden seemed to be warranted 
m characterizing the effort to discover impregnating organs in the 
Cryptogamia, as a mania. But by good luck, certain men who 
had this mania did not allow it to lead them astray in their 
researches, and as often happens, nature this time proved so rich 



that, not indeed was what had been sought found, but instead of 
this a series of conditions, the existence of which was previously 
altogether unsuspected. The researches relating to this point are, 
it is true, still far from their completion, since at the present 
moment nothing more than a preliminary notice of isolated con- 
clusions already arrived at can be given ; but these, although isola- 
ted, cause us to expect with certainty in this field a series of the 
most striking discoveries. 

The Mosses have served for a very long period as the main 
props of the view that two sexes and an impregnation occur in 
in the higher Cryptogamia. Not only was attention naturally 
called in these to the constant occurrence of the antheridia, and 
their great development, but trustworthy experience, formerly of 



Mousses! 3 55) 

of sporangia upon the same stem always bear fruit, while dioecious 


g out the mode 



A second family indicating the necessity of an impregnation, were 
the RhizocarpeaB, since numerous observations had shewn that the 

large and small spores of these plants could not be separated 


without preventing the former growing into new plants. Schleiden, 
indeed, had extended his theory of the development of the embryo 
from the pollen-tube to this family, and arranged them -with Phane- 

But nothing was gained by this, for, on the one hand, 
Schleiden's whole theory of impregnation proved a false beacon ; 
on the other, Schleiden's statements as to the Rhizocarpese were 
not confirmed, and this more particularly in the most essential 
point, the mode 

Then unexpectedly appeared Count Leszcyc-Suminski's essay 
on the development of Ferns ("Zur Entwicklungsgesch.der Farren- 
krauter" 1848), the contents of which at first seemed fabulous, so 
contradictory were they to all that was known of the organization 
and development of plants. But a more minute study of this treatise 
— a comparison of the author's results with nature — soon shewed 
that although he had been deceived in a few particulars, his ac- 
count was far from being a creation of the fancy, and that his re- 
searches had broken open a path to a long series of discoveries. 

In all families of the leafy Cryptogamia (with the exception of 
the Lycopodiacese*) antheridia have been discovered, exhibiting it 
is true considerable variations of external form and structure in 
the different families, but collectively agreeing in the circumstance 
of developing in their interior very delicately-walled cells, at first 
containing an amorphous substance coloured yellow by iodine, in 
place of which, at the epoch of maturation of the antheridia, a deli- 

* Now found in these also, see note further on. — A. H. 


** : 





thickened at one end and running off to a very fine point at the 

ments manifest lively motions 

according to the manner m which they are rolled up, in some cases 
while still enclosed in the cells where they are developed but 
more particularly after they have emerged into the water 'from 
anthendium which opens when ripe. Thus, when the filament 

motion is more 



In these movements 

the thin end of the fibre almost always goes first. Minute 

very difficult, both from 

dity of the motion (which however, is readily arrested by poisons) 
and the great delicacy of the whole structure, shews that the 
movements arise from extremely delicate and comparatively W 
eilias, of which two are usually found at the thin end of the fila 
ment, and which only seem to Occur in larger numbers in the 
• T*i T, fi ' am6 ? t itself exhibits no independent motion as 

term seminal til. 


filaments. r J ^"™ •* tnese 

Observ. The first observation on the motion of the contents of the 
antnendia was made by Schmidel (« Icones plantarum? 1762 85) in Jwy. 
germanma pusilla. The imperfection of the microscopes of 'that period 
however seems to have prevented his seeing the seminal filaments, and 
he probably only observed the cells in which the filaments were enclosed 
The same seems to have been the case with the observations made by Fr. 

£r,3/^£* { l ° ra i \ 822 > l'- 34) in the aHtheridia ofSphagLm. 
He considered the moving bodies which he saw to be globular monads 

and did not doubt their animal nature. The spiral filaments SemselvS 

nat. 2,Ser. xi. 257) ; in accordance with the then prevalent notions on 
spermatozoa, he regarded them as animals, and applied to them the 
name of Spirillum bryozoon. Recent years have scarcely added to his 
observations on the seminal filaments, more than the fact that two cilhe 
exist at the thin end of the filaments, which linger had overlooked (De- 
caisne and Thuret, "Ann d. So. nat. 3, Ser." iii 14)? Plate 1, figs. 26-28. 
Seminal filaments of Sphagnum; fig. 26, represents two anther-cells with 
the seminal filament s enclo sed ; fig. 27, one of the latter seen from the 
side (from linger) To me the filaments appear to have the form which 
1 have represented in fig. 28. 

structure of the Mos 

It consists of a 

simple sac, with a wa 11 composed of a single layer of cells, which, according 
to linger, are applied upon the outside of a large cell, while according to 
Schimper they are enveloped on their outer sides by a continuous mem- 

torT a r + 7° ° f ^Tr 11 ^ SUb8tanCe - When mat ™, ^is ooatl 
ftrfd, tue froS ^ ^ C ° ntentS ' D0W diSS ° lYed int ° a —ilaginous 

to It^ iff El °M he Li 7™ rt , S P ° S3 f S a / tructure completely analogous 
to that m the Mosses (Gottsche, "Act. Acad. Nat. Cur: xx. 1, 29 3), 



only the wall of the sac, at all events in many species, is composed of two 

layers of cells. 

The anthers of Chara, of which Fritzsche (« Ueher den Pollen;' 6) has given 
the most accurate description, possess a highly complicated structure Ir-to 
the globular cavity enclosed by the eight cells containing red-coloured gra- 
nules, projects a flask-shaped cell, almost as far as the middle; from its 
apex run out a mass of fine confervoid filaments, which are divided up 
very closely into j oints, and in each of the cells is developed a seminal 
filament. The existence of an iifusorial motion of these filaments was 
observed by Bischoff (« Gryptog Geir." 1, 13) ; their exact form (plate 1, 
fig. 25, from Thuret), and the two cdi^, by which they approximate closely 
to seminal filaments of the Mosses, were first made out by Amici (whose 
essay on tha subject has not been printed) and Thuret (« Ann. d. L not. 
2, her. xiv v 66). 

In the Ferns the most different parts had long ago been interpreted, 
without any judgment, as male organs, even the stomates of their leaves 



1, 168) made the unexpected discovery that antheridia containing mov- 
ing seminal filaments, occur upon their pro-embryo. This was contrary to 
all theory, yet as the observations of Thuret (« Ann. d. Sc. nat. 3 Ser " 
xi. 5) and Leszcyc-Summski shewed, nevertheless proved well founded 
The structure of the antheridia of these plants bears a considerable re- 


cell, in the cavity of which is formed a second cell, filled with the small 
cellules containing the spiral filaments. The entire organ bursts at its 
summit, and extrudes its mucilaginous contents enclosing the seminal 
filaments. The latter are ribbon-like and flattened down, possessing 
according to Suminski (plate 1, fig. 29) about six, according to Thuret 
numerous cilise. Schacht (" Zinnasa," 1 849, 758, &c.) agrees with the last 
statement, and states that the cilise are attached upon the narrow 
and not on the thick end at the widest curve of the filaments 



tt^ i 4. n j. ■ ° 7. n — 7 r l ""^' u " x U11C -^H uiseiacese. 

1 he last Cryptogamia on which the spiral filaments have been found 

are the Khizocarpese. 

/ Wiss. Botanikr iii. 199) suc- 

ceeded in finding them m P%lulwria. The pollen-grains (smaU spores) 
undergo a change after they have been discharged from the anthers by 
the inner coat bursting the outer, and afterwards tearing, itself to emit 
minute cellules which are filled with mucilage and starch In these 
minute cells a vacant space is subsequently formed at one end in which 
appears a spiral filament, turning round and round, and leaving the cell 

M 6 ++ /Tfp The S Tl P henome *a have been observed by 

Mettemus m Isoetes ("Peitr. z. Pot" 1, 17). y 

Thus have antheridia and seminal filaments been found in all the leafy 
Cryptogamia, with the exception of the Lycopodiace^. t Whether semi- 
nal filaments occur in any other of the Thallophytes besides the Charas 
remains to be seen. It is true that Niigeli (" Die neuer A Igensysteme "186- 
u Zeitschf. Wiss. Pot.." iii. 224; "Pot. Zeit? 1849, 572) has stated that 
antheridia occur in the Floridese, the essential parts of which consist of 

* t Hofmeister («Fruchtbildung,Keimung, &c, der Cryptogamen," Leipz 
1851) has since shewn that the small spores of Selaginella produce seminal 
filaments, exactly in the same way as those of Isoetes. A. H 






> V 



cells 1 -900th of line in diameter, with a scarcely visible spiral filament 
within ; but it may be permitted, considering the difficulty which such 
minute size of the organ opposes to observation, to doubt, with Mette- 
nius, whether there are really seminal filaments.* 


theridia of the leafy Cryptogamia, leaves no doubt, in spite of the 
difference of structure as above described, that these organs are 

The circumstance, however, that 



lopment ol the plants, must appear in the highest degree surpris- 
ing and indicative of altogether unlooked-for differences in the 
propagation of these vegetables. F: 







of the seed frequently involves the death of the parent organism. 
We meet with the same condition in the Mosses, in which the &n- 


same time 

ing of the anthers. In the Ferns, on the contrary, the condition 
is diametrically reversed. The development of the sporangia fol- 
lows the usual law, but the formation of the antheridia takes place 


be repeated in the plant 

j — _ _ 

mbryo. In the 


are first developed after the pollen-grains (small spores) have been 
shed ; they are as it were dioecious plants, in which only the fe- 
male plant arrives at perfect development, the male being arrested 
at the stage of a germinating pollen-grain, which only produces 

seminal cells, and then dies. 


fication oi these plants, it will be necessary to speak of the spores 
and their development. 

I have already indicated that the spores of the higher Crypto- 
gamia agree completely with the pollen-grains of the Phanero- 
gamia in regard to their development and structure. Not only 



with the theca of an anther in morphological respects (" Morpk 
Belracht des Svorana. d. m. Gefass. vp,trpK Krimtna " Mnhl 


m Schrift 

rfass. verseh Krypt 



out above, are completely in agreement with the development and 

The recent observations seem to indicate the existence of sexes in the 
Lichens, (« Itsigsokn" — Bot. Zeit. 1850,51), and the Fungi (" Tulasne, 
Comptes rendus" 1851, Berkeley and Broome, "Brit Association" 1851 ) 

—A. H. - 



structure of the pollen-grains. Just as the latter are developed in 
the anther without the co-operation of another organ, does this occur 
also in the spores. In certain Cryptogamia (the Rhizocarpese and 
Lycopodiacese) we find the peculiar condition, that spores of two 
kinds are developed simultaneously, in a wholly analogous manner 
in parent-cells, in capsular receptacles of two kinds, the spores 

larger and smaller, possessing exactly the same structure, except 

that one kind are larger and have a tougher outer coat. But in 
the Rhizocarpeae, only the larger exercise the function of spores, 
the smaller, as above stated, developing the cells which contain 
seminal filaments ; in the Lycopodiacese, on the contrary, both 
kinds of spores produce plants.* 

The germination of the spores is as little dependent as their 
origin upon a previous impregnation derived from the antheridia, 
unless perhaps this be the case with the Charas, in which the 

Fig. 50. 

Fig. 51. 

Pro-embryo of Funaria hygrornetrica (according* to 
Schimper) a> rudiment of a bud ; b, a young- stem ; c, first 
development of the pro-embryo from the spore ; d, deve- 
lopment further advanced. 

Young pro-embryo of Pteris ser 
rulata according to Leszcyc-Su 

relation of the antheridia to germination is altogether unknown- 
In germination (except in Ghara) the spore does not grow at 
once into a plant like the parent, but is first developed into a 
thallus-like, cellular structure, totally devoid of vascular bundles, 
the so-called pro-embryo, which appears under very different forms 
in different plants of these tribes. In the Mosses (fig. 50) it pos- 
sesses the form of a branched Conferva, in the Ferns (fig. 51) the 
shape of a cordate leaflet not unlike a frondose Liverwort, in the 

* An error. See page 121, note ; also Report on the Reproduction 
of the higher Cryptogamia, by A. Henfrey. " Trans. Brit Assoc''' 1851. 

—A. H. 



: : 











Equisetacese of an irregular mass of cells divided into many lobes. 
The development of the pro-embryo is extremely simple in these 
plants. The spore-coat (fig. 50 c. d.) becomes expanded in germi- 
nation, bursts through the outer membrane of the spore, sends out 
hair-like prolongations serving as rootlets on one side, and becomes 
prolonged on the other into the form of a cylindrical cell, which 
becoming divided by septa into a number of cells, and so on by 
continued growth and cell-multiplication, is gradually developed 
into the perfect pro-embryo. In these plants no part of the spore 
seems to be pre-determined for the production of the said parts, but 
every point of it to be capable of the development described ac- 
cording to the position in which it may be placed. 

_ But the germination of the large spores of Lycopodium, Mar- 
silea, Pilularia, Salvinia, and Isoetes, is more complicated ; in 
them not only is that part of the spore, which by the contiguity 


evidently three-sided pyramidal form, the only germinal point of 
it, but the pro-embryo is developed up to a certain stage in the 
interior of the spores, and issues from the rent in the outer spore- 
coat, as an already parenchymatous structure, of different form m 
different genera. 

The pro-embryo of the Mosses is capable of transforms ig on e or 
more of the cells seated upon its various ramifications, immedi- 
ately into buds, which grow up into leafy stems, so that here we 
have the peculiar condition of one spore giving rise to the deve- 
lopment of a number of plants. 

