CONTEIBUTIONS TO BOTANY. 
243 
gives of the order, where every other circumstance connected 
with the structure is carefully enumerated. 
Some indications, leading to a knowledge of the origin of the 
external crustaceous envelope of the seed in Rhamnacea may 
probably be drawn from Brongniart’s valuable memoir above 
quoted, in which he records the changes which he observed 
during the periods of the impregnation and growth of the ovule 
in that family. These details were published in 1827, a year or 
two prior to the appearance of Mirbel’s two celebrated memoirs 
on the development of the vegetable ovule, and before the mo- 
dem nomenclature of the parts of the ovule and seed was 
adopted. I will therefore briefly recapitulate such of his obser- 
vations as bear upon the subject under consideration. He 
noticed* that the stigmatic tissue terminated in a small cellular 
protuberance (since denominated the “telae conductrices in 
the inner angle of the cell of the ovary, close to the foramen of 
the anatropous ovule; and he remarked the condition under 
which the latter became fecundated : the ovnile is always sup- 
ported upon a somewhat elongated funicle filled with nourishing 
vessels, and surrounded by loose cellular tissue; this funicle, 
which is very contracted before impregnation, begins to swell 
from the moment that the stigma has received its fertilizing 
influence; it afterwards expands and extends itself over the 
foramen of the ovular tunic. Brongniart, who first traced the 
expansion of the boyaux of the pollen-grains, and their passage 
down the stigmatic channels f, was not then aware of their ulti- 
mate extension through the prominence he observed at the 
termination of those channels ; nor did he notice the continuity 
of one of these boyaux with the minute thread which he had 
remarked in connexion with the embryo-sac, and which he con- 
sidered to be an emanation from its neck : according to the 
notion he then entertained, he concluded that the act of impreg- 
nation was conveyed through the agency of the cellular tissue 
of the umbilical cord J, which the fact he recorded of the swell- 
ing of the funicular support, and its subsequent extension over 
the coats of the ovule, seemed to support. I now call attention 
to this last-mentioned circumstance, because it may serve to 
explain some essential points of structure in the seeds of the 
Rhamnacea, and may enable us to trace the source of the external 
tunic of the seed, which, on account of its crustaceous or cor- 
* Ann. Sc. Nat. x. 340. 
t Ib. xii. 152 & 256 ; read before the Academy Dec. 26, 1826. 
+ Ann. Sc. Nat. x. 343 : “Et c’est par I’intermediaire de ce tissu cellu- 
laire du cordon ombilical que je pense que s’opere I’impregnation de 
I’ovule,” — an opinion which he soon renounced after his subsequent im- 
portant investigations into the growth of the ovule : Ann. Sc. Nat. xii. 
chap. p. 242. 
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