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Witson: NortH AMERICAN PERONOSPORALES 73 
Cystopus spinulosus de Bary, in Rabenh. Fungi Europ. 479. 1862. 
Cystopus cubicus de Bary, Ann. Sci. Nat. IV. 20: 132. 1863. 
Cystopus pulverulentus B. & C. Jour. Linn. Soc. Bot. 10: 357 
1869. 
Cystopus brasiliensis Speg. Bol. Acad. Ci. Cordoba 11: 481. 1889. 
Albugo spinulosa Kuntze, Rev. Gen. Pl. 2: 658. 1891. 
Cystopus Tragopogonis spinulosus Davis, Trans. Wis. Acad. 11: 
165. 1897. (Hyponym.) 
Cystopus Mikaniae Speg. Ann. Mus. Nac. Buenos Aires III. 1: 
67. 1902. 
Sori hypophyllous or caulicolous, prominent, deep-seated, 
white or yellowish, pulverulent, rounded or elongate, I-3 x 1-8 
; Conidiophores hyaline, clavate, about 12-15 X 40-50; 
conidia light-yellow or hyaline, short-cylindric, the terminal larger 
and less angular than the lower, membrane with an equatorial 
thickening, 12-15 x 18-22; oospores produced in the stems and 
leaves of the host, dark-brown or almost black at maturity, very 
°paque, 44-68 2; epispore reticulate, areolae 2, wing bearing 
Papillate tubercles at its angles. 
The oospores, which are produced in the leaves or rarely in 
the stems of the host, have been examined from a number of 
Merican and European specimens on hosts representing A mérost- 
“ceae, Cichoriaceae and various tribes of Carduaceae. The wing 
of the reticulation is lowest in specimens from the first families 
mentioned, while those on Carduus are scarcely more pronounced, 
‘Ne Odspores from various species of Senecio have the widest 
wing, while those from Mazrricaria are intermediate between those 
last mentioned, Odspores produced on Parthenium have broader 
and lower reticulations than do the majority of specimens ex- 
aimined. It is however apparent that the American as well as the 
European material on the tribes Cynareae, Senecioneae, Anthemideae 
and Heliantheae belong to the same species. The only other North 
Merican hosts of this family for an A/éugo, so far as is known, 
“re of the tribe Zu/eae. As no American material on these hosts 
Contained odspores, they were studied from European specimens 
and found to be identical with those produced on other members 
of Carduaceae. It appears from this that the American material 
from hosts of this tribe should be referred to the present species. 
hile there are minor differences in the conidia and in the rela- 