The pro-embryos of Ferns, Rhizospermese, Equisetacese, and Lyco- 
podiacese, on the contrary, are incapable of the immediate produc- 
tion of leaf-buds, and produce upon the uppermost layer of cells, 
one, or mostly a number of peculiarly-formed organs, which, fol- 
lowing the example of Leszcyc-Suminski, are called ovules, 'from 
which organs^ but not until after an impregnation by the anther- 
idia, which discharge their contents at the same time, the future 
plant grows out under the form of a bud ; when this impregnation 
fails, the pro-embryo remains infertile. 

In the Ferns and Equisetacese the pro-embryo produces the an- 
theridia with the ovules, at the same epoch ; in the Rhizocarpese, 
on the contrary, the parent plant which furnishes the large spores' 
forms at the same time smaller, for the purpose of producing an- 
theridia, and these small spores, as already mentioned, in like man- 
ner exhibit a kind of germination, the product of which consists 
not of an embryo, but of antheridial cells. In the Lycopodiacese 
the conditions are still obscure. (See note p. 121.) 

The ovule consists of a large cell belonging to the tissue of the 
pro-embryo, with four cells or rows of cells overlapping it on the 
outer surface of the pro-embryo, and leaving an intercellular pas- 
sage between them leading down from the open air to that cell. 

Count Leszcyc-Suminski, the discoverer of these ovules in the 



Ferns, observed the penetration of the spiral filaments into the 

canal just referred to. His 

part of 

a spiral filament become transformed into the embryo, is doubtless 
the result of a mistake, readily to be pardoned in such difficult 
investigations, which does not damage the discovery we owe to 
him. There can be no doubt that in the rest of the plants under 
consideration, the spiral filaments are the bearers of the impreg- 
nating substance, since in the Khizocarpe^, the spores which are 
allowed to germinate separately from the small spores producing 
the spiral filaments, are capable indeed of forming a pro-embryo, 
but not of producing a plant from the ovules of this. 

The plant, which is developed in the lower cell of the ovule, is 

ro _ em k r y . j t - s a k U( ^ g row i n g 


descending axis. 


37— A. H.) 




the fruit of these plants remains undeveloped when no antheridia 
are produced. This is explained by Hofmeister's investigations ; 
according to these, the rudiment of the fruit of the Moss (the 
so-called arckegonium) greatly resembles the ovules of the 
Ferns, since underneath the so-called style, lies a large cell, which 
by subdivision is converted into a cellular body, growing down- 
wards and becoming blended with the stem at the one end, and 
becoming prolonged upwards, and developed into the sporangium 
at the other. So that while in the Ferns, &c, the spore only 
forms the pro-embryo without impregnation, and the impregnation 
is necessary for the development of a leaf-bud, which grows up 



this operation only causes the development of the spore-producing 
part of the plant (see W. Hofmeister, " ilb cl. Fruchthild. und 

Bot Zeit. 1849, 793: Mettenius, 


d. hoh. Ki 

"Beitr.z.Botri. \ 
der Cryptogamen 




>/ the British Association, 1851: and Memoir 

Nat H 


yf the Higher Oryptoqamia," &c. 


sec. 2. vol. ix., 1852 




Proceeding to the theory of the impregnation and the formation 
of the embryo in the Phanerogam] a, we arrive upon ground which 
has been levelled by the researches of the last ten years. In no 
part of our science has careful investigation, penetrating with un- 

ultimate details, vi elded more 

yet m no other part have the hardly-earned facts been so violently 
opposed, the conclusions, safely established, being even still contin- 
ually called in question on the strength of superficial investigations. 

V ' 





f . 



Observ. As the minute exposition of the historical development of the 
theory of the sexes of plants would occupy far too large a space, an indi- 
cation of the mam points must suffice. A ' ' ■" T ' ' - • • • 

Although the cultivation of 

many monoecious and dioecious plants might have led, even in ancient 
times, to the idea that plan ts were furnished with sexual organs of two 
kinds, this truth was not recognized until towards the end of the 1 7th 
century. First announced in England by Grew, Bay, and others, this 
theory obtained its first scientific establishment from B. J. Camerarius of 
lubmgen ("Be sexu plantarum epistola," 1694); but it was Linnaeus more 
especially who securely established this new theory by his researches, and 
gave it universal diffusion by the preponderating influence he exercised in 
^tany and by the displacement of all earlier systems by his Sexual System. 
W hen, finally, Kolreuter. succeeded by a longer series of experiments in 
demonstrating the possibility of producing Hybrids in the Vegetable King- 

™ ( \°nl a ^ ® a t richt eini 9- d - Gescklecht d. Pflanzen betreff. Versuche." 
i • T the0I 7 of the sexuality of plants was as firmly establish- 
ed as it could be without a knowledge of the changes which the pollen- 
grams undergo upon the stigma and the processes occurring in the 
ovule. The last century did not essentially advance further in reference 
to this point. The excellent researches of Malpighi, if not forgotten or 
misunderstood, were at all events not completed ; as to the structure and 
characters of the pollen and as to its relations to the stigma, numerous in- 
correct observations were published. With this imperfect knowledge of 
the processes occurring in the interior of the ovule, it might easily be 
tnought possible that fertile seeds should be perfected, at all events, in 
particular cases, without the co-operation of the pollen, and a number 
of observations were made known, partly in favour of such exceptional 
cases, and partly with the obj ect of refuting the entire theory of the sexes 

ct JL^ci J- tllUS S P alla ; nz ^ n i and others asserted that female specimens of 



borne fertile seeds ; Henschel 

road-dust, powdered charcoal, sulphur, &c, might be substituted for the 
pollen ; bchultz stated, as the result of his observations, that the pollen 
need not necessarily come in contact with the stigma, but might impreg- 
nate from a distance by an aura seminalis ; and Lecoq thought he had 
found that fertile seed might be developed without application of pollen 
to the stigma m monocarpic, but not in polycarpic, plants. The doubts 
thus excited were set at rest for ever by the brilliant discovery of 
Amici that the pollen- grains germinate upon the stigma and that their 
internal coat grows down in the form of a tube through the style 
into the ovary, and comes into connection with the ovule (1823— 
1830); a discovery to which Gleichen had already come very near, 
but had not properly followed out. The universality of this process 
has indeed been denied, but day by day the opposition becomes more 
completely silenced. Parallel with the researches on the structure of 
the pollen and its relation to the stigma, went the investigations on the 
ovule and the origin of the embryo, which had been taken up again from 
the last-mentioned period by Treviranus, and subsequently carried out 
further by Rob. Brown, Brongniart, Mirbel, Schleiden, Hofmeister and 
others. In the midst of this new development of the theory of impregna- 
tion, not the sexuality, but the respective import of the sexual organs 
was unexpectedly called in question, by Schleiden stating that he had disco- 




vered that the embryo was not the product of the ovule, but originated in 
the tube growing into the ovule from the pollen-grain, whence the pollen- 
grain was to be considered as the true ovule, the plants hitherto regarded 
as male as the female, and vice versd. Here again it was Amici, who by- 
decisive observation solved the doubts arising out of this theory, and de- 
monstrated the new doctrine to be false, a result which soon obtained full 
confirmation from other investigations, especially from the extensive ob- 
servations of Hofmeister and Tulasne. 

* The Pollen. 

As the development and structure of the pollen-grains have 
already been spoken of in the account of the development of cells, 
I shall confine myself here to a few remarks upon this organ. 

The perfect pollen-grain consists of a cell, usually roundish or 
elliptical (elongated into a filament in Zosteva), which, excepting 
in certain water-plants, is coated on. the outside by a membranous 
layer, which owes its origin to a secretion, and, in particular cases, 


The outer- 

most membrane, corresponding to a cuticle, is mostly rather tough, 
uniform, or covered with granules, spinules, projecting linear and 
often reticulated ridges, mostly coloured, and the seat of a more or 
less abundant secretion of a viscid oil. The internal coat is a co- 
lourless, uniform, soft, and extensible cellulose membrane. Its ca- 
vity is filled with a viscid fluid, rich in protoplasm, sometimes 


j_ / l «/ ^D 

(fovilld). In the pollen of very many plants the < 
one or more regularly arranged folds inwards, in which it very 
frequently exhibits pore-like, thinner places at one or more points ; 
in like manner, very many pollen-grains without the folds, have 
similar pore-like places, varying from one to a very considerable 
number, which when large are closed by a piece of the outer coat 

serving as a cover. 

When a pollen-grain comes in contact with water, it powerfully 
absorbs this, through the endosmose excited by its dense fluid con- 
tents, swells up and tears in many places, in consequence of the 
strong expansion its membranes undergo through the absorption 

of water. If the pollen-grain opposes the pressure of the absorbed 
water through the toughness of its membrane, the inner membrane 
is driven out, in such pollen-grain as have pore-like places in their 
outer coat, in the form of a papilla, which often extends into a 
rather long, cylindrical tube (e. g., in Dipsaceae, Geraniacese, Cu- 
cubitacese). As this phenomenon occurs in pollen-grains which have 
been long dried, and in fact very suddenly, it can be attributed 
only to mechanical expansion dependent on the peculiar structure 
of the parts referred to, and not to an actual growth. 

But when fresh, living pollen comes in contact with water which 
contains organic substance in solution, e. g., with the stigmatic 
secretion of the fluid of the nectaries of flowers, its inner coat 
grows out, in one or more places, in the form of a tube, the length 

* i 









of which, by true growth depending on nutrition, often comes to 
exceed the diameter of the pollen-grain a hundred times. 

Observ. The granules of the fo villa have given rise to many false asser- 
tions ; Ad. Brongniart, in particular, thought he had discovered that they 
agreed in form and size in each species of plant, and had an independent 
motion, whence he compared them with the spermatozoa of animals 
("Ann. d. Sc. naC xii. 40., xv. 381). Rob. Brown also ( u A Brief Account 
of Microscopic Observ. on the Particles contained in the Pollen of Plants " 
1828), although he discovered at the very time the molecular motion of 
the fo villa-granules, was of opinion that a change of form might be perceived 
in the larger granules (which he called particles). Against these state- 
ments I was compelled to declare most positively (« Ueber d. pollen? 30), 
I neither found a definite form and size of the granules in the pollen of 
any given plant, nor could detect in them movement of any other charac- 
ter than that of the molecular movement ; to similar results came Fritzsche 
(" Ueb. d. pollen? 24), who shewed that these very grains which had been as- 
serted by Brongniart and Brown to change their form, were nothing but 
starch grains, while other seeming granules were drops of oils ; the ma- 
jority of the smaller granules may however, as in all protoplasm, consist 
of proteine compounds. These granules are invisible in many fresh pol- 

lens, since the fluid in which they swim has the same refractive power as 
the granules, whence such pollen-grains are as transparent as glass lenses ■ 
when their fovilla is mixed with water the granules at once become 

The fovilla seems always to be at rest in the pollen-grain when 
it comes from the anther, unless Zostera (Fritzsche I. c. 56) forms 
an exception. But when the pollen-grain has germinated upon 
the stigma, the fovilla exhibits a circulation similar to that of the 
protoplasm of Vallisneria and Chara, flowing downwards in a 
broad stream into the pollen-tube, and back upwards on the oppo- 
site side. 

Observ. ^ This phenomenon was first seen by Amici in Portulaca (" Ann 
d. Sc. not." ii. 68), subsequently in other plants, especially in Gourds and 
in Hibiscus syriacus (" Ann. d. Sc. not." xxi. 329). Since it appears that 
no other observer (except Schleiden, who saw the circulation in pollen- 
tubes which had been developed in nectar) has been able to see this pheno- 
menon, it may be permitted me to mention how the observation is to be 
made. In Portulaca it is not difficult, if a freshly-impregnated stigma is 
exposed to bright sunshine for a few minutes, the style then removed 
from the flower with forceps, and the stigma upon which the pollen tubes 
are very quickly formed, is observed dry, with a power of at least 200 
diameters. In the Gourd (for as Amici told me himself, his observations 
were made on this plant, which in Italian is Zucca, and not on Yucca as it 
is stated in all books) a layer must be sliced from a stigma powdered 
with polleu an hour previously, and this slice pressed moderately between 
two glass plates, to heighten its transparency. 

In the development of a filament from the internal coat of the pollen 
we meet with a new analogy between the pollen-grain and the spores of 
Oyptogamous plants, since we have evidently before us a process of germi- 



nation resembling that we observe in the spore. But the pollen-grain 
does not seem to be capable of a further development, under favourable 
external circumstances, into a plant like the parent, yet Reisseck and 
Karsten observed that under certain circumstances, e. #., when pollen-grains 
were enclosed in hollow stems like that of the Dahlia, their inner coat was 
capable of an abnormal development, and of conversion into lower forms 

*-» i i ■ ^ 

of Fungi. 

** The Ovule. 

The Ovule (pvulum, Eichen), — of late years called by the ad- 
herents of Schleiden's theory of impregnation the seed-bud (samen- 
Jcnospe) or geinmule, consists essentially of a parenchymatous 
papilliform growth from the ovary, of the so- 
called nucleus (ei-kerne, nucleus ovuli fig. 52, Fig. 52. 
a), the tercine of Mirbel, in which towards the 
epoch of impregnation one cell becomes more 
enlarged, displacing a greater or smaller portion 
of the parenchyma of the nucleus and forming 
the embryo-sac (the quintine of Mirbel). 

In far the greater number of cases the ovule 
does not stand still at this first stage, in which 
it consists merely of a naked nucleus, but un- 
dergoes, before impregnation, a more or less 
extensive series of changes, which relate partly Transverse section of 
to the formation of enveloping, membranes, en- Emb^^ 
closing the nucleus, and partly to alterations of of the ovuie \primzne) ; 

n & 1( ? r , c* a v_ff 1 d, Outer CoaD (secun- 

torm dependent upon curvatures 01 the dinerent dine) ; e, Micropyie ; /, 

, r» j i i Chalaza : a. Funiculus. 

parts 01 the ovule. 

