SUMMER MEETING AT BUTLER. 69 



In many cases as in the potato blight and rot, or the smut on corn, 

 rust, etc., nothing more than this can be done, but in certain other 

 •cases, particularly when trees and vines are attacked, there are various 

 remedies which we believe are at least beneficial. 



As stated above, it is the weakest plants, that are most liable to the 

 attacks of the vegetable parasites, and they are also most injured by 

 them. • In some cases this^weakness is caused by over bearing, by 

 €old, by heat, by injuries, but generally it is the result (^i improper 

 food. The virgin soil of Missouri will produce healthy plants, but 

 after it has been cropped for five, ten or fifty years, some of the ele- 

 ments become deficient and unhealthy growth takes place. 



Another, and a freqarent cause of weakness, aflfects plants grow- 

 ing in a very rich soil, or on land which has received an application of 

 a large amount of some nitrogenous fertilizer, as barnyard manure, 

 which will cause a rank succulent growth, and in the case of peren- 

 nials, prevent the ripenning of the wood, and the cold of the winter 

 will then be of serious injury to the plants. 



The so called ^r«5/)e mildew^ which in some years injures the grape 

 crop of the country to the amount of hundreds of thousands of dol- 

 lars, is the work of fungi. 



There are two forms of the fungus, known respectively as Feronos' 

 pora and Uncinula. They appear at about the same time, the first 

 resembling frost work on the under side of the leaves, while the 

 Uncinula^ by some considered identical with the European Oidium 

 lucTceri, gives a mealy appearance to both sides of the leaves, and in 

 some cases extends to the berries themselves. One of the best mycolo- 

 gists at the east recommends strewing sulphur over the leaves as a 

 remedy for the attack of the Uaoinula. The mycelium of Peronos- 

 pora, however, penetrates the leaves, and no external application can 

 destroy it. The only remedy is to furnish such a supply of mineral 

 food as will enable the vine to mature its fruit and also nourish its 

 parasite. The Peronospora causes the leaves to drop, but does not 

 attack the berries. 



Prof. W. G. Farlow, of Harvard College, the authority mentioned 

 above, is of the opinion that tjiis dropping ot the leaves is a good 

 thing for the c-rop, as it lets in the sunlight and hastens the ripen- 

 ing. 



On this point most botanists and horticulturists differ from him, 

 claiming that if the leaves are removed from the vine before the fruit 

 is ripe, the berries will lose in quality, especially in sweetness, and per- 

 haps drop before maturing. 



