Mason. — Growth and Abscission in Sea Island Cotton . 477 
to four days in age. The results, which are recorded in Table II, show that 
9 6-5 per cent, of the bolls were shed within nine days from the plants which 
had been deprived of their leaves, and that only 39-6 per cent, were lost by 
the control plants in the same period. Of great importance is the fact that 
the maximum rate of shedding occurred on the fifth day after the operation ; 
the period intervening between the application of the stimulus and the 
completion of abscission was thus similar to that occurring under natural 
conditions. The rapidity and completeness of the response can only 
indicate, moreover, that the reserve food substances in the cotton-plant 
quickly become exhausted. 
Table II. Number of Bolls shed on Successive Days after Open 
Days after open flower stage on 
Flower Stage, 
1234 
5 
6 
7 
8 9 
which shedding occurred 
172 Bolls. Leaves removed 
1 4 
13 22 
47 
38 
*9 
11 1 
159 Bolls. Leaves not removed 
1 2 
5 
6 
H 
16 
10 6 
The Growth-rate of the Boll and Environmental Factors. 
The retardation in the growth-rate of the main axis, which occurred 
during periods of low light intensity, low evaporation, and daytime rain, 
conditions which it will be recalled were also followed by augmented rates 
of shedding, suggested the possibility that these conditions might also be 
recorded by a check in the growth-rate of the boll. 
The growth-rate of three lots of bolls, none of which was shed, are 
shown in Fig. 13. There were twenty-one bolls in the firs.t lot, thirty-eight 
in the second, and forty-six in the third. The results represent the mean 
growth-rates for each lot. Evaporation and rainfall are also shown for 
comparison with the growth-rates. The environmental conditions which 
prevailed on October 8th, 9th, and 10th were possibly responsible for the 
fact that recovery in the growth-rate of the first lot did not take place 
until the seventh day after the open flower stage. Moreover, it may not 
be a coincidence that the decline in the growth-rate of the second lot was 
particularly marked during the same period. It will also be observed that 
the growth-retardation following anthesis was less pronounced in the third 
lot than in the first two, and that this synchronized with higher rates of 
evaporation and only a relatively small amount of daytime rain. It is 
rather remarkable that the growth-rates of all the three lots should have 
been greatly augmented on October 18. The results, though not decisive, 
nevertheless suggest that the same external conditions which retard the 
growth of the main axis also depress that of the boll. 
