56 
IOWA ACADEMY OF SCIENCE 
ern part of the state. This shows that when the source of infection occurs that 
a disease may become troublesome and serious. 
Clasterosporium. Rudolph Aderhold^^ calls attention to the Clasterosporium 
carpopMlum which is especially destructive to cherry leaves in Germany, and 
that the same attacks the younger leaves more readily than the older. 
IMMUNITY AND DISEASE-RESISTANT VARIETIES. 
Acclimatization. In general acclimatization is the best dependence for im- 
munity from fungus diseases. A plant thoroughly acclimated is more disease- 
resistant than one not acclimated. 
Corn brought from tropical countries and cultivated in Iowa has a strong 
tendency to become affected by both smuts and rusts. 
A case of the kind was referred to by one of us'^^ on some corn from the 
Philippine Islands, a number of years ago; every ear was affected with smut, 
many nodes likewise containing the same fungus. 
A variety of Texas rust-proof oats^^ when grown on the College Campus was 
found to be more seriously attacked than acclimatized varieties. 
During the past few seasons, Mr. Burnett, has had under cultivation a large 
number of varieties of oats. Invariably the varieties not acclimatized were 
more subject to rust than other kinds. The Garton oats, well known for 
valuable qualities, when grown in cooler climates produce smaller crops on 
account of rust; after having been grown tw^o or three years in this country 
they are less subject than when first imported. Such acclimated varieties as 
Early Champion and Khersoen are much freer from rust than the non-acclimated 
varieties from Europe, the north or from the mountainous districts of our 
country. 
Prof. Bolley^% commenting upon the stableness of varieties states: “Though 
I have worked with many varieties and strains of wheat, flax and potatoes and 
ha(Ve found them all reasonably stable if given generally stable environment, 
I have never yet been sure that I have seen a stable plant or a stable strain or 
variety. Some change is continually taking place and any change I think, 
may be fixed just in proportion as we know the conditions which originate it.” 
Prof Bolley says®'^: “The North Dakota Experiment Station has had a very 
marked success in breeding and selecting flax with a view to gaining resistance 
to wilt and rust; indeed it has largely solved the problem so far as breeding 
for resistance in seed crop is concerned.” 
The work in selection of Clover resistant to Collet otricliiim trifoUi, by Bain 
and Essay®® resulted in a decided reduction of the disease. 
Of sugar-cane in Hawaii, Mr. Cobb®h says, “The chances seem distinctly to 
favor the ultimate securing of resistant varieties that are also highly pro- 
ductive.” 
The Le Conte pear succeeds best in the Gulf Coast and Southern Atlantic 
regions being quite free from blight, more so than Kieffer pear. 
'^iLa.ndw. Jahrb. 30:771. Biedermann’s Centralb. Agrikultur cliemie 32:23. 
®2Pammel, L. H. Monthly Review of the Iowa Weather and Crop Service. 2:9, 
^spammel, L. H. Fungus Diseases of Iowa Forage Plants. Pro. Iowa Acad. Sci. 1:93. 
=54Rept. Am. Breeder’s Assn. ^ 1908: 125, 128, 129. 
s^Rept. Am. Breeder’s Assn. .4 1908: 228. 
s®Bull. Tenn. Agr. Exp. Sta. 75. 
®"Cobb, Some Elements of Plant Pathology. 43. 
