EQUISETACE^E. 149 



over a considerable space of boggy ground, planted as a nursery with 

 young poplars. He (Mr. Wilson) told me that a botanical garden 

 formerly existed there." Phytol. 1846, vol. ii. p. 432. Mr. Samuel 

 (lilson, in 1843, speaks of it as growing " in an old stone quarry 

 near Warrington." This fern was found " in the above locality by 

 John Roby, Esq., of Rochdale." Phytol. vol. i. p. 492. 



ORDER XCY.-EQUISETACEiE. 



Perennial herbs with subterraneous creeping rhizomes. Stems 

 cylindrical, jointed, hollow, usually with verticillate branches at the 

 top of each internode, rarely simple ; internodes terminated above by 

 a sheath ending in teeth (a whorl of connate leaves) which embraces 

 the base of the succeeding internode. Branches jointed and sheathed 

 similarly to the stem, sometimes absent. Sporangia opening by a 

 longitudinal cleft, arranged 6 to 9 in a circle on the inner side of 

 stalked peltate verticillate plates, which are arranged in an ovoid 

 or oblong terminal spike. Spores very numerous, minute, similar ; 

 each furnished with 4 filiform appendages (elaters) which spring 

 from one point and are thickened at the apex, at first rolled spirally 

 round the spore, but ultimately uncoiling ; the elaters are hygrometric. 

 uncoiling when dry and rolling round the spore when damp. Pro- 

 thallium green, flat, lobed, commonly dioecious, producing archegonia 

 and antheridia resembling those of Filices. 



GENUS L— E QUISETUM. Linn. 



The only genus. Characters the same as the Order. 



Name from equus, a horse, and seta, a bristle. 



Section I.—VERNALIA. A. Braun. 



Stems of two kinds. Sterile stems appearing after the fertile 

 stems, and perishing in winter, green or whitish, branched. 

 Stomata level with the surface. Sheaths with persistent teeth. 

 Branches in regular whorls, except in depauperate specimens, without 

 any central cavity. Fertile stems appearing in early spring, decaying 

 before summer shortly after the spike is matured, succulent, whitish, 

 ultimately brown or fawn-colour, without branches. Spike obtuse, 

 at first whitish, afterwards fawn-colour. Rarely a few fertile stems 

 are produced after the sterile stems, and in that case they are thinner 



