AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
The leaves when removed were very brittle, and they were immediately 
placed in a wide-mouthed glass-stoppered bottle in order to prevent con- 
densation of water on their surfaces. In freezing the leaves with ice-salt 
mixture, the leaves were first placed in a glass-stoppered wide-mouthed 
bottle and then immersed in the freezing mixture until the leaves were 
frozen solid. The time of exposure was one hour. The bottle was then 
removed and carefully rinsed to free the outside surfaces of any adhering 
salt, and then wiped dry. The amount of leaves used in every case was 
50 grams of fresh leaves, which for Zebrina is approximately 125 leaves and 
for Iresine 250 leaves. 
For expressing the sap a special apparatus was constructed (fig. i). 
This consists of a steel cylinder, internal diameter four inches, and a closely 
Fig. I. Apparatus for expression of sap. The handle is unscrewed before the apparatus 
is placed in the press. 
fitting solid steel piston. At the base of the interior of the cylinder, around 
the circumference, is a small groove 1/16 inch deep and 1/16 inch wide. 
There is an opening from this groove leading to the exterior, which is fitted 
with a steel tube of a diameter of 1/8 inch. The purpose of the groove is to 
prevent the juice from being forced upwards between the cylinder and the 
piston and also to prevent the tissue from being forced outwards through 
