234 Green . — On the germination of the tuber of 
being converted into sugar, it being thus brought near to the 
point where it is changed. On the other hand, it may with 
greater probability be suggested to have another origin alto- 
gether, and to be caused by the supply of sugar being too 
rapid for the needs of the growing cells. The surplus sugar 
might in such a case be reconverted into inulin temporarily, 
till wanted. Such reconversion is a matter of constant oc- 
currence in the case of supplies of starch. 
Should the first-mentioned view of its presence be the cor- 
rect one, and the inulin itself be able to travel from the tuber 
to the growing-point, it suggests the question of the necessity 
of any ferment-transformation. But the easy transport of the 
carbohydrate-material is only one of the requisite conditions of 
the nutrition of the growing cells. We can hardly suppose, at 
any rate in the case of inulin, that it is transformed into sugar 
merely to be more easily moved about the plant. There still 
remains the question of the condition in which the carbohydrate 
must be to serve as nourishment to the cells of the growing- 
point. This must apparently be sugar, and hence we have 
always sugar supplied to the growing tissue. 
I have said above that the presence of the ferment is only 
to be expected where the carbohydrate material is being 
rendered available for use. It follows from this that it should 
not appear in the tubers till the onset of germination, and that 
consequently in a resting tuber none should be discoverable. 
In an experiment on this point some developing tubers were 
taken from the plant on which they were being formed, and 
their stalks carefully cut off close up to the tubers, so as to 
leave nothing but the latter. These were then mashed up 
carefully and covered with glycerine. After two days’ exposure 
to this liquid, the extract was filtered off. It was found to 
contain a good deal of sugar. Two dialysers were prepared, 
A and B. In A were put io cc. of this glycerine-extract and 
30 cc. of inulin-solution. B was made up similarly, but the 
extract was well boiled before adding it to the inulin. Outside 
the dialysers 200 cc. of water were placed. As sugar dialyses 
rapidly through parchment-paper, the dialysates were changed 
