214 CLASS CRYPTOGAMIA. 



moss, or Polytrichum commune, which in the northern 

 climates of Europe becomes long enough for brooms ; 

 with us it is always much shorter. In this genus the 

 capsule is covered by a hair-like brown calyptre ; be- 

 neath, the capsule presents a lid or operculum, and 

 finally appears a double peristome or fringe, the outer- 

 most consisting of 16, 32, or 64 short, flat, inflected 

 teeth ; the interior membranaceous and flat. 



One of our most common genera is the Hypnum, a 

 large creeping kind of Mosses common on the ground. 

 The capsules come out laterally from a cluster of 

 scales. The peristome is double ; the outer of 16 

 teeth dilated below ; the inner membranaceous, va- 

 riously toothed and torn, but commonly in 16 proces- 

 ses, with smaller capillary ones interposed. The ca- 

 lyptre is smooth. 



These characters are entirely microscopical, as, 

 indeed, are also the specific distinctions, and the in- 

 strument employed must have a considerable power to 

 bring them into view. 



Sea-weeds (Alce), Liverworts, and Lichens. 



This order of Linnaeus has been divided into the 3 

 above mentioned. The Sea-weeds, or proper Alg;e, 

 have leather-like, olivaceous fronds, with the sporse 

 inclosed in bubble-like, or inflated portions of the 

 frond. The Liverworts (Hepatic^e), containing but 

 few genera, are allied on one hand to the Lichens, and 

 on the other by Jungermannia, apparently, to the 

 Mosses, though somewhat obscurely. The Lichenes, 

 formerly the genus Lichen, includes a large group of 

 very natural and closely allied genera of various as- 

 pects. Some of them resemble foliaceous and leathery 

 expansions or fronds, which cling to stones or to the 

 bark of trees. These occasionally present roundish, wart, 



