\9:? 



LIFE-HISTORIES 



whether it be a seaweed, a lichen, a liverwort, or one of the 

 higher i)lants. In strictest botanical use it belongs onl}' to 

 about 5,000 species of small green plants which have pseudo- 

 leaves usually arranged spiralis' on a j^seudo-stem, and pro- 

 duce spores in urn-like cases opening mostly by a lid. 



Fig. 343. — Honied-liverwut { Aulhurrr't^ hrris, Horncd-livrTwort Family, 

 Aiitlwceroliic-ccc). Plant (ij with three "fruits" (sporophj'tes). (.Luers- 

 sen.) — Rather common in moist soil. 



Fig. 344. — Horned-liverwort. A, bramdied thallus. B, thallus (Y) '^'ut 

 vertieally to show tlie antheridia (nn), the pseiidt:)-roots (ic), and a 

 colony of Nosioc (k) which sonietinies !i\'es in the interior of this plant. 

 C, vertical section through tip of thallus C^;") showing beginnings of 

 archegonia (ar). D, section through older part of thallus C^^'''), show- 

 ing a fertilized archegoninm in which the egg-cell has begun to divide. 

 E, cnii^rvo of sporophytc showing shoot-part above and foot below. 

 (Hofiucister.) 



True mosses resemble liverworts except in having ii )itostlij erect 

 Omiiefophijle with psewlo-leaves spirally disposeil ahmit a pseutlo- 

 aieiti ivhich supports a sporangium dehiscing by a lid and lacking eki- 

 lers. Those peculiarities are shown in the jieat moss (Sphagnum, 

 Figs. 227, 346-.349) and the cord moss (Funaria, Figs. 350-356). 



The spores of Sphagnum (Fig. 346) germinate in water by send- 

 ing out a branched thread which resembles a filamentous alga. 

 Sooner or later this thread gives rise at several points to apical cells 

 I'iicli <jf which by its frequent obUciue divisions produces a ])seu(.lo- 

 stcni with pseudo-leaves. If, however, the spore falls upon moist 

 earth, its germination is more like such a li\'erwort as Anthoccros 

 or Marchantia, for the initial thread soon develops into a flat- 

 lobc(l thalhis, jiroducing slcndrr ])sciidci-roots below, and vertical 



