PHYSIOLOGICAL CHARACTERS 87 



soils, especially those abundantly supplied with nitrogen, luxuri- 

 ant growth is induced with diminished fruitfulness, and poorly 

 colored fruits, although the size may be increased. These are 

 general statements, to which there may be exceptions, and which 

 affect different fruits in varying degrees, but they illustrate 

 some of the kinds of variations that may be looked for in classify- 

 ing fruits taken from different environments. 



129. Variations caused by cultivation. — Used in its broad 

 sense to include tillage, pruning, irrigation, fertilizing, spacing 

 plants, thinning and all of the items of care which the cultivator 

 gives his plants, cultivation is as provocative of variations in 

 fruits as soil or climate. Apples grown in sod bear smaller 

 redder fruits than those from cultivated trees. Under irriga- 

 tion all fruit-plants produce larger fruits which are usually 

 thought to be less richly flavored than those on land not irri- 

 gated. Bunch and berry of the grape are modified by the method 

 of pruning the vine. In a study of varieties for classification, 

 identification, or to determine value, the student must take into 

 account the cultural treatment the plants have received. 



130. Variations caused by stocks. — To propagate true to 

 name cultivated fruit-trees are nearly always unions of two 

 plants. The fruiting part develops from a graft or bud taken 

 from a parent variety and is the cion. The stem or root upon 

 which the cion develops is the stock. In the adjustments of 

 stock and cion to each other there are reciprocal influences, 

 which, especially in the case of the cion, must be considered by 

 the systematist in pomology. The stock is found to influence 

 the cion in several ways: It usually modifies the size of the 

 cion ; the adaptability of a variety to a soil is regulated by the 

 stock; the relations of the variety to climate may be modified; 

 age of bearing, productiveness, and other fruiting habits are 

 influenced ; the time of maturity may be changed ; size, color 

 and quality of fruit are usually influenced ; some stocks shorten 

 and others lengthen the life of the trees of which they are a 

 part. These examples of variations caused by the stock make 

 plain the necessity of knowledge about the stock upon which 

 the tree and fruit to be classified were produced. 



