230 PRACTICAL COURSE IN BOTANY 



Practical Questions 



1. Would hybridization account for some of the diversities mentioned 

 in 170? (See 257.) 



2. To what cases would it not apply? (256; Exp. 79.) 



3. Would it be worth while to try to hybridize the potato and squash ? 

 The squash and pumpkin? The lily and rose? Sweetbrier and wild 

 rose ? Apple and peach ? Wild crab and sweet apple ? Blackberry and 

 strawberry? Blackberry and raspberry? Lemon and watermelon? 

 Lemon and orange ? Why, or why not, in each case ? (256; Exps. 

 78, 79.) 



VII. PLANT BREEDING 



MATERIAL. If practicable, visit a market garden, a florist's establish- 

 ment, or, lacking these, the fruit and vegetable stalls of a city market. 



260. Fixing the type. It is the tendency of plants to 

 vary under the influence of climate, soil, food supply, cross- 

 ing, and other causes perhaps unknown to us, that makes 

 the plant breeder's art possible. When a horticulturist sets 

 out to produce a new fruit or vegetable, he first forms in his 

 mind a clear idea of what he wants whether increase of yield 

 or size, resistance to cold, drought, or disease, improvement in 

 flavor, color, shape, etc., or change in the time of maturing or 

 flowering (early and late varieties). Suppose, for instance, 

 he wishes to produce an oxeye daisy with all the disk florets 

 changed to white ones like the rays. He will begin by selecting 

 plants with the greatest number of rays and the most conspic- 

 uous ones that he can find, and sowing the seeds of the flowers 

 which show the greatest tendency to the development of these 

 qualities. He will continue this process from generation to 

 generation, rigorously destroying all specimens that do not 

 approach nearer the ideal sought, until all disposition to 

 " rogue," as the tendency to revert is called, has been elimi- 

 nated. When variations cease to occur and the seed of the 

 new variety always " come true," the type is said to be fixed; 

 though some care will always be necessary to keep it so, 

 as the influence of changed surroundings and the danger of 

 mixture with foreign pollen must always be provided against. 



