TRANSLOCATION OF NUTRITIVE MATERIALS = 221 
when the conditions of carbohydrate formation are realised, 
that it may be relied on as a test for the absorption of carbon 
dioxide by the tissue in which it appears. 
In connection with the manufacture and fate of carbo- 
hydrates, we can now see that they may be met with in 
two different conditions: the one suitable for retention in 
the cell and hence capable of functioning as reserve, but 
not immediately nutritive, material: the other capable of 
diffusion, and hence serving as a translocatory form, or 
one in which it can pass from cell to cell, remaining all 
the time in a suitable condition to minister to the nutrition 
of any protoplasm which it reaches. 
The same considerations affect the manufacture, trans- 
port, and storage of proteins. We have already seen 
reason to believe that these, like the carbohydrates, are in 
the first Instance constructed in the leaves, if not by the 
chloroplasts. Our information about them is, however, 
very incomplete; we do not know even what form of 
protein is first formed, nor which kind is needed for 
assimilation by the protoplasm. Possibly it is a soluble 
and. diffusible form, such as a peptone or a proteose, but 
our only reason for thinking so is that such properties 
characterise the travelling forms of carbohydrates. We 
can, however, readily believe in the construction being 
greatly in. excess of the immediate need of the cell, and 
hence in the chain of events being similar to that in which 
the carbohydrates are concerned. 
The different properties of the two classes of bodies 
involve, however, some differences in their behaviour, 
and we can therefore expect similarity only and not iden- 
tity. The diffusibility of peptone, even, is very greatly 
below that of sugar; and we can hardly suppose therefore 
that peptone is the translocatory form of protein in the 
plant. It seems more probable that nitrogenous plastic 
material is transported in the form of some amino- or 
amido-acid such as asparagin. This view is supported 
by observations made upon the utilisation of the reserve 
