Feb. 12,1917 
Studies of the Genus Phytophthora 
255 
its contents are much larger than the original sporangium, and it is 
difficult to understand how the large swarm-spore mass was contained in 
the smaller sporangium only a few seconds before. After the liberation of 
the swarm spores, the vesicles begin to contract, all signs of the opening 
disappear, and if any zoospores remain they are unable to escape. Plate 
75 shows various stages in the germination of P. arecae illustrating 
these points. 
When no vesicle is apparent, the process of swarm-spore germination is 
essentially the same as described, but there is in this case a variation in 
the manner of emergence of the swarm spores from individual conidia. 
From the narrow papilla-like opening the swarm spores issue singly or in 
pairs, the time of emergence varying from 4 to 10 seconds. At times the 
swarm spores are held together at the opening for 2 to 3 seconds, after 
which they swim in all directions. Frequently for some reason a few of 
the swarm spores do not emerge with the majority. For instance, in one 
case thfe writer observed some of these swarm spores struggle for 55 
minutes to escape, but without success, although at times they were at 
the very opening. This gave the impression that the opening closed 
after the majority had escaped. In one particular case the swarm spores 
finally came to rest and germinated inside the sporangium, the germ 
tubes extending through the wall. In many cases two of the swarm 
spores after emergence seemed to stick together two or three seconds, 
being held by a fine protoplasmic thread or connection, and then each 
darted off by itself. 
The number of swarm spores in a sporangium varies with the size of 
the latter, and the species are not characterized by a definite number. 
Neither do the swarm spores show any marked difference in the various 
species. All are pyriform to kidney-shaped, and each is provided with 
at least one light-colored spot, probably a vacuole, which is located near 
the concave side and which appears to be the point of attachment of 
two flagella. The latter are unequal in size and vary from one-half to 
twice the length of the body of the swarm spore. After swimming for 
a time, the flagella having disappeared, the spores finally rest, become 
round, and germinate by means of tubes. In none of the species of 
Phytophthora has diplanitism as occurring in related genera been found. 
CHLAMYDOSPORES 
The term “chlamydospore” is applied to one of the spore forms found 
in a number of species of Phytophthora. The chlamydospores are 
spherical, smooth, thick-walled, and brownish to yellow. They differ in 
size from the conidia and oospores and are formed either terminally or 
intercalarily. Various investigators have interpreted their function in 
different ways. When working with P. faberi , Von Faber (12), Coleman 
