4 Bo Mason . — Growth and Abscission in Sea Island Cotton. 
growth-rates, and that it became especially pronounced during the periods 
of heavy shedding. It seems evident that this continued retardation is due 
to the fact that the growth of a relatively large proportion of bolls at this 
period was subnormal, that many failed to undertake the normal recovery 
due to the stimulus of fertilization and were ultimately shed. It is 
interesting to observe that, even when little or no shedding occurred, the 
coefficients of variability tended to increase for a few days following 
anthesis, and to diminish as recovery took place. It may be seen that the 
amount of growth which was made on the first and second day after the 
open flower stage diminished rather steadily up to December 25, and then 
increased. It is not improbable that this was due to a progressive stringency 
in the supply of assimilates available for fruit development, and that the 
recovery which subsequently occurred was due to the augmented food 
supply, which presumably occurs after a wave of shedding and tends no 
doubt to diminish the liability of the boll to undergo abscission. 
General Conclusions and Discussion. 
The results obtained disclose the intimate connexion which exists 
between growth and abscission. It was shown in the first place that the 
tendency of the plant to shed its young fruit was relatively small until 
growth in the main axis had almost ceased. 
Both of these phenomena, the cessation of growth in the main axis 
and the more pronounced susceptibility to shedding, were attributed to 
a correlation factor, which was introduced as a result of the development 
of fruit on the basal fruiting branches. It seemed probable that this factor 
was in some way associated with a deflexion of assimilates from the apical 
to the basal part of the plant, and that consequently the greater liability of 
young bolls, produced during the latter portion of the flowering period, to 
undergo abscission resulted from their inability to obtain the assimilates 
necessary for development in the presence of a large number of more mature 
bolls. An important consequence of this hypothesis, in support of which 
an experiment by Ewing was cited, is that the elimination of fruit by 
abscission or in other ways diminished the susceptibility to shedding ; this 
is due, no doubt, to the fact that a reduction in the number of competing 
centres necessarily augments the supply of elaborated food. It should also 
follow as a result of the progressive stringency in the supply of assimilates 
that a certain amount of shedding would occur, even under constantly 
favourable environmental conditions. In a word, it was concluded that the 
amount of shedding which takes place during any given period is determined 
on the one hand by the rate at which food is elaborated by the plant and 
on the other by the rate at which it is withdrawn by the developing fruit, 
and that consequently the advent of any factor which tends to limit 
elaboration augments the rate of shedding. 
