142 FIsHER: SEED DEVELOPMENT IN THE GENUS PEPEROMIA 
spores immediately become somewhat thickened. The micro- 
spores, which are uninucleate at first, become binucleate before 
the nucleus of the embryo sac mother-cell of the same flower 
divides. The walls of the pollen grains increase in thickness, 
and become roughened on the outside. Their nuclei do not divide 
further before germination. The mature microspore is therefore 
binucleate, and no cross-wall is formed between the nuclei. The 
tapetum and the thin layer of cells just inside the endothecium 
have practically disappeared by the time the microspores have 
become binucleate and the endothecium has become fully de- 
veloped. The pollen is shed sometime after the embryo sac of 
the same flower becomes eight-nucleate and before it becomes 
sixteen-nucleate. This is later than it occurs in P. pellucida 
(Johnson, 30). Very few pollen-tubes were seen, and none of 
those seen were in good condition. The details of the germination 
of the pollen were not made out. 
The embryo sac and seed develop in a manner closely similar 
to that described by Campbell (6 and 7) and by Johnson (30) 
for P. pellucida. The primary archesporial cell is single and 
subepidermal (Fic. 1). It divides to form a tapetal cell, and the 
definitive archesporial cell,* or the embryo sac mother-cell, as it 
has sometimes been called (Fic. 2). At the time of this division 
of the primary archesporial cell, the integument has grown about 
half-way up to the apex of the nucellus. The tapetal cell by 
repeated division gives rise to a cap of parietal cells. This cap of 
tapetum becomes two or three cells thick before the nucleus of 
the embryo sac mother-cell divides, and three cell-layers in thick- 
ness is about the limit of its development (Fic. 3). 
The reduction of chromosomes probably occurs in the first 
two divisions of the nucleus of the embryo sac mother-cell, as is 
indicated by the presence of synapsis before the first division 
(Fic. 5). In this respect the behavior is the same as that reported 
by Johnson for P. hispidula. 
The nucleus of the embryo sac mother-cell divides into two 
(Fic. 6), and these two divide into four nuclei (Fics. 7, 8), which 
usually at least are arranged tetrahedrally—that is, the four 
* The definitive archesporial cell is to be distinguished from the primary arches 
sporial cell which is the parent of the definitive archesporial cell plus the tapetal 
or parietal cell. : ; : 
