THE PHYSIOLOGICAL WATER REQUIREMENT AND THE 
GROWTH OF PLANTS IN GLYCOCOLL SOLUTIONS^ 
Alfred Dachnowski and R. Gormley 
The relation of plants to peat and humus soils has been of the ut- 
most importance to students of plant physiology because of the nature 
of the metabolism involved. It is of equally great interest to ecolo- 
gists in so far as the native social vegetation units covering an organic 
soil area take on a characteristic spacial distribution — a mutual 
exclusiveness — and yet gradually intrude upon and replace one an- 
other in a fairly genetically related succession in time. 
The contributions of the senior author (5-8) have been mainly 
with a view toward an analysis of the several habitat factors, and a 
study of the organic constituents of peat soils in relation to plant 
activity. Historical accounts and a number of experimental data on 
the causal and limiting factors of a bacterial, chemical, and other 
nature have been brought together in Bulletin 16, Geological Survey 
of Ohio, 1912 (7). 
The present paper, though only of a preliminary nature, is a 
continuation of the physiological studies and has been made in the 
hope that it will draw more pointed attention to the metabolic pro- 
cesses of a number of plants, some of which do, while others do not, 
seem to be able to extend their range of distribution beyond a typical 
habitat. In addition, the attempt is made with a view to understand- 
ing more clearly the nature of the "association factor" which seems of 
great importance in determining the geographical distribution of the 
higher vSocial vegetation units, and the edaphic "preferences" of plants 
more or less nomadic in their tendency 
The principal organic compounds from which peat and humus 
are derived are the various lignocelluloses, the carbohydrates, proteins 
1 Contribution from the Botanical Laboratory of Ohio State University, No. 82. 
2 A more explicit statement will appear shortly dealing with the association 
factor and the evolution of social vegetation types, based upon observations which 
one of the authors obtained during the recent International Phytogeographic Excur- 
sion in America. 
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