108 BREEDING CROP PLANTS 



same plant. According to Carleton, seeds of either form of 

 plant produce both kinds, and the ratio is not influenced by soil 

 quality. Dimorphism facilitates cross-pollination. 



Breeding Buckwheat. Little attention has been given to the 

 improvement of buckwheat by breeding. It shows considerable 

 variation, and undoubtedly strains could be isolated that would 

 surpass present commercial varieties. Selections for yield 

 are being made in the United States. In Russia some work is 

 under way to produce strains or varieties with four-faced seeds. 

 These are supposed to be more resistant to early spring frosts. 



RICE 



Rice is thought by Carleton (1916) to have ''originated some- 

 where in the region from China to India inclusive." It has not 

 been recorded with other cereals that were grown in Egypt in 

 ancient times. Little study has been made regarding classifica- 

 tion and genetic relationship of the wild and cultivated species. 



Cultivated races are classified into glutinous and non-glutin- 

 ous groups. Other characters of importance in varietal classifica- 

 tion are size, shape, and color of seed; color of glumes and leaf 

 sheath; awned or awnless glumes; and length of glumes, whether 

 long or short. A short summary of inheritance of some indi- 

 vidual characters is of interest. (See Table XVIII.) 



Inheritance of Characters. The endosperm of rice is glutinous 

 or starchy. The glutinous group is not grown in the United 

 States or generally in Europe as a commercial crop. On cooking, 

 it runs together into a pasty mass while the seeds of common rice 

 keep their shape when properly cooked. The starch of ordinary 

 rice is replaced by a sort of dextrine in the glutinous varieties. 

 Apparently one Mendelian factor difference separates these 

 groups. The color of the seed is also an endosperm character. 

 Blue is dominant over red and red over white. 



The inheritance of plant characters may be explained by the 

 usual Mendelian method. The ratios given show that color 

 inheritance may be explained by one or more factors. Ikeno 

 (1918) studied the inheritance of a number of size characters. 

 In some cases dominance was obtained in FI. In other charac- 

 ters the FI was intermediate. Complex segregation occurred in 

 F 2 but with no definite ratios. Multiple factors were used to 

 explain the results. 



