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ON THE SEXUAL ORGANS OF THE CTCADACE.E. 97
embryonic form persists much longer than usual. It is also much
more complex ; for, whilst among Angiosperms the proembryo only
forms a simple axis, represented sometimes by a single cell, and only
gives rise to a single bud, a single embryo, a single individual,—the
proembryo of Gymnosperms divides into branches, and produces, or
might produce, numerous buds or embryos. It imitates, to some ex-
tent, the higher sexless form, by its ramification and the production of
multiplied buds combined into one whole. If we consider the life of
the generating cells, the microspores and macrospores, as terminating
at the moment of their mutual union, a view which admits of support,
there woidd then be a triple alternation of forms within the limits of
the individual. But it seems more simple to consider the sexless in-
dividual of more perfect organization as producing by generation, or
dift'ereutiation, into two distinct states, a more simple organism of
short duration, returning finally to the original form with higher or-
ganization, and life indefinitely prolonged.
Among the vascular Cryptogams, alternate generation manifests it-
self more clearly, because the two forms appear distinctly at the exte-
rior, whilst among Phanerogams the cellular transitory organism is
enclosed in a portion of the higher organism. The spores produced by
the vascular sexless plant develope into organisms simple in structure
and wholly cellular {prothalUum), which produce the generating-cells.
Among the lower vascular Cryptogams, both sexes originate from the
same spore ; among the higher, from diff'erent spores,—the one set
microspores (male), the other macrospores (female). In both cases,
however, a new individual results from their union, which possesses
vascular bundles, is difi"erentiated into stem and leaves, and is destitute
of sex. Yet here the embryo does not proceed directly from the cen-
tral cell of the archegonium ; the first product is a proembryo, the ter-
minal cell of which becomes the embryo. Thus, then, among Phanero-
gams, the generating-cells occur on the higher essential form, among the
Cryptogams on the lower form.
Hofmeister has made the remark that the Coniferce (the Gymno-
sperms) are with respect to the development of the embryo, intermediate
between the higher Cryptogams and the Phanerogams. Among
the Gymnosperms, the embryo-sac soon becomes free and detached
from the tissues which surround it ; the formation of the endosperm is
comparable to the production of the prothallium ; the corpuscles are