TWENTY-FIBST ANNUAL MEETING. 77 



tan {Cystopus candidus No. 1518 also occurs on the same leaves); 1531, on leaves, 

 April 5, 1889, Manhattan; 1551, on leaves, April 14,1889, St. George, Pottawatomie 

 county; 1532, on leaves, April 17, 1889, Manhattan; 1611, on leaves and stems. May 

 29, 1889, Manhattan; E. Bartholomew No. 292, on leaves, stems, and capsules. May 

 29, 1889, Rooks county; 755, on leaves, June 1, 1885, Manhattan; 1612, on leaves and 

 stems, June 3, 1889, Manhattan; 1658, on capsules and stems, July 6, 1889, Man- 

 hattan. 



On Lepidiurn Virginicuni L. 



1560, on leaves and stems. May 13, 1888. 



This very abundant species is quite sensitive to moisture when brought into a dry 

 room; the conidiophores rapidly twist 1-4 times around, and the conidia fall off and 

 collapse. No mature oospores have as yet been found. 



20. Peronospora Potentillae De Bary, in Ann. Sci. Nat., ser. 4, t. XX, p. 120. [Bot. Gaz., 

 vol. VIII, p. 314; Syll., vol. VII, p. 253, No. 842.] 



On leaves of Rosaceae June, not common. 



On Geum album Gmelin. 

 1637, June 20, 1889, Manhattan; 1895, July 14, 1889, Manhattan. 



On Potentilla Norvegica L. 

 1571, June 17, 1888, Manhattan. 



In Sacc. Syll. 1. c, Berlese and De Toni put this species in the effusae. but accord- 

 ing to Farlow, Bot. Gaz. 1. c, it should be in the p)(^>^o,sitae. It is much more com- 

 mon on Potentilla than on Geum. 



21. Peronospora Cynoglossi Burrill, in litt.; N. A. F., No. 2206. (Name only.) 



'"Conidiophores slender, about 6 to 8 times dichotomously branched, widely 

 spreading, mostly somewhat flexuose; conidia subglobose to elliptical, with an 

 apical papilla, pale violet, 13-19 by 15-24//; oogonia thick-walled, brown, 40-50//; 

 oospores with thick, smooth, light-brown walls, 25-30//. Forming (on Cyno- 

 glossum) large, prominent, indefinite patches on the under surface of leaves, of 

 which the upper surface is yellowish, becoming dark-brown." 



(Occurs on Cynoglossum officinale L., Illinois.] 

 Var. (?) Echinospermi Swingle, nov. var. Not causing definite spots, usually occu- 

 pying nearly all of the upper leaves and also the stems of the plants attacked, 

 forming a rather dense, dusky coating on the affected leaves; conidiophores very 

 abundant, arising singly, or more often in groups of from 2 to 5, through the 

 stomata, hyaline, erect, 4-6 times sub-dichotomously branched, but almost always 

 with one branch much stouter and more erect than the other, 240-414// (mostly 

 275-400//) long, 8-12/v (mostly 9-11//) diam. at base, the unbranched basal portion 

 183-330// (mostly 200-280/^) long, sub-cylindrical tapering gradually above, sud- 

 denly somewhat narrowed at the base, sometimes slightly inflated just above 

 the narrowed base, branches short, stout, divergent, primary ramifications 2-5 

 (mostly 3-4) times branched with only a short unbranched portion, ultimate 

 branches short (5-16/0, rather stout, acute, straight or slightly curved, usually in 

 unequal pairs arising nearly at right-angles, the smaller one often curving back 

 slightly, the penultimate and ante-penultimate branches often somewhat curved, 

 sub-squarrose; conidia at first light-colored, oval or elliptical, when mature oval, 

 sub-globose, or rarely globose or elliptical, dusky or dull-brownish, very obtuse 

 at both ends, not papillate, 21-34x15-30//, mostly 23-33x17-28//, very soon decidu- 

 ous, wall thin, smooth, contents homogeneous or sparingly and irregularly gran- 

 ular; oospores not seen. 



On leaves and stems of Boragineae June. 



