DISTINCTIONS IN CULTIVATED BARLEYS. 5 



THE RATE OF DEVELOPMENT. 



The rate of development, like all physiological characters, is sub- 

 ject to considerable fluctuation within the strain. The distinctions 

 are naturally much less absolute than those founded upon morpho- 

 logical characters. They have, however, the advantage that they 

 permit a greater number of separations. A plant structure usually 

 has but two phases. It exists or it does not exist. With physiologi- 

 cal characters this is not the case. The length of time required for 

 one variety to mature may differ three days from that of a second 

 or it may differ three weeks. From the standpoint of observation, 

 the development of the plant is divided into three periods: (1) The 

 early development from germination to the time of jointing, (2) the 

 period of heading, and (3) the period of maturity. 



FARLY DEVELOPMENT. 



For some time the writer has maintained that the early growth is 

 the stage of development at which selections of barley are most 

 easily distinguishable. This period seems to have been neglected by 

 plant breeders. There are few records of notes taken during this 

 time, and even those breeders who have known the cereal crops best 

 have based their selections at this period on an intangible something 

 that enabled them to single out any new variation. 



During the summer of 1913 an attempt was made to analyze the 

 intangible, with most encouraging results. In addition to careful 

 observations on several hundred selections, 1,400 plants were chosen 

 in the nursery and 1,700 in drill rows, upon which exact records 

 were kept. One hundred plants were used in each variety. The data 

 included the day upon which each of the 3,100 plants produced its 

 second, third, and fourth leaves and its first tiller. The optically 

 plausible became mathematically evident, and it was soon seen that, 

 aside from the leaf character, there was ample justification for the 

 separations made on appearance during the early stages of growth. 

 As figure 1 shows, the selections rush through the early stages at an 

 astonishing rate. A centgener which is only two days, or even one 

 day, behind a second may be in an entirely different stage of develop- 

 ment and may therefore present an appearance which in no way re- 

 sembles that of the first. Yet the two barleys may be closely related 

 strains and inseparable or separated with difficulty at maturity. 

 The typical curves of the production of the second, third, and fourth 

 leaves are always very sharp. In figure 1 the curve of tillering is 

 more flat than is usually the case. The first of the third leaves 

 emerges about the time of the appearance of the last of the second. 

 The fourth leaf is produced in about the same relation to the third, 

 but perhaps a little earlier. The first tillers are usually simultaneous 

 with the fourth leaves, though in some varieties they appear earlier. 



