May, 1922] 
TRELEASE INCIPIENT DRYING AND WILTING 
University of the Philippines, at Los Banos, during April and May, 1918, 
in connection with class work in plant physiology. It is a pleasure to 
acknowledge indebtedness to Prof. B. E. Livingston for suggestions in the 
preparation of this paper; and to members of the class, especially Mr. Pedro 
David and Mr. F. de Peralta, for assistance in securing the measurements. 
Experimentation 
Excised pinna samples. To study the relation between water content 
and the degree of closure, pinnae were cut from a plant and taken to the 
laboratory, where the measurements were made. From near the middle 
of a pinna three 8-cm. lengths were cut. The pieces were weighed at 
intervals, the distance between the two free edges of each piece (here called 
its apparent width) being measured immediately after each weighing. 
After continuing the measurements for several hours, the area of one side 
of each piece was determined. They were then dried, and the water content 
was calculated for each weighing. 
The results of five similar tests, made in the laboratory (temperature, 
27° C.) with excised pieces of pinnae, are presented in table i, three pieces 
being used in each test. From the average apparent width of the pinna 
in each case has been derived the average magnitude of the angle between 
the two lower faces of the pinna wings; and the average angular magnitudes 
are given, for the several observations, in the last column of the table; 
this value may be called the angle of pinna divergence, which is taken as 
related to the turgor condition of the two pinna hinges. 
A 
Fig. I. Diagrammatic cross section of coconut pinna; lines AB and AC representing 
the two pinna wings, hinged to the midrib at A, and the line BC representing the apparent 
pinna width. 
If the diagram of figure i represents a cross section of a coconut pinna, 
lines AB and AC representing the two pinna wings, hinged to the pinna 
midrib at A, then line BC represents the apparent pinna width for the 
cross section used. Determination of the average apparent width of the 
pinna sample used was made at each time of observation, and the apparent- 
width values are given in column 6 of the table. Determination of the 
average width of each of the two (similar) wings was also made for each 
