158 ENGLISH BOTANY. 



are not grooved, slightly rough, green. Sheaths shortly cylindrical- 

 funnel-shaped, green, often pitchy-brown towards the apex ; teeth 

 5 to 12, mostly free, or more rarely some of them united in pairs or 

 threes, narrowly triangular, acute, dark brown or pitchy-black, with 

 very broad pure white hyaline margins. Branches usually in whorls, 

 but sometimes only 1 or 2 from a node, and sometimes wholly absent, 

 generally 5 -angular, but varying from 4- to 7-angular, with the ridges 

 separated by very shallow furrows, hollow, unbranched, their lowest 

 internode much shorter than the teeth of the stem-sheath below which 

 it is produced, and indeed reduced to little more than a sheath ; 

 sheath enclosing the base of the first internode of the branch pitchy- 

 brown or nearly black, shining, with deltoid-ovate obtuse teeth 

 having very narrow pale brown or whitish scarious margins ; sheath 

 at the apex of the first internode terminated by deltoid-ovate blunt 

 teeth ; teeth of the succeeding internodes ovate or ovate-lanceolate, 

 with a weak mucro. Fertile stem differing from the sterile one only 

 in being terminated by a spike which is ovoid-oblong or cylindrical- 

 oblong, obtuse, pitchy-black. 



In bogs and marshes, and on the shores of lakes and ponds and on 

 wet rocks. Common and generally distributed throughout England 

 and Scotland, extending to Orkney and Shetland ; frequent through- 

 out Ireland. 



England, Scotland, Ireland. Perennial. Summer. 



A very variable plant. The commonest form has erect stems, 

 1 foot high or more, but the length of the stem varies from a few 

 inches to 2 feet. The plant is of a rather dull green, and is narrowly 

 pyramidal when branched. When unbranched it is the var. nudum 

 of Duby, but unbranched stems may be seen springing from the 

 same rootstock as branched ones. The stems grow more in tufts 

 than in any of the preceding species, and in this respect resemble the 

 Equiseta hyemalia. Frequently the stem is decumbent or prostrate 

 and without branches, when it is the var. nudum of Newman (' Brit. 

 Ferns,' ed. ii. p. 49), but not of Duby, the var. alpinum of Hooker, 

 and var. subnudum of the London Catalogue of British Plants ; but 

 this appears to be merely a starved state of the plant. The spike 

 is i to J inch long, and is produced in June or July. 



An extraordinary state of the fertile stem, in which 1 or more of 

 the upper branches are terminated by spikes, has received the name 

 of var. polystachyum ; but this is evidently a monstrosity rather than 

 a variety. Very often the main central stem has been accidentally 

 injured, so that there is no spike at its apex ; but specimens occur 



