454 The Botanical Gazette. [December, 
ces Zygadent Pk. and Puccinta Hieracet (Schum.) Mart. begin 
forming also about April Ist. 
It is not always necessary that the summer spore-forms 
should be fresh in order to germinate readily, although fresh 
spores usually germinate best. Spores of 4icidium pustula- 
tum Curt. and Uredo Caeoma-nitens Schwein. collected at 
Lawrence, Kan., May 19, 1892, and placed in drop cultures 
at this station the next day, germinated freely in 31 hours, 
producing vigorous germ tubes. I have often germinated 
uredospores, after they had lain in the collecting can one or 
even twodays. Prof. B. T. Galloway, § several years ago called 
attention to the great scarcity of ash rust, 4icidium Fraxint 
Schwein., in 1888, and to the fact that various attempts, by 
the Division of Vegetable Pathology, to germinate it in dif- 
ferent media, were only partially successful at. that time. 
At the same time he suggested the question whether the rust 
might not germinate more readily in seasons of great abun- 
dance. As bearing upon this question, it may be of interest 
to say that in the summer of 1892 the rust was extremely 
abundant here, particularly on young trees, attacking the 
twigs as well as the leaves and sometimes entirely destroying 
large portions of the branches for a distance of two feet or 
more. At the same time, the spores were easily and repeat- 
edly germinated in ordinary watch glass cultures, although it 
had been difficult for me to germinate them at other times. 
I think I have observed the same fact with respect to other 
species. 
As to the length and rapidity of growth of germ tubes, 
there is great variation among the different species. ose 
of the uredospores of Puccinia Rubigo-vera represent about the 
average length, so far as my observations have extended. 
Those of Puccinia Hieracei are a little longer than the aver- 
age. (See pl. XXxvill, fig. 14.) Those of Puccinia grami- 
nis, and of various rusts on grasses, are much longer. The 
one figured in pl. xxxvill, fig. 12, has a length of 1.075 » 
and is but little, if any, longer than the average for that pat- 
ticular culture, of seventy-two hours. Uredospores of P#é- 
cinta Sorghi Schwein. sometimes show no indication of get 
mination during the first day, but finally, at the end of forty- 
eight hours, produce germ tubes of very fair length. Other 
species seem to produce their entire growth in twenty-fouf 
®Journ. Mycol. v (1889). 95. 
SS aoe lees eae 
