220 
of investigations were made which showed, as suspected, that the rusts in 
question do have other means than the teliospore of surviving the winter 
and that in all likelihood they are able to propagate themselves indefinitely 
in an asexual manner, and that without serious impairment of vigor. In 
this paper it is proposed to give the results of this work and to present 
some field data, chiefly trom Indiana, which was made available to the 
writer by his access to the Arthur herbarium. This data goes to indicate 
that what is true of the grain rusts is equally true of some others which 
because of their lack of economic importance have thus far escaped this 
sort of investigation. 
DURATION OF VIABILITY OF UREDINIOSPORES. 
Before entering on the discussion proper, however, it seems best to 
treat here two points which have a bearing on what is to follow; namely, 
the duration of the viability of urediniospores. and the distance to which 
they may be blown and produce infection. As to the duration of germina- 
bility in the urediniospore, more work has been done with the grain rusts 
perhaps than with any other. In the case of Puccinia graminis Hunger- 
ford reports’ finding germinable urediniospores at Madison, Wis., on timothy 
in October, November, December, January, and March; but it does not 
seem to be at all certain that the spores used on the last named date were 
wintered spores. On the contrary, it is altogether possible that they were 
but recently produced. Mercer,? however, was not able to find germinable 
urediniospores of the same rust on the same host during the winter in 
North Dakota; and Eriksson and Henning,’ as the result of several experi- 
ments with the rust on different hosts, came to the conclusion that the 
fungus does not pass the winter in the uredinial stage in Sweden. They 
also came to the same conclusion in regard to P. glumaruwms  Bolley’ 
reported the germination of 8-15% of urediniospores of P. graminis after 
twenty-one days in dry air in August. The same investigator has shown’ 
that the urediniospores of the leaf rust of wheat can be used for successful 
infection material after thirty days’ exposure to the outside air in July, 
while Freeman and Johnson consider it possible for urediniospores of P. 
graminis and P. rubigo-vera to survive the winter in Minnesota, North 
‘Phytopathology 4:337-338. 1914. 
21. ec. 20-22. 
*Die Getreideroste 38-47. 1896. 
41. c. 153-159. 
‘Centralblatt for Bakt. Par. und Infekt. 42:893. 1898. 
*Agricultural Science 5:263. 1891. 
