Vol. 6, 1920 
PHYSIOLOGY: W. H. REED 
399 
growing season. At the beginning of each cycle, growth was rapid, the 
leaves arising upon that part of the shoot were of maximum size and out- 
spread. As the end of a growth cycle was approached, the slower-growing 
portion of the shoot produced smaller and smaller leaves which had more 
of a tendency to curl. Simultaneously, the apical bud of the shoot was 
enlarged and became almost completely dormant. Following the partial 
dormancy of the apical bud, lateral shoots were often formed from sub- 
apical buds. However, within a week or two, the next cycle of growth 
would start and the shoot would repeat the processes described for the 
preceding cycle. 
If the shoots pass through distinct intra-seasonal cycles of growth, we 
h4 
A 
f 
\ 
/B C 
) 
B 
/o 
Time in weeks 
FIG. I 
Growth of apricot shoots represented as three cycles, 
lated from 
X 
, curve calcu- 
log 
a 
k (t - t), 
0000, observed values. 
should expect that the growth in each cycle should show evidence of being 
homogeneous and that it could be expressed definitely. We may, there- 
fore, examine each of the three cycles of growth of the apricot shoots with 
this end in view. From inspection of the data it seems proper to designate 
the first cycle as the time from 0 to 8 weeks, the second from 9 to 17 
weeks, and the third from 18 to 28 weeks. If each of these follows the 
course of a more or less independent autocatalytic reaction, we may 
compute their growth by the formula 
