402 BOTANY OF CROP PLANTS 



are from two to five blossoms, usually two, in each bud. 1'he 

 flowers are in umbels, as a rule. The flowers and fruit of 

 cherries are, morphologically, similar to those of plums. 



The leading commercial varieties of cherries grown in 

 Cahfornia have been shown to be self-sterile. It is altogether 

 possible that sterility in cherries is widely spread. 



Groups of Cherries. — ^According to Bailey the principal 

 cultivated cherries are from two species, Prunus avium, the 

 sweet cherries, and Prunus cerasus, the sour cherries. 



PRUNUS AVIUM (Sweet Cheny) 



Description. — The sweet cherry is a tall tree, strong-grow- 

 ing, long-lived, and frequently attains a diameter of i foot 

 or more. The bark is gray-brown, the outer layer often 

 being roughened; lenticels are inconspicuous. The leaves 

 are thick, oval, ovate or obovate, 4 to 12 centimeters long, 

 abruptly short-acuminate, irregularly and coarsely toothed, 

 or doubly so, green and smooth above, lighter beneath, 

 slightly hairy on the veins, more or less drooping, and with 

 long slender petioles. Flowers appear with the leaves, in 

 lateral, sessile umbels; the flower pedicels are 3 to 6 centi- 

 meters long; the petals are white, and the stamens 35 or 36. 

 SeH-sterihty has been reported in the sweet cherry orchards 

 of the Northwest. The fruit is variously colored, spherical 

 to heart-shaped, with flesh soft or hard, usually sweet, and 

 with the skin adherent to the flesh. 



GeographicaL — The species is a native of Europe. It has been cultivated 

 in this country for many years, and in some places has escaped from 

 cultivation. 



Groups of Sweet Cherries. — The sweet cherries include 

 four general groups: 



I. Mazzards. — The fruit is small, and varies in shape and 

 color. Mahaleb and mazzard stocks are the two common 



