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96 ON THE SEXUAL ORGANS OF THE CYCAUACE^.
reproductive organs of Cycads have any foundation, the two kinds of
organs seem to follow the same course in their development and nieta-
moi-phosis. 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 j^atites-Jilles'") from the
transitory amnios; tlie 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 fdles'').
The generatiiig-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 Alges, 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, tliat 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.
" Gemmae totidem herbse " (Linnaeus).
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 iiand, an unlimited existence, at least apparently
so, because in reality the circumstances are different. Each biid or
axis is, in eft'ect, a distinct individual. An axis which does not pro-
duce flowers only continues to exist as a point of insertion for siicces-
sive axes ; and an axis which has flowered, which has produced leaves
with microspores and macrospores, lives no longer. Among gyrano-
spennous plants in general, and especially among Cycads, the pro-