Translocation in Plant Tissues. 
297 
adjustments when equilibrium is disturbed ; it will take time for the effect 
produced in this peripheral portion of the vacuole to be transmitted (by 
diffusion of solute) throughout the whole of the cell sap. 
Emphasis must be laid upon the enormous area of the protoplasmic 
linings of plant cells compared with the volume of the tissue which they 
compose, for in this way innumerable small reservoirs are provided, and 
these are readily accessible to the protoplasm. There is therefore available 
very extensive machinery by means of which translocation can be effected 
in the manner to be described. 
It is now proposed to apply these considerations to the case of sugar 
transport within the plant. 
A normal green plant derives its sugars solely from the cells of the 
photosynthetic system. That is to say, there is never any question of the 
sugar having to enter such a plant from outside , since it actually arises 
within the assimilating cells, and presumably within the protoplasm itself. 
Now it follows from what has been stated above, that if any of the 
protoplasmic constituents can adsorb sugar to any extent, there will always 
exist a tendency to attain the specific relation between the amount adsorbed 
and the amount remaining in solution. 
It should be noted that true adsorption compounds of albumen, 
lecithin, and glucose are known to occur , 1 so that there is nothing improbable 
in the supposition that vegetable protoplasm contains elements capable of 
bringing about local concentration of sugar on their surfaces, possibly in 
varying degrees. (Cf. Fig. 1.) 
When in a given chlorophyll-containing cell a particular plastid has 
produced sugar, this in course of time will pass into solution in the 
immediately adjacent liquid phase of the protoplasm, and so into the sap of 
the vacuole presumably continuous with it ; in this the sugar will diffuse in 
accordance with the ordinary solution laws. 
Since, however, particles capable of adsorbing sugar are assumed to be 
distributed throughout the protoplasm, the sugar will tend to accumulate at 
their surfaces. 
Consequently, the two processes of diffusion through the solvent, and 
adsorption at the surface of protoplasmic components, would contribute to 
the transference of the sugar. 
If the adsorbing particles were few and relatively distant one from 
another the ultimate rate of movement of the sugar would be conditioned 
almost entirely by the rate of diffusion in the continuous liquid phase, that 
is, it would probably be extremely slow. 
If, however, the adsorbing particles were fairly numerous and com- 
paratively close together, the diffusing sugar molecules would not have far 
to travel before reaching the surface of one of them. 
1 Bayliss, 1 . c., pp. 57 and 66. Cf. also p. 65. 
