PHYSIOLOGICALLY ARID HABITATS AND DROUGHT 
RESISTANCE IN PLANTS: 
ALFRED DACHNOWSKI 
In the course of the investigations on the ecology of a local bog, 
the trend of the work has invited a closer consideration of a number 
of points of interest to a physiologist. The importance of these in 
life processes has been the occasion to offer, in the following, a state- 
ment of at least the more special cases. 
In previous papers (this journal) attention has been called to the 
fact that the physiological effect of bog water and bog soil to a great 
extent plays an important primary réle in the determination of the 
flora which can best succeed in bogs. It was shown that a number 
of cultivated plants and plants from different but neighboring habitats 
in the same locality fail to develop normally when grown in the bog 
or under laboratory conditions, and that the toxicity of the habitat 
appeared, therefore, to exert a marked influence in determining not 
only the character but also the distribution of plants within the same 
habitat. A difference was shown to exist between different species 
in their power of-resistance to the toxic action of the substratum, so as 
to leave no doubt that some species of plants are better adapted than 
others to growing in soils containing relatively large amounts of these 
toxins. It was further shown that in the effect of a salt of calcium, 
and especially in the presence of a number of insoluble adsorbing 
bodies, these differences are much less pronounced, and that the 
Substances tend very greatly to diminish, not ‘only the difference 
between different species as to their tolerance, but also the differences 
in physiological aridity existing between different zones within the 
Same habitat. With the establishment of certain definite relations © 
between toxicity and physiological behavior of plants, it seemed 
desirable to study somewhat more closely the nature of the resistance 
in bog plants to toxicity, and consequently to physiological drought. 
ne of the most effective methods of dealing with the problem, 
* Contribution from the Botanical Laboratory of Ohio State University, 55. 
325] {Botanical Gazette, vol. 49 
