76 



In the treatise of 1886 ') the reciprocal cross-breeding, viz., Tr. di- 

 coccum, weisser Emmer? x Tr. monococcum flavescens, Körnicke <?, 

 was discussed in the first place. This cross-breeding succeeded also 

 without difficulty (Beijerinck describes exactly the method foliow- 

 ed) and the grains of the fertilized mother-plant germinated as well 

 as those obtained with the earlier cross-breeding, The bastard obtained 

 herewith resembled the cross-breeding product described in 1 884 very 

 strongly, but small differences in the generative organs were still to be 

 found, to which Beijerinck calls special attention (with reference to 

 the work of Focke 2)) and which certainly are interesting but cannot 

 be discussed here. The flowers of the bastard developed perfectly 

 normally, and the ovaries also, but there was never found to be any 

 fruit-setting — Beijerinck says "zu meiner nicht geringen Verwun- 

 derung" — not even on pollination of the bastard with pollen from 

 the mother form, the male form, or with that of Tr. vulgare, Tr. 

 turgidum, or Tr. durum. 



In this treatise of 1886 Beijerinck describes furthermore a bastard 

 which he obtained by cross-breeding from Tr. dicoccum 3 with Tr. 

 monococcum [3 lasiorrachis Boissier ?, found wild. He communicates 

 that he received this "wild baeotic wheat" from Mr. H. Vilmorin 

 under the name of Tr. haeoticum, but Beijerinck doubted the cor- 

 rectness of this indication and changed it into the one just mentioned. 

 The sturdy hybrids obtained were also sterile. 



We mentioned above that Beijerinck in his first publication re- 

 pudiated the opinion defended by de Candolle, among others, that 

 the various species of the cultivated cereals descended from one and 

 the same wild form. In his second treatise he returns, however, to this 

 opinion. Referring to the sterility of the bastard obtained from Brassi- 

 ca rapa and Br. napa, he considers his observation on the sterility of 

 the wheat bastards obtained as insufficiënt proof for rejecting the said 

 hypothesis, which attracts him very strongly. 



On account of the morphological properties, Beijerinck considers 

 the descent of Tr. monococcum from the wild Tr. monococcum ^ lasior- 

 rachis as practically beyond doubt. With regard to the descent of Tr. 

 dicoccum, however, he recognizes that doubt here is justifiable, and 

 he therefore once more discusses at length the various other possibili- 

 ties in its descent. The significance of a clearer knowledge of this des- 

 cent he considers especially important, because, to his mind, Tr. di- 

 coccum in its turn is to be regarded as the original form of the most 

 important cultivated wheats, namely of Tr. Spelta, Tr. turgidum, Tr. 

 durum, and Tr. vulgare. He arrivés at the conclusion, after these 

 comparisons, that the strongest reasons point toward the above- 



1) Ueber die Bastarde zwischen Triticum monococcum und Triticum dicoccum, 

 Nederlandsch Kruidkundig Archief, 2e serie, 4e deel, 4e stuk, 455-473, 1886 {Ver- 

 zamelde Geschriften 1, 415-426). 



2) W. O. Focke, Die Pflanzenmischlinge. Ein Beitrag zur Biologie der Gewachse. 

 Berlin 1881. 



