96 ON THE SEXUAL ORGANS OF THE CYCADACESR. 
reproductive organs of Cycads have any foundation, the two kinds of 
organs seem to follow the same course in their development and meta- 
morphosis. Generating-cells originate at determinate points in the 
parenchyma of the leaves; the embryonal vesicles in the nucleus of 
the ovule, as the third generation (“ cellules petites-filles”) from the 
transitory amnios; the male cell, that is the pollen-tube or included 
cell of the intine, as the third generation from the androphyll or its 
loculi. Among Angiosperms the generating-cells are formed by a 
shorter course, as immediate products (“ cellules filles"). 
The generating-cells have, like macrospores and microspores, their 
proper period of life. Produced, as the result of nutrition, by an indi- 
vidual of more elevated organization, although sexless, they each run 
through the phases of a brief existence; finally, they unite to produce 
the proembryo. It is only, indeed, among the Alge, and perhaps 
some other lower plants, that fecundation produces the plant properly 
so-called—that is to say, the embryo; the embryonal vesicle, after fe- 
cundation, developes into a distinct structure, an individual wholly 
composed of cells (united in a linear direction, in one or more ranks). 
This is an axial product, the last cell of which, that of the summit, 
divides and produces the embryo by the repeated formation of new 
cells. The embryo is therefore its terminal bud, destined to produce, 
by its further development, the complex sexless individual, the plant 
properly so-called. The embryo, according to this, is not the germ of 
the plant, but the plant itself, which, after a period of physiological 
rest, will commence a fresh evolution, whence will spring a complete 
vegetable organism,—that is to say, an individual of a higher grade, 
composed of axes and buds, forming, as it were, as many single indi- 
viduals. “ Gemme totidem herbæ " (Linnzeus) 
The two successive forms of the plant have, in the same way, a very 
unequal duration of existence. The first, the proembryo, dies as soon 
as the embryo is definitely constituted ; the vascular, sexless plant ex- 
hibits, on the other hand, an m€— existence, at least apparently 
so, because in reality the circumstances are different. Each bud or 
axis is, in effect, a distinct individual. An axis which does not pro- 
duce flowers only continues to exist as a point of insertion for succes- 
sive axes; and an axis which has flowered, which has produced leaves 
with microspores and macrospores, lives no longer. Among gymno- 
spermous plants in general, and especially among Cycads, the pró- 
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