CHAPTER XXIV 

 CALAMITES AND LYCOPODS 



I. THE HORSETAILS (EQUISETALES) 

 EQUISETUM 



333. Habitat and Distribution. As the names of some 

 of the various species indicate, representatives of the 

 genus Equisetum occur in a rather large variety of habitats. 

 Thus we have the swamp-equisetum (E. palustre) , meadow- 

 equisetum (E. pratense), the field-equisetum (E. arvense), 

 and so on. .They are frequently found along railroad 

 embankments in exposed situations, while other species 

 occur only in shaded or very moist locations (Fig. 266). 

 They are distributed throughout the northern hemi- 

 sphere, but only one species has been reported from South 

 America. Twenty species have been described from the 

 temperate and tropical North America, but none has ever 

 been found in Australia. Fossils of near relatives of the 

 genus have been found in the rocks of previous geological 

 ages, and some of the fossils in the coal-bearing rocks of 

 the Carboniferous age are thought to belong to Equisetum 

 itself. In temperate America the horsetails vary in height 

 from only a few inches to several feet. One species (E. 

 debile), found near Lahore, in India, attains a height of from 

 10 to 15 feet, needing the support of neighboring trees in 

 order to stand erect, while E. giganteum, found from the 

 West Indies to Chili, reaches a maximum height of 



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