322 



ESSENTIALS OF BOTANY 



or by continued selection first of a set of choice parent 



plants, then of their best offspring, and so on for several 



generations. 



Hybridizing sometimes (but not nearly always) aids the 



plant breeder by giving him a large number of marked 



variations from which 

 to select. 



High cultivation 

 together with plant 

 breeding have brought 

 about many astonish- 

 ing results. Plums 

 three inches long have 

 recently been produced. 

 A hybrid beach-plum 

 bears so abundantly 

 that the twigs are liter- 

 ally hidden by the fruit. 

 The largest cultivated 

 apples are many hun- 

 dred times the bulk of 



Fig. 225. 



Effect of Cultivation upon the 

 Size of Apples. 



The Bismarck apple, with a, the wild Asiatic 

 crab apple {Pyrus baccata), and 6, the Euro- 

 pean wild apple (P. maius). (All half nat- their remote wild an- 



ural size.) 



cestors. A new variety 

 of blackberry plant covers one hundred and fifty square 

 feet of soil and bears a bushel or more of fruit. Most culti- 

 vated roots and tubers have been greatly changed from 

 their wild condition, losing in the proportion of woody 

 fiber which they contain and gaining immensely in size 

 (Fig. 221). 



One of the most important problems for the plant 

 breeder is how to secure varieties immune to diseases. 

 Two of tiie most notable achievements of our Department 



