4 
Journal of Mycology 
[Vol. 10 
stalk, the latter being formed when the zoospore is prevented 
from coming in contact with the host cell by an envelope of gela¬ 
tine with which some algae are provided. Even in the appa¬ 
rently sessile forms there is a short slender stalk which pierces 
the outer lamella of the host cell wall. The stalk expands into a 
disk shaped holdfast in the middle lamella, but in the smallest 
species this has not been certainly determined. When the plant is 
mature it is divided by a thin cross wall near the base into a 
small sterile basal part, and an outer long part, the sporangium. 
The tip of the sporangium gelatinizes and permits the escape 
of the zoospores which are oval and 1 -ciliate. The zoospores 
either swim about with great rapidity in the water, or first show 
slight amoeboid movements, and then dart off with great rapid- 
itv. and finally come to rest on the host or in the gelatinous sheath 
surrounding the host, and attach themselves. The sterile base 
now forms a secondary sporangium in the empty one, and this 
may be repeated several times as in Saprolegnia. The plant 
probably is not derived from Saprolegnia by degeneration, but 
more likely is an example of the differentiation of a simple chy- 
trid into a sterile and fertile part, the sterile part perhaps repre¬ 
senting a rudimentary hypha. 
My first knowledge of the genus was in 1896, when I found 
it at Ithaca, N. Y., parasitic on Spirogyra and rarely on Zygnema. 
This species proved to be Harpockytrium hedenii Wille, which 
has also been found in France, Tibet (Asia), and Patagonia (S. 
Am.), and Sweden. 
Since the publication of my paper in the Annales Myco- 
logici ( 1 . c.) I have received drawings of a species of Harpochy- 
trium from Dr. Lagerheim, a notice of which it seems desirable 
to incorporate in this note. His pencil sketches I have redrawn 
and they are here reproduced in text figures 24-26. These plants 
were growing on threads of Vaucheria. They are interesting as 
showing from the illustration that the base of the organism does 
not penetrate the cell wall, but expands into a disk-like holdfast 
and absorbent plate on the outer surface of the wall. This may 
be because of some peculiarity of the cell wall of the host. I am 
inclined to think that in some cases the form from Tibet is fur¬ 
nished with the disk-like holdfast on the outside of the cell wall, 
especially in the forms on threads of Zygnema which are cov¬ 
ered with a thin slime layer. The slime would tend to prevent 
the zoospore from coming in contact with the cell wall directly 
and a very short slender stalk is developed to reach the host 
just as a longer stalk is developed in H. hyalothecae on the 
desmids with a thick slime layer. Text figure 26 represents a 
peculiar form of the plant, with a tendency to develop a short 
conic out-growth at one side as if there was a tendency to 
branch. A similar form I found in 1896 at Ithaca, but for 
