1907] VINSON—INVERTASE IN DATES 395 
found also that banana pulp not only reduced its own cane sugar 
rapidly, but could invert large amounts of added cane sugar. 
Bartry,'° however, states that he failed to find any enzymic action 
in the ripening of the banana, but his figures show a dropping-off of 
cane sugar after the yellow-brown stage. 
In a set of tests for invertase with very green, yellow, and black- 
ripe bananas, made in this laboratory, a feeble inverting power at 
room temperature was found in the two latter conditions, but not at 
all comparable with that of an invert sugar date under like conditions. 
It is possible that cane and invert sugar bananas may be found. In 
the banana, however, the reserve material in the fruit itself is largely 
starch and is finally converted into cane sugar, either directly or by 
way of maltose. Nevertheless, it would seem that some cane sugar, 
as such, may come into the banana ripened on the tree, for both 
BurGNet’ and Riccrarpi'? agree that when ripened naturally this 
fruit contains more cane sugar and less invert sugar than when 
ripened artificially. Substantially the same is true with the cane 
- sugar date. It is not untenable, however, that some other soluble 
carbohydrate may enter the fruit and be rapidly synthesized to cane 
sugar, for BRown and Morris’3 have shown that the excised barley 
embryo, cultivated on maltose solution, formed cane sugar very 
rapidly by the ‘action of the living embryo cell.” They found also 
that living embryos did not synthesize cane sugar from glucose. This 
difficulty is not insurmountable, for Hi1x'4 demonstrated the revers- 
ible nature of enzymic action by synthesizing maltose from glucose in 
very dilute solution by the aid of maltase. The maltose formed was 
later found to be isomaltose,'s but that does not necessarily mean 
that, under cell conditions, true maltose would not be formed. The 
reverse action of enzymes has been shown to be influenced, at least 
with regard to speed, by the presence of a third body. Thus ethyl- 
butyrate is formed more sare by lipase in the presence of lecithin.*® 
t° Jour. Biol. Chem, 1:355. 19 
™ Compt. Rend. 49:276-278. Hn through Bull. 94, Bur. of Chem. 
™2 Compt. Rend. 95:393. 1882; ibid. 
13 Jour. Lond. Chem. Soc. 57:458 (517). 1890. 
14 Jour. Lond. Chem. Soc. 73:634. 1898 
ts Through Lors, Dynamics of living matter 11. New York 1906. 
16 HEWLETT, ibid. p. 10. 
