THE EMBRYO-SAC OR FEMALE GAMETOPHYTE. 173 
period of duration. In many plants they disorganize immediately 
after they are formed; in others they may divide repeatedly, giving. 
rise to a larger or smaller mass of tissue which remains functional for 
a comparatively long time. The development of the antipodal cells 
into a mass of tissue, whose function is probably concerned with the 
absorption and elaboration of food materials, may occur in the most 
widely separated families—a fact which goes to show that this phe- 
nomenon is a special adaptation in each specific case and in no way 
_ indicative of a closer phylogenetic relationship or a primitive condition. 
The typical embryo-sac, or female gametophyte, consists, therefore, 
of seven cells, one of which, the egg-cell, is the female gamete, while 
the other cells may be looked upon as vegetative or prothallial cells 
(Fig. 73, C). The egg-cell may be regarded as the homologue of the 
egg-cell in the Gymnosperms, and hence a rudimentary archegonium. 
Whether the synergide are to be regarded as rudimentary egg-cells, or 
merely prothallial-cells, can not be determined at the present state of 
our knowledge. 
As stated in a preceding paragraph, no attempt will be made even 
to summarize the numerous variations in the development of the 
embryo-sac that have been observed by the many investigators, since 
the vast majority of these variations may reasonably be considered as 
special adaptations, and as such are of small theoretical importance, 
One of the many interesting cases about which there is likely to be 
‘much diversity of opinion will be briefly mentioned. This is found 
in the development of the embryo-sac of Peperomia pellucida, as 
described by Campbell (’99, ’o1) and Johnson (1900). In this species 
sixteen nuclei are present in the mature embryo-sac. Of these one 
becomes the nucleus of the egg, one the single synergid, and several, 
usually eight, fuse to form the endosperm nucleus. The remaining 
nuclei, according to Johnson, degenerate, but Campbell finds that they 
are scattered in the sac, each developing about itself a cell-wall much 
as do the antipodal cells of many Angiosperms. Johnson regards the 
peculiarities of the embryo-sac in Peperomia as secondarily acquired 
from the typical form, while Campbell looks upon them as primitive, 
recalling such forms among the Gymnosperms as Guetum gnemon 
(Lotsy, 1900). 
‘In the development of the embryo-sac, as typified by ZLz/cum, the 
two cell-divisions which result in the axial row of four cells in Hed/e- 
éorus are wanting, and the question arises whether the hypodermal 
cell of Zzlzum, for example, which develops directly into the embryo- 
sac, is homologous with the hypodermal cell of Hed/eborus, or only 
