How Domestic Varieties Originate 225 



more good varieties there are of any species, the more 

 widely and successfully that species can be cultivated. 

 A knowledge of Mendel's laws of heredity assists the 

 breeder to secure more rapidly the proper combination 

 of qualities and to fix them. 



4. Do not desire contradictory attributes in any variety. 

 A variety, for example, that bears the maximum number 

 of fruits or flowers cannot be expected greatly to increase 

 the size of those organs without loss in numbers. This is 

 well shown in the tomato. The original tomato produced 

 from six to ten fruits in a cluster, but as the fruits in- 

 creased in size the numbers in each cluster fell to two or 

 three. That is, increase in size proceeded somewhat at 

 the expense of numerical productivity; yet the total 

 weight of fruit to the plant has greatly increased. The 

 same is true of apples and pears ; for whilst these trees bear 

 flowers in clusters, they generally bear their fruits singly. 

 Originally, every flower normally set fruit. The reason 

 why blackberries, currants, and grapes do not increase 

 more markedly in size, is probably because the size of 

 cluster has been given greater attention than the size of 

 berry. Plants which now bear a full crop of tubers can- 

 not be expected to increase greatly in fruit bearing, as 

 already explained under Rule 1. This fact is illustrated 

 in the potato, in which, as tuber-production has increased, 

 seed-production has decreased, so that growers now com- 

 plain that potatoes do not produce bolls as freely as they 

 did years ago. 



5. When selecting seeds, remember that the character 

 of the whole plant is more important than the character 

 of any one branch or part of the plant ; and the more 



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