95 
Leaf Surface of Cucumis sativus. 
inwards, and great care is needed in these cases to avoid injury in measuring. 
It sometimes happens that leaves are markedly asymmetrical, so that the 
median vein does not bisect the angles subtended at the base by the lateral 
points. In such cases the same procedure was followed as if the leaves were 
of normal shape. 
Care must be taken not to confuse the angles subtended by the points 
with the angles between the lateral veins running to the points, since these 
are smaller than the angles required. 
C. Experimental Procedure. 
The results presented below are based on the results of a series of 
experiments carried out in one of the experimental greenhouses of the 
Experimental Station, Cheshunt. 
Ten plants were kept under observation in each experiment. The 
method of cultivation was that usually adopted in horticultural practice. 
The seeds were not graded by weight, but were selected for plumpness and 
uniformity. During their entire course of development the plants were 
kept at the south end of the greenhouse and were fully exposed to sunlight. 
The plants were thus kept under perfectly normal conditions. The 
temperature of the house was recorded by a thermograph, and the radiation 
by a Callendar radiometer. 
Three sets of experiments were started on 10/11/16, 21/2/17, and 
11/6/17 respectively, and each experiment was carried on for 30 days. The 
dimensions of the leaves were taken, each day at 10 a.m. A specimen entry 
from data of Expt. Ill for July 2 is shown on p. 96. 
