1915] 
DAVIS—ENZYME ACTION IN MARINE ALGAE 791 
third their volume, when the scum that formed was filtered 
off; this filtrate was then further evaporated to about one- 
fifth the original volume on the water bath. At this point 
the two lead acetate portions were placed together. Ninety- 
five per cent alcohol was added to each of the lots to about 
80 per cent concentration when a flocculent precipitate came 
down rather slowly. With the Ba(OH)2 portion this was 
copious, with the lead acetate, slight. After two hours the 
precipitates were filtered off, washed with absolute alcohol, 
redissolved in a small amount of distilled water, and then 
reprecipitated with 4 volumes of absolute alcohol, the result- 
ing precipitate being dried over CaCle. From the Ba(OH):. 
portion, 4.2 grams of a creamy white powder were obtained 
that gave a very slightly reddish tinge with iodine, did not 
reduce Fehling’s, and was easily soluble in water, giving a 
clear solution. Upon hydrolysis with weak H2SOu, a reducing 
sugar was split off. The lead acetate portion gave but two 
grams of the same material. This powder was taken to be the 
laminarin described by Kylin. 
The determination of reducing sugars.—The reduction of 
copper, or in the case of maltose and lactose, the increase in 
the reducing value of the substrate plus the enzyme over that 
of the checks, was taken as the measure of carbohydrate 
hydrolysis. In this determination the permanganate titra- 
tion method, as modified and described by Shaffer (714), was 
used, it being possible with it to determine amounts of sugars 
as low as 2 milligrams! very accurately and quickly. Shaffer’s 
description may not be generally available to plant workers 
who may desire to use this really splendid method, and so 
the various steps in the process as used here are set down in 
some detail. 
Ten cc. of the carbohydrate-enzyme substrate were placed 
in a large test-tube containing 5 cc. of water, and just brought 
to a boil. At this point a drop of 50 per cent acetic acid was 
added. When the slight protein precipitate formed, 5 ce. of 
1 Shaffer determines values below two milligrams, but as used here, con- 
sistent results could not be obtained where less than that amount was involved. 
Below this point the relative increase in the experimental error is large. 
