1915] 



DAVIS — ENZYME ACTION IN MARINE ALGAE 793 



baskets having wooden bottoms and tops were nsed, the tops 

 containing holes large enough for the free insertion of the cen- 

 trifuge tubes, and the bottoms, slight depressions into which 

 the tubes might rest. It is always necessary to run blanks 

 with Fehling's solution since some reduction always takes 

 place. The cuprous oxide solvent must be free from ferrous 

 iron, and this can be assured by the addition of a trace of per- 

 manganate. 



Method of setting up experiments. — Fifty cc. of the sub- 

 strate to be used were placed in 125 cc. Erlenmeyer flasks with 

 2 per cent toluene as an antiseptic. If the series were main- 

 tained longer than six weeks, another 2 per cent toluene was 

 added. As previously noted, in these carbohydrate experi- 

 ments the material used for enzyme action was an alcohol 

 precipitate from a water extract of algal powder or pulp. 

 This was diffused in water so that 10 cc. of the diffusion 

 represented 2 grams of the original tissue. Usually this 

 amount was added to the substrate to be tested. Duplicates 

 and checks were set up in accordance with the following model 

 series for starch : 



1. 50 cc. starch, 10 cc. enzyme diffusion. 



2. 



50 cc. starch, 10 cc. enzyme diffusion. 

 50 oc starch, 10 cc. boiled enzyme diffusion 



starch. 10 cc. boiled enzvme diffusion 



3. 50 



4. 50 cc. starch, 10 cc. boiled enzyme 



5. 50 cc. starch, 10 cc. distilled water. 



6. 50 cc. starch, 10 cc. distilled water. 



3 To make this table more generally available, it is printed here in full. 



Shaffer's table of copper-glucose equivalents 



mgms. 



mgms. 



mgms. 



mgms. 



mgms. 



copper 



glucose 



copper 



glucose 



copper 



0.7 



.47 



6.0 



2.74 



20.0 



1.0 



.62 



7.0 



3.21 



25.0 



1.5 



.88 



8.0 



3.68 



30.0 



2.0 



1.11 



!).0 



4.15 



35.0 



2.5 



1.32 



10.0 



4 . 65 



40.0 



3.0 



1.50 



12.0 



5.61 



50.0 



3.5 



1.67 



14.0 



6.61 



60.0 



4.0 



1.82 



16.0 



7.61 



80.0 



5.0 



2.27 



18.0 



8.65 



100.0 



mgms. 

 glucose 



9.71 

 12.25 

 14. SO 



17.40 

 20.00 

 25.00 

 30.10 

 40.40 

 50.70 



