Mason . — Growth and Abscission in Sea Island Cotton . 475 
stimulus to fruit development. In order to ascertain whether this was so 
or not, two lots, each of twenty-five flowers, were tagged. The stamens 
were removed from both lots on the day preceding the opening of the 
flower. On the following day one lot was pollinated and the corollas of 
both lots were closed with string. All the bolls which had been pollinated 
completed development, whereas twenty-two 
of the non-pollinated lot were subsequently 
shed. The three bolls of the latter lot which 
were not shed appeared to have normally 
developed seeds, and therefore presumably 
had been pollinated, possibly by ants or thrips 
entering at the base of the flower between 
the petals. Inspection of the graphs in Fig. 12 
will show that recovery from the initial decline 
in the growth-rate is dependent on the stimulus 
communicated by fertilization, for though only 
thirteen of the bolls which were shed are repre- 
sented in the figure, yet none showed any indi- 
cation of recovery. The conclusion seems 
justified that the pronounced liability of the 
boll to be shed when about seven days old 
is associated with the growth- retardation which 
occurs for some days following the open flower 
stage, and that this in turn is due to the lag 
which occurs between the completion of fertilization and the communication 
of the stimulus for fruit development. The metabolic transformations which 
precede abscission are apparently initiated during this critical period of 
growth-retardation, and doubtless in some way inhibit the stimulus to 
augmented growth arising from the process of fertilization. The tendency 
,of the flower-buds to be shed at a very early stage of development is 
conceivably also to be attributed to the slow rate of growth at that 
time, though no direct evidence in support of this view is obtainable. It 
will be observed that the assumption has been made that the growth-rate 
is an index to the rate of metabolism or physiological activity, and that 
low rates of metabolism render the flower-bud or boll especially liable 
to undergo abscission. A more extended discussion of this point will be 
deferred until the results of some additional experiments have been presented. 
Fig. 12. Showing recovery in 
the growth-rate of the boll due to 
stimulus of fertilization. 
Abscission and the Supply of Assimilates. 
The ages of two lots of bolls at shedding, one of 25 and the other of 
30, are shown in Table I. The growth-rates of 13 of the first lot were 
considered in the preceding paragraph (Fig. 12). Pollination was prevented 
in both lots by the removal of the stamens on the day prior to flowering. 
L 1 2 
