THE TRUE MOSSES 



525 



moss-branches above (Fig. 347). In either case these vertical pseudo- 

 leafy shoots are homologous \A-ith the ascending branches of ^lar- 

 chantia; but as seen in Fig. 348 they are much more elaborately 

 constructed. At the surface of the stem are developed usually 

 several laj^ers of large cells with very thin walls which are kept from 

 collapsing by ridge-like thickenings, and communicate with one 

 another and with the exterior by pores (D) of considerable size. 

 These cells soon lose their protoplasm and then form a sponge-like 



Fig. 349. — Peat mosses. A, tip of female branch of S. acutifolium, cut 

 vertically to show the archegonia {ar), protective leaves {ch) still 

 j'oung, and older ones {y) acting like bud-scales. B, young "fruit," 

 cut vertically to show the sporophyte of which the foot {sg') is fixed 

 in the head (r) of the stalk or pseudopodium (;;s), and the spore-case 

 (sg) IS still enveloped by the calyptra (c) bearing above the old neck (ar) 

 of the archcgonium. C, ripe sporophyte of .S. squarrosum, showing its 

 lid id) and spore-case {sg) emerged from the torn calyptra (c) and borne 

 upon a pseudopodium pushing it beyond the formerly protecting 

 pseudo-leaves {ch). All magnified. (Schimper.) 



or wick-like envelope which draws water from below by capillarity, 

 and stores it ready for use. The pseudo-stem is streng-thened by a 

 uniform thickenmg of the walls of an inner cylinder of cells. The 

 pseudo-leaves are made up chiefly of large, thin-walled cells {B) 

 like the outer cells of the pseudo-stem, similarly reinforced by 

 ridges and similarly perforated. They supply water to a net-work 

 of small cells containing numerous chromatophores in which the 

 work of photosynthesis is carried on. Vegetative reproduction so 

 far as known takes place only through the separation of branches 



