HYBRIDISATION AND WHEAT HYBRIDS 385 



presumed hitherto to be due to successive annual fertilisation by wind- 

 borne pollen. 



It is possible, however, that the later generations are self-fertile, and 

 that their increasing resemblance to ordinary wheat is brought about by 

 the elimination of the Aegilops chromosomes in the abnormal heterotype 

 divisions which Bally found in the primary hybrid A. triticoides. 



In these irregular divisions the wheat chromosomes sometimes collect 

 at the poles of the spindle before the Aegilops chromosomes leave the 

 equatorial position, and in some of the pollen-grains nuclei may form which 

 contain only wheat chromosomes, the Aegilops chromosomes or fragments 

 of them appearing distributed within the cytoplasm of the cells, where 

 they probably degenerate or enter into the formation of dwarf nuclei, 

 which take no part in the fertilisation process when such grains are trans- 

 ferred to the stigmas of wheat flowers. 



(b) Aegilops triaristata, Willd. $ xTriticum vulgare $ (=A. triti- 

 coides, Req.). Planchon crossed these two species, and Fabre states that 

 examples of A. triticoides arise from individual grains of fallen ears of 

 A. triaristata as well as from A. ovata ; thus the name A. triticoides is 

 used for two different hybrids. 



Inflorescences of the hybrid from ovata have the glaucous character 

 of the mother with somewhat closely packed spikelets ; those from 

 triaristata are non-glaucous like the mother plant, and yellowish some- 

 times becoming dark brown when ripe, with the spikelets more distant 

 from each other on the rachis. 



(c) A. ovata 9 x T. Spelta $ (Bearded Form). Godron records 

 the production of two examples of this hybrid, but gives no descrip- 

 tion of them. Greenland also obtained the same hybrid which was 

 sterile. 



(d) A. ovata $ x T. turgidum $ . Greenland obtained five samples 

 of this hybrid ; they produced a few grains in the first and second years, 

 but became quite sterile and died out in the third season. 



(e) A. triaristata $ x T. durum " barbatum " <3 , A long -bearded 

 hybrid was produced but not described by Godron. 



(/) A. ovata $ x by all the different races of wheat. 



A. cylindrica $ x by all the different races of wheat. 



T. Spelta ? x A. ovata 3 . 



T. Spelta 9 x A. cylindrica <$ . 



These hybrids were obtained by Tschermak : all were sterile, and 

 attempts to cross them with the wheat or Aegilops parents failed. 



(g) A. triuncialis ? x T. vulgare $ . Loret discovered this hybrid 

 wild in the south of France. 



(h) A. ventricosa $ x T. vulgare $ . This hybrid was produced by 

 Vilmorin and Greenland : it is quite sterile. Henslow also obtained a 



2 C 



