236 
Walter Stiles 
Determinations of the Effect of Temperature by the Method 
of the Rate of Linear Shrinkage of Turgid Tissues 
The first critical research on the influence of temperature on cell 
permeability to water is that of Miss Delf (1916). Her method was 
similar in principle to that used by van Rysselberghe, but was con¬ 
siderably more sensitive. By means of the optical lever, which had 
already been introduced into plant physiology by Bose (1906) to 
record small movements in plants, changes in length of short strips 
of tissue could be observed under a magnification of 350 diameters. 
The apparatus devised by F. F. Blackman and used by Miss Delf 
is directly applicable only to the investigation of hollow cylindrical 
structures, those used by Miss Delf being onion leaves and dandelion 
scapes. 
The essentials of the method are as follows. The lower end of 
the plant cylinder is firmly fixed by means of cotton to a glass 
tube of narrow bore which passes through a cork held immovable 
by a metal clamp. The upper end of the cylinder is pierced by a fine 
glass hook attached to a loop of very fine waxed cotton which at 
its upper end is itself attached to the projecting wire arm of the 
optical lever, which carries a small mirror reflecting the image of an 
illuminated cross wire on to a millimetre scale. Contraction of the 
cylinder can thus be very accurately measured by the movement 
of the image of the cross wire on the scale. For details of the 
apparatus and procedure, including the method adopted for ob¬ 
taining different constant temperatures, reference must be made to 
the original paper. 
The material selected for investigation already noted above was 
chosen because the inner surface of the hollow cylinders of which it 
is composed is lined entirely with cells possessing thin cellulose 
walls. Solutions of cane sugar in various concentrations (0*18, 0*3, 
0*5 and 0*731 weight-molecular solutions) were allowed to flow 
through the hollow cylinders of plant tissue and the contraction 
resulting followed by the optical lever arrangement. The total con¬ 
traction produced by these solutions varies somewhat with the age 
of the material, but very greatly with the concentration of the 
solution. Thus dandelion scapes in 0*30 M sucrose contracted to 
the extent of 0*2 to 0*4 per cent, of the original length, while in 
0*731 M sucrose the contraction was as much as 2 to 2*5 per cent, 
of the original length. Similarly, onion leaves in 0*18 M sucrose 
contracted 0*3 to 0*5 per cent, and in 0*731 M sucrose 3 per cent. 
