FISHER: SEED DEVELOPMENT IN PEPEROMIA 229 
the preceding, the difference being that two evanescent cell-walls 
appear after the second division in the embryo sac, and that the 
lowest nucleus in the sac degenerates, so that the mature sac 
‘contains but three nuclei, which have arisen from the morpho- 
logical equivalent of two megaspore nuclei. 
If we accept this view of the phylogenetic sequence of the steps 
in the reduction of the development of sporogenous tissue, it is 
evident that Peperomia, as well as Saururus, Ornithogalum, and 
Oenothera, illustrates the first stage in the abbreviation of the 
development of megasporogenous tissue. The number of cell- or 
nuclear divisions from the definitive archesporial cell to the mature 
embryo sac has been reduced from five to four. 
From the same point of view, Piper, as well as Lilium, Cyp- 
ripedium, and Podostemon, illustrates the second stage in this 
reduction, where the number of cell or nuclear divisions from the 
definitive archesporial cell to the mature embryo sac has been 
reduced to three. This is the condition found by Yamanouchi 
(80) in Fucus, that is, the number of nuclear generations from the 
beginning of the reduction divisions to the mature egg is three. 
As Miss Pace (57) has pointed out, if reduction should go one 
step further, we should have the condition present in the matura- 
tion of the animal egg. But no case showing reduction of the 
female sporogenous tissue to two cell-generations has been re- 
ported in plants. 
It may be added that no unquestioned case of more than five 
cell and nuclear generations from definitive archesporial cell to 
mature embryo sac has been reported. Dessiatoff (16) reported 
a case of six cell-generations in Euphorbia virgata, but Modilewski 
(52) later got different results when working on the same species. 
As has been frequently pointed out, there is much more vari- 
ation in the development of embryo sacs than was formerly 
thought. Coulter & Chamberlain (14, p. 76, 77) call attention to 
the great variability in the family Liliaceae. The Podostema- 
ceae, also, show considerable variation, as shown by Magnus (44). 
Sometimes the variability is very great in a single genus. 
In the genus Burmannia, Ernst & Bernard (22, 23) found 
an interesting series of cases. In the species studied, the sub- 
epidermal primary archesporial cell becomes the definitive 
