SUCCESSIONS IN BOGS 29 



bog according to the nature of the determining soil process. A 

 few members are in a sense transitional and can assume an aquatic 

 or terrestrial habit. Up to this stage in the process the marginal 

 and shore plants still may receive better aeration and sanitation 

 on account of the more frequent stirrings by waves and surface 

 current action. The physico-chemical and biological conditions 

 of the substratum are yet favorable for rapid growth, and any 

 gaseous or other injurious products due to partial decomposition 

 of the debris are in dilutions not to inhibit functional activity of 

 many plants. In fact their presence in small quantities carries 

 with it a corresponding intensification in the growth rate of some 

 species. Nevertheless, it is interesting to note that a number of 

 the components of this succession show striking devices such as 

 aerenchyma, internal air-containing spaces, respiratory roots 

 and lenticels to secure sanitation. The following associations 

 are the most typical in furnishing the transition to a bog succes- 

 sion. 



1. Decodon verticillatus association. The botanical structure 

 of the association is best described as follows: Facies or pre- 

 dominating species Decodon verticillatus, frequently accompanied 

 by Typha latifolia and T. angustifolia as principal species. Among 

 the secondary species are Radicula aquatica, Cardamine bulbosa, 

 Cicuta bulbifera, Sparganium eurycarpum, Sagittaria sp. Several 

 minor societies are seasonal aspects ; they are determined by such 

 species as Hibiscus moscheutos, Bidens trichosperma, Rumex sp., 

 Solanum dulcamara and others. 



2. Carex-Juncus-Scirpus association. In only a few lake and 

 peat deposits are the important forerunners and mat formers 

 species of sedge (Carex filiformis, C. interior, C. comosa). With 

 them are found occasionally Juncus acuminatus, J. tenuis, Carex 

 lurida. Among the plants which share the habitat of the sedges 

 is Calla palustris in the bogs of northeastern Ohio. In a few 

 inland lakes and especially along the shore of Lake Erie Scirpus 

 validus and S. americanus are the forerunners of a pure marsh. 



3. Typha association. There are numerous tracts in which 

 the cat-tails are the most conspicuous plants. They give but 

 little opportunity for the growth of secondary species. Poly- 



