1907] VINSON—INVERTASE IN DATES 407 
quicker in boiled solutions than in unboiled, and it was therefore not 
an enzyme reaction. We found oxygen essential to the color develop- 
ment, because solutions kept in an atmosphere of hydrogen over alka- 
line pyrogallol never turned pink, even in the bright sunlight, where 
they were heated to 500r 55°C. Either in the dark or in the sunlight 
the color developed readily if free access of oxygen was allowed. This 
change was never noticed when using invert sugar date extracts. 
Whether or not it has any connection with the invertase is unknown. 
Aside from the chemical classification into cane and invert sugar 
dates, there is also a physical one into dry and soft dates. We find 
both cane and invert sugar dates in the dry class as well as in the soft. 
The Deglet Noor is a typical cane sugar date, yet decidedly a soft 
date. The M’Kentichi Degla is also a cane sugar date, but of the 
hard class. The Saffraia, on the other hand, is as typical a hard date 
as the M’Kentichi Degla, but for all that practically an invert sugar 
date. The Halloua is a hard but only partial cane sugar date, some- 
what similar in sugar content to the artificially ripened Deglet Noor, 
i.¢., about 20 to 25 per cent. of cane sugar. In ripening, the hard 
dates do not soften or change color; they remain yellow. They 
shrivel somewhat, but this cannot be used as an index of ripeness, 
because the shriveling begins before the astringency disappears. 
The origin of the cane and invert sugar dates is obscure, and the 
varieties have existed several hundred years. Nothing is known as 
to whether they originated from seedlings or were sports. They are 
now propagated only from suckers. It will prove interesting to study 
the seedlings to determine whether a cane sugar date can be obtained 
from a cane sugar date seed. This is an inviting field of investigation, 
but, due to the slow development of the plant, would require several 
generations of investigators. 
AGRICULTURAL EXPERIMENT STATION 
Tuscon, ARIZONA 
