8 
Peronospora obducens, Schrcet, upon Impatiens fulva , lias not 
been met with during tbe last three years. It is not a common species 
in the most favorable season. 
Peronospora geranii, Pk., was not found last year upon the com¬ 
mon host Geranium maculatum , but in May was collected by A. S. 
Hitchcock upon Geranium Carolinianum, at Iowa City. During June 
of 1888 the mildew was very abundant upon G. maculatum; in fact, 
more so than any other species at that time. 
In May last a Peronospora was found upon the common water leaf 
{\Hydrophyllum Virginicum). I am not aware that Dr. Parlow, to whom 
specimens were sent, has determined the species. It was growing over 
the same areas, and closely associated with the Spotted Cranesbill af¬ 
fected with P. geranii. It is very interesting to note that the same 
species was first discovered by Mr. Holway about a fortnight earlier, at 
Decorah, Iowa, and also found by Mr. Hitchcock, of Iow r a City, at al¬ 
most the same time as at Ames. 
Peronospora pygmaia, Unoer, on Anemone sp., was not observed 
last year, but in 1888 it flourished in late May and early June. 
Peronospora gangliformis, DBy., occasionally appeared upon 
the lower leaves of Mulgedium leucopliceum , in 1887. The other hosts 
prefer dry ground, and in their dwarfed condition were not infested. 
During the year just closed it could be said to be common upon Prenan- 
thus and Lactuca hosts. 
Peronospora parasitica, Tul., is one of the most common species 
upon various cruciferous hosts. In ordinary seasons Lepidium Virgini- 
eum , is badly infested, having its branches strangely distorted. Last 
year the pepper grass was quite free from the parasite, if we except the 
seedlings, which were attacked for a few weeks in spring. Tbe Perono¬ 
spora was most abundant upon Nasturtium palustre. In June the 
lower leaves of the host, lying close to the moist ground of borders of 
streams, were quite generally affected. A little later, when the drought 
had progressed, it was not abundaut. In some specimens the conidio- 
phores were not more than one-fourth the normal size. Early in 1888 
the mildew was abundant upon the pepper-grass, and continued so un¬ 
til July. 
Peronospora potentillje, DBy., was common on Potentilla Norve- 
gica , early in 1887, when the host was growing on the borders of low 
wet places. It disappeared as the dry weather of late spring arrived. 
Last season it did not appear in abundance until July, when whole large 
plants were found attacked. 
Peronospora Arthuri, Farlow, was not common three years 
ago, but during 1886-’87 it was found only on a few plants growing along 
the shady bank of a stream. It has not been common the last season 
and is peculiar in only attacking here and there a whole plant. 
Peronospora effusa, RABH.,is a common species upon Ghenopodium 
album , but was far less abundant than usual during the two dry 
seasons. 
