1912} GRIGGS—RHODOCHYTRIUM 131 
leaves from withering and dying, and reinfections on healthy 
portions of the plant are difficult to secure. 
The most convenient way to obtain the zoospores is to tease to 
pieces fragments of tissue containing the cysts, liberating the 
zoospores by rupturing the sporangia. It is difficult to observe 
the normal exit of the zoospores on account of their minuteness as 
compared with the massive tissues from which they emerge. But 
with patience one can study the discharge. LAGERHEIM states 
that the plug of the zoosporangium is dissolved before the escape 
of the spores. In only one case was I able to observe the discharge 
under satisfactory conditions, and then I saw neither the fate of 
the plug nor the very beginning of the discharge. The whole mass 
of zoospores appeared to expand as swarming began, and those 
nearest the opening were forced out in a solid stream by the 
pressure of those below them. In the case observed they con- 
tinued to escape at the rate of about 150 per minute for 10 minutes 
(that is, approximately 1500 spores). The last ones from the 
rhizoidal end of the sporangium were not at first so well formed 
as the others, and did not escape with them, but after an interval 
of 5 minutes began to swarm violently inside the sporangium and 
some of them escaped one by one. Not all of them were able to 
find the opening, however, and those which failed became quiescent 
after about 15 minutes. 
Along with the ripe zoosporangia many immature ones, of 
course, are torn open in teasing apart the material for mounting. 
Such of these as have advanced far, though not yet mature, are 
apparently able to form zoospores under the stimulus of rupture. 
When first discharged the contents of these cysts undergo euglenoid 
contortions, but in a few minutes become ciliated and break up 
into.spores. Such zoospores, however, are very irregular in size, 
and abnormal forms compounded of several individual spores are 
common. Among these are some which might easily be confused 
with conjugating gametes, being associated in pairs side by side. 
More commonly such double zoospores are joined at their posterior 
ends, forming much elongated bodies, pigmented and ciliate at 
both ends. Frequently a third member is attached to the middle 
of such a couple, forming a projection at right angles. Others are 
