HYBRIDISATION AND WHEAT HYBRIDS 389 



was very variable, consisting of plants with glabrous stems and ears of 

 " Squarehead " form, as well as others with more slender lax ears : some 

 of the plants were quite sterile, while others yielded viable grain in varying 

 amounts. 



The descendants of Rimpau's hybrid were still grown in various 

 localities in Germany in 1912, more than twenty generations after the 

 original cross. Such plants are remarkably constant, and exhibit char- 

 acters intermediate between the two parents. The ears are long and 

 narrow, some bearded, others beardless, with strongly keeled scabrid, 

 rye-like glumes, which open widely and remain separated some consider- 

 able time at the period of anthesis. Much of the pollen is deformed 

 and sterile, and the ears set a few grains only, even when pollinated with 

 wheat pollen. Miczynski also obtained a naturally fertilised F 2 generation. 



More recently Love and Craig produced hybrids of wheat and rye, 

 most of which were sterile in F, and in morphological characters resembled 

 those obtained by other workers. Two of the hybrids, however, were 

 fertile. One of them, resulting from the crossing of Dawson's Golden 

 Chaff wheat (a beardless red-chaffed white-grained variety) with common 

 rye, had brown glumes intermediate in colour between those of the two 

 parents, and ciliate keels like those of rye. 



The hybrid was not quite sterile. A single F 8 plant raised from it had 

 ears with short awns and sharply keeled ciliated glumes like the rye parent. 



Only one seed was obtained from the F,. This gave rise to a more 

 wheat-like plant (F s ) with much increased fertility. The succeeding 

 generation (F 4 ) had wheat-like ears, some of them fully fertile, others 

 almost sterile. The grains varied in form ; and in respect of length of 

 awn, colour of chaff and grain, there was much variation with apparent 

 segregation in the simple Mendelian 3 : i ratio. 



With the exception of the F, plants, none of the later generations showed 

 any of the rye-like pubescence of the upper internode. The plants of the 

 F 4 generation showed an increasing resemblance to wheat, although some 

 of them exhibited traces of rye characters. 



The true fertility of the F, wheat * rye hybrids obtained by Carman, 

 Rimpau, Love and Craig cannot be decided with certainty, for it is 

 possible that in these cases the generations after F, were the result of 

 chance pollinations from neighbouring wheat plants ; nevertheless, the 

 negative evidence of Tschermak, Nakao, and Jesenko cannot settle the 

 matter. It is probable that the fertility may be dependent upon the 

 varieties of wheat and rye used in the cross. 



Crossing the F, hybrid with one of the parents has been carried out 

 by Carman and Jesenko. The former pollinated an car of a F, wheat ; 

 rye hybrid with rye. From this he obtained 17 grains, from which 14 

 F, plants were raised, most of them sterile ; the fertile plants crossed 



