98 D. T. MacDOUGAL 



ment in one case was with nutrient solution in which the salts 

 were more concentrated than in the swamp water used in the 

 other. The final swelling in the second case is greater and may 

 be attributed to the initial salt action. 



In a partial repetition of the above test the sections placed in 

 nutrient solution swelled 861% in twenty hours. Lengthening 

 the immersion in acidified potassium nitrate to fifty-five hours 

 was accompanied by a swelling of 55%. Replacement with dis- 

 tilled water set up a slow increase which resulted in a gain of 

 111% in thickness in forty hours. The total increase was 

 1027%, while the one finished in swamp water swelled 1388%. 



The relative effects of swamp and bog water on biocolloids 

 were tested in still another way. Plates of agar-oat-protein 

 were prepared in which strips of webbing of cotton were imbedded 

 in the soft material as it cooled for the purpose of testing the 

 influence of certain purely mechanical features on swelling. 

 Portions of the plates dried down to a thickness of 0.18 mm. in 

 the clear portion of the plate and sections from this swelled 

 2111% in bog water and 1195% in swamp water at 15°C. Sec- 

 tions containing webbing were 0.58 mm. in thickness and the 

 actual increase of such sections was 491% in bog water and 

 distilled water and 371% in swamp water. If the increase be 

 calculated on the assumption that the webbed sections included 

 as much biocolloid as the free sections the proportions would 

 be 1583% in bog water and distilled water and 1195% in swamp 

 water. 



The foregoing paragraphs describe a series of tests made for 

 the purpose of deteraiining the effects of the water of sphagnum 

 bogs and sedgy swamps upon plants. Detailed analyses of water 

 characteristic of both habitat have long been available, but it 

 has not been possible to explain some of the more marked effects, 

 on the basis of such information. 



An effort has been made to find such an explanation by further 

 studies of the mechanism of hydration of protoplasm. Living 

 matter swells in solutions in the same manner as biocolloids con- 

 sisting of salted mixtures of varying proportion of agar and pro- 

 tein or albuminous derivatives. The swelling of biocolloids 



