69 
Date Endosperm for Self- Digestion . 
freshest, so that seeds saved from such fruit are large and nearly all capable 
of germination. The seeds so obtained are partially cleaned, but it is 
always necessary to wash them thoroughly without soaking, after which 
they may be stored in a dry place for use as needed. The fleshy mesocarp 
contains reducing sugar. 
In all the material used embryo substance was absolutely excluded. 
This was accomplished by rotating the point of a pocket-knife in th j 
embryo cavity of each and every dry seed until, by examination, all traces 
of embryo substance were removed. In all the material used this task was 
done by myself. Since the membranaceous endocarp which still clings to 
the seeds as so far cleaned contains tannin, it is necessary to remove this in 
some way. This may be accomplished either by sifting over an air blast 
after each grinding, and before the powder becomes at all fine, or by wash- 
ing and drying rapidly after each time through the mill. By either method 
so little tannin remains that digestion in water at ordinary temperature for 
six hours gives a liquid which does not react with ferric chloride. Both 
methods were used : the former before it was known that the contained 
proteids are insoluble in water, and the latter after. 
Estimation of the hydrolytic product . — Having found Fehling’s solution 
unsuitable for my purpose, I decided to find a method which would give me 
more reliable data. Since starch, dextrine, and enzyme are insoluble in 
95 per cent, alcohol, while the reducing sugars arising from enzyme activity 
are soluble, this reagent was employed for separation. The following test 
shows the efficiency of such a method. A solution of soluble starch 1 was 
made, and its content of anhydrous starch per cubic centimeter determined 
by evaporating over steam triplicate volumes, drying the residue at no°C. 
for one hour, cooling in the desiccator and weighing. The anhydrous con- 
tent of a filtered solution of amylopsin was similarly determined. It was 
thus possible to titrate a given weight of starch with a given weight of 
enzyme, and then to determine the weight of the hydrolytic product as 
follows: After digestion the solutions were made 95 per cent, alcoholic 
and then allowed to stand until the precipitate settled. The alcoholic 
solution was decanted, filtered, the precipitate washed with alcohol and 
the filtrate then evaporated to dryness over steam in tared beakers. The 
residue was air-dried at no 0 C. to constant weight. This residue is brown, 
with a sweetish, toast-like odour, very hygroscopic, easily soluble in water, 
and reduces Fehling’s solution, but the reaction is not precise, and much of 
the precipitate remains in suspension for some time, but finally settles. 
From the following tables it is evident that the hydrolytic product soluble 
in alcohol is very constant for a given ratio of enzyme to starch. 
1 Dry potato starch was extracted with glycerine (i8q°-I 90° C.) for thirty minutes and precipi- 
tated with alcohol. Purification was accomplished by reprecipitation with alcohol from aqueous 
solution. 
