KING: CYTOLOGY OF ARAIOSPORA PULCHRA. 
241 
Summary. 
The plants may be found from April to October; they are most 
abundant in April and May when the oogonia and antheridia are 
produced in great numbers. During the remainder of the season, 
the sexual organs ar$ rarely found. 
The cytoplasm of the vegetative parts is chiefly confined to the 
region of the inner surface of the cell wall. It consists of a con¬ 
tinuous, and to some degree granular, mesh work in which are 
numerous nuclei. The enclosed vacuoles are traversed by cytoplas¬ 
mic strands. 
The vegetative nuclei stain less deeply and are probably poorer 
in chromatin than those of the reproductive organs. 
The cytoplasm of the zoosporangium has the general structure of 
the vegetative plant except that its meshes contain more granules 
and in consequence stain more deeply. It is never uniformly granu¬ 
lar as in the Saprolegniaceae. 
Contiguous zoospores are separated by an almost simultaneous 
constriction of connecting meshes. Frequently, the original plasma 
membrane is the last to be ruptured. 
The zoospores are uninucleate, coarse meshed, and usually contain 
one or more vacuoles. Within a few hours, they secrete a cell wall 
and germinate. 
The cytoplasm and nuclei of young oogonium and parent filament 
are similar in appearance. After the oogonium is cut off, its cyto¬ 
plasm assumes a more uniform mesh work. 
There are from thirty-five to fifty-five nuclei in an oogonium. 
The average number for the larger oogonia is less than fifty. 
The nuclei migrate to the periphery and the peripheral vacuoles 
arise between them. These vacuoles increase in size at the expense 
of others in the interior. 
During these changes, many small, isolated, fine meshed, cyto¬ 
plasmic patches arise. These patches migrate to the center of the 
oogonium where they fuse into one conspicuous, deeply staining, 
fine meshed mass. 
This differentiated central region retains its form until after the 
sperm enters it. It then begins to spread out into the peripheral, 
coarse meshed ooplasm. 
