1907] VINSON—INVERTASE IN DATES 399 
The following scheme for the translocation of sugars from stems 
and leaves to fruit seems then to be in accord with all known facts 
and contradicted by none. In the early stages cane sugar or mixed 
sugars move into the fruit until osmotic equilibrium is reached. 
After that, excess of cane sugar may be stored as starch within the 
fruit, as in the case of the banana and apple, thus diminishing the 
osmotic pressure for that sugar; or a part may be reduced to invert 
sugar, farther reducing the cane sugar pressure. On ripening, the 
starch is again transformed to soluble sugars. In those cases where 
no starch occurs in the fruit itself, but in the stem, the latter is probably 
a laboratory and not an ordinary storage tissue. The plant would 
scarcely have found it advantageous to thrust storage duties on the 
Invertase 
«+Diastase 
Re 
Maltasé 
stem when the fruit was fully capable and destined to receive the 
same material later. It seems more probable that after osmotic equi- 
librium is reached between the fruit and sap, those sugars against 
which there is osmotic pressure would be changed to starch at the 
threshold, and this starch in turn hydrolized by an amylase into 
maltose. Maltose, against which there is little or no osmotic pressure, 
would enter the fruit and there be split up into glucose or rearranged 
into cane sugar, which would be inverted where it comes into contact 
with invertase. Probably all these reactions take place to a greater 
or less degree in any ripening fruit, but the predominance of one or 
the other leads to a special type. If the main reaction were maltose 
to giucose, fruits of the grape type would result. If maltase secretion 
were suppressed, the maltose would follow the transformation it takes 
in fruits of the date type. 
* 
