402 Witson: NortH AMERICAN PERONOSPORALES 
4. Rhysotheca Heliocarpi (Lagerh.) 
Plasmopara Heliocarpi Lagerh.; Pat. & Lagerh. Bull. Soc. Myc. 
France 8: 123. 1892. 
This species is known only from the type locality in Ecuador, 
where it occurs on the leaves of Heliocarpus americanus L. Ac- 
cording to Dr. Rose * the host name as given in the original de- 
scription has been applied very loosely to various members of the 
Tiliaceous genus AHeliocarpus, the species of which are widely dis- 
tributed in tropical America. It is, therefore, not improbable that 
the fungus is of more than local occurrence and that it infests 
several hosts. 
5. Rhysotheca obducens (Schrét.) 
Peronospora obducens Schrot. Hedwigia16:129. 1877. 
Plasmopara obducens Schrét. in Cohn, Krypt. Fl. Schles. 3' : 238. 
1886. 
Peronospora Impatientis Ellis & Everh. Proc. Acad. Nat. Sci. Phila. 
1891:86. 1801. ) 
Plasmopara Impatientis Berlese, Icon. Fung. Phyc. 15. 1808. 
Hypophyllous, usually on the cotyledons, the affected area 
irregular in outline, following the veins, or covering the entire sur- 
face of the leaf, white-cottony ; conidiophores fasciculate, 2-4 from 
a stoma, slender, 300-500 x 7-12 y, flexuosely branched, the 
branches usually 4-5 times branched, ultimate branchlets about 
6-9 long ; conidia broadly ellipsoid, 12-14 x 12-21 as odspores 
light yellowish-brown, 25-30 #4; epispore slightly wrinkled, or 
smooth; odgone 40-50 p. 
In his monograph Berlese recognizes both Plasmopara obdu- 
cens and P. /mpatientis as valid species, due apparently to a mis- 
interpretation of the original description of the latter species. In 
this the height of the unbranched portion only of the conidiophore 
is given. Otherwise the descriptions of the two species tally as 
closely as could be expected. Nor is this resemblance accidental, 
as the type of Peronospora Impatientis shows no perceptible points 
of difference from European material of P. obducens which was de- 
termined by Schréter himself. 
* Cont. U. S. Nat. Herb. g: 315. Ig05. 
