Witson: NortH AMERICAN PERONOSPORALES 403 
On BALSAMINACEAE : 
_ Impatiens aurea Muhl., Alabama, Zarle & Underwood ; 
Indiana, Arthur ; lowa, Holway. 
Linpatiens biflora WNalt., Connecticut, Underwood 2981 ; 
Delaware, Commons (type of Peronospora Lmpatientis 
Ellis & Everh.) Jackson 1572, District of Columbia, 
Williams » Indiana, Olive, Underwood, Wilson; Mass- 
achusetts, Farlow, Halsted & Farlow (N. Am. Fungi 
207), Seymour (Econ. Fungi A7a, on “ Impatiens 
sp."), Zrelease ; Michigan, Merrow (Econ. Fungi A7é, 
on ‘ /mpatiens sp.”); New York, Dudley & Under- 
wood ; Wisconsin, Davis, Pammel. 
Impatiens sp., West Virginia, Sheldon. 
Type Locauity : Rastatt, Germany, on /mpatiens Nolitangere L. 
DistRIBUTION: Vermont to Minnesota, southward to Alabama. 
Also in Europe. 
Icon: Berlese, Icon. Fung. Phyc. p/. r5. 
6. Rhysotheca Halstedii (Farl.) 
Peronospora Halstedii Farl.; Ellis, N. Am. F ungi 209. 1879. 
(Hyponym); Proc. Am. Acad. 18:72. 1883. 
Peronospora Halstedii Ambrosiae Ellis, N. Am. Fungi 2ro. 1879. 
(Hyponym.) 
Plasmopara Halstedii Ber\. & De-Toni, in Sacc. Syll. Fung. 7 : 242. 
1888. 
Hypophyllous, on cotyledons and leaves, the affected area 
small, 1-3 mm., or extending over the entire leaf; conidiophores 
fasciculate, slender, 300-750 w, 3-5 times branched, ultimate 
_ branchlets 8-15 » long, verticillate below the apex of the branch- 
_ ing axis which is frequently swollen and ganglion-like ; conidia 
_ Oval or elliptic, 18-30 x 14-25 “; odspores 30-32 #; epispore 
yellowish-brown, somewhat wrinkled. 
: This is the most unsatisfactory species of a difficult genus. 
| The conidiophores are very variable, especially in the laxity of their 
__ branches and the development of the ganglion-like swelling from 
which the ultimate branchlets arise. Several forms are clearly 
distinguishable and are apparently valid species, but further search 
has invariably brought to light intermediate forms connecting the 
extremes with the typical form and with other forms. Until an 
