160 ENGLISH BOTANY. 



Var. a. genuinum. 



Babenh. Crypt. Vase. Europ. Exsicc. No. 74. 



E. limosum, Linn. Spec. Plant, p. 1517. Fries, Sunim. Veg. Scant!, p. 59. 



E. limosum, var. Linnseanum, Doll; Milde, Fil. Europ. p. 227. 



Stem unbranched, or with a few irregular solitary or subsolitary 

 branches. 



Var. /3. jiuviatile. 



Babenh. Crypt. Vase. Europ. Exsicc. Nos. 75 and 124. 



E. fluviatile, Linn. Spec. Pant. No. 1517. Fries, Summ. Veg. Scand. p. 59. Non 



Smith. 

 E. limosum, var. verticillatum, Doll ; Milde, Fil. Europ. p. 227. 



Stem with regular whorls of branches. Stem stouter than in 

 var. a, and when barren with a longer point. 



In lakes, ponds, and ditches, growing in the water, or rarely in 

 wet places out of water. Frequent and generally distributed 

 throughout England and Scotland, extending to Orkney and Shetland. 

 Common in Ireland. 



England, Scotland, Ireland. Perennial. Summer. 



Rootstock hollow. Stems erect, dark green, scarcely striated, when 

 growing easily compressible from having a large central hollow and 

 thin walls, which are not strengthened by a cylinder of thickened 

 cells as in all the other British species of Equiseta. In var. a they 

 vary from the thickness of a crow-quill to that of a swan-quill ; but 

 in var. ft they are frequently as thick as a man's little finger. The 

 unbranched forms are nearly as common as the branched. When 

 growing in bogs or shallow water the branches are commonly absent, 

 but they are so also not unfrequently even in deep water, in which 

 the plant attains its greatest development, reaching a height of 

 3 or 4 feet, or even more. It is in deep water too that the barren 

 stems terminate in a long naked point. The spike is ^ to § inch 

 long, less cylindrical than in the preceding species, and often paler 

 in colour. A ' polystachyum ' form occurs, but much more rarely 

 than in E. palustre. 



The absence of furrows on the stem distinguishes all the forms of 

 this plant from those of E. palustre when the plants are fresh. In 

 the dried state the outside of the stem shrinks so that it appears 

 furrowed ; but the narrower teeth, without conspicuous white 

 margins, should be enough to distinguish this from E. palustre. The 

 want of a cylinder of thickened cells is a characteristic of this species ; 

 indeed, it occurs in only one other European form, namely, E. littorale 

 of Kiihlew, which is generally believed to be a hybrid between 



