106 The Principles of Fruit-growing. 



net return of not far from one and one -half dollars 

 per tree." 



Some kinds of fruits may be advantageously pro- 

 tected by covering them with temporary (or even per- 

 manent) screens. This is extensively done in pine- 

 apple culture, in which the better varieties are grown 

 under lath or slat sheds, for the purpose of protection 

 from frost, sun and drought. Small or amateur 

 plantations of strawberries, or even of bush -fruits, 

 may be easily covered with lath screens when frost is 

 feared. 



Adding vapor of water to the air. The most 

 serious frosts usually occur when the air is dry. 

 An abundance of watery vapor in the air probably 

 tends to check the radiation of the earth's heat, and 

 the evaporation of water has a pronounced influence 

 in raising the dew-point. The means of adding 

 vapor to the atmosphere are several : Spraying, 

 flooding and irrigating, mulching and tilling. A 

 thorough spraying of plants with ordinary cold 

 water at nightfall, when a frost is feared, is one of 

 the most efficient means of protection from light 

 frosts. The machinery which is used in spraying 

 for insects and fungi may be used for this purpose. 

 Strawberries and other low plants may be wet at 

 nightfall by means of a sprinkling cart. Elaborate 

 stand-pipe devices, connecting with underground 

 pipes, have been used in California to facilitate the 

 spraying of orchards.* The flooding of fruit -plan- 

 tations to protect the plants from frost is practi 



* Se Galloway, Yearbook, U. S. Dept. Agric. 1895, J56, 



