DEPARTMENT OF BOTANICAL RESEARCH. 



65 



The imbibition of Iridcea laminarioides indicates a high proportion 

 of amino-acids, while the species of Gigartina studied probably contains 

 a higher proportion of pentoses or agar-like substances. 



Smooth young laminae of Gigartina exasperata were washed in fresh 

 running water for 24 hours to remove most of the sea-salts and then 

 dried between filter-papers. Trios of sections of these dried laminae 

 were swelled in N/100 HCl, in N/100 NaOH, in distilled H2O, and in 

 the sea-water solutions mentioned above, with results as follows: 



Per cent of swelling. 



Thickness, mm 0. 1016 



Sea-water +NaOH N/lOO 393 . 7 



Sea-water +HC1 N/100 590.5 



DistUled H.O 1,476.0 



Thickness, mm 0.0508 



NaOH N/100 2,755.9 



HCl N/100 2,066.9 



DistiUed HjO 4,330.7 



A chemical analysis of this dry material gave the following results: 



Average p. ct. 



Ash (salts) 11 .70 



Moisture 15 . 70 



Gelatine-like material 14.95 



Carbohydrates — agar-like material 57.65 



The gelatinous or mucilaginous material was extracted from each of 

 these species by heating several grams of the plants, which had previ- 

 ously been washed for 24 hours, dried, and finely ground, for 2 or 3 

 hours at the temperature of boihng water, and then straining through 

 four thicknesses of mushn. The extract so prepared was a pale straw- 

 colored viscous fluid which would not sohdify completely when cold 

 but became very thick and viscous. The extract from all of the 

 species was fairly uniform in character. Plates were made from 9 

 grams of agar and the extract from 10 grams of the dry Gigartina 

 exasperata. Trios of sections from these plates were swelled. The 

 proportionate increase in water in the solutions is characteristic of a 

 mixture of agar with a small proportion of albumen or protein as indi- 

 cated by the data obtained by MacDougal. This implies that the 

 extract of the alga was chiefly gelatinous and probably consists largely 

 of amino-acids. The swelhng of the dried sections alone, however, is 

 more characteristic of agar. 



Thickness of sections, mm 0.2286 



NaOH N/100, per cent swelling . 809 . 



HCl N/100, per cent swelling ... 809 .0 



Distilled H2O, per cent swelling. . 2,296 . 



Thickness of sections, mm 0.2032 



NaOH N/100, per cent swelhng. 910 . 4 



HCl N/100, per cent swelliDg ... 984 . 2 



Distilled H2O, per cent swelling . 2,460 . 