The coats of the ovule originate in this way : at a variable dis- 
tance from the summit of the nucleus, an annular collar of cells 
makes its appearance, growing into a thicker or thinner coat which 
gradually rises up round the nucleus and contracts over its apex 
leaving only a little orifice, the micropyie (ei-munde, fig. 52, e), 
In the majority of ovules, a second coat (fig. 52, d) is formed in the 
same way, lower down than the first (fig. 52, e) which it encloses. 
That part of the ovule where the simple or double coat is connect- 
ed with the base of the nucleus (fig. 52,/), is named the chalaza, 
and when beneath this there exists a cylindrical portion, it is 

called the funiculus (nabelstrang, fig. 52, g). 

Observ. Since the changes of form, which the ovules of most plants un- 
dergo in the course of their development, exercise no influence upon their 
impregnation, I shall be content to indicate briefly their principal modifi- 
cations. When the axis of the ovule remains straight, as it is always at 
first, so that the micropyie is situated at the summit of the ovule, and the 
chalaza coincides with the hilum, both lying at the extremity of the ovule 
opposite the micropyie, the ovule is called orthotropous or atropous (gerad- 
laufig). When the ovule curves over on the end of the funiculus, so that 
the upper part of the latter comes to lie parallel with one side of the 
ovule and grows together with it, the ovule is named anatropous (gegenldu- 
Jig). In an ovule of this kind the chalaza lies at the geometrical summit of 


















tlie whole, the funiculus coherent with the ovule forms a ridge running 
along one side (the raphe), the hilum (the point of insertion of the funicu- 
lus) lies beside the micropyle, at the lower end of the ovule, and the axis 
of the nucleus is straight. But when the nucleus itself is curved to one 
side by an unequl growth of its two sides ; so that the micropyle comes 
to lie beside the chalaza at the base of the ovule, and the highest point of 
the ovule is formed by the curved side-wall, the ovule is called campylo- 
tropous (krummldufig). 

Although not difficult of investigation, the knowledge of the structure 
of the ovule advanced very slowly. An excellent foundation was laid by 
Malpighi ; but it was Robert Brown, who first opened the path to 
further progress, by his description of the ovule of Kingia. The researches 
of Brongniart and Mirbel, which latter clearly unfolded the mode of ori- 
gin of the different forms of the ovule from the orthotropous, but gave a 
very incorrect account of the coats of the ovule, were followed by the ob- 
servations of Fritzsche, who cleared up the latter point, and the extensive 
investigations of Schleiden, who, through a large quantity of detailed re- 
search, earned very great credit by making known the different modifica- 
tions of the structure, — the varying number of the coats, — the universal 
occurrence of the embryo-sac, — the origin of this from a cell, &c. Hof- 
meister (" D. Entsteh. d. Embryo der Phanerog. ") traced back the earliest 
stages of development of the ovule further than any previous observer, and 
found (in the Orchidese) that it takes its origin from a single cell of the 
epidermis of the placenta, this cell dividing by a cross section into two 
cells, one lying above the other, the upper of which, is converted by further 
subdivision into the cortical layer of the nucleus, and the lower, into the 
central cellular cord, the uppermost cell of which becomes the embryo-sac. 

According to the ordinary view, the ovule is to be considered as a bud, 
the axis of which is metamorphosed into the funiculus and nucleus, the 
leaves into the coats of the ovule. The order in which the coats are de- 
veloped, might certainly be fairly urged against this opinion ; but I can- 
not question its correctness, since it is not unfrequent in malformed ovaries, 
for the ovules to grow out into leafy shoots. 

"With regard to the physiological import of impregnation, it is perfectly a 
matter of indifference whether the ovule is regarded as a product of the 
carpellary leaves, according to the theory advocated by Robert Brown 
and De Candolle, or it is assumed, with Schleiden, Endlicher, and Unger, 
and others, that the placenta is always an axial structure. It would lead 
me too far to relate the reasons for and against these two theories ; each of 
which is true of a portion of the Vegetable Kingdom, but neither of 
which, and especially the latter, can be exclusively applied to all plants, 
without coming into contradiction to the clearest facts. 

Detailed researches on the structure of the ovule are to be met with, 
especially in the works of Mirbel ( " Bech. sur la structure et developpement 
de r ovule vegetale" Ann. des Sc. nat. xvii), Schleiden (" Ueb. die. Bildung 
des Eichens" Act. nat. cur. xix. p. 1. " Grundz der wiss. Botanik"), Hof- 
meister ("Die Entstehung des Embryo der Phanerog." and Ttilasne {"Ann. 
des Sc. nat Sme BerT xii.). 

-x * 


The Origin of the Embryo 

The impregnation of the ovule by the pollen is an indispensable 
condition to the origin of an embryo in it. It is true that the 



grow up into a fruit, and the ovule into a seed 


capable of germination, because it contains no embryo. In the 

Cyeadese and Coniferse), the 


pollen falls upon the freely-exposed ovule, and impregnates it 
immediately ; in the rest of the Phaner ogamia, in which the 
ovules are enclosed in an ovary, the impregnation is effected 

edium of the pistil, with 


In the majority of plants, the ovary is not perfectly closed 
above, its cavity being prolonged upward into a very narrow canal, 
which runs through the substan ce of the style ; or if the borders 
of the carpellary leaf where this forms the style, are not blended 
together, it has the form of a groove running on the inside of the 
style. The cellular tissue which forms the wall of this canal, is 
distinguished from the rest of the tissue of the style by softness 
and transparency, and frequently also by the absence of colour. At 
the epoch of the perfect development of the pistil, there exudes 
among its cells (which are usually much elongated, but may also 
be roundish) a mucilaginous fluid, which so loosens the connection 
of the cells, that they may be readily separated, and through the 
expansion caused by the excreted fluid, they frequently quite close 
up the canal of the style. This cellular tissue, which, after 
Ad. Brongniart, is called the conducting tissue, appears at the 
upper orifice of the canal, where it is frequently enlarged into a 
large globular or lobulated body, free to the external air, and this 
constitutes the stigma. The cells forming the stigma are ordi- 
narily less elongated than those lying in the interior of the style, 
and are often more firmly blended together. The outermost layer 
of them does not form a continuous, smooth epidermis, but its 
cells are usually in the form of papillae of variable length ; and 
papillae of this kind present themselves along the whole of the 
canal of the style, upon the surface of the conducting tissue. At 
the opposite extremity of the canal, the conducting tissue stretches 
into the cavity of the ovary, and here, in general, runs on its wall 
to the points of insertion of the ovules, where it appears in very 
different forms, varying according to the structure of the ovary, 
the number and position of the ovules, &c. ; sometimes covering 
* the many-ovuled placenta as a broad layer ; sometimes running, 
in the form of a narrow strip, to a single ovule ; sometimes pro- 
jecting, in a conical shape, into the cavity of the ovary, and 
coming into direct contact with the micropyle of an ovule, &c. 
The conducting tissue is by no means to be regarded as a special 
organ, but consists of a modification of the tissue of the carpellary 
leaf, occurring at particular parts,— usually of its upper surface, 
where this forms the canal of the style. In other cases, however, 
this modification of the tissue may go out through the substance 
of the carpellary leaf to its posterior surface, as in the Asclepiadeae, 

k 2 



- m 













in which this forms but a very small part of the colossal style, or 
in Lomatogonium, where the coherent borders of the carpellary 
leaves consist of stigmatic substance along the whole of the ovary. 
The pistil is incapable of fertilization, until after the secretion 
of the above-mentioned viscid fluid upon the stigma, for though 
the pollen-grains indeed adhere to the stigma from being more or 
less glutinous, they cannot be any further affected. But as soon 
as this secretion has appeared, the germination of the pollen- 
grains commences, often in a few minutes, in any case in a few 
hours. The inner coat breaks through the outer in the form of a 
cylindrical tube, which applies itself to the stigmatic papillae 
(sometimes, as in Matthiola annua, penetrates into them), grows 
downwards among them, and penetrates between the cells of the 
conducting tissue. Ordinarily only one tube is emitted from each 
grain, but in those grains which possess several pore-like points 
on their outer coat, and in which the portion of the inner coat 
situated beneath those places always becomes developed into a tube, 
one grain not unfrequently produces several tubes, the number 
having been seen by Amici to amount to 20 — 30. The pollen-tubes 
make their way, by continuous growth at their ends, through the 

conducting tissue of the style into the ovary, attaining, in long- 

styled plants, like Cactus grandiflorus, for instance, a length 

which may exceed the diameter of the pollen-grain several 
thousand times. This considerable length alone, but still more the 
circumstance that the wall of the pollen-tube is often exceedingly 
thin in proportion to its cavity, shews that its formation does not 
depend upon mechanical extension of the pollen-membrane, but 
on a growth, the requisite nutriment for which is drawn from the 
viscidfluid poured out among the cells of the conducting tissue. 

The rate at which the growth takes place varies very much 
in different plants, and is not subject to any universal rule. The 
first result of it is an attachment of the pollen-grain to the stigma, 
so that it can no longer be readily wiped off the latter. According 
to Gartner, this often takes place in even half a minute, while, in 
other cases, many hours may elapse (in MirabUis and the Mai- 
vacece, as many as 24 — 36). The growth of the pollen-tube down 
the style likewise occupies very varied periods in different plants. 
In many plants, several weeks pass before the pollen-tubes have 
passed through a style only a few lines long, while in others, 
even when the style is very long, a few hours suffice (e.g., in 
Cactus grandiflorus and Colchicum). After the pollen-tubes 
have penetrated the stigma, the secretion of the latter ceases, and 
its tissue begins to die away, while the lower part of the pollen - 
tube is still in a growing condition. The fovilla passes down- 
wards in proportion as the tubes are elongated, so that the pollen- 
grains collapse on the stigma soon after their application upon it. 
The pollen-tubes being so long, the fovilla must certainly become 
more and more considerably diluted by the absorbed fluid, yet it 






seems always to become more or less granular and opake 
pollen-tubes are distinguishable from the cells of the conducting 
tissue, partly by their opake contents, and partly by their smaller 

V / 1 • 1. ' „.ft^ ,T»tr am oil a n IT) Qvoh.l.fl MOf%0 aDOUt 

1-1 80th of a millim, in Digitalis purpurea l^lQ6th in Oheii- 
anthus Gheiri l-280th, in Capsella Bur sa-pastor is 1-33%). 

Arrived in the ovary, the pollen-tubes, when not immediately 
led to the mouths of the ovules by special arrangements oi the 
conducting tissue, creep in a mostly very serpentine course along 
the placenta, among the ovules, and finally penetrate singly, or 

Observ A considerable time elapsed from Amici's first observation on 
the emission of the pollen-tubes upon the stigma of Portulaca (lb23), 
before their further path to the ovule was detected ; for though Brong- 
niart (1826) demonstrated, by numerous observations, that the pollen-tubes 
penetrated the conducting tissue, he thought he found that their lower 

ductin" tSsue. Amici (1830, "Ann. d. Sc. nat." xxi. 329) discovered the 
Set course to the ovule, but even in 1832, Robert Brown was stall m 
doubt whether the tubes penetrating the ovules of the Ochidese were 
pollen-tubes, or, more probably, tubes formed in the style, and to which 
he applied the name of mucous tubes, a doubt which was completely 
settled by Amici's researches, as was also the opinion advanced by many 
later observers, that this phenomenon does not occur m all the Bhanero- 

-shewn to be totally mistaken, by the extensive researches oi 

gamia : 


It is one of the most puzzling phenomena existing, that the ends of the 
pollen-tubes reach the micropyles of the ovules, the admission to which is 
xot always very simple j since this rencontre seems to be left to pure acci- 
dent it might be conjectured that for this purpose a very large number 
of pollen-tubes were necessary. Yet such is not the case. It is true 
that in the majority of plants, the number of pollen-tubes which are deve- 
loped upon the stigma is very considerable, and we not unfrequently see 
whole bundles of them penetrate the ovary, which is readily accounted 
for by the vast number of pollen-grains found in the flowers, a tolerable 
Proportion of which generally reach the stigma. Thus Kolreuter found 
4863 pollen-grains in the flower HiUscus Tnwwm, and according to 
Amici's estimate the pollen-grains of an anther of Orclns Mono can fur- 
Ssh 120 000 pollen-tubes. But the number of pollen-grams necessary 
for knpTegn^iTis by no means large. For example in Kolreuter s 
experiments on HiUscus Trionum, 50—60 pollen-grams sufficed to impreg- 
nate all the ovules in the ovary (over 30) ; when fewer pollen-grams 
were placed upon the stigma the ovules were not all impregnated, for in- 
stance by 25 pollen-grains only 10—16 ovules. In MtraUhs Jalapa and 
lonaidora one, or at most three, sufficed to impregnate the ovule 

Tis not necessary to the success of an impregnation that the pollen 
should pass immediately from the anther to the stigma, for it seems to 
remain capable of fertilizing for some days m all plants, while m some it 
.retains it/power even for a yea. Thus Ko renter found th a*4he po en 








■ I 





- ' 



being preserved for a year in the East ; and the same time has been 
asserted for Cannabis, Zea, and Camellia. (See Gartner " Befruchtimg der 

Gewachse" 1, 146.) 

In order to explain the course of the processes which go on in 
the interior of the ovule, it will be necessary for me to return to 

its structure. 


sac has mostly become greatly enlarged in proportion to the other 
parts. In many plants it is still enclosed in the interior of the 
nucleus, so that its upper end, directed towards the micropyle, is 
still covered by one or more layers of parenchymatous cells be- 
longing to the nucleus. In other plants (for example in the Or- 



o vule) 



come so much elongated that it projects freely out of the micro- 
pyle. The pollen-tube which has penetrated into the micropyle 
(pi. 1, % 14, p : ] 5, p.) in its further elongation, thus comes either 
immediately in contact with the apex of the embryo-sac, or with the 
layer of cells covering it ; in the latter case it penetrates between 
these cells, and in this way likewise reaches the embryo-sac. 

