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IOWA ACADEMY OP SCIENCES. 
blights, and many other varieties growing in this vicinity. I 
am inclined to think that the dry season during the flowering 
period this year has had much to do with the spread of the 
disease. Blight has also been general this year in many parts 
of the state. My observations made here for several years 
show that blight usually occurs on the young twigs, affecting 
not only Fyrus communis but P. coronaris, P. makes and P. pmeni- 
folia. This year it affected more especially P. malus, especially 
blossom blight. M. B. Waite* has shown that insects are 
important in carrying the disease from one flower to another. 
The disease entirely disappeared during July and August and 
trees have been unusually free during the latter part of the 
season. 
Bacillus sorglii Burrill. This organism, so abundant every 
year, has not been so common the past season as during pre- 
vious ones. 
Bacillus cleaceae Jordan. Has not been observed by me the 
past season on the College grounds, although some years it is 
extremely abundant. 
Bacillus campestres (Pammel). The rutabaga and turnip 
rot so common the past three or four years has_not made its 
appearance on the cultivated rutabagas or turnips on the Col- 
lege grounds. 
PERONOSPORACEAE. 
The members of this group have been on the whole very 
scarce during the past season. Early in May and the latter 
part of April some of the species occurred on our weedy plants 
but our cultivated plants have been nearly free from these 
mildews. 
PcTonospora pctrisiticci DeBary. This fungus occurred 
in April and May abundantly on the leaves of Lepiclium inter- 
medium, completely infesting the whole plant, giving them a 
yellow appearance and stunted in growth. It also occurred on 
Cap>sella hursa-jmstoria, but less abundantly. Very little of thi 
fungus was seen during the rest of the season on any of the 
other crucifers. 
Poronospora p)otentillae De Bary. This species was only found 
once in a shaded place near a house on the leaves of Potent ilia 
norvegica. 
Sclerospora graminicola (Sacc.), Schroter. This fungus has 
been abundant at times in past years on Setceria viridis; occurred 
* Proceedings Am. Assn. Adv. of Science. Washington Meeting, 1891, p. 315. 
