Seed development in the genus Peperomia* 
G. CLYDE FISHER 
(WITH PLATES 3-6 AND A TEXT FIGURE) 
[Concluded from page 156] 
GENERAL DISCUSSION 
Whether the sixteen-nucleate embryo sac of Peperomia is to 
be regarded as primitive, depends upon the homologies assumed 
or proved for the various structures found in this unusual type of - 
embryo sac. In view of this, and since no axial row of megaspores _ 
is formed, the first question that naturally arises is whether the 
first four nuclei in the embryo sac are the morphological equiva- 
lents of four megaspore nuclei. 
It is quite generally agreed that the cells of the axial row in the 
nucellus formed by the division of the definitive archesporial cell 
in most Angiosperms are homologous with those having a similar 
development in Gymnosperms; in both cases they are almost 
universally known as megaspores. There exists a further homol- 
ogy, although not quite so close, between the megaspores of 
Angiosperms and Gymnosperms and those of the heterosporous 
Pteridophytes. The tetrads of microspores, also, in all of these 
groups are homologous with one another, and, in a slightly different 
degree, with the megaspores in the same group. The evidence for 
these views has been well presented by Strasburger (73, 75), 
Overton (55, 56), Juel (36), Kérnicke (40), Coulter (13), and 
others. 
That the first four nuclei in the embryo sac of Peperomia are 
homologous with megaspore nuclei seems equally clear. The 
following facts indicate the correctness of this conception: 
(1) The cell, the nucleus of which gives rise to these first four 
nuclei, may be considered, without valid objection, a megaspore 
mother-cell. It is developed in the position of the axial row. It 
is derived from a single primary archesporial cell, which cuts off 
ST mele iealiiidacnsn 
* Botanical Contribution from The Johns Hopkins University, No. 35. 
221 
