[sAUNDERs] INHERITANCE IN BARLEY • 17 



Cross No. 901 



The first cross (No. 901) was between Arlington and 465C. It 

 possessed a six-row head with well-developed awns (about three inches 

 long) on the two median rows and with decidedly shorter and feebler 

 awns (about one and a quarter inches long) on the four lateral rows. 

 These heads were very brittle. The long awns of the head photo- 

 graphed have been somewhat broken and therefore do not show 

 quite their full development. The interesting point about this type 

 is that it is clearly an intermediate, so far as awns are concerned. 

 The awns on the lateral rows may be fairly described as just half 

 developed. They represent the middle point between the awnless 

 condition of these rows in the Arlington and the fully awned state in 

 the other parent, 465C. That the median rows show well-developed 

 awns in this case is what would be expected, considering that these 

 rows in the Arlington barley very often carry fairly well developed, 

 though never very long, awns. 



The second generation from this cross behaves as would be 

 anticipated: it produces 50 per cent, of heterozygous plants (type III, 

 like the first generation), 25 per cent, of the ordinary six-row, bearded 

 type (type I, like the ancestor 465C), and 25 per cent, of the Arlington 

 type (type II). The photograph (plate B) shows these three types 

 together, namely, type I, six-rowed awned, type II, Arlington, and 

 type III, the intermediate form. The head marked III in the photo- 

 graph, having been very carefully preserved, shows clearly the 

 difference in length between the fully developed awns on the median 

 rows and the half-developed awns on the lateral rows. 



It should be noted that in type I the awns on the median rows 

 are somewhat longer and better developed than those on the lateral 

 rows. The head marked 90 IS shows this very well. Yet there is a 

 perfectly clear distinction between this condition and that found in 

 the true type III. Seed from 90 IS was sown and was found to produce 

 only fully bearded plants, thus proving that it belonged, as was 

 supposed, to type I, although showing rather more than the usual 

 difference in the length of the awns. 



When seed is sown from these three types, types I and II breed 

 true, while type III breaks up exactly as before. The actual numbers 

 obtained by sowing seed of type III were as follows : Type 1 , 44 plants ; 

 type II, 67 plants; type III, 114 plants. These figures are rather far 

 from the theoretical ratio of 1:1:2, but the total number of plants 

 was small and some of them (owing to poor development or damage 

 by wind) were very hard indeed to classify. 



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