SEcTION IV, 1916 [55] TRANS. RS. EC. 
The Abscission of Flower-buds and Fruits in Gossypium, and its Relation 
to Environmental Changes 
(Abstract) 
By Francis E. Lioyp, F.R.S.C. 
(Read May Meeting, 1916) 
The purpose of the work was to determine (a) the method of 
abscission or “‘shedding’’ in the flower-buds (‘‘squares’’) and fruits 
(“‘bolls’’) in the cotton plant, Gossypium herbaceum; and (b) the cause 
or causes leading up to shedding in the field. The conclusions herein 
set forth are based on daily records of shedding and environmental 
changes for the whole of two growing seasons, 1911 and 1912 at Auburn, 
Ala., together with experimental data obtained during a third season, 
1913, at West Raleigh, N. Car. Records embodying data obtained 
on alternate days during 1906 and 1907 at Auburn, Ala., were placed 
at the writers disposal, and the present study has embraced these also. 
The environmental factors measured were rainfall, soil and air tem- 
peratures, superficial soil moisture and evaporation (atmometrically). 
THE METHOD OF ABSCISSION 
The method of abscission is essentially identical with that which 
the writer has described at length for Mirabilis Jalapa! and consists 
fundamentally in the alteration of cell-membranes (pectose and cellu- 
lose) by hydrolysis, so that one transverse tier of cells is set free from 
the next tier above. The actual completion of this hydrolysis is 
preceded by more or less growth in the lower tier of cells, usually, 
though not always, accompanied by cell-division in these cells. The 
older the organ, the more extensive the cell-division; in very young 
bolls, it may not intervene. But while the occurrence of cell-division 
appears to depend on the age, and therefore on the size and condition 
of the membranes in the organ involved, the evidence obtained 
strongly suggests that the intensity of the stimulus and the consequent 
rapidity of the response, are also in some degree responsible. The 
exact period required for the reaction of abscission, is, for reasons 


! Lloyd, F. E. Abscission in Mirabilis Jalapa. Bot. Gaz. 61: 213-230. pl. 13 
March, 1916. 
