18 Scientific Proceedings, Royal Dublin Society. 



from other sources, as merely to demonstrate its presence and record its 

 distribution. 



A 1 per cent, sucrose solution has been employed, and to this the powdered 

 leaf is added. 



The following measures were adopted in order to minimize as far as 

 possible all sources of error : — 



1. The sucrose solution was tested for reducing substances before each 



experiment. 



2. Toluol was used as an antiseptic. 

 6. All flasks were sterilized by heat. 



4. The nature of the reducing sugars produced was determined by means 

 of phenylhydrazine. 



Two flasks were used in the following experiment : — 



The first contained 50 c.c. of a 1 per cent, sucrose solution, to which 

 2 grams of the leaf-powder of Polytrichum had been added. It was boiled 

 to destroy the enzymes, and furnished a means of making allowance for any 

 sugars the leaf -powder might contain. 



A second flask containing 50 c.c. of a 1 per cent, sucrose solution was 

 boiled, thus ensuring against any active material that might exist in either 

 the sucrose solution or in the flask. It was then cooled, and the 2 grams of 

 leaf-powder were added. 



After four days' incubation at 35° the sugar solution in each flask was 

 filtered from the leaf-powder, which was thoroughly washed with distilled 

 water, and made up to 100 c.c. The following figures show that the leaves 

 of Polytrichum commune contain an active invertase: — 



Grams CuO reduced before incubation by 100 c.c. of 



1 per cent, sucrose . . . . . = 0'00. 



Grams CuO reduced after four days' incubation . = 1"45. 



For the detection of the invertase in the various parts of the stem of 

 Polytrichum, and in other mosses, two test-tubes are used : each is half-filled 

 by a 1 per cent, sucrose solution ; to one a small quantity of the leaf-powder is 

 added, and the whole is boiled for several minutes, cooled, toluol added, 

 corked, and incubated at 34°. The other test-tube is boiled before the leaf- 

 powder is added, and then treated in a similar manner to the first. After 

 twenty-four hours' incubation, both test-tubes are examined for reducing 

 sugars with freshly made Fehling solution and phenylhydrazine. 



In P. commune invertase has been found both by day and night, and in all 

 parts of the stem ; even after the plants had been subjected to four days' 

 darkness its presence could be detected. 



