Wilson: Studies in North American Peronosporales 199 
nia with a thick, yellowish membrane which does not collapse ; 
oospores subglobose, 25-50 /*, epispore yellowish-brown, wrinkled. 5 
On Brassicaceae : 
Arabis virginica (L.) Trek, Alabama, Underwood. 
Bursa Bursa-pastoris (L.) Britton, Kentucky, Kellerman. 
Coronopus didyma (L.) J. E. Smith, North Carolina, Wilson. 
Lepidium apetalum Willd., Iowa, Wilson; Nebraska, Sheldon. 
Lepidium Virginicum L., Illinois, Seymour (Econ. Fungi 
258a) ; Kansas Bartholomew (Fungi Columb. 2129) ; Ken- 
tucky, Kellerman (Fungi Europ. 2870, N. Am. Fungi 1460b ) ; 
New Jersey, Hoisted (Econ. Fungi 258b ) ; North Carolina, 
Stevens. 
Lepidium sp., Idaho, A. A. & E. G. Heller, jopo. 
Roripa palustris (DC.) Bessey, Iowa, Hitchcock. 
Roripa sp., Alabama, Underwood. 
Sophia sp., Colorado, Bethel. 
Distribution: New Jersey to Alabama and Colorado. Also 
in Australia, and probably in Europe. 
Type Locality: Ardmona, Victoria, Australia, on Lepidium 
ruderale L. 
The three species on Cruciferous hosts may be briefly charac- 
terized as follows : P. parasitica, with much branched conidio- 
phores, the branches forming a dense tangled head, P. Niessleana 
having an open headed conidiophore which branches 2-4 times, 
the branches widely spreading and with the extremities rather 
recurved, P. Lepidii with the main branches of the conidiophore 
ascending, but not forming a dense head as in P. parasitica. 
Peronospora Schachtii Fuckel, Fungi Rhen. 1508 — 
Symb. Myc. 71. 1869 
This species, which is readily distinguished from the others 
which inhabit Chenopodiaceous hosts by the straight branches of 
5 Hypophyllis vel caulicolis, caespitulis densis, albis ; conidiophoris 3-8 
fasciculatis, 130-223 X 4-9/i, 3-8-ies ramosis, ramis inferioribus rectis, angu- 
lato-divergentibus, penultimis et ultimis subulatis, acutangulo-divergentibus, 
rectis vel saepius recurvatis, subaequalibus, circa 3 X 8fi; conidiis late ellip- 
ticis vel fere globosis, 15-22 X 18-35 /u., hyalinis ; ooginis e tunica crassa, 
pallide-lutea, persistenti formatis 35 — 60 yu. ; oosporis subglobosis, 25-50 /x, epis- 
poris luteo-bruneis, rugosis. 
