410 Witson: NortH AMERICAN PERONOSPORALES 
Icones: Rep. U.S. Dep. Agr. 1871: p/. z; Bull. Bussey 
et te Pl cfr pl.3i:f. 2-8 ; Bull..I. Lab Nat. Hist ae 
Par. Fungi pl. 2. f. 6,7; Rep. U. S. Dep. Agr. 1886: Mycol. pl. 
1; Berlese, Icon. Fung. Phyc. p/. 77, 78. 
10. Rhysotheca Viburni (Peck) 
Plasmopara Viburni-Peck, Rep. N. Y. State Mus. Nat. Hist. 43: 
: 74. 1890. 
Hypophyllous, affected areas irregular in outline, 3-10 mm. 
in diam., marginal or following the larger veins, sparingly white- 
downy, epiphyllous discoloration none to dark reddish-brown 
or chocolate-colored; conidiophores fasciculate, sparingly 2-3, 
rarely 4 times branched, 300-600 x 6-8 yp, ultimate branchlets 
6-8 »; conidia broadly elliptic, rarely globose, 15-30 X 12-15 #, 
or larger ; odspores unknown. 
The present species and the two following ones form a distinct 
group, and are very closely related ; all of them are poorly under- 
stood and by no means common in collections. The present 
species is especially close to R. ribico/a, from which it differs in its 
taller conidiophores, its sparser covering and more pronounced 
discoloration of the host. 
On CAPRIFOLIACEAE : 
Viburnum acerifolium 1, District of Columbia, Waite; 
West Virginia, Waite. 
Viburnum dentatum L., New York, Peck (cotype), Thom. 
Viburnum nudum L., Alabama, Earle (Phyc. Prot. 81). 
Viburnum Opulus L., Maryland, Fairchild. 
Viburnum pubescens (Ait.) Pursh, West Virginia, Wazte 721- 
TyPE Locaity: Baiting Hollow Station, Long Island, N. Y., 
on Viburnum dentatum L. 
DistripuTion: Central New York to Alabama. 
ee 11. Rhysotheca ribicola (Schrot.) 
. _ Peronospora ribicola Schrot., Jahrb. Schles. Ges. Vaterl. Kult. 
eas 1883: 139. 1883. 
Plasmopara ribicola Schrot. in Cohn, Krypt. Fl. Schles. 3': 238- 
2 1686, : 
_ Hypophyllous, infected area usually near the main veins, It- 
egular in outline, up to 15 mm., loosely downy, epiphyllous dis- 
