VARIATION 353 



mediates with the parent form. In some cases the new characters are 

 not constant, while in others they are hereditary sports of the latter class, 

 being usually designated mutations or mutants. There is scarcely a 

 single character normally present in wheat which may not thus arise 

 spontaneously among forms of wheat in which it has not previously 

 been observed, and the new feature may be either a Mendelian dominant 

 or a recessive. 



Among beardless wheats bearded forms appear, and among bearded 

 forms beardless plants arise. 



In regard to the colour of the glumes, red-chaffed varieties arise 

 among white-chaffed wheats, and white-chaffed plants among red. 



Varieties with black awns sport to white- or red-awned forms, and 

 vice versa. 



Among lax-eared wheats plants suddenly appear with compact ears, 

 and in dense Squarehead wheats varieties with long lax ears are found. 



Glabrous glumed forms give rise sometimes to forms with pubescent 

 glumes, and vice versa. 



Investigations to determine the nature and origin of the sports 

 enumerated have proved that many of them arc natural hybrids, and their 

 progeny exhibits simple Mendelian segregation. Breeding tests of 

 others show that they are segregates hcterozygotes, homozygous domin- 

 ants and recessives of natural hybrids which have escaped observation 

 in previous seasons. The majority of such examples generally involve 

 only one or two allelomorphic pairs of characters. A few sports, however, 

 which I have observed in pedigree cultures of 7*. vulgare, T. comfwctum, 

 and T. Spflta were much more complicated and gave rise to an extra- 

 ordinarily heterogeneous mixture of descendants. In Fig. 215 is illus- 

 trated the remarkable variety of forms obtained from a sport of a Chinese- 

 beardless smooth-chaffed bread wheat, received from Chungking under 

 the name " Kwang T'ou Mai." The grains from a single ear were sown 

 in 191 1, and from the progeny, which was apparently uniform, a single ear 

 clubbed at the apex and lax at the base, as in car I, was selected and its 

 grains sown in 1912. These yielded 57 plants in 1913, one of them a 

 cumpactum form (ear 3) like the upper half of the original clubbed ear, 

 but with pubescent glumes, the rest smooth-chaffed and of uniform 

 density (ear 2). 



From the cumfxictum sport 36 plants were raised, among which 12 

 distinct forms were found (line A). Some of these had long lax cars, 

 others possessed intermediate or short and compact ears. Clubbed as 

 well as uniformly dense-eared plants were obtained, the majority beard- 

 less, but a few with short awns at the tips of the ears. In regard to tin 

 pubescence of the glumes, some were densely hairy, others only slightly 

 pubescent, while several were quite glabrous. 



2 A 



