37 8 THE WHEAT PLANT 



II. HYBRIDS OF THE WILD WHEATS T. aegilopoides AND 

 T. dicoccoides WITH CULTIVATED WHEATS 



1 . T. aegilopoides x T. dicoccum. 



(a) T. aegilopoides $ x T. dicoccum $ . Beijerinck records the cross- 

 ing of these two species, the female parent being a winter black-chaffed 

 variety of T. aegilopoides (T. nigrescens of PantEic or T. aegilopoides, var. 

 Pancici), the male being the strong-growing form of T. dicoccum, var. 

 farrum (p. 197). 



The F! plants were quite sterile and had ears 18 cm. long each with 

 38-40 spikelets. The rachis was hairy and very brittle, like that of the 

 female parent, the form of the empty glumes resembling that of the 

 male. 



(b) T. dicoccum, var. farrum ? x T. aegilopoides, var. Larionowi $ (Fig. 

 219). I successfully crossed these two wheats in 1917. The hybrid 

 (F x ) plant was completely sterile and exhibited characters of both parents. 

 In length and arrangement the hairs on the upper surface of the young 

 leaves resembled those of the mother. The ears were fragile, intermediate 

 in breadth and thickness between the two parents, with reddish empty 

 glumes like those of the pollen parent, but similar in form and terminating 

 in an incurved apical tooth like those of T. dicoccum. 



The base of the spikelets and edges of the rachilla were as hairy as 

 those of T. aegilopoides, and the flowering glumes terminated in long 

 awns like those of the latter plant. 



2. T. dicoccoides x with Cultivated Wheats. In his paper on "Rare 

 Cereal Hybrids " Tschermak states that T. dicoccoides crosses with T. mono- 

 coccum, T. dicoccum, T. durum, and T. Spelta, but gives no descriptions. 



The wild T. dicoccoides crosses readily with T. vulgar e and T. durum. 

 Natural hybrids of these occur in Palestine and Syria and are frequently 

 obtained when the cultivated races are grown in the garden in proximity 

 to the wild species ; in fact, it is difficult to preserve a pure line of T, 

 dicoccoides where other wheats are grown. 



In the cross made by Tschermak between T. dicoccoides and T. vulgar e 

 the Fj plant closely resembled the wild species. In F 2 appeared T. 

 dicoccoides and a mixture of T. dicoccum, T. durum, T. vulgare, and T. 

 Spelta. 



I have also frequently observed the similar production of a variety of 

 forms of T. dicoccum, T. durum, T. Spelta, and T. vulgare in the F 2 genera- 

 tion from natural hybrid F x plants found in pedigree rows of T. dicoccoides. 



The following is an example of the great diversity exhibited among 

 the segregates of these sporadic hybrids (see Figs. 220, 221). 



A single ear of T. dicoccoides, var. Aaronsohni, gave a natural hybrid 

 from which were obtained the following forms in the F 2 generation : 



