THE TRUE MOSSES 525 
moss-branches above (Fig. 347). In either case these vertical pseudo- 
leafy shoots are homologous with the ascending branches of Mar- 
chantia; but as seen in Fig. 348 they are much more elaborately 
constructed. At the surface of the stem are developed usually 
several layers 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 
Fic. 349.—Peat mosses. A, tip of female branch of S. acutifolium, cut 
vertically to show the archegonia (ar), protective leaves (ch) still 
young, 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 (v) of the stalk or pseudopodium (ps), and the spore-case 
(sg) is still enveloped by the calyptra (c) bearing above the old neck (ar) 
of the archegonium. C, ripe sporophyte of S. squarrosum, showing its 
lid (d) 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 strengthened by a 
uniform thickening 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 
y 
