Nov. 1905 ] The Genera Bala?isia a?id Dothichloe ) Etc. 
263 
host, or to some accidental injury. Having once obtained a foot¬ 
hold in the new host there would be a chance of its adaptation to 
the new environment and the acquirement of new biological prop¬ 
erties which would enable it to attack other individuals of the 
same host, just is it is possible now, by artificial means to trans¬ 
plant one biologic form of a parasite from its normal non-resist¬ 
ant host over to another host which under ordinary conditions is 
immune or not susceptible to this biologic form 34 . 
The development of new varieties of grasses as well as the 
tests of feral species which are now being carried on by the 
United States Department of Agriculture for the purpose of se¬ 
lecting those species which are suitable for cultivation, and also 
the cultivation of these or old varieties under new conditions of 
environment or with more intensive methods of cultivation or se- 
letion may play an important part in opening the way for the 
propagation, distribution and increasing adaptation of these fungi 
so that their injuries may be greatly increased. Some such course, 
or phase of evolution as outlined here probably has marked the 
history of most of the fungi parasitic on domesticated plants and 
accounts in a measure for the sudden outbreaks of biologic forms 
on hosts formerly immune, of the sudden appearance of a para¬ 
site in greatly increased virulence of attack which formerly pro¬ 
duced very limited injury, or of the migration of parasitic fungi 
from ferel plants to domesticated ones where in the new and often 
more favorable environment the disease caused by it does great in¬ 
jury and becomes a permanent menace to the successful cultiva¬ 
tion of the host. 
Balansia hypoxylon has been found on Danthonia spicata in 
the Northern United States and in Nova Scotia and probably oc¬ 
curs sparingly throughout the normal distribution of this host. 
That it occurs on other species of grasses is shown in its collec¬ 
tion by Long in Texas on an undetermined species of grass, 
which however is not Danthonia spicata, and possibly it is the 
same species of grass on which was collected the conidial stage, 
Ephelis mexicana in Mexico, and it also occurs on a grass in South 
Carolina as shown above. The fungi on these hosts are probably 
one species and are so, treated in the present paper. This indi¬ 
cates that the fungus may in the future be found on other hosts 
or even may spread to new ones. Whether the forms on the dif- 
34 See Salmon, E. S., Cultural Experiments with Biologic Forms of 
the Erysiphaceae, Ann. Bot., 18 , 320, 321, 1904. Proc. Roy. Soc., 73 , 116- 
118, 1903. Proc. B. A. A. S. Southport meeting, 1903. On specialization in 
Parasitism in the Erysiphaceae. Beihefte 2, Bot. Centralb., 14 , Heft 3, 
261-315, pi. 18, 1903. 
Cultural experiments with the Barley Mildew, Erysiphe graminis 
D. C., Ann. Myc., 2 , 70-79, 1904. The New Phytologist, 3 , 109-121, 1904. 
Ann. Myc., 3 , 172-184, 1905. On Erysiphe graminis D. C., and its adap¬ 
tive parasitism within the genus Bromus, Ann. Myc., 2 , 255-267, 307-343, 
1904. 
