426 



BOTANY 



PART II 



between them, together represent the sexiiul 



generation. 



Many 



Liverworts possess a thalhis consisting of dichotomously branching 



Fio. 305. — Fvnaria liyciromeiricci. A, germinating spore ; ex, exine ; B, protonema ; Tin, bnd.s : 

 r, rhizoids ; s, spore. (After Muller-Thurgau ; magnified.) 



lobes, which is attached to the substratum at its base or on the under 

 side by means of rhizoids, thus repeating the vegetative structure of 

 many Algae (Fig. 369). In the higher Hepaticae, on the other hand, 



and in all the Musci, 

 there exists a distinct 

 differentiation into stem 

 and leaves (Figs. 375, 

 381). Rhizoids spring 

 from the lower part of 

 the stem. True roots 



are wanting in the Bryo- 

 phytes, which thus do 

 not attain a higher grade 

 of organisation than the 

 differentiated thallus 

 already met with among 

 the Brown Algae, for 

 exam})le in Sargassum. 

 The stems and leaves of 

 Mosses are also anatomic- 

 ally of a simple structure; 

 if conducting strands are present, they are composed merely of simple 

 elongated cells. The sexual organs (antheridia and archegonia) are 



Fill. 300. — Marchitntia polymorpha. ^, nearly ripe aiitlieridium 

 in <jptieal section ; p, parapliyses. B, sperniatozoids fixed 

 with 1 per cent perosmic acid. (A x 00, B x 600.) 