In the latter there is always a more or less abundant quantity 
of protoplasm. In the later period, just before the pollen-tube 
reaches the embryo-sac, a portion of the protoplasm becomes at- 
tracted into the upper end, next the micropyle. In this proto- 
plasm nuclei appear, usually to the number of three (pi. 1, fig. 12), 
and give rise to the formation of as many cells (pi. 1, fig. 1 3, 6 ; 14)^ 
which more or less completely fill up the upper part of the cavity 
of the embryo-sac, and are termed the germinal vesicles (embryo- 
hlascheri). The triple number, although usual, is not universal 



Agrostemma Githago, according to Hof- 
jerminal vesicle is formed, while in other cases 


Hofmeister observed in Canna, may- 


rest before impregnation through its predominating enlargement. 
With these cells necessary for the origin of the embryo, a variable 
number of other cells are also formed in other parts of the embryo- 
sac (pi. 1, fig. 4, /), chiefly in the end turned away from the mi- 
cropyle, more rarely in the central region. But this cell-formation 
is neither an universal phenomenon, nor does it stand in relation 
to the impregnation. 

When the pollen-tube has reached the upper part of the embryo- 
sac, its growth is either immediately arrested, or it becomes elon- 
gated a very little more, so that its obtuse, somewhat inflated end 
usually penetrates laterally between the embryo-sac and the sur- 









In extremely rare 


through the membrane of the embryo-sac, and thus comes imme- 
diately in contact with the germinal vesicles. In the great majority 
of cases, however, as already observed, the pollen-tube is separated 
from the germinal vesicles by the membrane of the embryo-sac, 
andfrequlntly even, the point at which the end of the pollen-tube 
I in contact with the embryo-sac, does not correspond exactly to 
the point at which a germinal vesicle lies in the inside of the m- 
brvo-sac Col 1 fig. 15). Therefore the only way in which a mate- 
rXffect can be'produced by the pollen-tube upon the germinal 
viclfis by the Ld part J the fovilla transuding throng the 



take piace, but it is in the highest degree probable, since it is in- 

uc ^ Jt 7 , ? # u „ , ^.^T.TYiir^Q.1 \r&<z\n. p. noil 1(1 



UU1I1 Ul V/ll VJJ.UX ,v a. v ~-~ '. J. O 

take place without it. 

The pollen-tube begins to decay ~- * ~ 

has reached the emb?yo-sac. Its growth is arrested as before 
noW, and the fovilla contained in it undergoes a visible change 
in its characters, acquiring a granular, half coagulated aspect ; the 
Lien-tube itself is by this time evidently dead and disappears 
sooner or later (sometimes, however, not until the seed is ripe), 

apparently through absorption. 
Thortly after the meeting of the pollen-tube with the embryo- 
sac but only when this hat occurred, the further development of 
he germiil vesicle begins, this exhibiting a rapid growth and 
nsually displacing the two other germinal vesicles which oral 
narHy accompany it (pi. 1, fig. 15) ; it is only m rare cases that 
two Jr more of these vesicles simultaneously undergo enlargement. 
The form which the growing germinal vesicle assumes is very un- 
like in different plants ; in many it grows but moderately in 
the longitudinal direction, and thus becomes ovate ; in others 
particulLly in the Scrophularineae and Crucite, it grows into a 
long cylinder, which frequently does not much exceed the pollen- 
tube in diameter, and exhibits a clavate expansion at its lower 
extremity. During this enlargement, the protoplasm which ori- 
Srally filled up the germinal vesicle pretty uniformly becomes 
Principally collected at the lower end, after which cell-formation 
L di^sion commences (pi. 1, % 15, 16) In this ^—m of 

name of pro-embryo (yorkevm 

In all cases the 

S present themselves in different plants In all eases the 
vesicle fast divides by a transverse wall into two cells, one above 
the other (pi 1 fi K . 16, a, b.) ; the lower of these may at once be- 
come inverted into a parenchymatous body (the embryo) by sue- 













the pro-embryo has been changed into a compound cellular body 
by successive subdivisions. In this process there may be forma- 


(pi. J , fig. 1 7 

18, a) frequently elongated 

row of cells lying one above another (for example, in the Scro- 
phularinese and Cruciferse), or the filamentous pro-embryo may 
pretty early pass into a mass of cellular tissue by longitudinal 
division of its cells (for instance, in Statice, Tropceolum, Zea, Fri- 
tillaria, &c). Whichever takes place, the terminal cell of the 
whole structure is sooner or later metamorphosed, by preponder- 
ating growth and cell-division in different directions, into a eel- 

form (pi. 1, fig. 17 


which, the more fully it becomes developed, the more marked 
contrast does it present to the other part of the pro-embryo turned 
towards the micropyle end (called the suspensor, Trager, or 
ifhangefaden). The ulterior development shews that this 


ment of the embryo. It may persist, in plants with the so-called 
** homogeneous embryo" (e. g., in the Orchidese and in Monotropa), 
in the form of a globular or elliptical body, composed of a variable 
number of cells (pi. 1, fig. 18) ; but usually the cotyledons shoot 
out at the end turned away from the suspensor, a little below the 
actual extremity (in the Monocotyledons in the form of a sheath- 
ing leaf, in the Dicotyledons in the form of two opposite leaves,) 





Its radical extremity, as is evident from the mode of origin 
of the embryo, is not free, but blended with the cells of the pro- 
embryo ; frequently it does not at once become clearly distin- 
guishable from the cells of the pro-embryo, but the line of de- 
marcation becomes continually more definite with the advancing 

Jl ~1 - J • il n r* i t •* - rt 



contain only a little opake sap, and are thus far more transparent 
than those of the embryo, from which they are also frequently 
distinguishable by much greater size. The further the develop- 
ment of the embryo progresses, the more, in most cases, does vege- 
tation cease in the cells of the suspensor, so that, if even, as in the 
Orchidese, it still exibits a considerable growth during the deve- 
lopment of the embryo, and exists when the seed is ripe, it at all 
events forms but a dead, readily detachable appendage of the 
radicle, upon the embryo of the ripe seed. 

The origin of the embryo, which is formed out of a cell of the 
pro-embryo, and not free in the cavity of the embryo-sac, bears great 
resemblance to the formation of a bud, and especially to the for- 
nation of the stem-producing buds developed on the pro-embryo of 





the Cryptogamia ; yet there exists an important distinction from 
the formation of buds, in the fact that the lower end, connected 
with the suspensor, becomes detached from this and is capable ot 

mbryo can become 

termination, as 

a tap-root, which is not the case m any buds, . or in the young 
stems of the Cryptogamia,* the axis of which is only capable of 
prolongation upwards. 

Observ. 1. Schleiden's theory of the origin of the embryo (« Mnige 
Blicke aufdie Entwickelungsgeschichte des veget Organismus, Wiegmann s 
"Archiv " 1837 1, 289—" Ueber die Bildung des EicJwns und Jintstehung 
des Embryo" Act. acad. not. Cur. v. xix., p. 1.) is completely opposed to 
the foregoing description of this process, since, according to him, the 
embryo is not formed in the cavity of the embryo-sac, but in the lower 
end of the pollen-tube, which introverts the wall of the embryo-sac, and 
penetrates more or less deeply into the depression thus formed. If this 
theory were true, the germinal vesicle would not be an independent pro- 
duct of the ovule, but of the clavate, expanded extremity ot the pollen-tube, 
and the suspensor would be the remainder of the latter, running into the 
introverted portion of the embryo-sac. In the whole province of Vege- 
table Physiology, seldom has a theory excited so much curiosity as this 
theory of impregnation. No conviction was more firmly established than 
that the pollen was the impregnating organ, hence the wonder that it 
should be exactly the reverse. The confusion was great, for the theory 
emanated from a man who shewed by his numerous and excellent re- 
searches on the ovule, published at the same time that he possessed an 
acquaintance with his subject, such as few others had, and who m every 
word expressed the conviction that the matter did occur as he asserted, 
- ... l - . i . — -j- -^4--u~ ^,,^+i^-r. And others were not want- 


and that a mistake was out of the question . 


vms ' 1838, Oct.; GSleznoff, « Bot. -Zettung," 1843, 841), or to support 
the new doctrine on theoretical grounds, and teach it as a settled truth 


(Endlicher and linger, « Grundz. der Botanik' ). It is true that the old 
notion had its defenders, but these maintained the fight a long time with 
little success. Some who did not know how to use the microscope thought, 
nevertheless, that an opinion might be arrived at here, m which the thing 
depended wholly and solely upon a fact to be determined by the micro- 
scope from other grounds, but such was utterly without value by itself ; 
others Meyen in particular (« Physiologie? iii), certainly had recourse to 
the microscope, but were content with superficial observations, and thus 
were not very fortunate in their intended refutation of the new theory, 
for observations, in some of which not even the penetration of the pollen- 
tube into the ovule, or the embryo-sac were seen, were not calculated to 




It was Amici again who now for the second time came 

forward with an observation marking an epoch in the theory of impregna- 
* An error ; the axis of thelw, &c, originates from a free embryonal 

vesicle, and has an 

A. H. 

abortive descending axis, like the Monocotyledons. 


I I 

■ ••• 



1 28 



tion, and, by his researches on the impregnation of the Orchidese (" Sidla 
fecundazione delle Orchidee" — Giorn. Pot. Italian. Anno 2), made an end of 
the new theory at one blow. Amici's treatise was soon followed by a 
confirmation of what he had seen by myself ("Bot. Zeitung" 1847, 465), 
and others ; and these were quickly succeeded by the extensive researches 
of Hofmeister (" Die Entstehung d. Embryo d. Phanerogamen") and of 
Tulasne ("Ann. d. So. nat. 3 Ser. xii), which contained a full confirmation 
of the results obtained in the Orchidese, and demonstrated that the im- 
pregnative process is the same in its essential circumstances throughout 
a long series of Phanerogamia, so that this subject may be considered as 
quite settled in its principal features. 

Obs. 2. The so-called naked-seeded Dicotyledons (the Cycadese and 
Coniferse) present some very important differences from all other Phane- 
gamia, in reference to the production of their embryo ; the circumstances 
are unfortunately not all cleared up by the foregoing researches, 
differences depend, not so much upon the fact, that the pollen-grains fall 
immediately upon the naked ovules in these plants, for nothing is essen- 
tially altered by this, since the pollen-grains here germinate on the point 
of the nucleus in the same way as in other plants, and are thus spared the 
circuitous route which the pollen-tubes have to make through the con- 
ducting tissue of the pistil. The distinctions lie in a great complication 
of the structure of the ovule, and in the manifold deviations in the struc- 
ture of the embryo. 

In the Conifers, the nucleus is in great part displaced by the enlarge- 
ment of the embryo-sac ; the latter becomes filled with cellular tissue, 
out of which from three to six cells, arranged in a circle near the upper 
end, become more considerably enlarged than the rest, and these consti- 
tute what are called, by Robert Brown, the corpuscida, — by Mirbel and 
Spach, the secondary embryo-sacs, — and also become filled up with cellular 
tissue. The pollen-grains germinate on the point of the nucleus, and send 
down their tubes through the upper part of it ; and the slowness with 
which this process takes place in many species is remarkable, for in Larix 
europcea, according to Geleznoff, the pollen-tubes do not emerge from the 
granules till after thirty-five days ; and in Pinus sylvestris, Pineau states 
that full a year passes before they grow down through the nucleus to the 
embryo-sac, whereby evidently the impregnation is also postponed for this 
long period. When the pollen-tubes have arrived at the embryo-sac, they 
break through it, and through the cellular tissue lying between its mem- 
branes and the secondary embryo-sacs. The observations on their subse- 
quent course are discordant. Pineau believed he had discovered that the 
ends burst, and poured out the fovilla into the secondary embryo-sacs. 
According to Geleznoff, the pollen-tubes would break through an inner 
membrane immediately enclosing the fovilla, and grow into the secondary 
embryo-sac. In like manner, there is an obscurity as to the origin of the 
embryo. Apparently there originates in the secondary embryo-sacs, 
from the cells already contained in them, a pro-embryo of most peculiar 
form : in Pinus, the upper part of it is composed of a rosette of four to 
five cells, to which an equal number are applied be! ow, these extend them- 
selves into a long filament, which again bears four cells at its extremity 
constituting the rudiment of the embryo. As the intermediate cells 
grow down in the filamentous form, they break through the lower end of 








the secondary embryo-sacs, grow onward in the cellular tissue lying in a 
cavity of the primary embryo-sac, and push the embryo out of the secon- 
dary embryo-sac. In this way are formed as many embryos as there are 
secondary embryo-sacs ; but the four or five cells forming the thread-like 
suspensor may separate from each other, and every one form a special 
embryo. The embryo itself, moreover, exhibits a peculiar growth, for 
while its cotyledonary end is composed of a connected, well-defined mass 
of cells, its radical extremity is formed of a loose mass of cellular tissue, 
which grows back on the suspensor, its cells only becoming more com- 
pactly conjoined at a later period. Finally, in Thuja, a whole mass of such 
suspensors are formed, which terminate in an embryo below, side by side, 
in one embryo-sac. The numerous embryos originating in one ovule seem 
all to be equally capable of living, and are developed up to a certain point, 
but then from some unknown cause, all die away except one. (Robert 
Brown "On the Plurality and Development of Embryos in the Seeds of 




Nat. Hist., 1. Ser. xiii. 368 ; Mirbel 



2 Ser xx 257; Pineau, " Sur la Formation de VE miry on chez les Coni- 
ffre-s? —Arm. des Sc. nat. 3 Ser. xi. 83 ; Geleznoff, "Bur VEmbryogenie du 
Meleze, Bulletin, de la Societe de Natural, de Moscou" xxii., " Ann. des So. 

natr 3 Ser. xiv.)* . 

