4 LOUISE DOSDALL 



piration is decidedly less than that of deciduous shrubs and of 

 herbaceous plants in summer, but greater in winter, the xero- 

 morphy of these plants is real xerophyty, occasioned funda- 

 mentally by the necessity of protection when exposed to winter 

 conditions and used advantageously by these plants during the 

 summer. 



2. SUCCESSIONAL RELATIONS OF EQUISETUM 



(1) In the Hydrosere 



Equisetum is found in such a wide range of places that its 

 natural position in the development of vegetation is somewhat 

 puzzling. From Clements (1916: 184-278) summary of climax 

 formations we find that Shaffner, Jennings, and Tyler in their 

 description of the concentric zones about Brush Lake in Ohio 

 found Equisetum fluviatile in the swamp zone along with Carex 

 and Scirpus. Cowles in sketching the general course of suc- 

 cession on rock hills, sand hills, clay hills, and lake bluffs found 

 the secondary succession on the lake bluff beginning with 

 xerophytic herbs such as Melilotus, Aster, Equisetum, and 

 various grasses. Resoll found a pool which in 1898 contained 

 little but Sparganium minimum a dense mass of Equisetum 

 fluviatile in 1912. Burns (1911: 106) in his description of the 

 distribution and position of zones in the bogs of southern Michi- 

 gan gives Equisetum fluviatile as a member of the floating sedge 

 zone. This together with the two succeeding zones, bog and 

 tamarack, is called the xerophytic region of the habitat. Berg- 

 man and Stallard (1916: 339) reported Equisetum fluviatile often 

 occurring as a socies in the Scirpus-Zizania associes. "In 

 places it forms rather extensive areas of pure growth, notably 

 on Leech Lake near the mouth of Boy river and at the west end 

 of Long Lake near Ely. Usually, however, Equisetum occurs 

 mixed with other species of the associes." It is also reported 

 among the plants often occurring in small numbers in the Carex 

 associes. 



