1912] GRIGGS—RHODOCHYTRIUM 129 
haematoxylon, for some reason, was hard to handle with this 
material. 
Observations on living material 
Through the kindness of Mr. HALt, supplies of infected ragweed 
were sent to me at frequent intervals. By this means it was 
possible to determine the approximate sequence of events through 
the year. It would be interesting to compare the seasonal cycle 
of the parasites in North Carolina and in Ecuador, but LAGERHEIM 
has left us no data concerning the seasonal history of his plant. In 
regard to the characters of the living cysts and the behavior of 
the zoospores, I cannot add in any important particular to 
LAGERHEIM’s account, though my observations confirm his at 
almost every point. 
According to my observation, the parasite does not appear at 
Raleigh until rather late in the season. Seedling ragweeds, 
gathered among the stubble containing the old resting spores on 
April 20 and May 20, showed no infection on arrival in Columbus, 
and did not subsequently develop any when grown in the green- 
house. Young plants gathered May 31, however, showed a few 
parasites. At first nearly all of the cysts become zoosporangia, 
but before June has passed, resting spores begin to appear in num- 
bers, the zoosporangia become gradually scarcer and scarcer, until 
finally, about August 1, practically the only cysts found are the 
quiescent resting spores which undergo no further change until the 
following spring. These are even more conspicuous than the 
zoosporangia, but for any observations, either biological or cytologi- 
cal, material must be gathered while zoosporangia are still abundant, 
that is to say before the middle of July, preferably during the latter 
half of June. 
With a little care the two sorts of cysts can be distinguished in 
_the hving state under a hand lens. The resting spores are more 
regular in shape and more deeply buried than the zoosporangia, 
and they are usually more deeply pigmented, since their protoplasm 
is more compact and less vacuolate. 
The first infections observed were mostly on early leaves, which 
soon wither and drop off in the natural development of the plant, 
