224 Plant-Breeding 



tending towards extinction. Monotypic genera those 

 which contain but a single species are usually of local 

 or disconnected distribution, and are probably, for the 

 most part, vanishing remnants of a once important type. 

 As a rule, most of our widely variable and staple culti- 

 vated species are members of large, or at least polytypic, 

 genera. Such, for example, are the apples and pears, 

 peaches and plums, oranges and lemons, roses, bananas, 

 chrysanthemums, pinks, cucurbits, beans, potatoes, 

 grapes, barley, rice, cotton. A marked exception to this 

 statement is maize, which is immensely variable and is 

 generally held to have come from a single species ; but 

 the genesis of maize is unknown, and it is possible that 

 more than one species is concerned in it. Wheat is also 

 a partial exception, although the original specific type is 

 not understood ; and the latest monographers admit three 

 or four other species to the genus, aside from wheat. 

 There are other exceptions, but they are mostly unim- 

 portant, and, in the main, it may be said that the domi- 

 nant domestic types of plants represent markedly poly- 

 typic genera. 



3. Breed for one thing at a time. The person who 

 strives at the same time for increase or modification in 

 prolificacy and flavor will be likely to fail in both. He 

 should work for one object alone, simply giving sufficient 

 attention to subsidiary objects to keep them up to normal 

 standard. This is really equivalent to saying that there 

 can be no such thing as the perfect all-around variety that 

 so many people covet. Varieties must be adapted to 

 specific uses, one for shipping, one for canning, one for 

 dessert, one for keeping qualities, and the like. The 



