118 The Polytrichacea of Essex County. 



is supposed to be analagons to that of the stamen and pistil 

 in the higher plants. The pistillidium elongates and rises 

 to a considerable height, constituting the pedicel; and en- 

 larges at its apex into the capsule, which is surmounted by 

 a caplike organ, called the calyptra. On the ripening of 

 the capsule the calyptra falls off, but when studied with 

 other structural differences, it forms a good criterion to 

 divide the many species into the several genera, Thus, in 

 Polytrichum proper, the calyptra is densely hairy, while 

 the capsule, which it invests, becomes, when mature, of a 

 four or six sided figure. The name Polytrichum is derived 

 from an allusion to the character of the calyptra, polus being 

 the Greek for many and thrix Gr. for hair, so that it may 

 be familiarly termed, the haircop or the many haired moss. 



In Pogonatum, the calyptra is hoodshaped and also dense- 

 ly hairy, while the mature capsule is cylindrical, so that 

 these forms distinguish it. From pogon Gr. beard we derive 

 Pogonatum the bearded hood moss, or bearded cap moss. 



In Atrichum, the calyptra is smooth, but its tip is spinu- 

 lose, its form is hood shaped, and the capsule is elongated- 

 cylindraceous and slightly curved. Hence the smooth ca- 

 lyptra is signified in the generic name, a, (privitive) without 

 and thrix Gr. hair, the hairless cap or smooth cap moss. 



Further distinctions need not be pointed out ; these general 

 and more obvious characteristics being deemed sufficient 

 to our present purpose. We come to an enumeration of the 

 species according to our plan. 



1. POLYTRICHUM COMMUNE. Linnesus Species Plantarum, 

 p. 1573. Hooker and Taylor's Muscologia Britannica, 2d 

 Ed., p. 46, table X. Smith's Linnaeus Flora Lapponica, 

 pp. 322. 326. Sullivant in Gray's Botany of the Northern 

 United States, &c. &c. 



This species is to be found in moist places, and as its 

 name implies is a common plant. It varies considerably in 

 sizes. Its capsule is four sided and acute-angled, which 

 the ferruginous colored hairy calyptra completely "covers, 

 extending below the base : its operculum (the lid covering 

 the orifice of the capsule) is short* The stem } which rises 



