TWENTY-FIB ST ANNUAL MEETING. 81 



26. Peronospora grisea Unger, in Bot. Zeit. 1847, p. 315. Botkytis gbisea Unger, Die 

 Examtheme der Pflanzen, S. 172 (1833). [Bot. Gaz., vol. VIII, p. 330; Syll., vol. 

 VII, p. 255, No. 8.52.] 



On leaves of Scrophulariaceae May; not common. 



On Veronica peregrina L. 



1549, May 13, 1888, Manhattan. 



27. Peronospora Hedeomae Kell. & Sw. n.sp. Not causing definite spots, usually occu- 

 pying nearly all of the lower leaves of the plant (or portion of the plant) attacked, 

 forming a rather sparse, dusky layer on the under surface of the leaves, or more 

 rarely on the stems or floral-bracts. Conidiophores hyaline, erect, 4-9, mostly 

 5-8, times dichotomously branched, but almost always with somewhat unequal 

 branches, 160-465// long, mostly 225-390//; 6-12//, mostly 8-11// diameter at base. 

 The unbranched basal portion 80-240//, mostly about 100-200// long, nearly cylin- 

 drical or tapering above, abruptly narrowed at the base, sometimes once or even 

 twice inflated at a short distance from the base; branches long, rather stout, 

 somewhat spreading, primary ramifications straight, unbranched for a consider- 

 able distance; ultimate branches short (6-12//), thick, sub-acute, slightly curved 

 or straight, usually in unequal pairs arising nearly at right angles to each other, 

 never forcipate; the penultimate and ante-penultimate branches often curved so 

 as to be nearly parallel for some distance. Conidia at first globose hyaline, but 

 when mature fuscous, obovate or obovate-elliptical, sometimes elliptical or oval, 

 usually more acute at the base; not papillate, 21-32x13-22//, mostly 24-30x14-17//, 

 very early deciduous; wall very thin, smooth, contents homogeneous. Oospores 

 globose or sub-oval, nearly hyaline or of a slightly yellowish color, 22.2-31/' diam., 

 mostly 25-29// diam.; epispore rather thin (2^-3//), smooth, often marked with 

 rather short hyaline elevations, contents finely and evenly granular, sometimes 

 with a large central gutta; oogonia large, usually somewhat oval, 30-50x27-36//, 

 mostly 33-45x30-35/', not fitting the oospores closely. 



Oospores and conidia on leaves and stems of Labiateae February and May to 

 June; most abundant in May. 



On Hecleoma hispida Ph. 



1576, on leaves, February 3, 1889, Manhattan; 1548, on leaves and stems, with 

 young oospores, May 4, 1888, Manhattan; 1610, on leaves and stems, with a few 

 oospores. May 18,1889, Manhattan; 1550, on leaves and stems, with mature oospores. 

 May 20, 1888, Manhattan; 1(571, on leaves and stems, with immature oospores, May 

 20, 1889, Manhattan; 1613, on leaves and stems, with mature oospores. May 22, 1889, 

 Manhattan; 1595, on leaves, with mature oospores, June 6, 1889, Manhattan; 1636, 

 on leaves and stems, with a few oospores, June 18, 1888, Manhattan. 



This species is rather abundant on plants about Manhattan. The diseased plants 

 are stunted and become yellowish-green, or sometimes reddish-green. The afflicted 

 leaves finally turn black, and usually fall to the ground, leaving the stems bare. It 

 differs from Peronospora Lamii and P. Sivinglei in the shape and size of the conidia, 

 and from P. Swinglei in having much smaller oospores. It differs from P. Lophanthi 

 in having stouter conidiophores, without forcipate tips, in the shape and size of the 

 conidia, and in color of the oospores. All attempts to induce germination of the 

 conidia failed. 



—6 



