Mason. — Growth and Abscission in Sea Island Cotton . 483 
6 . Removal of the foliage leaves from plants on which there were 
a number of maturing bolls resulted in the abscission of §6*5 per cent, of 
the young bolls within a period of nine days. The interval between the 
operation and the maximum rate of shedding was approximately similar to 
that normally occurring between the causative environmental conditions 
(cf. 4) and the completion of abscission. 
7. The growth-rate of the main axis was only slightly retarded during 
the hours of sunshine, from which it was concluded that incipient drying 
was not pronounced under the humid conditions of St. Vincent. 
8. The growth-rate of the boll declined for some days following 
anthesis ; recovery was found to be dependent on fertilization. 
9. It was concluded that the metabolic transformations which preceded 
the formation of the absciss layer were especially liable to be initiated during 
this period of growth-retardation. 
10. Negative growth-rates were generally shown by the boll for some 
one to three days prior to the completion of abscission. It was suggested 
that inability to secure the assimilates necessary for normal development 
diminished the water-absorbing power of the boll until a stage was reached 
at which the tension in the water-columns of the plant led to a suction of 
water from the boll. This, it seemed, was the cause not only of the negative 
growth-rates, but was actually the factor initiating abscission. 
11. The general conclusion was drawn that the proportion of shedding 
over any given period was the resultant of two opposing factors, the rate 
at which food was synthesized by the plant and the rate at which it was 
utilized in the maturation of the fruit ; and that any check in the former 
augmented the rate of shedding. 
12. It was emphasized that any factor which injured the boll — fungous 
and bacterial diseases, insect depredations, &c. — caused the shedding of the 
boll, provided the injury was sufficiently pronounced as to interrupt the 
translocation of food into the boll. 
In conclusion, the writer wishes to record his indebtedness to Mr. C. A. M. 
Marshall for his indefatigable assistance throughout the progress of the 
work. 
St. Vincent, 
March 1922. 
