288 Del/,— Studies of Protoplasmic Permeability by 
an experiment within i° C including the change from water to the 
plasmolysing solution. 
When the chamber temperature was constant, the tap K (Fig. i) 
admitting the water current was turned off, the outlet M of the chamber 
blocked, and the chamber lowered by removing the block of wood P 
upon which it stood. The metal clamp containing the glass nozzle was 
removed from its socket, and the piece of tissue was then fitted to the 
nozzle and bound tightly. The nozzle was then inserted in the clamp, 
the clamp fixed in position again so that the material was vertical, and 
the glass hook inserted so that the spot of light from the mirror occu- 
pied a convenient position on the scale. The chamber was then raised, 
and the tissue therefore at once submerged in the water of the chamber 
at the required temperature. The tap K was at once turned to admit 
water, the exit-tube M unblocked, and a reading of the scale taken. The 
whole process of fixing on the plant after the temperature was estab- 
lished was a matter of about one minute, so that there was no unneces- 
sary preliminary exposure of the tissue before the beginning of the 
observations. 
During the course of an experiment, readings of the scale were made 
at frequent intervals, concurrently with readings of the thermometer in 
the chamber. At high temperatures the readings were often taken every 
half-minute when first the plasmolysing solution was turned through the 
apparatus. 
Just before the sugar solution was to be given to the plant, and 
whilst the latter was still supplied with water, the sugar current was 
circulated through the path Y, R, N (Fig. i) and out to a waste receiver. 
The rate of this current was adjusted until it was equal to that of the 
water current through the chamber, and in a few minutes its tempera- 
ture was that of the water leaving the water-bath. The water current 
was then diverted from the plant to the ‘ by-pass ’ J (Fig. i) by the 
three-way tap K and the taps of X and Y (Fig. i) reversed so that the 
paths of the sugar and water currents were interchanged. The sugar 
reached the chamber tube z in thirty seconds, and the tap K was turned so 
that the sugar passed up the coil and through the plant. Immediately 
after turning the tap K a reading was made of the scale, and in about 
thirty seconds, when the denser sugar solution could be detected stream- 
ing over the edge of the cylinder, a second reading was made. During 
the replacement of water by solution there was no variation in the position 
of the spot of light on the scale. In some cases after plasmolysis had been 
observed, the water current was again turned through the plant, in order to 
observe the course of deplasmolysis, 
