66 CARNEGIE INSTITUTION OF WASHINGTON. 



IMBIBITION AND WATER-RELATIONS OF PLANTS. 



Effect of Bog and Swamp Waters on Plants and on Biocolloids, 

 by D. T. MacDougal. 



Hitherto it has been impossible to establish an adequate causal 

 connection between the main physico-chemical features of bog and 

 swamp water and their effects on plants, except that Clements has 

 recently demonstrated that the lack of dissolved oxygen in the water 

 of sphagnum bogs may account for its retarding action on growth and 

 development. The composition of water from a sphagnum bog near 

 Ronalds, Washington, as determined by Dr. J. M. McGee, included 

 the following constituents per Uter: Soluble organic matter 0.106 gm., 

 ash (chiefly CaS04) 0.048 gm., total soluble residue 0.154 gm.; reaction 

 neutral. 



A similar sample from a sedge swamp near Anoka, Minnesota, gave 

 the following per liter: Soluble organic matter 0.094 gm., ash (CaS04 

 with trace of NaCl) 0.128 gm., total soluble residue 0.222 gm.; reaction 

 neutral. 



The principal difference between the waters of the two habitats 

 is that of the calcium sulphate in the swamp-water. The vegetation 

 of the two places is of course quite dissimilar. 



When a test was made as to the direct action of the water on 

 sections of living plants and on plates of biocolloids the following 

 hydration expansions were obtained for Opuntia discata (at 15° C): 

 Distilled water 18.2 per cent, bog water 18.3 per cent, swamp water 

 13.6 per cent, calcium nitrate 15.5 per cent. 



The calcium-nitrate solution is of the concentration in which this 

 salt enters into nutrient solutions. 



Dried median slices of this plant gave swellings as follows: Dis- 

 tilled water 660 per cent, bog water 640 per cent, swamp water 530 

 per cent, calcium nitrate 625 per cent. 



The nutrient solution used in all of these tests included four salts 

 as follows: Potassium nitrate 1 M., di-potassic phosphate 2.38 M., 

 magnesium sulphate 2.97 M., and calcium nitrate 2.95 M. 



Attention was now turned to the biocolloids, to ascertain whether 

 the action of plant material living and dried would find a parallel in 

 the action of mixtures of known composition. Sections of plates 

 composed of agar (90) and oat protein (10) were found to show the 

 following swellings at 15° C. : Distilled water 1,928 per cent, sphagnum 

 water 2,082.5 per cent, sphagnum water (neutralized) 2,228 per cent, 

 bog water 1,200 per cent. 



The degree of acidity of the sphagnum-bog water was such that 

 1.1 c.c. of N/10 potassium hydrate was necessary to neutralize 100 c.c. 

 of water. The acidity of the grass-sedge water was scarcely a third of 

 this, but 0.35 c.c. N/10 potassium hydrate being necessary to neutralize 

 100 c.c. 



