44 



BREEDING CROP PLANTS 



same for the incrossed and crossed seed. Results are presented 

 in Table VI. .^, 



TABLE VI. WEIGHT OF SEED OF INCROSSED PARENTS COMPARED WITH 

 WEIGHT OF THE IMMEDIATE CROSS 



All three crosses between varieties of T. vulgare gave increases 

 over incrossed seed. These appear significant in relation to the 

 computed probable errors. Of the crosses between wheat species 

 only one gave a difference which appears at all significant. In 

 the cross between Velvet Chaff and Mindum the incrossed seed 

 seems somewhat heavier in the light of the probable error than 

 the crossed seed. These results show an immediate effect of 

 pollination on seed size in crosses between varieties of T. vulgare. 



The emasculation and artificial pollination causes a reduction 

 in seed size as compared with normally produced seed. In- 

 crossed, normally produced seed and crossed seed were grown in 

 the greenhouse under controlled conditions and the comparative 

 vigor of parents and crosses was determined. As there were no 

 significant correlations between size of seed planted (even when 

 incrossed seed was compared with normal seed) and resultant 

 plant vigor, the differences between the parents and crosses may 

 be explained on the basis of inheritance. 



Average yield of plants in grams of seed will be used as a 

 measure of vigor (see Table VII). 



The crosses between varieties of T. vulgare and the crosses 

 between T. vulgare and T. compactum gave in every case slightly 

 greater yields per plant than the average of the parents. On 

 the other hand, F\ crosses between durum or emmer varieties 

 and varieties of common or club wheats were all significantly 

 lower in yield than the parents. The low yields of these species 



