432 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



furnished at the mouth with dehcate processes, which close the 

 orifice, or leave it open for the escape of the spores, according to 

 the hygrometric condition of the air, as in mosses. In some 

 cases the spores are unattended by any threads ; in others there 

 are numerous threads attached to the walls, whose cavity is 

 traversed by one or more spirals, performing, in fact, the same 

 function as the teeth round the orifice of the moss capsule. 

 Whatever questions may have been raised formerly as to their 

 sexuality, there is no doubt about the question now. Hof- 

 meister has in every group, following the steps of Unger, 

 Mohl, and others, traced out the formation both of the anthe- 

 ridia and archegonia, and has shown in most cases, that in the 

 former spermatozoids are generated ; while Thuret and others 

 have taught that these bodies combine the characters of those 

 of Algae, with a closer approximation to the true spermatozoa 

 of animals. 



476. Besides the essential fruit, many species are propagated 

 largely by gems produced at different parts of the plants. 

 These are sometimes seated on distinct pedunculate processes, 

 sometimes at the tips of the leaves, sometimes at the base of 

 cup-shaped or luniilate receptacles, like the sporangia in the 

 cup of a Nidularia. They appear first as single cells pro- 

 jecting from the surface, and then by cell-division are trans- 

 formed into bodies of various forms and thickness, which are 

 at length detached, and propagate the plant like the buibi- 

 form buds of Dentaria, Lilium, &c. 



Hepatic^, L. 



Fertile sacs opening regularly or irregularly, without any 

 definite lid ; borders of the fissure naked, not provided with 

 any series of teeth (peristome) single or double. 



477. This group comprises three very distinct natural orders, 

 Ricciacea, Marchantiacece, and Jungermmmiacece, whose 

 characters will be described under the respective heads. The 

 species are known in England under the name of Liverworts, 

 though they are confounded more or less in popular phraseo- 

 logy with the Peltigerous Lichens. Where the frond is not 

 Licheniform, the leaflets have seldom the more or less ovate 

 form of those in mosses, but often assume strange outlines, 



