450 BOTANICAL GAZETTE [DECEMBER 
Fig. 24 represents a stage in which they should be apparent if present. 
In the last division (fig. 26), cell plates are formed on all the spindles. 
These give rise to walls cutting off all of the nuclei except those which 
are to fuse to form the endosperm nucleus, but leaving these eight free 
in the cytoplasm (figs. 27, 28). These walls are thin at first and might 
be easily overlooked, but later they become much more prominent. In 
the eight-nucleate stage two nuclei are always found together at the 
micropylar end (jig. 25). The presence of spindles show these to 
be sisters (fig. 24). In the last division one of these gives rise to the 
egg, the other to the nucleus with the position of a synergid (figs. 
26-29). The sisters of the egg and synergid fuse with the sisters of the 
six peripherals to form the endosperm nucleus. As in P. pellucida 
(JOHNSON ’00) the peripherals are arranged singly against the embryo 
sac wall (jig. 29) and finally degenerate. About the time of fertiliza- 
tion the eight nuclei which form the endosperm nucleus migrate 
toward the base of the sac and fuse into one large nucleus. 
STRASBURGER (05) assumes that owing to their position the polar 
nuclei in the ordinary angiosperm are not surrounded by cell walls 
and that their fusion is due to the fact that their development has 
stopped and that they are in a single cell. This explanation may 
apply to the eight fusing nuclei in P. Sintensii. 
A peculiar phenomenon was noted in fertilization. The male and 
female nuclei at this time are in the resting stage and have one of more 
cavities with their concave sides facing each other (fig. 29): The 
edges fuse so that a mass of cytoplasm is apparently held in the fusion 
nucleus (fig. 30). The wall around this mass of cytoplasm grows 
faint and finally disappears. : 
The mature seed resembles that of P. pellucida (JOHNSON 00). 
There is a small oval embryo, while the rest of the sac is filled with 
a much larger endosperm, which is cellular from the first division. 
The sac is about the same size as at fertilization, but the cells of the 
nucellus have become filled with starch to form perisperm. 
Peperomia arifolia 
The development of P. arifolia was followed only as far as the 
sixteen-nucleate sac. pak 
The development of the flower and of the embryo sac agrees T°" 
