54 BOTANICAL GAZETTE. [ March, 
found in small quantities in ordinary seasons, has not been 
met with the past year. : 
Peronospora Geranii Pk. upon its common host, Geranium 
maculatum, has not been observed this year; but in May 
Mr. A. S. Hitchcock collected it upon G. Carolinianum at 
Iowa City, and thereby adds a new host for the state. It 
was not at all commor. 
Peronospora pygmea Unger on Anemones has not been 
obtained this year. 
Peronospora gangliformis DBy. was very ‘“‘ shy,” as the 
horticulturist might say. Occasionally it appeared upon the 
lower leaves of Mulgedium leucopheaum. The Nabalus al- 
bus and species of Lactuca, which are hosts, grow mostly 
upon dry ground, and in their dwarfed condition the present 
species upon various cruciferous hosts. In ordinary seasons 
Lepidium Virginicum is much infested and has its branches 
over the winter in these seedlings, and when the spring 
comes the mildewed plants communicate the trouble to other 
plants by means of the multitudes of conidial spores. The 
vigor of its attacks upon the young pepper-grass makes this 
d-destroyers. It deals in the 
Same way with the shepherd’s purse. During the present 
upon Nasturtium palustre. 
ee lying close upon the moist ground, on the borders 
of s 
progressed farther, it was not ata 
specimens examined the conidiophores 
however, Showed all gradations, and it 
ata | i ell 
ai tte Hieak, ata leaf parasite may be dwarfed as w 
Peronos ora -Potentill fle 
Norvegica ie : we@ DBy. was common on Potent 
y In the season was growin: 
on the sloping ‘bord » Where the host was g 
ay 
pagest 
ers of | disap- 
peared as the dry weat oF low, wet places. It soon disap- 
her of late spri ived. 
eronospora Claytonie Farl. is sin ewig 
I 
cies, and has not been seen in Iowa. It was abundant in 
