462 PRACTICAL BOTANY 



peaches are yery perishable, most of the crop (as is the case 

 with strawberries) must be taken to market in refrigerator cars. 



Nectarines, apricots, and almonds are very closely related 

 to peaches. 



Plums, cultivated in various parts of the United States, 

 belong to about ten groups, of Asiatic, European, and Ameri- 

 can origin. Some highly successful varieties are of hybrid 

 origin (Fig. 341). One of these is derived from the little 

 beach plum 1 so well known along the Atlantic coast, and 

 the common wild plum 2 which ranges from New England 

 to Colorado and Texas. This hybrid is extraordinarily hardy 

 and prolific. Among the most valuable plums are those which 

 can be dried whole for prunes, and these are now extensively 

 grown in California. 



Cherries in cultivation are of two types, the sour and the 

 sweet, both derived from European species. The sour varie- 

 ties are grown throughout a large portion of the country, the 

 sweet ones principally in California. 



427. Citrous fruits. The plants which bear oranges, grape- 

 fr,uit, and lemons, are not hardy but thrive in tropical or semi- 

 tropical climates. They may grow in regions where frosts are 

 rare and light. In the United States the leading citrous-fruit 

 orchards are in Florida and California. The wild orange is 

 probably a native of southeastern Asia. Its fruit is sour, but 

 the tree is more hardy than some of the improved sweet varie- 

 ties. Because of this hardiness the sweet varieties are some- 

 times grafted upon the wild stock in order to make use of the 

 stronger wild plants. By means of experiment and cultivation 

 many hundreds of varieties of oranges have been produced. 

 Attempts are still being made to produce trees which will 

 withstand the colder winters of the region farther north and 

 at higher altitudes than where they are now grown. These 

 efforts have been partially successful. 



Oranges, lemons, and the grapefruit or pomelo, as well as 

 the more recently developed varieties, as the tangerine and 



1 Prunus maritima. 2 Prunus americana. 



