[From the BULLETIN oF THE TORREY BoranicaL Cuus, 34: 61-84 1907. 
Studies in North American PeronosPorales—I!, The genus Albugo 
Guy WEsT WILSON 
The North American species of Peronosporales offer a rich 
field for investigation. Containing as this order does some of 
the worst fungous pests of the farm and garden, extensive studies 
of certain species were undertaken at an early date in our myco- 
logical history, yet our present knowledge of the group is very 
fragmentary. The greater part of the printed information con- 
cerning it consists of notes on various species scattered through 
articles of a general mycological nature. Some species have been 
made the subject of independent articles, while few papers deal 
with a considerable number of species. Only two of these are 
comprehensive in scope. One is a series of notes by Swingle * 
upon the specimens in the herbarium of the Division of Vegetable 
Pathology, the other is Dr. Farlow’s monograph,{ which includes 
thirty-eight species and requires less than an octavo page for a 
complete host index. Since then the number of species credited 
to North’‘America has almost doubled and the list of hosts increased 
Many fold, 
The genus Albugo constitutes the family A/éuginaceae, the spe- 
cies of which bear a superficial resemblance to the Uredinales, from 
which they are readily distinguished by the light color and glisten- 
Ng appearance of the sorus and by the unsculptured conidia which 
are borne in chains. More marked points of difference, but not so 
readily observed, are the germination of all spores by zoospores 
Instead of by germ-tubes, and the production of sexual oospores. 
The odspores of all the North American species have been 
Studied, in the preparation of the present paper. Upon the basis of 
S°spore-characters the species fall into two well-defined groups. 
The first of these includes the North American A. candida, A. 
Lpomocae-panduranae and A. Lepigoni, and the foreign A. sibirica and 
A. tropica. This group is characterized by having the epispore of the 
*Jour. Myc. 7: 109-130. 1892. 
Tee, Gaz 8: Pie gece 9: 37-40. 1883-84. 
61 
