Corda on the Impregnation of Plants. 321 
We left the pollen-tubes when they had reached the endostome 
of the secundine. In order to ascertain how far the pollen-tubes 
penetrate, I made a longitudinal section of an ovule, while yet en- 
closed in the scale, in such a manner (Tab. 43, fig. 14,) that a great 
part of the secundine was removed, while the nucule (f) and the 
embryostome (f’) were left entire ; by this means the course of each 
pollen-tube (a’) was manifest from the endostome (e*) to the very 
bottom of the nucule (a?. 
I saw the pollen-tubes pass through the orifice of the secundine 
to the mouth (the embryostome) of the nucule (f’); pass through 
the latter into the cavity of the nucule, where they become some- 
what attenuated, or suddenly enlarge, (Tab. 43, fig. 14, a’,) and 
empty their contents as a turbid, originally amorphous, fluid mass. 
After this deposition, the pollen-tube still remains in the endos- 
tome, the embryostome, and the cavity of the nucule, appearing as 
a slender, empty, and transparent bag. The deposited matter is 
soon perceived to become organized, and the sac of the embryo 
(Tab. 43, fig. 15, E) is formed, which increasing rapidly in size, 
often appears flaccid, or thrown into folds on one side or the other ; 
and its contents are still turbid. It is still fixed to the pollen-tube, as 
we have represented in Tab. 43, fig. 15—18, Ea’. 
During the growth of the sac of the embryo a peculiar change 
takes place in the minute polyhedral bodies which occupy the cells 
of the tissue of the nucule ; these particles become fluid or disap- 
pear as it were by absorption, until the cells again appear perfectly 
clear and pellucid, (Tab. 43, fig. 18.) 
At this period there may be found, especially in Pinus Abies, 
more than one embryo-sac in each ovule; there are ordinarily two 
or three placed side by side,* (Tab. 42, fig. 7,10, 11.) These 
embryo-saes are found, on examination, to consist of an integument 
(Tab. 42, fig. 11, p) loosely enclosing a kernel (q.) The kernel 
has a gelatinous consistence, and is composed of large, oblong cells 
(Tab. 42, fig. 12,) mixed with fine knotty threads, to which minute 
drops of a fluid adhere, (Tab. 42, fig. 13, mn.) The connexion of 
the pollen-tubes with the embryo-sac continues for some time after 
* The fact of the general existence of a plurality of free in the impregna- 
ted ovule of Coniferee and Cycadee was announced by Dr. Brown to the British 
Association at their aaa, in Edinburgh in 1834, a few i previous to the 
date of this paper, which was read Sept. 1834. This announcement was, of course, 
unknown to M. Corda at that time.— Trans. 
Al 
Vou, XXXL~No: 2 
