488 
PHANEROGAMS. 
bipartition, the pollen-cells are produced from their mother-cells in a similar manner. 
Moreover, in the points here indicated Gymnosperms again appear as a connecting 
link between Cryptogams and Angiosperms ; the pollen-sacs of Cycadese and of 
some Coniferse closely resembling, in form and position, the sporangia of some 
Vascular Cryptogams. 
The general result of these observations is that the Phanerogam, with its 
pollen-grains and its embryo-sacs, is equivalent to the spore-producing (asexual) 
generation (Sporophore) of the Vascular Cryptogams. But as in Vascular Cryp- 
togams the sexual differentiation first makes its appearance (in Ferns and Equise- 
taceae) in the prothallium only, and next (in Rhizocarpeae and Ligulatae) in the 
spores themselves, so, in Phanerogams, this process is carried back a step further, 
the sexual differentiation arises still earlier, being manifested not only in the forma- 
tion of embryo-sac and pollen-grains, but also in the difference between ovule and 
pollen-sac, and between the leaves bearing them (carpels and stamens), and even 
earlier in the distinction between male and female flowers, and last of all in the 
dioecious condition of the plants themselves ^ [The sexual generation (Oophore) 
is represented in the pollen-grains (microspores) by the formation of cells within 
them which correspond to a male prothallium, and in the embryo-sac (macrospore) 
by the formation of the egg-apparatus, antipodal cells, and endosperm, which together 
correspond to a female prothallium. A distinct alier?iation of generations can there- 
fore be traced in the life-history of a Phanerogam.] 
The fertilised oosphere of Phanerogams produces a Suspensor, growing towards 
the base of the embryo-sac and dividing, a structure which we have already met with 
in Selaginella, on the apex of which there is a mass of tissue at first almost globular, 
which is the embryo. The development of the embryo usually proceeds, even 
before the maturity of the seed, to such an extent that the first leaves, the primary 
axis, and the first root, can be clearly distinguished. It is only in parasites and 
saprophytes devoid of chlorophyll that the embryo usually remains rudimentary until 
the dissemination of the seeds without discernible external differentiation; while 
in those Phanerogams which contain chlorophyll the embryo not unfrequently 
attains a very considerable size and external differentiation (as in Pinus, Zea, 
^scuhis, Quercus, Fagus, Phaseolus, &c.) Independently of any curving of the 
embryo, the primary apex of its stem always lies originally pointing towards the 
bottom of the embryo-sac (the base, chalaza, of the ovule) ; the first root (primary 
root) coincides with a posterior prolongation of the primary stem ; it faces the apex 
(micropylar end) of the embryo-sac, and is of distinctly endogenous origin, inasmuch 
as its first rudiment at the posterior end of the embryo is covered by the nearest 
cells of the suspensor. 
The apical cell of the punctum vegetatioms, which is easily recognised in many Algae, 
in Characeae, Muscineae, Ferns, Equisetaceae, and Rhizocarpeae, as the primary mother- 
cell of the tissue, has already, as we have seen, been replaced by a small-celled 
primary meristem in the Lycopodiaceae. The apical growth of the axes, leaves, and 
roots of Phanerogams also can no longer be referred to the activity of a single apical 
cell from which the whole primary meristem has proceeded. Even in those cases 
* Compare what is said on Dichogamy in Book III. 
