221 
Dakota, and Wisconsin.’ Fromme has shown’ that the period of viability 
in the leaf rust of oats, P. coronata, may be as extended as eighty-four days. 
The spores in this case were stored dry in a gelatin capsule. Marshall 
Ward’ succeeded in securing germination of unrediniospores of P. dispersa 
which had been for sixty-one days in dry air in the diffused light from a 
north window. Thus, while urediniospores are capable of germinating as 
soon as mature, they are capable under proper conditions of maintaining 
their viability for a period of two to three months and probably more. 
One of these conditions seems to be dryness. Probably the most common 
limiting factor to long life of urediniospores in nature is a combination of 
warmth and moisture. In such a case germination probably takes place, 
thus of course forestalling any long duration of life in the spore. ‘There 
Seems to be no good reason, however, if germination can be avoided, why 
urediniospores might not survive the winter. That coldness of weather 
does not destroy ability to germinate is attested by the fact that a number 
of investigators—Hungerford,”, Ward," Carleton,” and others—have col- 
lected viable urediniospores of various grass rusts during the winter 
months. 
DISTANCE WHICH WIND BLOWN SPORES TRAVEL AND PRODUCE INFECTION. 
It seems to be a fact, although from the nature of the case not fully 
proved, that urediniospores of the rusts may travel long distances by the 
wind and produce infection. This, of course, is to be expected of a struc- 
ture which can stand drying for so long a time and is so light in weight. 
Klebahn™ calls attention to a sand storm which arose in northern Africa 
and progressed northward over Europe, transporting various mineral 
particles to various places in Europe. He adds that without doubt the rust 
spores, which are much lighter than the mineral particles, are much easier 
transported by air currents. Under the circumstances they would remain 
suspended much longer and could be carried at least as far and perhaps 
farther than the mineral particles. The same investigator proved the 
presence of spores in the air high off the ground by constructing traps for 
the spores and exposing them in trees and on buildings. He was able in 
7Bur. Plant Ind. Bull. 216:52. 1911. 
sBull. Torrey Club 40:518. 1913. 
“Ann. Mycol. 1:138. 1903. 
Phytopathology 4:337-338. 1914. 
Ann. Mye. 1:132. 1903. 
“Div. Veg. Phys. and Path. Bull. 16:44. 1899. 
13Die wirtswechselnden Rostpilze 68. 1904. 
141. ¢. 68. 
