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. 
EARLY 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. 
