PLANT BREEDING 



369 



developed from sports. Very likely the same, thing is true 

 of the cabbage. At any rate, the plant which is thought to 

 have been the original of the cultivated cabbage, and which 

 still grows wild 

 on the seaside 

 cliffs of western 

 and southern 

 Europe, has no 

 head, but in- 

 stead a cluster 

 of root leaves. 



376. Hybrid- 

 ization. Some- 

 thing was said in 

 Chapter XVII 

 ( 288) about 

 the production 

 of crosses or 

 hybrids when the 

 stigma of a 

 flower is dusted 

 with pollen from 

 a flower of an- 

 other variety or 

 of another spe- 

 cies. A hybrid FlG 2og _ The ^ Brassica O i eracea (A), from 

 usually pos- which the cultivated plants shown are believed to 

 Sesses some of have been derived; B, kohlrabi; C, cauliflower; 



nolifi^c nf D > cabba g e ; > Welsh or Sav y cabbage; F, Brussels 

 the qualities of sprouts MtT Smalian- 



one parent com- 

 bined with some of the qualities of the other parent. Hybrids 

 frequently result from the carrying of pollen from flower to 

 flower by the wind or by insects. Such accidental hybrids 

 are sometimes troublesome in plant breeding, because they 

 introduce impurities into varieties that it is desired to keep 