Observ. 3. If Schleiden's theory of impregnation had proved true, it 



the ovule without application of pollen to the stigma, 
fir mat ion of the earlier view of the import of the pollen-grain, the doubt 
a^ain arises whether the geminal vesicle is not in isolated cases capable of 
development into an embryo without impregnation. Improbable as such 
an exception seems, when we look at the thousands of experiments which 
declare the necessity of impregnation, the absolute impossibility of it can 
the less be proved that undoubted cases of the possibility have been 
shewn in the Animal Kingdom. The greater the accuracy in the observa- 
tions indeed, the more clear it became that the cases in which it was 
supposed that the development of fertile seeds without impregnation had 
been observed, in the hemp, spinach, &c, arose from mistakes, but certain 
cases still remain in which the problem has not yet been solved. In 
reference to this, mention must particularly be made of the Euphorbia- 
ceous plant, Ccelobogyne ilicifolia, described by John Smith (" Linn. Trans." 
xviii. 510), in. which not a trace of anthers could be found, either by 
Smith, or by Francis Bauer, Lindley, and others, and yet it bore perfect 
seeds. ' Gasparrini likewise asserts {"Ann. d. Sc. nat" 3 Ser. v. 206) that 
the fi°'s developed in summer never contain male flowers, and yet produce 
seeds which contain an embryo. 



Although plants in general appear completely fixed and motion- 
less, a close examination leads to the detection of movements of 

* Hofmeister has recently shewn that great analogy exists between 
the Corpuscula and the Archegonia of the Cryptogamia. See Hofmeister, 



&c, Leipzig, 1851 ; 
nia? &c. — " Ann. 



~ ~* 



t I 




the most diverse of their organs, which are sometimes dependent 
on the influence of certain universally-diffused agents, such as 
gravity and light, sometimes are excited by stimuli accidentally 
affecting them, and sometimes occur independently without the 
existence of any demonstrable external cause. Great as the simi- 
larity to animal motion is in many of these movements, they are 
always devoid of the character of volition, so that altogether no 
more definite and profound distinction between plants and ani- 
mals can be found, than the total want of voluntary motion in 
the former and the presence of this same in the latter. 

O&sem'^IJnfortunately it is extremely difficult to make out, in many 
cases, whether a motion is voluntary or not, yet repeated unprejudiced 
observations will very rarely leave a doubt about it. In no other inves- 
tigation does the observer need calm reflection in so high a degree as 
here, for hundreds of examples shew how readily the imagination steps 
in and leads to erroneous conclusions in the observation of the enigma* 
" ' ' n "* ' Warning examples are furnished by ob- 

spores of Algae, on the Diatomacese, 

tical movements of plants. 


servations on the 
Oscillatoriese, &c, in abundance ; shewing how soon, when once the kind 
of motion has been mistaken and these plants conceived to be animals, 
their entire structure has become misunderstood, and imaginaiy eyes, 
intestines, feet, and other animal organs have been discovered, which 
more temperate observers have recognized as things differing as widely as 
the poles. 

In examining the movements of plants we must first of all 
exclude those cases in which motion of an organ is caused by the 
more or less complete drying up of different layers of it, producing 

unequal contraction and thereby curling of the parts. The rapidity 

of the motion produced m this way depends on the mechanical 
conditions of structure ; it may be slow or very rapid. The former 
is the case when no external hinderance opposes the movement of 
the drying organ, the latter when the curving part is blended with 
other parts, so as to be hindered from following its contraction, 

whereby a gradually increasing tension arises in it, the final re- 
sult of which is a rupture and a sudden relief of the stretched 
part, like the recoil of a metal spring. . In general, the layers of 
an organ which contract most strongly in drying are those which 
are composed of larger, thinner-walled, and more globular cells, 
while a layer composed of thick-walled, small, and elongated 
cells suffers less contraction, and therefore forms the convex side 
of the curved organ. 

* Observ. Examples of these hygroscopic movements are of every-day 
occurrence, and it will suffice to indicate a few of them. Among these 

are, the contraction into a globe, which the ramified stems of. many 

plants, such as Anastatica hierochontica, Lycopodiwm lepidophylhim, un- 
dergo in drying ; the dehiscence of anthers, the bursting of most dry 
fruit, the rupture of the outer seed-coat of Oxalis, the twisting of the 
awns of many grasses. In particular cases even isolated pieces of cell- 
wall exhibit movements of this kind, when their various layers differ 




from one another in hygroscopical respects, e. g., in the elaters of Eqmse- 
turn, the peristome of the Mosses, &c. The cause of these motions is 
usually so conspicuous, and the proof that they result from desiccation so 
readily shewn, since wetting the dried organ brings it back into its old 
form, that the cause has but rarely been misconceived, and such motions 
ascribed to a vital force, irritability, &c, in the way Purkinje so strangely 
did, in regard to the opening of the anthers, in a special work (" Be 
cellulis antherarum fibrosis," 1830). 


movements of living plants, we meet 


lower aquatic Algse, the Diatomacese, Desmidiacess, and Oscilla- 
toriese, which, on account of this, have been so frequently re- 
garded as animals. In the Diatomacese and Desmidiacese, the 
motion consists of a slow waving backwards and forwards in the 
direction of their longitudinal diameter, during which no change 
of form, such as curvature or the like (which indeed would be_ im- 
possible in the Diatomacese, on account of their siliceous lorica), 
can be observed in the cell constituting the plant. Neither can 
special organs of motion (such as cilise) be discovered, and Ehren- 
bero-'s idea that he detected a moveable foot, similar to that of 

Mollusca, must 


The organic process upon which this motion depends is alto- 

Qattungen der einzelliger 




gether w . . 

A Igen," 20) explains the motion by supposing, that in the absorp- 
tion and excretion of fluid matters connected with the nutrient 
processes of these plants, the attraction and repulsion of the fluids 
are irregularly distributed over the portions of the surface, and 
that these currents are so active as to overcome the resistance of 
the water ; but this explanation is devoid of any positive basis. 
The external circumstances in which the plants are placed have 
influence over the motion so far, that when the little plants lie 
hidden in mud, they rise up to its surface if the sun shines upon 
it, and they bury themselves in the mud when its surface be- 
comes dried up (Haifa's, " British Desmidem" 20). • 

The motion which presents itself in the Oscillatorice is more 
complicated, since not only does the entire plant move backwards 
and forwards like a little rod, but a pendulous swinging of the 
filaments to and fro occurs, together with a curvature in a 
spiral direction (See Kiitzing, " Phycol. Generalis," 181 ; Frese- 
nius, " Ueber Bau and Leben der scillarien," in the Museum Sen- 
henbergianum, iii. 284). This curvature deserves our attention in 
a higher degree, that these plants are composed of a simple row of 
flattened cells enclosed in a membranous sheath. Under these 
circumstances, a curvature of the filament cannot depend (as in 
the higher plants) upon a different relative contraction or expan- 
sion of different cells lying side by side, but must arise from a 
different behaviour of the different lateral surfaces of the two side 


■ ' 








ANATOMY and physiology of 

walls of the individual cells, either the side becoming concave in 
the motion nndergoing abbreviation, or the opposite side expand- 

The locomotion of the entire filament is influenced in the 


same way as that of the Diatomacese and Desmidiacese by illumi- 
nation or drying up of the mud, and the movement from a dark 
towards an illuminated place, is, in particular, very distinct (Du- 
trochet, " Memoir es," i. 1 1 2). 

Observ. This is, of course, not the place to enter into the much con- 
tested question whether these beings are actually plants, and not rather 
animals. The former is, as I at least believe, incontestibly proved by 
Kiitzing ("Die Kieselschaaligen Bacillmien), Ralfs (" British Desrmd%e<e;') 
and others. But it deserves mention that the contraction into a spiral 
form occurs not unfrequently in still higher degree than in the Oscilla- 
toriece, in most undoubted plants, namely, the Zygnemece (See Meyen, 
" Physiologie," hi. 5Q6). 

Eapid advancing and retreating movements, like those the 
lower Alg*e exhibit, are unknown in those organs of higher 
plants, consisting of a single cell or row of cells, which might, in 
reference to their structure, be compared with the plants above 
referred to, yet we find in such simply constructed organs, pheno- 



many respects, wixn wie phenomena of motion. I include among 
these the phenomenon, that many filiform cellular processes 
orow in a definite direction, and attach themselves upon foreign 

bodies. . 

The pollen-tubes are, above all, to be recalled to mind here, 
curving, as they do, after their exit from the pollen-grain, to come 
in contact with the hairs of the stigma, applying themselves upon 
these, and penetrating into the conducting tissue of the style. 
This phenomenon has often been compared with germination, and 
correctly, for in that curvature, in the penetration of the pollen- 
tube into the conducting tissue, we meet with the same pheno- 
mena, only in a more simply organized part, as in the radicle of a 
germinating plant. Still greater is the analogy with the radicles 
of many Cryptogamia, whether these are protrusions of single cells, 
as in many Conferva? and in the Liverworts, or simple rows of cells, 
as in the Mosses. In these capillary roots we find the same ten- 
dency to grow downwards, and the same adherence to foreign 
bodies. One might be inclined to seek the cause of this curvature 
of the cells, and their adherence to foreign bodies, in a retardation 
of the oxowth of those parts of the cell-membrane which come in 
contac? with the foreign bodies, behind that of the free parts of 
the membrane. But it is possible that the conditions are far more 
complicated. For if we compare these phenomena with the pro- 
cesses which are presented to us in the compound organs of the 
higher plants, we find in the movements of these capillary organs, 
corresponding processes to those which, in the higher plants, are 




produced by not less than three causes (the influence of gravity, 
light, and contact of solid bodies). Since, however, the external 
influences upon which these movements depend, are as yet alto- 
gether unexamined, and thus nothing but empty guesses can be 
expressed regarding them, I feel that I ought to be content 
with the indication, that even in the simple cell, phenomena of 
motion occur which are comparable with those of the compound 


With regard to the motions of the parts of higher plants, so tar 

as they are connected with their growth, we are first struck by 
the determinate directions of the root, the stem, and the leaves. 


To no phenomenon have we been rendered— by haying it daily 
before our eyes — more indifferent, than to the definite direction 
in which every part of a plant lies in reference to a perpendicular 
line ; and yet in the circumstance that the stem grows upwards, 
the root downwards, and the leaf with its upper surface turned 
towards the sky, we behold a series of the most wonderful pheno- 

the causal relations of which are unfortunately but too 
little ' understood. These positions of the various organs seem 
to us so natural, that it is only by the exceptions which occur m 
many plants, and by the effort of a dis-arranged part to regain 
its normal position, that our attention becomes attracted to the 
fact that this position is the result of a series of mysterious pro- 
cesses, which, though unnoticed, are ever active in the plant. 

Experiments of the simplest kind, in particular such as were 
made by Duhamel, have long since shewn that the earlier endea- 
vours to explain the growth of the root downwards and of the 

stem upwards, from the influence of the darkness and moistui 



the position and the surrounding media of a germinating seed 

what they may, whether this germinate in the earth, in air or in 

water, in darkness or under the influence of light, the radicle and 

the plumule will curve until they have acquired their normal 

direction. The acuteness of Knight ("PhU. Trans." 1806; "A 

- - - - " 124) obtained the first 


success in demonstrating sure evidence of the connexion of this 



which circumstances the radicles turned towards the periphery, 
and the plumules towards the centre of the wheels. This experi- 
ment was afterwards extended by Dutrochet to the leaves, where- 
by he shewed that the leaves are also subject to the effect of 
gravity, for these turned their lower faces towards the periphery 
of the wheel (Dutrochet " Memoir es," ii. " iN 


Observ. It is difficult to conceive how any naturalists could question 
the value of the evidence furnished by this experiment, in which the 







effect of gravity was replaced by that of centrifugal force. But on the 
other hand, the explanation given by Knigb t of the mode of action of 
gravity in determining the direction of plants must be regarded as un- 
successful. In this explanation Knight started from the different manner 
in which the stem and roots grow longitudinally. The root, as is well 
known, grows only at its extreme points. Knight believed that the half- 
solidified substance of these points immediately followed the attraction of 
gravitation, and curved downwards. With regard to the stem, on the 
contrary, in which a series of internodes are undergoing elongation simul- 
taneously, Knight thought that gravity could not act upon its al ready 
formed, solid, organic substance, but affected only its contained nutrient 
juices, that in a stem out of the perpendicular direction those juices 
would be drawn to the lower side, which would consequently be more 
actively nourished, thence would grow more vigorously in the longitu- 
dinal direction than the upper side, and so cause a curvature of the stem 
upwards. If this explanation were correct in regard to the roots, it 
would follow from it that the point of a root could not penetrate into a 
fluid of greater specific gravity than its own substance ; but the experi- 
ments ofPinot, Mulder, and Durand (« Ann. des. Sc. not. 3 Ser," iii. 210— 
Botanical Gazette, i.) shew, that the radicles of germinating seeds pene- 
trate into mercury, whence it is clear that the points of the roots are not 
directly attracted downwards by gravity, but that the latter causes alter- 
ations in the root, through which an active curvature downwards is 

brought about. 


