164 Varietäten, Descendenz, Hybriden. 



c) Where the colour has becn found to be due to the interaction 

 of more than one factor, the simultaneous presence of all colour 

 factors appears to be necessary for the production of colour at all. 



W. Neilson Jones. 



• 



Howard, A. and G. L. C. Howard. On the inheritance of 

 some characters in wheat. II. (Mem. Dep. Agric. India. Bot. 

 Ser. VII. p. 273—285. 1915.) 



The present paper forms the continuation of earlier results pu- 

 blished in these same memoirs 1912. Two characters only are dealt 

 with here, bearding and felting. 



The study of the literature concerning the inheritance of awns 

 in wheat is rendered difficult by the same terms not always being 

 employed similarly — wheats with short awns and with none being 

 both described as 'beardless'. In the present investigation, two 

 distinct phenomena were observed in crosses between bearded 

 wheats and what are usually described as beardless. In one series 

 the plants of F x were intermediate or half-bearded, in the other 

 only very short tips to the glumes occurred. These differences 

 were found to be correlated with differences in the beardless pa- 

 rent — which in the first series had short tips to the glumes while 

 in the second it was absolutely beardless. In what follows, these 

 two classes are considered separately under the names of 'tipped' 

 and 'beardless'. 



The results of crossings were as follows. Be ar de d X Tipped. 

 F 1 was half-bearded, while these broke up in F 2 into Bearded, half- 

 bearded and tipped in the ratio of 1:2:1 The three classes were 

 distinct and the ratios based on the examination of 2836 F 2 plants. 

 In F 3 , bearded and tipped plants bred true, and the half-bearded 

 split as before. 



Bearded X Beardless. F l with very short tips to glumes. 

 F 2 a series of forms which could be grouped with some difficulty 

 into Bearded, nearly fully bearded, half bearded, tips of varying 

 length, and beardless. If the variously bearded and tipped plants 

 are classed together as 'bearded', the ratio of bearded to beardless 

 is 15:1, indicating the presence of two factors. It is suggested that 

 one factor (T) produces a short tip only; the other (B) when added 

 to this, results in the bearded condition. Working on this hypo- 

 thesis, attempts were made to isolate the two factors and to obtain 

 confirmation of the hypothesis. As a result of raising many fami- 

 lies, carried in some cases to F 4 , the occurence of types and the 

 ratios in which they appeared confirmed the hypothesis completely. 

 The types to be distinguished are: Fully bearded: BBTT, minute 

 tips': BbTt, half bearded: BBTt, nearly fully bearded: BbTT, long 

 tips: BBtt, minute tips: Bbtt, short tips: bbTT, minute tips: bbTt, 

 beardless: bbtt. 



During the experiments it was noted that the development of 

 the bearded or. tipped character was not always uniform but that 

 there was a considerable ränge of Variation in the ears of a spike, 

 the first formed and largest ears having the largest awns. The 

 same kind of Variation was noticed in the cultures as a whole. The 

 unequalness of development appears to be largely a matter ofvigor 

 and to be a good example illustrating the necessity of growing a 

 culture to perfection , so that each character attains its füllest expres- 

 sion, if satisfactory comparative results are required. 



