98 Rhodora [May 
L., which although apparently not common in America, certainly not 
in New England, is widely distributed, practically all over the United 
States. As most European fresh-water algae occur in America, there 
seemed to be reason to expect C. Zemnae, and by the kindness of Dr. 
B. L. Robinson, the writer was able to make an examination of the 
Lemna trisulca in the Gray herbarium. The result was satisfactory, 
as in the first specimen examined every frond contained many indi- 
viduals of the Ch/orochytrium, in various stages of development. The 
specimen was from Seabrook, New Hampshire, collected by Mr. A. 
A. Eaton, 18 July, 1896. That this species belongs in our flora is 
therefore certain, but that it is common is unlikely, for on examina- 
tion of the other specimens, about twenty-five in all, from all parts 
of North America, not a single instance of the occurrence of the 
endophyte was found. 
The cells of the Chlorochytrium show as relatively large, ovoid or 
ellipsoid, dark green bodies, between the cells of the host; they are 
to be detected only by microscopic examination, but are then seen 
easily with relatively low powers. When fully mature, the contents 
of the cell is transformed into numerous biciliate zoospores, of the 
usual ovoid form; the cells of the host plant have been pushed apart 
by the growth of the CA/orocAytrium so that when the wall of the 
latter breaks, the zoospores pass out into the water, not free, but 
enclosed in a gelatinous vesicle; within this they conjugate, and the 
4-ciliate zygote then escapes from the gelatine and swims freely for a 
while; then it comes to rest. Unless it settles upon a frond of Lemna 
trisulca, it perishes; but if attaching itself to this frond, it germinates, 
the pointed end, from which the cilia have fallen, pushing in between 
the cells of the host, till it reaches a comparatively open space, when 
it expands, and the protoplasm is drawn in, only a small button-like 
appendage remaining to show the point of entrance; the cell then 
grows to the full size, and zoospores are again formed. 
There are several other endophytic algae found in Europe, whose 
development more or less resembles that of this species; a search 
for some of them was made in the Gray Herbarium, without results. 
An herbarium specimen is usually selected to show a plant in its 
best condition, while the endophytes usually do not reach their full 
development until the host has passed its prime; better success may 
be expected from an examination of living plants of the suspected 
hosts. The following European species have been well studied, and 
