BBTOPHTTA. 211 



rounded by an envelope of protective cells (Fig. 123, 1-V). 

 The archegones of the common Liverwort are clustered 

 upon special branches a few centimetres in height. These 

 branches expand into lobed disks at the top, and beneath 

 these the archegones appear. They grow out as trichomes, 

 and finally consist of a rounded cell (germ-cell) enclosed 

 in a flask-shaped vessel (Pig. 133). 



388. Fertilization takes place in wet weather by the 

 antherozoids swimming to and down the open neck of the 

 archegone. As a consequence the germ-cell begins divid- 

 ing, and finally develops into a spore-fruit containing many 

 spores, intermixed with spiral threads called elaters. The 

 use of the latter appears to be to aid in the dispersion of 

 the spores (Fig. 133, X). 



389. In most cases the spore-fruits split open to permit 

 the escape of the spores, which soon germinate and pro- 

 duce a thalloid mass ; this develops directly into a new 

 plant in the lower forms, and in the higher soon begins the 

 development of a stem and leaves. 



390. There are about 3000 species of Liverworts, dis- 

 tributed among three orders, viz. : (1) the Liverworts 

 proper (Order 31, Mabchantiace^i;), 

 terrestrial thalloid plants, including 

 the common Liverwort (Marchantia 

 polymorpha) and the Great Liverwort 

 (Conocephalus conicus), both large, 

 flat, branching plants growing in moist 

 places about springs, brooks, ditches, fig. izi.— a Horned 



'■ J. o Liverwort (Antlioceros 



etc. : (3) the Scale-mosses (Order 33, toyis), natural size, 



' ^ ' ^ with spore-fruits, K, K, 



JUNGERMANNIACB^, Fig. 131, //), splitting open. 



mostly leafy creeping plants growing on moist earth, 

 rocks, and tree-trunks ; (3) the Horned Liverworts (Order 



