June 14, 1924 
Leaf Rusts of Rye and Barley in the United States 
1121 
These results are the more striking when one considers that the teliospores 
were subjected to sudden and extreme temperature changes, from low winter 
temperature to the warm temperature of the greenhouse. They then were 
placed out of doors and again suddenly subjected to low temperatures and the 
drying effects of freezing. Such treatment certainly would be expected to be 
fatal to any except the most hardy spores. This may explain why some of the 
collections did cease to germinate before spring. From the information now 
available, it would appear that in this country the teliospores of the leaf rust of 
rye, as a general rule, are capable of germinating whenever conditions are favorable 
either in the fall or, surviving the winter, in the spring, or both. The repeated 
germination of some of the collections would indicate that differences existed 
among the teliospores as to dormancy, otherwise one would expect all the spores 
to germinate when germination was first observed. 
It is difficult to draw conclusions with reference to a rust of this type in which 
the telia long remain covered by the epidermis, as the length of time the epi¬ 
dermis remains over the telium may prove to be a factor. It is well known, 
however, that in some species of rusts, especially short-cycled species of Puccinia, 
there are to be found in the same telium spores which germinate at once and 
others which germinate only after a considerable resting period. 
What the significance of the difference in action of the collections may be is 
difficult to say. While most of the collections which germinated in the fall con¬ 
tinued to germinate until well into the winter, one showed germination only on 
September 12, and, although tested 13 times during the winter and spring, gave 
no more evidences of germination. Four others germinated only up to January 
5. On the other hand, one collection gave no germination until March 8, although 
tested previously 10 times throughout the fall and winter. It is possible that in 
this country the leaf rust of rye may be made up of different strains differing, 
among other things, in the length of time which it takes to mature their telio¬ 
spores and in the ability of these to overwinter. On the other hand, these differ¬ 
ences may be due largely to environmental conditions under which the spores 
developed. These are questions which are difficult to solve as the leaf rust of 
rye, unlike some of the leaf rusts of native grasses, does not form its teliospores 
upon seedlings, and the time and care which would be necessary to grow different 
pure cultures of leaf rust of rye on maturing plants under controlled conditions 
has made it thus far impracticable to attempt to investigate this phase. 
The writers’ observations to the effect that all the teliospores of Puccinia dispersa 
necessarily do not germinate in the late summer and fall, but some at least may 
remain dormant during the winter, support the original statements of DeBary 
(3) as to the germination of the teliospores of this rust after overwintering, which 
have been somewhat questioned. It always has been difficult to determine how 
the aecial infection occurring in the fall can figure importantly in the winter 
survival of the rust. Certainly if the rust should not hibernate in the uredinial 
stage on the rye plant itself, the autumnal aecia can not be a factor in its survival. 
On the other hand, under such conditions, those teliospores which remain dormant 
until the next spring may be of importance in regions where the rust does not 
overwinter on rye itself and the aecial host is present. 
From still another point of view, it is interesting to note the germinative 
ability of the teliospores of Puccinia dispersa subsequent to their winter survival. 
Eriksson was influenced to separate the leaf rust of wheat as a species, Puccinia 
triticina , from the leaf rust of rye largely because the former, unlike the latter, 
was unable to infect Anchusa and because the teliospores of the leaf rust of wheat 
germinated only after overwintering, while those of rye germinated shortly after 
harvest and did not overwinter. Here it may be pointed out that during the 
