204 
Mycologia 
rounded, while the conidiophores present still more marked con- 
trasts. In the American species the conidiophores are more 
branched than in either of the European species, the branches are 
rather flexuose and incurved, forming a denser head than in either 
of these species. In our species, the conidiophore branches are 
more slender and the ultimate branchlets longer than in the Euro- 
pean. As this series of differences is sufficient to warrant the 
separation of our form as a distinct species, a diagnosis follows, 
under the name Pcronospora Chamaesycis, as all its hosts belong 
to this segregate of Euphorbia. 
Peronospora Chamaesycis sp. nov. 
Hypophyllous, forming a dense bluish felt-like growth on the 
host, epiphyllous discoloration not prominent, rather chloratic or 
somewhat yellowish ; conidiophores solitary or only two or three 
from a stoma, 200-450X6-10 /x, branching 6-9 times, the branches 
elongate, slender, more or less flaccid, and having a tendency to 
be incurved, more or less flexuose, the ultimate branchlets at 
right angles, subequal, the axial longer, somewhat subulate, slen- 
der, straight, 5-8X2-4/A; conidia globose to ovoid, 20-28X12- 
20 fi, violet ; oogonia thin walled, yellowish ; oospores 30-40 fi, 
yellowish-brown, epispore smoothish or more or less wrinkled. 12 
Type, on Chamaesyce serpens (H.B.K.) Small, Rooks County, 
Kansas, E. Bartholemew, Aug. 25, 1902. Issued as Fungi Col- 
umbiana 1750, in the herbarium of the New York Botanical 
Garden. 
On Euphorbiaceae : 
Chamaesyce glyptosperum (Engelm.) Small ( Euphorbia glyp- 
tosperum Engelm.), Nebraska, Bates (Fungi Columb. 2338). 
Chamaesyce humistrata (Engelm.) Small ( Euphorbia humi- 
strata Engelm.), Indiana, Wilson. 
Chamaesyce maculata (L.) Small ( Euphorbia maculata L.), 
Illinois, Conkling; Indiana, Arthur Wilson; Iowa, Hitch- 
cock ', Wilson; Massachusetts, Farlow (N. Am. Fungi 216) ; 
New Jersey, Ellis. 
12 Maculis epiphyllis decoloratis, griseo- vel diluto-aureiis ; conidiophoris 
hypophyllis, dense caespitosis, 1—3 e stomatibus erumpentis, 200—450 X 6 —io/x, 
6-9-ies ramosis, ramis elongatis, gracilibus, flaccidis, incurvatus, flexuosis, 
ultimis subequalibus, axilibus longiore, subulatis, rectis, 5-8 X 2-4 /a; conideis 
globosis vel ovoideis, 20-28X12-20^, violaciis; oogoniis auriis ; oosporis 
30-40 /x, aureo-bruneis, episporeis crassis. 
