KING: CYTOLOGY OF ARAIOSPORA PULCHRA. 
219 
mass is limited by the original plasma membrane, it must respond 
exactly as a single cell, which it really is. In the meantime, however, 
plasma membranes are being developed about the individual zoo¬ 
spores which, when these are formed, also function as separate cells. 
Their membranes are in contact on the outside with the water in 
which the plants live and on the inside, with the denser liquid of the 
central vacuole. In such a case it is possible that liquids might 
enter the individual zoospores from without, thereby increasing the 
hydrostatic pressure and turgidity of the zoospore mass and serve as 
an aid in forcing it out. 
The zoospore .— The zoospore is uninucleate. The nucleoli are 
distinctly larger than those of the vegetative filament and the 
nuclei themselves stain more deeply. There is a distinct nuclear 
membrane enclosing the hyaline nuclear substance in which the 
nucleoli are imbedded. The nucleus stains more deeply just inside 
the membrane. On the outside of the nucleus adjacent to its mem¬ 
brane there is frequently an accumulation of more deeply stained 
granules. The cytoplasm of the zoospore consists of a distinct 
meshwork and is not conspicuously granular (pi. 11, fig. 7-8). 
Among the meshes it is not uncommon to find one or more vacu¬ 
oles, another indication that the zoospores may be expelled in the 
manner indicated above. 
In many zoospores there are a few small, deeply staining bodies in 
the meshes of the cytoplasm (pi. 11, fig. 8). These bodies occupy 
no definite position in the zoospore; they may be near the nucleus or 
out on the periphery. No cilia were observed on the stained mate¬ 
rial, although they are present when the zoospores are alive. In the 
discharge of the zoospores it is quite common for a few to be left 
behind in the zoosporangium. It should be mentioned that the 
study of the zoospore was confined exclusively to those remaining 
in the zoosporangium for the material was usually somewhat mixed 
with various JSaprolegniaceous forms and one could not be certain of 
zoospores found outside. The zoospore germinates at the expiration 
of a few hours. In one case in particular, two zoosporangia 
opened simultaneously at 11 : *80 in the morning and in a few min¬ 
utes all the zoospores had escaped but six and eight respectively. 
In the afternoon at 3:45, each of these fourteen zoospores had 
developed a cell wall and put out a germ tube. These varied in 
length from the diameter of the zoospore to six times this length. 
