IOWA ACADEMY OF SCIENCE 
57 
With regard to blight of pears Waite®® says, “The thrift that makes a tree 
bear good fruit also makes it susceptible to blight. Check the tree by with- 
holding tillage so that it makes a short growth and bears small fruit and it 
will be in a better condition to withstand blight than it would were it culti- 
vated.” 
Borne Resistant Varieties. Some varieties of apples have been found to be 
more resistant to rust than other varieties; Oldenburg, Hibernal, Pameuse and 
Canada Baldwin in Iowa®® are more or less resistant. 
In observations with rust of the apple, the Mercer County crab was found 
to become affected by the Gymnosporangium macropus, while the Russian va- 
riety Tetofsky on which it was grafted, was free. 
Within recent years wide infection has resulted to the Wealthy apple from 
proximity to the Cedar apple fungus on cedar trees. Duchess and its type are 
quite free from apple scab; Wealthy is quite generally affected. 
The Early Richmond and Montmorency cherries are very subject to leaf -spot 
iCylindrosporium padi). 
Immunity from One Disease Caused Tjy Presence of Another. Regarding 
peculiar conditions obtaining in the relationship of fungus and host, Dr. Hal- 
sted®® observes that one fungus develops in the host immunity from another. 
The rust Puccinia mamillata while common upon the ordinary plants of the 
climbing smartweed {Polygonum dumetorum) was nearly absent from all in- 
fested with Ustilago anomala. It would seem that the smut had taken posses- 
sion of the plant and the latter did not longer furnish the proper feeding ground 
for the rust. The same thing was found to be true with smutted specimens of 
Panicum sanguinale, the leaves of which are rarely affected with Piricularia 
grisea, while the normal plants have foliage spotted with it. 
Transplanting. Burchard®^ calls attention to the fact that the American 
clover when grown in Europe, in spite of its more hairy character is more sub- 
ject to mildew than the home grown varieties. 
Boil Conditions as Affected by Manures. Emil Laurent®® found that the 
same variety of potato on which different fertilizers had been used showed dif- 
ferent conditions for bacteriosis. Nitrogenous and potash manures made the 
potatoes more immune toward Bacillus coli communis of artificial infection. 
The author thinks that the ability of a potato to resist bacteriosis rests upon 
the ability of the cells to produce soluble cell substances whose strength is 
utilized by alkaline conditions. 
Toxin. Miss C. E. Marryat®® states that a very susceptible variety of wheat 
was cultivated to study the effect of immunity the germ tube entering readily 
by means of passing through the stomata. In the case of a resistant Einkorn 
the germ entering through the stomata but in a short time the hyphse began 
to break up. The author suggests that immunity is due to the production of 
a certain toxin or antitoxin. 
BIOLOGIC SPECIES. 
Biological experiment with fungi is of great importance and considerable 
work has been done of recent years with the biologic species of rust and 
mildews. 
^sWaite. Report U. S. Dept. Agr. 1895:299. 
'^'’Pammel, Cedar Apple Fungi and Apple Rust. Bull. Iowa Agr. Exp. Sta. 84 :36. 
®0Mycological Notes IV. Bull. Torr. Bot. Club. 26:12-20. 
®iLandw. Wochen. bl. f. Schleswig Holstein 51 :34. 
®-Ann. De I’lnst. Pasteur 1.3:1. Centralb. f. Bakt. .u. Par. 2 Abst. 5:685. 
®3Jour. Agri. Sci. 2:129. 
