DISEASES OF VINES 95 



lessness. It may be caused by handling the berries while 

 being thinned or by draughts of cold air, but the most 

 likely cause of rust is the application of sulphur to the 

 hot- water pipes soon after the grapes have set a stage 

 of growth when the berries are very susceptible to injury 

 from coming in contact with the hand, clothing, hair of 

 the thinner's head or cold currents of air, but more 

 especially by being subjected to a sent-up volume of 

 hot sulphurated air for a period of two hours. Should 

 there be occasion to apply sulphur to the hot- water 

 pipes after the berries have stoned, or even during the 

 process of stoning, it may be done with perfect safety if 

 done in the manner recommended for mildew. 



Warts on back of Leaves. The appearance of con- 

 glomerate excrescences on the back of vine leaves is 

 answerable for the name " warts," under which these 

 symptoms are known. The so-called "warts" may be 

 the result of some sudden change in the way of heat 

 and moisture young, strong, free-growing vines being 

 subjected to a rather close, high temperature, surcharged 

 with moisture, have the flow of sap excited in the young 

 leaves to such an extent as to rupture the epidermis, 

 resulting in the exudation of sap and the formation of 

 the so-called warts. 



In order to prevent the spread of these excrescences, 

 reverse somewhat the atmospheric conditions by dis- 

 tributing only sufficient water in the house to produce 

 and maintain a growing atmospheric temperature, and 

 by admitting a free circulation of fresh air during the 

 heat of the day. The application of sulphur to the 

 hot-water pipes would cause the disorganised organic 

 warty matter to turn brown. But the case does not call 

 for special consideration in this direction. Growers 

 should guard as much as possible against having cause 

 for applying liquid sulphur to highly-heated pipes or for 

 fumigation by tobacco, or even by nicotine compound. 



