WHITE-PINE BLISTER EUST. 49 
SORI ON COTYLEDONS. 
The cotyledons of young Ribes seedlings are apparently quite sus- 
ceptible to infection by seciospores and urediniospores of Cronartium 
ribicola. Relatively heavy infection has resulted from inoculations 
on the lower surface of cotyledons of Ribes americanum, R. missouri- 
ense, R. oxyacanthoidas, R. rotundi folium, R. glandulosum, and R. 
fasciculatum seedlings in the greenhouse and on R. glandulosum in the 
field. 
SORI ON FLORAL BRACTS AND BUD SCALES. 
Infection was secured by Gravatt from inoculations of the floral 
bracts of Ribes aureum in several different cases in the greenhouse. 
Infection of opening buds and of bud scales merits more investiga- 
tion. McCubbin (85) suggested the possibility of infection of partially 
open buds in the fall and the overwintering of the fungus, but he 
could not prove that it occurs. Infection of young leaves scarcely 
out of the bud occurs, but it seems to be limited t© leaves that are 
relatively mature, though small. (See discussion on pp. 44 to 46.) 
Search for infections of buds on heavily infected Ribes nigrum bushes 
failed to reveal any infections (151 , p. 44) . Gravatt made inoculations 
of buds about to open, but with no success. York 30 has inoculated 
successfully an inner bud scale of Ribes nigrum. 
SORI ON PETIOLES. 
Next in frequency to infection of the lower surface of the leaf 
blade is infection of petioles. The first published account of this, 
so far as the writer knows, was given in 1912 (133, 134, 135) and 1913. 
At that time it was considered to be very uncommon. Since than 
a considerable number of such cases have been noted both in the 
greenhouse and out of doors. The following species have developed 
uredinia or telia, or both, upon petioles, as many as 25 or more 
petioles on a single plant being thus attacked: Ribes americanum, 
R. aureum, R. bracteosum, R. cereum, R. culverwellii, R. cynosbati, 
R. divaricatum, R. eryihrocarpum, R. fasciculatum, R. giraldii, R. 
glandulosum, R. inerme, R. lacustre, R. nevadense, R. nigrum, R. 
parishii, R. petraeum, R. robustum, R. setosum. The following 
cultivated varieties have had petiolar attacks: Ribes nigrum hort. 
vars. Black Victoria, Climax, and Seabrook Black; R. reclinatum 
hort. vars. Berkeley, Golden Prolific, Poorman, Transparent, and 
Van Fleet; R. vulgare hort. var. White Imperial. Some 10 or 12 
as yet unidentified species collected by Beattie in the Rocky Mountain 
and Pacific coast regions have exhibited the same phenomenon. 
so York, H.H. Op.cit. 
46103°— 21— Bull. 957 4 
