162 BOTANICAL GAZETTE [FEBRUARY 
whether Rhodochytrium is an alga or a fungus. As will be seen, 
the answer depends not so much upon any interpretation of the 
facts of the case, as upon the point of view of the student. 
Among the Chytridiales, Entophlyctis, of the family Rhizidi- 
aceae, is strikingly similar to Rhodochytrium in gross morphology. 
Both are characterized by an external button connecting by a 
narrow neck with the main body of cyst. The rhizoidal system, 
if not exactly of the same appearance in the two cases, is of the 
same type, and the differences may be supposed to be due to the 
character of the substrata, which in one case is the soft protoplast of 
an alga and in the other the tough vascular bundle of a seed plant. 
The life cycles are identical; both start from a free swimming 
zoospore that penetrates the host, giving rise to an internal ampulla 
which on maturity becomes either a resting spore or a zoospo- 
rangium. Altogether Entophlyctis is so similar to Rhodochytrium 
that the comparison is exceedingly suggestive. 
Nevertheless, there does not seem to me to be any good reason 
for connecting Rhodochytrium and Entophlyctis. The comparative 
anatomy of the Rhizidiaceae would seem distinctly to forbid such 
an idea. Within the family Rhizidiaceae there are apparently all 
transitions from purely epiphytic parasites with as little penetration 
as possible, to complete endoparasites. At the beginning of the 
series may be placed Rhizophidium brevipes,t which barely pene- 
trates the wall of its host, without putting out any rhizoids to 
gather nutriment. Further stages are shown by various species of 
Phylactochytrium, which not only have extensive rhizoids, but 
develop a small basal portion of the plant body itself within the 
host. In P. equale the internal portion of the body becomes as 
large as the external. From this condition it is an easy step to 
Entophlyctis by the enlargement of the internal portion at the 
expense of the external, with consequent transference of the spo- 
rogenous function. This has every appearance of being a natural 
phyletic series. In it the parasitic mode of life would appear 
4 Harpochytrium is even more surely an epiphytic parasite, since it does not 
penetrate its host at all, being merely attached to its wall; but it is not used in the 
present comparison because its relationships have been subject to some difference of 
opinion among different observers. WILLE (33), for example, believes that it is a 
colorless member of the Protococcoideae. 