certain resemblance to Knight's explanation of the growth of the stem. 
With reference to the latter, it is at once clear that Knight regarded as 
a self-evident fact, the circumstance that the curvature of the stem is a 
consequence of its growth. But this seems in the highest degree impro- 
bable, if we note on the one hand, that in many organs, even when they 
exhibit no further growth (as in leaves, tendrils, &c), curving movements 
occur which depend upon a frequently very transitory expansion of their 
cellular tissue wholly independent of their growth ; and remember, on 
the other hand, that nothing is more common in stems and branches, 
than the manifestation of a much more vigorous growth on one side, 
givino- to them a very eccentric position, without any curvature being 
produced by this one-sided growth. Still less tenable must this explana- 
tion appear when we consider that the direction upwards does not occur 
in the stem of all plants, but that many follow a horizontal course, and 
that the shoots of many plants, for instance, of the Weeping Ash, have a 
very strongly marked tendency to grow downwards, without any ob- 
servable occurrence of a diffence in the mode of growth from that of the 
stems growing upwards. This indicates that there must exist in the dif- 
ferent stems differences of organization unconnected with their longitu- 
dinal orowth, on which it depends that the same external conditions 
cause in one a curvature downwards, and in the other a curve upwards. 
That these modifications of the internal organization are based upon con- 
ditions not very readily detected, may be concluded from the fact, that 
the shoots of different varieties of the same plant, as of the Ash or Beech, 
may behave quite differently in this respect ; that in almost all our trees, 
for instance in the Firs, a difference of direction exists between the 
primary and secondary axes, and that frequently, on a sudden, without 



I . v . ■■ s; 



upward and grow in the vertical direction in the manner of the trunk, of 
which large specimens of Pinus Cembra in particular exhibit the most 

beautiful and striking examples. _ 

To Dutrochet belongs the merit of having called attention to tne dil- 
ference between the organization of the stem and the root, which must 
incontestibly be taken into consideration before all else, in discussing the 
movements now referred to, and gives hope that their further investiga- 
tion will solve much that is still doubtful in respect to the movements of 
plants. Dutrochet (<< M'emowes? ii 1) endeavoured to trace the curva- 
ture of the stem upward and that of the root downward from the endos- 
mose exercised in the parenchymatous cells of these organs. He found 
that a plate cut longitudinally, in the direction of a radius, from an her- 
baceous stem, curved in water so as to render the epidermis concave ; 
while a plate cut out of a young root exhibited the opposite curvature 
The cause of these different curvatures he found, in the decreasing size of 
the pith-cells from within outwards in the stem (these alone coming into 
consideration on account of the preponderating size of the pith and the 
proportionately small thickness of the bark), and in the decreasing size 
from without inwards of the cortical cells of the root, these alone being 
of importance in regard to the root where the rind is so much more deve- 
loped. This tendency to curve exists, although in less degree, when the 
different parts are not placed in water, in consequence of the cells being 
full of sap, as in the natural condition of plants. The different sides of 
the root and stem possess the tendency to this curvature in an equal 
degree so long as these organs are in a perpendicular position, and thus 
the force of one side is kept in equilibrium by that of the opposite side. 
But when a stem or root is placed in an inclined position, according to 
Dutrochet's view, the effect of gravity causing a flow of the concentrated 
sap toward the lower side of the organ, limits the endosmose exercised 
by the cells of this side, while the cells of the upper side which come m 
contact with a less concentrated sap are unrestrained in their endosmose, 
and in their expansion consequent thereupon. Thus the tendency to 
curvature arising from the endosmose in these acquires the preponderance, 
and causes an upward curvature of the stem and a downward of the root. 
Notwithstanding that many errors occur in the statements of Dutrochet s 
treatise, and that the manifold modifications which present themselves in 
the directions of stems and shoots in different plants, a few only of which 
have been indicated above, cannot as yet be explained from their struc- 
ture, yet this author has the credit of having d emonstrated the element- 
ary truths : 1, That the curvature of the root and the stem is independ- 
ent of their growth j 2, That the moving organ must be looked for in 
the soft parenchymatous cells ; and 3, That the curvature effected by the 
cells is not produced by a contraction of that side which becomes con- 
cave, thus drawing over the other part of the organ, but, on the contrary, 
the curvature arises from a swelling of that side of the organ which be- 

comes convex. 

Both stem and root are only capable of retaining the perpen- 
dicular direction which they assume through the influence of 
gravity, when they are wholly removed from light, or light is 
freely admitted to all sides of them ; when the light shines only 

J L 












■ ■ 

* * 

on one side of a plant, the latter becomes more or less diverted 
out of its normal direction. 

It is an every-day's experience that this is the case in a high 
degree with young and still soft stems, since in plants which re- 
ceive light on one side only, the stems curve strongly towards the 
side whence the light comes. In plants which are very sensitive 

to light, like germinating; Cruciferse, I found that the influence ot 

light might wholly overcome the effect of gravity, for when I sus- 

pended some of these in a horizontal direction, in a blackened box, 
closed on all sides and at the top, and lighted through the open 
lower end by a mirror, the plants were compelled to turn their 

stems vertically downwards. 

This curvature is produced in unequal degrees by the differently 
coloured rays of the spectrum, and this independently of their 
illuminating power, being caused most of all by the blue rays ; 
and, according to Payer (" Comptes rendus" xvii), in general 

ipectrum lying between F and H, a 
statement, which, however, would undergo some modification 
through the experiments of Dutrochet (which, it is true, were not 
made with the aid of a heliostat, but with red glass, and conse- 


the red rays produced curvature, although in slight degree ("Ann. 

des. Sc. not. 2 Ser" xx. 329). 

It is proved that this curvature is produced by the illuminated 
side, and that the convex side only mechanically follows its cur- 
vature, by the fact that when the concave side is removed from 
the convex side by a longitudinal incision, it curves more strongly 
than before, and the convex side springs back into the upright 

position (Dutrochet, " Memoires, 



Observ. The fact last stated completely refutes De Candolle's explana- 
tion, which appears, at first sight, to give a very simple cause for the cur- 
vature of the stem towards light falling on it. De Candolle thought 
("Mem. d. I. Societe d'Arcueil" 1809, ii. 104) that in accordance with the 
common experience of plants which receive but little light growing very 
much longitudinally ; plants jfe&ich received light only on one side would 
grow much longer on the dark side than on the lighted side, and thus 
would curve towards the source of light. 

We find a similar contrast in the dependence of stem and root 
upon light, to that of the movements produced in these parts by 
gravity, for the root turns away from the light ; a phenomenon 
which was first discovered by Dutrochet in germinating plants of 
Viscum album, was subsequently demonstrated more extensively 
by Payer ("Comptes rendus," xvii), Durand, and Dutrochet 
( u Ann. des. 8c. not. 3 Ser," v. 65), by experiments, chiefly on the 
roots of Cruciferse and Compositse : and of which proof may fre- 
quently be obtained in hot-houses, from the aerial roots of Cactus 
grandlflorus and other plants. The only cases in which this re- 


"i ■ ^ 




treat from light lias been shewn with certainty in upward i < 
ing parts of plants, are the tendrils oijitis and . Ampelopsis 



Phil. Trans. 


1812 314 • " Physiol. Papers," J 64) ; while other tendrils which 
tested in this respect either gave no decided result, or turned to- 

- Winden der Romken u. Schlingpfl 

zenj r ii). 

Observ Dutrochet asserts that the stems of all twining plants have 
the property of turning away from light. From very numerous obser- 
vations on plants with climbing or twining stems, 1 must declare this to 
be altogether incorrect, for, like other plants, they turn towards the light. 
But I °have no definite experience to enable me to decide whether the 
hook-like curvature of the end of the stem of Vitis, Corylus, &c, and 
further, the downward direction of the shoots of Fraxinus pendula, are 
(as Dutrochet asserts) to be attributed to the influence of light. 

We are quite deficient of anything like a sufficient explanation of the 
curvature of plants caused by light. It is not even made out whether 
this curvature is a result of an irritability of the cellular tissue, or of the 
alteration of endosmotic condition of the cells through the mcreased eva- 


poration caused by light. 

the circumstance, that th„. „ 

is under water as when in air ; at any rate we have at present no evidence 

that lio-ht causes an excretion of water from the submerged parts of 

plants which it shines on, as in plants which are exposed to air. The 


absence of the green colour, since the light-avoiding tendrils of tne V me 
are coloured quite as green as the stems of most plants, and since the 
roots of certain plants (of A Ilium Cepa and A Ilium sativum, according to 
Durand and Dutrochet) turn towards the light. 

An explanation must, of course, give an account as well ol why par- 
ticular parts avoid light, as of why others curve towards it ; I may, there- 
fore pass over the earlier explanations, which only refer to the latter 
point and many of which are vague in the highest degree, as for ex- 
ample « liorht attracts the plants," &c. ; but the explanation given by 
Dutrochet 5 (" M em. n ii. 60; "Ann. des. Sc. not. 3 Ser," iv. 72) must be 
touched upon. Dutrochet derived the curvature of the stem and root 
from the supposition, that the cortical cells of the illuminated side lose a 

» ,i • :,, „^ n />m 10 n,>o r>f Hip Trnnwii pfifict, of lip-nt. to in- 


the evaporation from plants, and the cells therefore contract. 

i ii +i^ c+^i-i^+.nvA r>f +hfi cortical laver whether, in c< 

[ It 

crease muxd ovojju"*^" jt ' . , 

depends then on the structure of the cortical layer whether, m conse- 
quence of such contraction it curves so as to become concave or convex on 
the outer surface ; in the former case, the illuminated organ will curve 
towards the source of light ; in the latter case, in the contrary direction. 
Now, Dutrochet asserts it is a general rule that the larger cells lie exter- 
nallv in rind of all those stems which curve towards tne light, on which 
account when a strip of such rind is laid in water it curves inwards ; a 
rind possessing such a structure; in consequence of this, curves outward 
and draws the stem with it, when it loses part of its sap through the in- 
fluence of light. On the other hand, all stems and roots avoiding light 
possess a rind of opposite structure. In criticising this theory we will 







I I 




leave out of the question the doubt above referred to^ the complete un- 
certainty whether light can cause greater amount of discharge of aqueous 
juices from the cells of the illuminated side of the rind of plants lying 
under water ; but we must therefore the more distinctly advance that the 
statements of the anatomical facts given by Dutrochet are altogether 
erroneous, he himself having contradicted these statements by anatomical 


With . _ 

of the stem of plants striving towards light, the statement that these 
curve inwards in water is most decidedly incorrect, of which I have con- 
vinced myself in a great number of plants, and in particular in the Phy- 
tolacca clecandra, especially cited as an example by Dutrochet, for the 
rind of all the plants which I investigated in reference to this question 
curved outwards in water. It is equally untrue that the rind of roots 
curves outwards, for in most roots just the opposite occurs. But when 
Dutrochet, in explaining the avoidance of light by roots, ascribed the said 
structure to their rind, he forgot that he had stated directly the reverse 
of this structure of the rind, in explaining the direction of the root down- 
ward. In this way he mixed the anatomical facts together, like a con- 
juror does his cards, just as they were requisite at the moment to explain 

any movement. 


the explanation of the movement of the stem, according to which the 
fibrous parts of the stem, i.e., the young wood, were caused to curve out- 
ward by absorption of oxygen. He states that as light sets free oxygen 
in the green cells of the rind, a portion of this is conveyed to the young 
wood, the latter then, by curving, assists the curvature commenced by 

the rind. 


of the wood through the absorption of oxygen rests upon very uncertain 
experiments, two circumstances are opposed to it ; in the first place, the 
curvature of plants is almost exclusively produced by blue light, while this 
is completely incapable of causing evolution of oxygen from green parts ; 
in the second place, according to Payer's experiments ("Comptes rendus" 
1842, 26th December), the curvature takes place also in nitrogen and hy- 
drogen. Since the pretended curvature of the young wood would be in the 
way of the movement from the light in the tendrils of Vitis, in the shoots 
of the Weeping Ash, &c, they are eliminated by the statement that in these 
plants the young woody layer is so thin and weak that its effects are im- 
perceptible. It is clear the author knew how to get out of a difficulty. 

While the stem and the root only exhibit movement when they 
seek to regain the natural position out of which they have been 
removed, it is different in the leaves, for these have not only the 
power, in a high degree, of returning to their natural position, 
when artificially disarranged, but (with the exception of the stout 
leathery or fleshy leaves) almost all thin leaves, and particularly 
compound leaves, present different arrangements by day and by 
night, a phenomenon to which the terms sleeping and waking 
have been applied. As in the stem the normal position is the 
perpendicular, with the point of the stem turned upwards, so in 
the leaf is the horizontal, in which its upper, darker^-coloured sur- 
face is turned towards the sky ; into this position it is brought 
back by the influence of gravity, when it is disarranged, and it is 




diverted from it by the influence of light falling obliquely on it 
or artificially thrown upon it from below, the leaf constantly 
striving to turn its uj>per face to the light. 

