Wilson : Studies in North American Peronosporales 205 
Chamaesycc serpens (H.B.K.) Small ( Euphorbia serpens 
H.B.K.), Kansas, Bartholomew (Fungi Columb. 1750). 
Chymaesyce stictospora (Engelm.) Small ( Euphorbia sticto- 
spora Engelm.), Nebraska, Bates (Fungi Columb. 2128). 
Distribution : Throughout the northeastern United States. 
Peronospora Trifoliorum De Bary, Ann. Sci. Nat. IV. 
20: 1 17. 1863 
This species, which has been known in America until recent 
years as most abundant on certain species of Astragalus, has 
appeared on alfalfa ( Medicago sativa ) in numerous localities 
from New York to California. In some localities it appears to 
be of rather slight economic importance, while in others it is re- 
ported to cause serious trouble. To judge from the specimens 
available for study the form on Medicago is slightly more slender 
than that on Trifolium, and several times as abundant, even in 
Europe, on that host as on all the various species of Trifolium 
together. It would appear that the species is made up of races 
only slightly different from each other morphologically, hut with 
unequal virulence. 
Peronospora Plantaginis Underw. Bull. Torrey Club 
24: 83. 1897 
This is a quite different species from the older and better known 
P. alta Fuckel, which is common in the northern states on Plantago 
major and other broad-leaved perennial species of the genus. The 
conidiophores of P. Plantaginis are a trifle stouter, with a smaller 
head, and straighter branches, with the ultimate branchlets much 
smaller. The conidia are also shorter and not so blunt as in P. 
alta. This species is found on Plantago aristata from North 
Carolina to Alabama. In the region of Raleigh, North Carolina, 
where the writer had the opportunity of studying the fungus in 
the field it was very abundant, sometimes appearing to he quite 
injurious to its host. 
The oospores of neither P. Plantaginis nor P. alta have been 
described. It is consequently a matter for regret that the speci- 
men on Plantago pusilla from Alabama in the Ellis collection has 
no conidiophores so that the species of Peronospora could he de- 
