248 



Plant-Breeding 



fact that the Ignotum tomato, as I first knew it and bred 

 it, appears now to be lost to cultivation, although the name 



is still used for the legitimate 

 family of descendants from my 

 original stock. All this experi- 

 ence illustrates how quickly varie- 

 ties pass out by variation and by 

 the unconscious and unlike selec- 

 tion practiced by different per- 

 sons." Bailey, earlier editions. 



The longevity of any variety 

 is inversely proportional to the 

 frequency of its generations. An- 

 nual plants, other conditions 

 being the same, run out sooner 

 than perennials, because seed-re- 

 production or the generations 

 - intervenes more frequently. 

 Trees, on the other hand, carry 

 their variations longer, because 

 the seed generations in which 

 departures chiefly take place 

 are farther apart. Of all the so- 

 called fruit plants, the strawberry 

 runs out soonest and the varie- 

 ties change the oftenest, because 

 a new generation can be brought 

 into fruit-bearing in two years, 

 whilst it may require ten years or 

 more to bring a new generation of apples or chestnuts into 

 bearing. " Yet, my reader will remind me that the Wilson 



FIG. 64. Swede turnip 

 (top) ; kohl-rabi (middle) ; 

 cauliflower (bottom). 