The movements which the leaves make under these circum- 
stances frequently take place so quickly, that the leaves of many 
plants follow the daily course of the sun ; at the same time they are 


roan Not only is the leaf in general far more capable of curva- 
ture ' of its flat and extended substance, in consequence of the 





number of leaves, there lie, both at the base of the petiole and 
in compound leaves, also at the base of each leaflet, little enlarge- 
ments (articulations) composed of soft, succulent parenchyma 

menus i ujl t±uux<xu±v/xxoy wux^ VM v- — - 7 ^ *. ~„a 

which, on account of the abundance of their cellular tissue and 


through the middle of the articulation can oppose but slight re- 
sistance to the curvature, are capable of a far stronger degree of 
curvature than the other stem-like parts of the plant. _ 

That the various positions to which the terms waking and 
sleeping are applied, are produced by the alternating influence 
and absence of light, and that the diminishing temperature and 


any essential part in this, is shewn especially by the experiments 
of De Candolle, who succeeded in reversing the periods of the sleep- 



In very sensitive plants, also, 

Keeping unem ±ijl ujllo ucwiv ksj ^.^j . j-ax v ^ j r 

artificial withdrawal of the light, even for a short time, as the 
dim light which exists during a great eclipse of the sun, suffices 
to make the leaves go to sleep ; while, on the other hand many 
plants, especially the different species of Oxahs, require bright 
sunshine to make them expand their leaves fully. # 

The movements made by leaves in going to sleep differ in the 
hio-hest degree in different plants : sometimes they consist of a 
sinking, sometimes of an elevation, of the leaf, in compound leaves 
at once of sinking, elevation or twisting sometimes of folding to- 

gether of the leaflets ; in 

general the leaves present a smaller 

Expansion during sleep than by day not, however so that we can 
say with E. Meyer, they always seek to return to that position 
which they possessed in the bud; since not unfreqnently, for ex- 
ample in Oxalis, the position of the sleeping leaf dihers essentially 
from its position in the bud. Neither must the term sleep lead 
to the assumption that the movements by which leaves pass into 
their nocturnal position depend upon a relaxation since, on the 
contrary, the parts from which the motion issues, that is the joints, 
are in a state, of considerable tension during the sleep of leaves. 

The flowers of a large quantity of plants exhibit changes of 
position by night analogous to those of leaves, the corollas told- 







I { 




up ; in the Composite the capitules shutting up, &c. Here 

also the times of sleeping and waking have been reversed by- 
artificial illumination (Meyen, u Physiologie" iii, 495). 

Undoubted as it is that the movements of sleeping and waking, 
both in leaves and in flowers, are dependant upon the influence 
of light, yet they do not always occur in such a way that the 
waking takes place in the morning when the daylight has reached 
a certain definite degree, and the sleep begins in the evening 
when the twilight has brought the light down to the same de- 
gree, but the waking frequently precedes the dawn of day by 
several hours (e. g., in the leaves of Mimosa pudica), while the 
sleep commences when there is still tolerably strong light. This 
condition presents itself in a still more striking degree in many 
flowers, than in leaves. As a general rule, the openness of the 
flowers is indeed regulated by the light, so that the majority open 
in the morning from six to seven, and close in the evening at 
from six to seven, but in many flowers the opening takes place at 
the very commencement of dawn, while they go to sleep even 
before noon, or at least early in the afternoon ; on the other hand, 
some plants require a longer illumination by the sun to cause 
their opening, so that the flowers of various plants open gradu- 
ally at the different hours of the morning until noon, on which 
peculiarities Linnaeus founded his "flower-clock." These varia- 
tions may be partly independent of light, and may be caused by 
the circumstance that every species of plant requires a certain 
degree of temperature to open its flowers. (See Fritzsche, " Sitz. 
berickt der Acad, zu Wien" Jan. 10, 1850.) In the flowers of 
many plants we meet with the remarkable deviation that they 
open first in the evening, reach their full expansion at midnight, 
and close again in the morning, a phenomenon which, so far as we 
know, has no parallel in the leaves ; perhaps this phenomenon is 
analogous to the circumstance that the tendrils of Vitis turn 
away from the light. 

Observ. Since the far simpler movements which the influence of light 
produces in stems and roots have not yet been adequately explained, we 
can much less expect that the experiments to elucidate the movements of 
leaves should have been more happy. The full development of the cel- 
lular tissue in the articulations of the leaves renders it much easier to 
demonstrate in them, than in the axial organs of plants, that the motions 
of plants are caused by curvature of the parenchymatous tissue, and not 
by contraction of the spiral vessels or elongated cells (as was assumed by 
Malpighi and all physiologists up to "Link's time, evidently misled by an 
erroneous idea of analogy between the movements of plants and those of 
animals depending upon contraction of the muscular fibres). To demon- 
strate this is merely required the easily performed experiment of cutting 
away the cellular tissue, without injuring the vascular bundle, in the 
articulation of any leaf possessing a distinct thickening there ; this opera- 
tion lames the leaf. Our whole knowledge is essentially confined to this 





t <- TiW mnt >h as has been written concerning the sleep of plants, 
%Lj%£££«Z£ <* of the manner in whieh Hght ^aets upon 
tWelhdar tissue whether, as Treviranus assumes (" Phymlofie. 11. 73"), 
£ « rf & latter 'is excited by light in -n^uene^efan ™- 

«f ^SXn^i^ntrthr^Lfrof light 

S4 aho^Sreased ILnt of sap, and a ™^ — tS t 
the eellular tissue, or, on the contrary, ace ordmg t Daaens *Jg£f - 

ofleal sonfe If which sink down while others rise up m sleep, have 
it /Jt hee°n traced bach by anatomical rese^ch to an, "^ e ^ 
of organ^ *- It is true Dutrochet {-Memoes, i 469 to ok umch 
pains in endeavouring to make out the cause of mot ^^f^ t ^X 
cal investigation of stems and leaves, whereby he arrived at results similar 
To thole in his above-mentioned investigation of the axial organs, since he 
hougM L found besides the curable cellular f^fj^*^ 
young fibrous tissue produced by absorption of oxygen , but ^^ 
exnosition of his views appears to me to be superfluous. The complaint 
ribermade, in other^uart-s, of the work of ^^J^^ 
incomprehensible. I would not complain of tms so much, as ™*»™ e 
Xg^rconclusions of the author, and the arbitrary sty e m ^ he 
introduces unfounded statements of facts (with winch . Imve steady 
, found fault above), have increased in proportion ™*,^^$^J 
the phenomena which were to be explained. A wide but difmaut neia 
still lies open here to the experimental physiologist. 



ternai material muucuwa, ^"T 1 , x 1tt ii^,^ ti 1P 

are met with in a number of plants, ensuing only through the 
Son of stimuli accidentally effecting them, whence a sens^ve- 
ness or irritability has been ascribed, to these plants. 



a noTvIry large" ^ • oiplnts of the families of Legumfoos, Oxa 
X andWerace*. Among the Leguminos f , it JlWj^ 
of the genus Mimosa, of which M. pudica, above all, las been the sub 
t ct of Site invest gation ; besides these, there are the various species 
jectj>t # mmuTO mvcb «*^ ^ ^ ^^^ Smithia and Desmanthus ; 

muscipula have a most 

o\(^ of Drosera onlv exhibit traces of it. «,'"•"• 14. 

In mfifofon, a^dull irritability exists in the stems of twining plants, 

^ThT^me property is exhibited also by the stamens of species of Ber- 
hJL and Mahonia'hj Sparmannia africana, of many species of Cactus 
clLsoi many plants of the section GynarocephaU ; moreover by the 








Martynia and Mimulus, the style of Goldfi 


and the column of the style of Slylidium. 


Among the plants possessing irritable organs, Mimosa \ 
especially has been the subject of repeated investigations, 
common petiole of this plant is connected with the stem by a 
much enlarged articulation, and similar articulations are met with 
at the bases of the secondary petioles and of the individual leaflets. 
When strongly irritated, as for example by shaking, the entire 
leaf sinks by a bending of the articulation situated at the base of 
the inner petiole, the secondary petioles approach together, and 
the leaflets, curving forwards and upwards, apply themselves to- 
gether, like tiles on a roof, upon the secondary petioles, so that 
the whole leaf assumes the position of a sleeping leaf, which gave 
rise to the idea formerly entertained generally", that this motion 
is the same as that which occurs when the leaf goes to sleep, an 
opinion incorrect in many respects. 

The motion of the articulation of the petiole may be produced 
by direct irritation of it. but the stimulus must act upon the 
under side of the joint, that becoming concave in the motion ; 
even a slight touch upon the joint in this part will cause a sink- 
ing of the leaf, while strong stimulus, even wounding, of the 
upper side of the joint has no effect. But at the same time sti- 
mulus affecting other parts of the plant is propagated to the joint 
and causes it to move, provided the irritation be strong enough. 

The articulation is composed of an accumulation of parenchy- 
matous cells containing chlorophyll, each also 
interior a larger or smaller globular mass of a substance strongly 
refracting light (oil ?). The latter substance, however, does not 
appear to be essential since it is absent from the cells of other 
irritable organs. Through the middle of the joint run the vas- 
cular bundles entering the petiole, united into a comparatively 
slender cord. There is nothing at all peculiar in these anatomical 
conditions, they perfectly resemble what w T e find in many other 
plants, not irritable. The only circumstance to be regarded as 
essential is, that the parenchymatous tissue existing in compara- 
tively large quantity, exhibits a considerable distention, so that it 
strives to occupy a larger space than is allowed by the mechanical 
conditions in which it is placed. If we cut a plate longitudinally 
out of the middle of the joint, which of course will consist of the 
woody bundle in the middle, and of a layer of parenchymatous 
cellular tissue at each side, and then cut this plate lengthways 
into thin strips, the middle of which is composed of the vascular 
bundle, and the two sides of cellular tissue, the latter pieces 
immediately expand about l-5th longitudinally, whence it is evi- 
dent that the vascular bundle is too short in proportion to the 
tumescent mass of cellular tissue of the articulation, and that the 

exhibiting in its 

latter is compressed in the direction of the longitudinal axis in 
the uninjured joint. 






According to the description of Dutrochet ("Keek sur la 

struct, intime des anim. et veget. 



of the Swer ^xd under side of the articulation has a tendency to curve 
£^&gly. I do not find this confirmed. Of course if a strip of 
Cascutar bundle is left connected with the ^F^J^^ 
parenchyma above-mentioned, only the outer side of the ceUular tissue 
can expand while expansion is prevented on the inside by the rigid 
v^cuS bundle ; unde'r these circumstances a curvature of the whole 
plate must naturally take place. 

In uninsured articulations, the expansion of the cellular tissue 
of the upper side maintains equilibrium with the cellular tissue 

?ornnn, the under side, whioh>venta ^jf™ °f ** wh °t 
BuUf the cellular tissue is cut away down to the central vascular 
bundle on the upper side of the articulation of a leaf still attached 
lTl t th i cellular tissue of the under side havmg now lost 
^t4onttc e an1^ue its expansion, and the £**£*££ 
at once pressed upwards at a sharp angle ; the reverse occurs 

when the cellular tissue of the under side b removed. 

the discovery he established was made a second time by Dutrocnet { w 
Za sfcractf. intime" &c. 1824). 

A ccording; to the common statement, which rests upon the 
extrimente of Dutrochet, a leaf robbed in the above described 
3 oTone side of its thickened joint, loses its power of motion 
Tntirely and after the removal of the lower portion of the cel- 
££££■» of its articulation ,can ^^ « o m or , an d can sink 



•7 ^^~^"~ * 7 

forms the movements 


removed) ; and moreover 

be 'mentioned She" on, IZ not altogether lost ikinUfc 
De menuuiieu JL^™™^^ rvf *. Wf upwards and do^ 


wards" deptndTt upon one-side expansion of the cellular tissue 
rf the articulation, may take place in a variety of ways In the 

first nkcTif the cellular tissue of the upper side- swells up and 

requires a P-^rance over that .« ^ under ^cur- 
^dSolte^uet^h^ on tiie other hand 

tunZof Sowing its natural tendency to expand. It is possible 

X. that both these conditions may exist at the same time. 

From the erroneously assumed immobility of a leaf, in which 






I l j 



the cellular tissue has been cut away from one side of the articu- 
lation, Dutrochet ("Nouv. rech. sur V endosmose" 47), drew the 
conclusion, that the movement of the leaf always occurred through 
the cellular tissue of that side of the articulation which becomes 
convex in the curvature, expanding actively, while the tissue of 
the side which becomes concave remained perfectly passive. As 
already observed, the fact upon which this conclusion rested, is 
not perfectly correct. A leaf which has had the upper side of its 
articulation cut away, of course immediately rises up nearly per- 
pendicular, but it does not remain in this position ; in a few days 


sleep-movements (sinking and rising). It is, therefore, clear that 
the expansion of the under side of the articulation, produced by 
removal of its antagonist, as a general rule, raises the leaf higher 
than in the natural condition, yet at the same time that this ex- 
pansion is not constant, but undergoes a daily increase and de- 
crease. The same circumstance (only in less degree) presents itself 
after the under side of the joint is removed. We must conclude 
from this that the expansion of one side of the articulation plays 
the principal part in the elevation and depression of the leaf, but 
that in this motion the opposite side likewise undergoes a change, 
and, indeed, a relaxation. 

If the said view of Dutrochet was not wholly correct in regard 
to the sleep-movements, still less was it in reference to the irritable 
movements. It is clear that if the depression of a leaf resulting 
from irritation is caused by the active expansion of the upper 
side, overcoming the resistance of the under side, the tension must 
increase in the whole articulation, and the latter must become 

rigid. Now 


440) shewed that the articulation of 

an irritated leaf becomes in no slight degree relaxed when this is 
depressed ; we must, therefore, assume that the motion arising 
from irritation depends not upon an increased expansion of the 
upper side of the joint, but principally upon a relaxation of its 
under side. This is also borne out by the circumstance, that a 
leaf of which the upper side of the articulation has been cut away, 
sinks (although not to the same extent as an uninjured leaf) when 

irritated, which would be impossible if the movement had its 
source solely on the upper side. 

