DISTIXCTIOXS 1^" CULTIVATED BARLEYS. 



21 



ments at St. Paul and at Aberdeen were made by the writer, while 

 those at Chico were made by Mr. E. L. Adams. The result is shown 

 in figure 16. As a whole the variations were parallel, Xos. 6 and 35 

 being strikingly so. The four less dense selections showed an extreme 

 variation of only three units, while the two dense selections varied 

 much more. In No. 32 this was due in part to poorly developed 

 heads ; at St. Paul, particularly, its spikes were so short that it was 

 impossible to find many in which five successive nodes bore fertile 

 florets. The effect of sterility is to lengthen the internode of the 

 rachis. All types were most dense at Chico and least dense at St. 

 Paul. The effect of irrigation as shown 

 at Aberdeen was very slight, especially 

 when compared with the effect of the 

 combined factors of geographical loca- 

 tion. 



The character of the curves was in- 

 fluenced even less than their relative 

 density. Table Y shows the distribu- 

 tion into their various densities of 100 

 spikes from each of 59 plats of barley. 

 By referring to Table V it will be seen 

 that some selections always present a much 

 sharper curve than others, and thus af- 

 ford opportunity for varietal distinc- 

 tions in the distribution of the measure- 

 ments. Avoiding the extreme examples, 

 it will be noted that the spike of Xo. 30, 

 for instance, which has already been 

 condensed three or four units by the use 

 of the formula for density, is still less 

 compact than Xo. 35, which by the same operation has been made 

 to appear slightly less compact than it really is. At St. Paul, Xo. 35 

 has a total of 85 per cent of its spikes within three units in one in- 

 stance and 91 per cent in another, while Xo. 30 has but 82 per cent 

 within this limit. At Aberdeen, under irrigation, Xo. 35 has a total 

 of 91 per cent of its spikes within three units, while Xo. 30 has but 

 T8 per cent ; upon the dry farm at the same place, Xo. 35 has a total 

 of 81 per cent of its spikes within three units, while Xo. 30 has but 

 77 per cent : and at Chico, Xo. 35 has 94 per cent of its spikes within 

 three imits, while Xo. 30 has 91 per cent. 





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Fig. 16. — Curves shewing the 

 average density of six selections 

 of barley grown at Chico, Cal., 

 at St. Paul, Minn., and on irri- 

 gated and unirrigated land at 

 Aberdeen, Idaho. 



