19X2] DACHNOWSKI—BOG PLANTS 513 



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becomes 



1 



when the injurious organic substances are in excess. The wide 

 variations in this functional reaction are probably of greater impor- 

 tance than external factors. It seems a tenable hypothesis, there- 

 fore, that the survival or the extinction of invaders may depend 

 more upon the degree of functional plasticity than is generally 

 admitted. 



The experiments here cited furnish nothing more than an indi- 

 cation of the relative importance of some of the factors involved. 

 The weight of evidence is obviously incomplete, for numerous 

 important considerations have received no attention whatever in 

 the present paper. The problem of absorption is not one of simple 

 solution, but an intricate and coordinated process, and much needs 

 to be known of the energy relations between plants and habitat 

 and the organization of the protoplasmic membrane of absorbing 

 organs. From the present study the following relations may be 

 summarized : 



1 



* Physiological investigations of peat soils have brought out 

 clearly the fact that the character of the obligate bacterial flora 

 and the nature of the organic compounds produced form a very 

 important factor in the relative fertility of peat soils, in the causes 

 of vegetation succession, in the distributional and genetic relation- 

 ships of associations, and in the characteristic xeromorphy of 

 both ancient and modern bog vegetation. 



2. In view of the widely differing behavior of agricultural 

 varieties in a bog water solution, and the interesting observation 

 that the plants respond differently to the same solution, the con- 

 clusion is inevitable that here the source of the difference must 

 logically be looked for not in the solution alone, but in the condition 

 of the plants as well 



3. Since certain of the organic compounds eventually penetrate 

 the protoplasmic membrane of absorbing organs and inhibit 

 growth, it is evident that much importance must be ascribed to the 

 influence exerted upon the plasmatic membrane, to the consequent 

 differences in its diosmotic properties, and to the pathological 

 changes induced which accompany the absorption of the injurious 

 substances. 



