522 



LIFE-HISTORIES 



whether it be a seaweed, a Uchen, a Uverwort, or one of the 

 higher phints. In strictest l^otanical use it belongs only to 

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

 leaves usually arranged spirally on a pseudo-stem, and pro- 

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



Fig. 343. — Horned-liverwort (Anthoceros 1(fv{s, Horucd-livorwort Family, 

 Anthocerotacco') . Plant (i) with three "fruits" (sporophytes). (Luers- 

 sen.) — Rather common in moist soil. 



Fig. 344. — Horned-liverwort. A, branched thallus. B, thallus (V) cut 

 vertically to show the antheridia {an), the pseudo-roots (w), and a 

 colony of Nostoc {k) which sometimes lives in the interior of this plant. 

 C, vertical section through tip of thallus {^\^) showing beginnings of 

 archegonia {ar). D, section through older part of thallus ('5"), show- 

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

 E, embryo of sporophyte showing shoot-part above and foot below. 

 (Hofmeister.) 



True mosses resemble liverworts except in having a mostly erect 

 gametophyle with pseicdo-leares spiraUy disposed about a pseudo- 

 stem which supports a sporangium dehiscing by a lid and lacking ola- 

 ters. These peculiarities are sliown in the peat 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 tlu'ead gives rise at several points to apical c(>lls 

 each of which by its frequent oblique divisions produces a i)seu{lo- 

 stem with pseudo-leaves. If, however, tlic spore falls upon moist 

 earth, its germination is more. like such a liverwort as Anthoceros 

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

 lobed thallus, producing slender pseudo-roots below, and vertical 



