WATER REQUIREMENT AND ADAPTATION IN EQUISETUM 5 



(2) In the Paleosere 



Equisetums reached their most luxuriant growth during the 

 Pennsylvanian Period of the Carboniferous Age. The Calamites, 

 great tree-like equisetums one to two feet in diameter and often 

 sixty to ninety feet in height, are reported by Grand Eury to 

 have formed great forests in Central France. According to 

 Chamberlin they probably frequented swamps and lowlands. 

 The evidence of the present day water relations of Equisetum 

 substantiates the view of Clements (1916: 421) that the reed 

 swamp associes of today was probably represented by the 

 smaller Calamites in the paleosere. 



(3) The climate of the Carboniferous age 



The following, from Chamberlin and Salisbury, is a summary 

 of the plant life of the Pennsylvanian Period and the inference 

 as to climate. The Coal Flora was made up of the following 

 groups of plants: Filicales, Cycadofilices, Equisetales, Sphen- 

 ophyllales and Lycopodiales. Equisetales were represented by 

 Calamites, whose branches and leaves were arranged in whorls. 

 The leaves were much reduced in size but not so much so as in 

 the present day forms. "The structure was of the type adapted 

 to dry weather as in the pine and many desert plants, and also, 

 strangely enough, in undrained swamp plants. They (Calam- 

 ites) probably frequented swamps and lowlands." The opinion 

 of some geologists is that the climate of this period was more or 

 less dry and cold. Their judgment is based on the xerophytic 

 nature of the dominant plants, the lepidodendrous, sigillarias, 

 calamites, and cordaites. 



"The force of the inference from the xerophytic aspect of 

 the overgrowth is much weakened, however, by the fact that the 

 vegetation of undrained swamps and bogs assumes many of 

 these xerophytic features, which in such cases, obviously become 

 pseudoxerophytic. A satisfactory explanation of this phenome- 

 non has not yet been found, nor has its extent and its limitations, 

 either in respect to the nature and degree of swampiness neces- 