This relaxation, as Brucke also shewed, either does not occur at 
ail in a sleeping leaf, or at least in a far weaker degree than in an 



irritated leaf. Hence 

grounds (" Ueb. die Reizbarkeit der Blatter von Robinia. 
"Verm. Schrift"), that the movement of irritability is n^*, ^^ox- 
cal with the sleep movement. Evidence of this is also offered by 
the circumstance, that a sleeping Mimosa leaf is at least quite as 
sensitive to irritation as a waking one, and performs the move- 
ments of irritability very rapidly and to quite as great an extent. 
Concerning the internal occurrences, on which the relaxation 



of the lower half of the articulation, resulting from irritation, 
^tds-whether, as Bracks assumes, but as appears c .highly 
improbable a portion of the cell-sap issues out into the mteicei 
ff^or a relaxation of the cell-walls takes P lace-we 

know simply nothing. 



tTJ^T^o^^S *£ moment downwards does not 
delnTupon the expansion of the cellular tissue of the upper side of the 
aXulation but upon curvature of the younger layers of wood which 
^conC^nce of the irritation, absorb oxygen from their vicinity ma 
wnot farther explicable, and are thereby caused to curve downwards. 
waynotiuini i , om ^u v 1IT1 known cause, this oxidation 

„7 t he \ or ul S^s^ne po^ of curving hanging tethec* Uu, 
lar tissue a^m acts, and causes the elevation of the leaf Leavmg the 

!S££ character of the whole «**&~*ZZ^JX& 


^ faSSKSS ^sXnof the leaf is connected with relaxatio 
Zi the articulation, for if the articulation were bent by the curvature of 
le woody bundle the cellular tissue of the under side would be strongly 
impressed, which must rather increase than dimmish the tension of the 

me leaf of Mimosa is sensitive to stimuli of every kind ; 

*S* wounding, . ourning, contact of ^^2^ 

j oint. 



££££&££ 'the sensitiveness towards it tol f aWy f on 



to be. 

It has already been observed that the direct irritation of the 
articulation of the leaf is not necessarily required to produce the 
movement of irritability, but that the effect of a stimulus acting 
on a distent part is conducted tot* >•****%, ™*» [*± «£ 



In reference to 

this induction of the stimulus, the researches of Dutrochet and 
Meven led to the conclusion that it was conveyed by the vascular 
bundles and not by the parenchymatous cellular tissue ; for on 
the one side the conduction of the stimulus was interrupted by 
cutti™ away the vascular bundles, and on the other side wounds 
on thfrind when the incision did not penetrate the wood were 
on tiieimu^wiie ^ ^^ n f +t, p w V p S - This conduction is 


nonmarativelv slow ; according to Dutrochet's measurements, it 
amounted tc , 8-lT millimeters in a second in the petiole, to only 

-6 millimeters in uue snwu. 

Investigation of the other irritable plants, the leaves of Dionwa, 
OxaUs and liobinia, the stamens of Berbens, Cactus, &c., iur- 







f ' 



nished no result which admits of any essential addition to what 

The moving organ was always found 



however, did not differ from ordinary cellular tissue in its visible 
properties, and the contents of which, in like manner, presented 
nothing characteristic, since they consisted of the usual substances, 
starch, chlorophyll, &c, so that the conjecture is, indeed, not over 
bold, that irritability may be a property belonging to cellular 
tissue generally, which, however, can only display itself outwardly, 
when developed in a higher degree, and where especially favour- 
able conditions exist in the structure of an organ. The ci 


marked in Mimosa 

effects of long-continued irritation. 

the sensitive organ, which becomes concave in the movement, is 
alone capable of receiving the stimulus, while the opposite side is 
perfectly insensible, appears to be universal; at all events this 
condition exists in like manner in the leaves of Dioncea, the 
stamens of Berberis, and in tendrils. 

In the majority of cases, the movement of an irritable plant is 
very transitory, when the plant is not organically injured by the 
stimulus applied. Few experiments have been made on the 

An experiment of Desfon- 
taines affords evidence that a plant may become accustomed to 
a weak stimulus ; that author carried a Mimosa with him in a 
coach, and in a short time the plant became accustomed to the 
jolting motion, and its leaves, which at first had closed up, re- 
opened. It is otherwise with tendrils and twining plants, which, 
when they come in contact with a foreign body, curl over the 
point of contact, and in this way partially embrace the support. 
A return to the former position is impossible, since through this 
curvature a portion of the tendril or twining stem lying above 
the point first irritated is brought in contact with the support, 
and in like manner stimulated to the curving movement ; in this 
way the movement of curvature advances up the plant until the 
whole length has become wound round the support. 

Observ. The view propounded by me (" Ueber den Ban und das Winden 
der Banken und Schlingjiflanzen") that the curling round the support 
results from an irritability excited by contact, has not had to boast of 
any particular approval, yet 1 do not find that anything better has been 

746) says that this 

put in its place. When 

phenomenon is caused by a slowly and inertly acting elasticity, which is 
chiefly called into activity by contact with foreign bodies, I must confess 
that the meaning of these words is quite incomprehensible to me ; and 
when Schleiden ("Grundzuge" 2. ed. xi. 543) states it is a phenomenon of 
growth, which determines the direction, that is, the peculiar form of the 
tendril, and the growth of the twining plant, he appears simply to be 
ignorant of the fact which comes under consideration, since every accu- 
rate examination of tendrils and twining plants shews that the curlin 
round the support is a phenomenon totally independent of the growth. 






The external action of ponderable or imponderable agents is 
necessary to the production of all the movements Utato mo- 
tioned • but besides these, there occur in isolated cases motions 
Xch, so far as existing experience reaches, are wholly mdepend- 
ent of external influences. . . , , 

Itis M4-» epical phenomenon that a Wuong jtat 

reaches this in order to grow up it ; tne cause uyo » — 6 - 
sometTmes in a mysterious* power in these plants of seeking out 
thT supports, sometime, in' their asserted property of turning 

from liffht, &c, but the matter 

"owed. * Th^ounge;* internode, of twining stems are quite 

strand their vlscnllr hnndles rnn, like those f other fm. 


attained a certain age it begins to curl (according i ^> thes^ 
of plant, to the right or left) around its own axis m co ^ ue ^ e 
of which the vascular bundles acquire a spiral course. This curl- 
ing occurs only in a short length of the stem m each single period 
Sut ^ advances gradually from below upwards proceed- 
W from one part of the Item to another, without ever becoming 
refurrent The upper part of these stems, always slender and 
pliable hangs over in a curve ; and since it must follow the curl- 
C of the lower part, it is continually carried round m a circle 
Hke the hand of a P clock ; then if a solid body stands within the ■ 
circle described by the point of the stem, the latter becomes pressed j I 
upon the solid body, the irritability peculiar to it becomes excited ^ 
and thus the twining round the support is P^^L^^ 
more minute details of this process, see my essay above refeired 
to ^ We do not at present possess an explanation ot these move- 
ments and of the circumstance that they occur constantly, either 
to the right or to the left, in each species of plant ; but it cannot 


also has its origin in the 

parenchymatous cellular tissue, since the perfectly visible distinc- 
tion between the stems of twining plants and those of other vege- 
tables, depends on the relative abundance of succulent cellular 
tissue in the former, and since in many p ants, e^g mCynanche 



to twine, the 


locality in which it grows. 

uoserv The circular movement of the stem just described has nothing 
to do with the twining round the support ; in fact, that part of the stem 


to do wron wie twining i^ux^ — — ~ rr — , „ , . * i ± 

which has undergone the torsion is incapable of twining round a support, 
and the movement of curvature, which causes the twining, occurs only m 
the younger part of the stem, the fibres of which stall retam their straight 
course. This may he caused not only by the younger parts of the stem 
being the softer, more juicy, and, in consequence of this more moveable 
but also and principally, by the circumstance that m old curled parts of 







' I 



the stem the cellular tissue of the rind has already attained a considerable 
longitudinal extension, compared with the parts situated nearer the axis. 
Whether the movements which Dutrochet observed (" Ann. d. Sc. not. 
2 Ser." xx. 306) in the stems of Pimm sativum, are identical with the 
above-described circular movements of twining plants, with which, as I 
shewed in the " Botcmische Zeitung," 1845, 118, Dutrochet was but very 
imperfectly acquainted ; or whether, as appears to follow from his descrip- 
tion, they depend upon a rotation of the stem unconnected with torsion, 
I cannot decide, since I have not yet repeated these observations. 

Motion is also produced without external influence in tendrils, 
which, in like manner, is capable, although in less degree than 
the circular motion of twining plants, of bringing them in contact 

For, when a tendril has attained its full 

with foreign bodies. 

length, up to which time it is straight, it curls up together spirally 
from its point to its base, in such a way that its upper side form 
the outer side of the spiral. ™ T1 — - Ll - '- *--- "* "■ * n " ■ • 


tact with a foreign body by this movement, its irrSability'is 
excited at the point of contact, and the above-described convolu- 
tion round the support commences, which progresses from below 
upwards along the tendril. 

These movements of tendrils and twining plants have not at- 
tracted the attention of naturalists in so high a degree as the move- 
ments of the leaves of Hedysarum gyrans. This plant possesses 
ternate leaves ; the middle leaflet exhibits the ordinary sleep- 
movements, sinking by night and rising by day, but the very 
small side-leaflets present, day and night, a jerking motion, by 
which they are alternately raised and depressed. Similar move- 

Mirbel. also of H. 


H. cuspidatum 

yf N. Amei 



H. Iceviqatum. Fe 

plants have been so much observed on account of a physio- 
logical peculiarity, as Hedysarum gyrans, but unfortunately all 
attempts to give a tenable explanation of its movements have 
been fruitless. 

A similar motion, occurring without external cause, was dis- 
covered by Lindley in the labellum of an Orchideous plant, Mega- 
clinium falcatum, and more minutely observed by Morren ("Ann. 
des 8c. nat 2 Ser. xix. 91). This movement consists of a slow 
depression and elevation of the labellum, repeated in periods of a 
few minutes. From Morren s anatomical investigation, it appears 
that this motion must be caused by an alternating expansion 
first of the upper, and then of the under, part of the cellular tissue' 
which forms the claw of the labellum ; but the cause of these ex- 
pansions remains just as obscure as that of the movements of the 
leaves of Hedysarum gyrans. 





MANUAL OF BRITISH BOTANY : containing the Flowering 
M pfanttand Ferns, arranged according to -the Natural q Orders 

By Charles C. Babington, M.A., F.L.S., &c. 12mo., inirci 

Edition, 10s. Qcl. 
THF PTTDIMENTS OF BOTANY. A familiar Introduction to 
™he ttudy of Plants. By Arthur Henerey, FL.S Lecturer 

on Botany at St. George's Hospital. 16mo., with ulustrative 

Woodcuts, 3s. 6d. 

Also by Mr. Henfrey — 

THE VEGETATION OF EUROPE: its Conditions and 
Causes. Foolscap 8vo., price 5s. „ T « Trt « T «»T 

BOTANY. With 18 Plates, Foolscap 8vo., 10s. Oct. 

THE ELEMENTS OF BOTANY. By M. Adrien be Jussieu 
Translated by J. H. Wilson, F.L.S., F-R-B-S., &c Small 
8vo., with 750 Woodcut figures, price, 12s. bd. 
W Generic and Specific Descriptions of all the known British 
splcieTof SeaWeeds, with Plates to illustrate all the Genera. 
By W. H Harvey, M.D., M.R.I.A., Keeper of the Herbarium 
of the University of Dublin, and Professor of Botany to the 
Royal Dublin Society. 8vo., 21s. ; coloured copies, 31s. 6d. 

Also by Professor Harvey 

NEREIS BOREALI-AMERICANA ; or Contributions to- 
wards a History of the Marine Alg* of the Atlantic and 
PacificUoasts of North America. Royal 4to., with coloured 
plates. Part I. 15s. 
WALKS AFTER WILD FLOWERS ; or, the Botany of the 
Bohereens. By Richard Dowden (Richard). Fcap. 8vo., 

4s. 6d. 
t?t OT! A C A LPENSIS. Contributions to the Botany and Topo- 
FL Z£y of GiStar and its Neighbourhood By E E Kelaart, 

M D , F.L.S., Army Medical Staff. 8vo., cloth 10s. 6d. 

^AS?I ByN B Ward, F.R.S., F.L.S. A Second Edition, 

Post 8vo., Illustrated, 5$. 











This Series of Works is Illustrated by many Hundred Engravings ; 
every Species has been Drawn and Engraved under the immediate 
inspection of the Authors; the best Artists have been employed, 
and no care or expense has been spared. 

A few copies have been printed on larger paper, royal %vo. 

THE QUADRUPEDS, by Professor Bell. A new Edition 

* preparing. 
THE BIRDS, by Mr. Yarrell. Second Edit., 3 vols. U. 14s. 6d. 

by Mr. Hewitson. A New Edition preparing. 

THE REPTILES, by Professor Bell. Second Edition, 12s. 

THE FISHES, by Mr. Yarrell. Second Edition, 2 vols. 3£.* 

THE CRUSTACEA, by Professor Bell. Now in Course of 
Publication, in Parts at 2s. 6d. 

THE STAR-FISHES, by Professor Edward Forbes. 15s. 

THE ZOOPHYTES, by Dr. Johnston. Second Edition, 2 vols. 
21. 2s. 

Professor Ed. Forbes and Mr. Hanley. Now in Course of 

Publication, in Parts at 2s. Qd. ; or Large Paper, with the Plates 
Coloured, 5s. 

THE FOREST TREES, by Mr. Selby. 28s. 

THE FERNS, by Mr. Newman. Third Edition. 

Now in the 

11. Us. 6d. 

■ ■ » in r ■ -^^^m^^^^m mil_i ___ LIU ' ' 

Professor T. Rymer Jones. 8vo. A new Edition preparing. 

* u This book ought to be largely circulated, not only on account of its 
scientific merits— though these, as we have in part shewn, are great and 
signal— but because it is popularly written throughout, and therefore likely 
to excite general attention to a subject which ought to be held as one of 
primary importance. Every one is interested about fishes— the political 
economist, the epicure, the merchant, the man of science, the angler, the 
poor, the rich. We hail the appearance of this book as the dawn of a new 
era in the Natural History of England."— Quarterly Review, No. 116.