410 Witson: NortH AMERICAN PERONOSPORALES 
Icones: Rep. U.S. Dep. Agr. 1871: pl. 4; Bull. Bussey 
Mate SF of. 2. oh 7. f, 2-8 > Bull. Til: “Lab: Nat. Hist; 2° 
Par. Fungi pl. 2. f. 6,7; Rep. U. S. Dep. Agr. 1886: Mycol. pl. 
1; Berlese, Icon. Fung. Phyc. /. P7526. 
10. Rhysotheca Viburni (Peck) 
Flasmopara 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- 
or chocolate-colored ; conidiophores fasciculate, sparingly 2-3, 
rarely 4 times branched, 300-600 x 6-8 y, ultimate branchlets 
6-8 «4; conidia broadly elliptic, rarely globose, 15-30 X I2-15 #, 
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. ribicola, from which it differs in its 
taller conidiophores, its sparser covering and more pronéunced 
discoloration of the host. 
ON CAPRIFOLIACEAE : 
Viburnum acerifolium L., District of Columbia, Waite; 
West Virginia, Waite. 
Viburnum dentatum 1., New York, Peck (cotype), Thom. 
Viburnum nudum L.., Alabama, Earle (Phyc. Prot. 8 Z). 
Viburnum Opulus L., Maryland, Fairchild. 
Viburnum pubescens (Ait.) Pursh, West Virginia, Waite 721. 
TYPE LOCALITY: Baiting Hollow Station, Long Island, N. Y., 
on Viburnum dentatum L. 
Disrripution: Central New York to Alabama. 
11. Rhysotheca ribicola (Schrot.) 
Peronospora ribicola Schrot., Jahrb. Schles. Ges, Vaterl. Kult. 
1883: 130. 1883. 
Plasmopara ribicola Schrét. in Cohn, Krypt. Fl. Schles, 3): 238. 
1886, . 
Hypophyllous, infected area usually near the main veins, ir- 
regular in outline, up to 15 mm., loosely downy, epiphyllous dis- 
