230 
plainable by assuming that some urediniospores or mycelium survived the 
winter. 
It seems fair, then, to judge from the foregoing that a good many rusts 
can pass the winter and propagate themselves for a long time, and probably 
indefinitely, without the intervention of sexual reproduction. This is in 
line with the experience of Freeman and Johnson, who carried Puccinia 
graminis, P. rubigo-vera, and P. simplex through 52 uredinial generations 
Without apparent degeneration, and of Fromme," who similarly carried P. 
coronifera on oats through thirty-seven uredinial generations, and of car- 
nation raisers generally, who still find the carnation rust an ehemy to be 
fought although it has in all probability never produced an iecium on this 
continent. 
The evidence, therefore, which is to be gained from the behavior of the 
rusts concerning the question as to whether or not a plant species can long 
Inaintain a high degree of vigor without sexual reproduction is quite 
definitely in fayor of the idea that it can. True it is that in the long cycled 
rusts an effect of stimulation follows the stage in which the sexual fusions 
take place, but this effect becomes dispelled by one or two uredinial genera- 
tions, so that the rust is then back at the old level of vigor; and it remains 
there through an indefinite number of uredinial generations. 
Purdue University, 
Lafayette, Indiana. 
“Bur. Plant Ind. Bull. 216:34. 1911. 
“Bull. Torrey Club 40:510-511. 1918. 
