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Very abundant on the oak leaf. This is a remarkably beautiful species 
growing its mycelium in orbicular and stellate patches, which enable one 
to recognize it at a glance. 
Microspheera diffusa C. and P. 
On Desmodium leaves. 
Erysiphe lamprocarpa (Wall.) Lévy. 
Found on many hosts, notably on Composite. 
In addition to the host mentioned by Rose are added Aster cordifolius, 
Aster undulatus, Ambrosia trifida and Verbena stricta. In one instance 
a few asci were found containing three spores, which is contrary to what 
has formerly been regarded a strong specific character. This variable- 
ness of spores led to another classification of this species by Burrill and 
Earle (Bull. Ill. State Lab. Nat. History, Vol. I, p. 404). 
Erysiphe Euphorbize Peck. 
On ‘Euphorbia corollata. The host bearing this species was in a 
withered and very sickly condition, whether from action of the mildew 
could not be affirmed. 
Erysiphe communis (Wall.) Schl. 
On Ranunculus recurvatus and an aster growing in the same place 
which had probably received the mildew from its neighbors. The ap- 
pendages of the perithecium found on Ranunculus were fifteen to thirty- 
five in number and two to four times the diameter of the perithecia in 
length. 
Erysiphe tortilis (Wall.) Lk. 
On Clematis Virginiana. This species has been found on this host 
several times, but this specimen differed from all others described in ap- 
parently not affecting the host, which was in a vigorous condition, though 
the mildew was very abundant on its leaves. 
Erysiphe horridula Lévy. 
On Verbena stricta and Eupatorium purpureum. It was difficult to 
decide whether this was E. horridula or E. lamprocarpa, as it closely re- 
sembles the latter, with the exception of having three to four spores in 
every ascus. 
Recent research with improved instruments reveals many facts un- 
known to the early mycologists who made the first classification of mil- 
dews. Many of the characteristics forming generic and specific distine- 
tions in their classification are found to be changeable and not always 
