DISTINCTIONS IN" CULTIVATED BARLEYS. 7 



Differences are revealed in two ways by a comparison of the 

 behavior of strains. There is an actual difference of date in any 

 stage and, still more important, a relative difference between various 

 stages. This is shown to some degree in figure 3, and to a still 

 greater degree in figure 7, which will be discussed later. Figure 3 

 shows the date upon which the greatest number of plants in 17 

 selections sown in drill rows reached the three stages of development. 

 It will be noticed that the average date of the occurrence of the 

 second leaf varied over scarcely more than 1 day, while the third 

 extends over 2^ days, and the production of tillers over 5 days. No. 

 5, for instance, produces the third leaf 2 days after the second, while 

 No. 13 requires another half day. Yet No. 13 requires but 3 addi- 

 tional days to produce tillers, while No. 5 requires 5| days. 



EMERGENCE OF THE AWNS. 



The time of heading is a general agronomic note, and there is no 

 doubt that an observation of this period is of great value in plant 

 breeding. Distinctions at this time shoi Id be easily made and 

 should be more reliable than those of any later date. The difference 

 between selections is greater than in the earlier stages, and the 

 effect of season is not apparent in any abnormal hastening of devel- 

 opment, as it is later in ripening. In any climate, most barleys 

 develop in a fairly normal manner until flowering time. The time 

 of heading, for these reasons, should be of great use. It has, how- 

 ever, one disadvantage. It is an extremely difficult note to obtain, 

 and hence inaccurate. Barleys differ very much in their manner 

 of heading. Some heads are exserted rapidly and completely, others 

 slowly and only partially. The observer has not only the difficulty 

 of maintaining an arbitrary mental standard, but is confronted by 

 numerous exceptions that never conform to any standard. 



In a study of this difficulty it was noticed that just previous to 

 heading, the tips of the awns in all awned varieties projected from 

 the. boot of all plants in the selection with suggestive uniformity. 

 The date of the emergence of the awns was substituted for the date 

 of heading, with excellent results. The personal error was imme- 

 diately removed and, as the facts could be gathered at a glance, the 

 note taking was greatly accelerated. The change made a valuable 

 plant-breeding observation out of a dubious agronomic note. 



Analyzed, the curve of date of emergence of the awns is almost 

 as sharp as those representing the production of the leaves and 

 tillers. Figure 4 shows the curve of 13,108 plants, a summary of 

 the observations of a large number of selections. It will be noticed 

 that nearly two-thirds of the plants pass through this stage in two 

 days. A difference of a single day serves to change the appearance 



