226 FISHER: SEED DEVELOPMENT IN PEPEROMIA 
spore walls of other Angiosperms, that is, if it be admitted, as it is 
so generally, that megaspores occur in Angiosperms. 
From these significant relations—from the origin of the embryo 
sac from what seems clearly a megaspore mother-cell, from the 
occurrence of the reduction division of its nucleus, from the tetra- 
hedral arrangement of the first four nuclei, from the complete 
number in the tetrad, from the resting period following the forma- 
tion of the tetrad, from the increased number of nuclei in the sac, 
and from the appearance of evanescent walls—from all these 
facts in favor of our view, together with the fact that the ger- 
mination of all four megaspores and the participation of all of 
them in the formation of one embryo sac do not constitute valid 
objections to the theory, we are very strongly inclined to the 
view that the first four nuclei in the embryo sac of Peperomia are 
the equivalents of megaspore nuclei. 
This theory of homologies is in harmony with the classifications 
of embryo sacs by recent workers (Ernst, 20; Coulter, 13; Samuels, 
59) with regard to the number of genetations of nuclei from the 
beginning of the reduction division to the mature sac. 
TExtT FIG. I illustrates diagrammatically the known types of 
derivation of the mature embryo sac from the definitive arche- 
sporial cell. The order in which these are arranged will suggest 
the phylogenetic sequence in which certain chief steps in the 
reduction of the number of cells or nuclear divisions between the 
definitive archesporial cell and the mature sac may have occurred. 
It also indicates the number of degenerating megaspores formed, 
where any occur. 
In the type illustrated by TEXT FIG. Ia, there are five cell- and 
nuclear generations (the first two being cell-géenerations, and the 
last three being nuclear generations) in the development from the 
definitive archesporial cell to the mature embryo sac, which latter 
is of the common eight-nucleate type. The embryo sac is here 
indisputably the product of one megaspore, which divides three 
times. 
In the type illustrated by TExT ric. 1), the case is similar to 
that in TEXT FIG. 1a, but the upper cell formed by the first division 
of the definitive archesporial cell does not divide further. The 
embryo sac here contains eight nuclei, and is again clearly the 
roduct of but one megaspore, which divides three times. 
