BRIEFER ARTICLES. 
PHYSICAL PROPERTIES OF BOG WATER. 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY. LVIIL. 
TuHaT many plants growing typically in the peat bogs of the north- 
ern United States and Canada exhibit the same structural characters as 
do those occurring in very dry soils of the same region has long been 
known by students of plant distribution. But the question why these 
so-called xerophytic swamps differ so entirely in the nature of their 
vegetation from the drained or river swamps near by has never received 
a decisive answer. The idea is generally current among workers in this 
field that the factor determining the nature of the vegetation in bog 
areas lies, somehow, in the nature of the soil. Schimper states clearly 
that only xerophytes thrive in peat bogs, “because of the humous acids 
in the soil.”* In another place (/.c., p. 4) he says that a soil may be 
ae physiologically dry” for various reasons, among which are (1) “abun- 
dance of soluble salts” and (2) “richness of the soil in humous acids.” 
In still another place (/. ¢., p. 657) the same writer describes the sphag- 
num bog (“high moor”) as having a soil solution which “contains 
humates of alkalis in solution besides the humous acids,” in which char- 
acter these bogs differ from the ‘meadow moors,’ or grassy marshes. 
It becomes evident immediately that if the “ physiological dryness” 
' of the bog be due to humous acids or humous salts, these substances 
may check absorption of water by plants either physically —by high 
osmotic pressure —or chemically—by toxic or stimulation effects. The 
question as to whether or not bog waters have a concentration appre- 
ciably higher than those of river and lake swamps near by should be easy 
of answer. Therefore, in 1901, the writer began a series of determina- 
tions of the osmotic pressure of the bog waters which were available. 
By the well-known Beckmann apparatus, determinations of the lower- 
ing of the freezing point were made, and frora the data thus obtained 
the approximate osmotic pressure of. the solution at 25°. C. was 
calculated.? 
*SCHIMPER, A. F. W., Plant geography upon a physiological basis. Translated 
by W. R. Fisher. Oxford. 1903. P. 8. 
2For methods of procedure see LivincsTon, B. E., 
osmotic pressure in plants, part I, chap. VI. Chicago. 1903. 
1904] 383 
The réle of diffusion and 
