CL LL  ———— 
Witson: NortTH AMERICAN PERONOSPORALES 7S 
Cystopus spinulosus de Bary, in Rabenh, Fungi Europ. 479. 1862. 
Cystopus cubicus de Bary, Ann. Sci. Nat. 1V. 20: 132. 1863. 
Cystopus pulverulentus B. & C. Jour. Linn. Soc. Bot. 10: 357. 
1860. 
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.) f 
Cystopus Mikaniae Speg. Ann. Mus. Nac. Buenos Aires III. 1: 
B7.- 1902. 
Sori hypophyllous or caulicolous, prominent, deep-seated, 
white or yellowish, pulverulent, rounded or elongate, I-3 x I- 
mm.; 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 18-222; odspores produced in the stems and 
leaves of the host, dark-brown or almost black at maturity, very 
opaque, 44-68 2; epispore reticulate, areolae 2 y, wing bearing 
papillate tubercles at its angles. 
The odspores, which are produced in the leaves or rarely in 
the stems of the host, have been examined from a number of 
American and European specimens on hosts representing Ambrost- 
aceae, 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. 
The oospores from various species of Senecio have the widest 
_ wing, while those from JMatricaria are intermediate between those 
last mentioned. Odspores produced on Parthenium have broader 
and lower reticulations than do the majority of specimens ex- 
amined. 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 
American hosts of this family, for an Albugo, so far as 1s known, 
"ate of the tribe Zuu/eae. As no American material on these hosts 
_ Contained odspores, they were studied from European specimens 
| 4nd found to be identical with those produced on other members 
| % Carduaceae. It appears from this that the American material 
- ftom hosts of this tribe should be referred to the present species. 
While there are minor differences in the conidia and in the rela- 
