XVI.] THE LAWS OF VARIATION. 195 



and also in their tendency to become hereditary, and in 

 their greater tenacity the longer they have been inherited 

 through successive generations. 



There is this important difference between functionally- 

 produced changes and spontaneous variations, that func- 

 tionally-produced changes are necessarily produced during 

 the lifetime of individuals, though they may be transmitted 

 to the offspring ; but spontaneous variations appear to take 

 their rise in the act of originating a new individual. They originates 

 sometimes arise in the production of a new individual °'^'^ -^^'^^'^ 

 without sexual generation, as in the case of plants that dividuais. 

 produce " sports " from buds ; for every branch produced 

 from a bud may in some sense be regarded as a new indi- 

 vidual.i A long list could easily be given of " sporting " " Sport- 

 plants : by this term gardeners mean a single bud or offset, ^^f^^^ 

 which suddenly assum.es a new and sometimes very dif- 

 ferent character from that of the rest of the plant. Such 

 buds can be propagated by grafting, &c., and sometimes by 

 seed. These sports are extremely rare under nature, but 

 far from rare under cultivation.^ Variations, or new varie- Variations 

 ties, are, however, oftener obtained by sexual generation. abui"T^*t 

 There are some species — as, for instance, the potato — in cases of 

 which have been rendered so variable by cultivation, that generation, 

 new varieties are produced whenever they are raised from 

 seed. Eeproduction from seed is reproduction by sexual 

 generation ; and, as I have shown, there is some degree of 

 mixture of race in all sexual generation. This is probably 

 to be regarded as true even of a flower that fertilizes itself ; 

 for the anthers and the pistils, though in the same flower, 

 are distinct elements of the organism. But of course the 

 mixture of race is greater when the pollen is brought from 

 another flower on the same plant, and greater still when it 

 is brought from another plant. And, as already stated, 

 the greater the mixture of races, the greater is the pro- 

 bability of variation in the offspring — provided, of course, 

 that they are races that breed freely together, and produce 

 fertile offspring; for the tendency to variation does not 



^ See Note at end of chapter. 

 * Darwin's Origin of Species, p. 9. 



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