| 
f 
el 
=e ae, renee cece 
1907] VINSON—INVERTASE IN DATES 403 
taken. It seems more rational to consider the composition of each 
sample as we find it, together with its apparent condition of ripeness, 
the average weight of the individual fruits, the average weight and 
percentage of seeds, and finally the general relation which the indi-’ 
vidual fruits forming the sample seem to bear to the whole. By 
reduction to any other basis, some of these points, especially those 
involving personal equation in the greatest degree, are masked but 
not equalized. 
Study of the analyses reveals a marked similarity in the composition 
of the two varieties up to the time of maturity in size. The Deglet 
Noor shows an inclination toward cane sugar even in the early stages, 
but from this point on it gains chiefly in cane sugar until ripeness is 
approached, when some inversion takes place. The amount of this 
inversion seems to be influenced largely by the temperature to which 
the ripening date is subjected. Under normal conditions, 20 to 25 
per cent. of invert sugar is formed; but under the conditions neces- 
sary for artificial ripening, 45 to 50° C for several days, a much larger 
proportion is inverted. The sample ripened on the tree after frost 
shows less inversion. The invert sugar date shows an increase in 
invert sugar parallel to the increase in dry matter. At the period of 
maximum ripening, when dry matter is accumulating very rapidly, 
cane sugar appears in considerable quantities. This I attribute to 
the formation of cane sugar at a greater rate than the invertase is 
capable of inverting it. - The same is also undoubtedly true with other 
invert sugar fruits, their sugar passing through cane sugar which Is, 
at times formed more rapidly than inverted. Many varieties of 
dates have been examined in this respect, and cane sugar is always 
observed to accumulate just before the date softens. At the time of 
softening the invertase, which before this cannot be dissolved by 
water or glycerin, is now readily extracted by these solvents. In the 
thick syrupy juice of the date this increased mobility of the invertase 
must greatly accelerate its action. This accounts for the more rapid 
disappearance of cane sugar after ripening. ae 
The difference in behavior of the two classes of dates during ripen- 
ing suggested that the presence or absence of invertase must be the 
determining factor, and accordingly, the inverting power of a Deglet 
Noor glycerin extract was tested as follows: 100°¢ of date extract was 
