620 Price . — Some Studies on the Structure of the Plant Cell 
the protoplast — the vacuole wall layer. These vesicles, then, probably 
represent the sort of structure which must be attributed to the vacuole wall. 
The vesicle generally encloses numerous sap particles, which are very 
conspicuous and show their usual Brownian movement. The general mass 
of the protoplast, which is also shown in this focus, is as already described, 
the larger microsomes showing their accustomed oscillation, and the outer 
layer being somewhat differentiated. 
Focus c (PI. XLI, Fig. 3), just inside the wall, gives the appearance of 
a very large number of closely packed fine particles in very rapid oscillation, 
the whole producing quite a cloudy appearance. It is very difficult to decide 
whether this represents a layer lining the inside of the wall, or whether the 
particles are in the space lying between the wall and the protoplast, but 
I am rather of the opinion that the former is the case. If this is so it must 
represent a very thin layer of protoplasm with a fine structure left attached 
(by viscosity?) to the outer wall. It may be a fine layer connected by 
fibrils with the main protoplast (see (b) below). This layer was not made out 
in all cases of plasmolysis, but the fact that it sometimes occurs, whatever 
its nature may be, seems worth recording. 
In Mongeotia somewhat similar phenomena have been observed. The 
protoplast usually contracts, leaving a vesicular structure at each end, the 
wall of this being practically transparent. This vesicle wall seems to be 
rather in a gel condition, and not as the vesicle wall in Spirogyra . No 
movement of particles could be observed in this wall, and also, in a case of 
fragmentation of the protoplast of the type shown, no movement in the 
colourless membrane connecting the two portions could be seen. This 
finally became a thread with no visible structure. It seems rather surprising 
that the structure of this membrane and the protoplast generally should be 
so different in two genera of Algae so closely allied. 
The material of Cucurbita hairs also furnished some good cases for the 
study of plasmolysis, especially as there are practically no chloroplasts to 
interfere with observation. Plasmolysis was effected with potassium nitrate 
5-10 per cent., cane sugar 20 per cent, and 30 per cent., and other agents. 
The simplest case observed was probably that in which the protoplast 
gradually contracts from the wall and masses itself towards the middle of 
the cell. In this process fine protoplasmic fibrils are usually produced, 
showing the typical features of these. As the protoplast slowly comes 
away from the wall the outside is seen to be bounded by what seems 
to be a definite membrane of a transparent nature as shown by the 
bounding line in PL XLII, Fig. 4. The finer particles of the protoplast are . 
present towards the outside and seem continuously to impinge on this 
transparent membrane or surface layer. It is quite possible that a distinct 
boundary between a slightly viscous colloid in the sol state and a watery 
liquid would possess this appearance, but the probability of the presence of 
