Pilices. 
—\v— 
328 
A lateral bud is evolved from the bark, whose centre is 
uced from the radiated cellular matter of the trunk, 
surrounded with spiral sap-vessels ; and a cone of wood 
is in like manner formed around it, whose base, during 
the first season, is gradually encircled by a layer of the 
contemporaneous maternal wood. 
During the second year, therefore, the base of the 
young shoot can receive no addition to its dia- 
meter, except where it is unencumbered by the wood of 
the trunk: so that at its origin, a branch resembles the 
summit of an inverted cone, enveloped by the circles of 
maternal wood. 
Opinions of As to the order of the developement of the various 
Malpighi 
amd Grew. 
Experi- 
ment of 
Duhamel. 
Palisot de 
Beauvois* 
experiment 
inconclu- 
sive. 
parts of the stem, Malpighi supposed, that the internal 
cireles of bark were subsequently condensed into wood ; 
while Grew concluded, that the young wood was elabo- 
rated by the bark. 
But the well-devised experiment of Duhamel demon- 
strated, that the bark itself, as well as the young wood, 
derive their origin from the gelatinous part of the sap, 
(the eambium,) exuding from the central and radiated 
cellular substance. in which new sap-vessels are devel 
annually during the season. Theexperiment of Duhamel 
alluded to, consisted in removing completely the bark 
of a cherry-tree, from the trunk of which he afterwards 
observed the sap oozing, and forming a new bark, un- 
der which new circles of wood were afterwards formed. 
- We are aware, that the accuracy of this riment 
has been lately called in question by Palisot de Beau- 
vois, in a memoir read before the Institute of France, 
who observes, that when a portion of the bark of 
a tree is removed, and the from which it is ta- 
ken is well rubbed, so as to leave no remains either of 
bark or cambium, neither the young nor old wood pro- 
duce any thing, but that the edges of the divided bark 
extending over the bare wood then produce new wood, 
which unguestionably is derived from the former bark. | 
But it does not seem that this experiment of M. de 
Beauvois mvalidates the truth of M. Duhamel’s conclu- 
sion ; on the contrary, it is perfectly reconcilable with 
it. The efforts of nature are by no means limited to 
one mode of effecting her purpose. _ In fact, in both ex- 
periments the bark was formed from the cambium, from 
which the bark first, and subsequently the new wood, 
derive their origin ; but in De Beauvois’s experiment, 
the cambium oozed from the trunk covered with the re- 
maining bark ; whereas in Duhamel’s, it necessarily ex- 
uded from the bare trunk. 
It ought. to be mentioned to the credit of Malpighi, 
that Duhamel’s experiment partly confirmed the sagacit 
of his opinion, “ Conquituritaque in horizontalibus utri- 
culis et medulla ipsa succus, ut futuris et proxime erup- 
turis gemmis, et tenellis foliis Presto sit.”* For it is evi- 
dent that the increased diameter and elongation of these 
plants depend on the same cause, viz. the annual expan- 
sive motion of the sap in the lymphatic vessels and cel- 
lular substance of the stem, and the subsequent formation 
and condensation of both into bark and wood, assimila- 
= probably b Ay _ —— of the r ive 
plants, p e leaves, and distributed ‘h 
the doaenting vessels, , rt 
From this general view of the manner of growth and 
organization of the stems of dicotyledonous trees, we 
shall perceive how remarkably they differ in both from 
The second period of the growth of these plants ma 
be said to commence, when the conieal lobes, having 
* Anatom. Plant. passim, et de Caudicis Augmento, p. 20. 
FILICES. 
this early 
on a of a triangular 
with the sti a tri 
sesbuttitg ‘tht letter r, and, with the mi ves- 
sels may be seen elegantly ramified, diverging trom the 
central stipes in every direct ion ; whereas, in the se- prarr 
minal lobes, which are cellular and of a darker~ CCLIV. 
hue, no ramified vessels can be distinguished, The Figs. 1, 2, 
tem fibrous radicles of the seminal lobes, as well 3 4 5s 6 
as themselves, now no longer of use, begin to fade, and 
their dark green sap being evidently for the 
nutrition of the young plant, from the tuberous stem of 
which the true root now descends exactly as in dicotyle- 
donous plants. A second frond is soon perceived shoot- 
ing from the axil of the first, and opposite to it, but with 
an additional lobe. In the same manner the fronds. 
are thus evolved one after another, with a gradual addi- 
tion to the number of lobes ; the stem, during tat on 
riod, acquiring only a slight addition of diameter, 
out any perceptible increase of length. Another cirs 
cumstance to be remarked in the of these - 
plants, is, = even — the second year, an stems, 
at least of the native European species, frequ ger- 
minating in the crevices of our sandstone cli a 
Gothic ruins, are very far from attaining their utmost 
diameter. It is no doubt probable, that the slow growth 
of these plants must be greatly influenced by their situa- 
tion and soil, as well as by the temperature of our 
northern climate, but ill to foster the om 
reve. 
i thelr 
of plants, which only attain their fall perfection in- 
luxuriant forests of the tropics. Were it, however, : 
missible, under ‘circumstances where observations are 
 vonkt cman tint thane gual irene ng 
it would seem that these plants possess a sit ana- 
logy with palms, in this and other i 
Both Kempfer and Daubenton have remarked, that 
the Phcenix or date-palm, and others of this series, require 
several years before they acquire their utmost diameter ; 
and that previous to this their stems do not b 
to elongate, nor do their fronds acquire their p -form 
and size. Now, inall these circumstances, th ratly 
the gro ‘ 
of ferns 
with that of 
palms. 
Mie arth: i ember beers cigs oaks he 
but having closely examined this supposed root, in the 
Diudtiie Conarionsia is, gee jum aureum, and other 
species asserted to be stemless, we found that they pos- 
are bm mivowin gr eel sem 
bent stems, detaching at in sp roots, 
and diverging branches, and like es attionehddine ec 
lucing fronds from the numerous buds at the 
mity. hether certain ies, however, are altos 
destitute of stems, it is impossible to determine with 
certainty ; but such a circumstan mln Se : 
and it is far more likely that such as arethus figured by = _ 
Plumier and others, are plants in the second period of 
their growth, whose eee had not yet commenced. 
It is certain, however, th p smi 
species possess real, though very short stems, 
. 
