194 



perforated by large holes. By means of capillary attraction, water 

 is thus raised to the summit of the stem. Similarly constructed 

 cells are also found in the leaves, but they are sui'rounded by a net 

 of very narrow, chlorophyll-containing cells (Fig. 199 F), whose 



colour is thus to a great extent lost 



amongst 



those which are 



FIG. 199. Sphagnum acutifolium. A The upper portion of a plant : a branches with 

 antheridia ; cJv branches with terminal archegonia and perichaetia; b the upper stem- 

 leaves. B A male branch whose leaves are partly taken off in order to show the 

 antheridia. C Group of three archegonia : the central one (a) is formed from the apical 

 cell. D Sporogonium in longitudinal section : the broad foot (sg') is sunk in the vaginula, 

 D ; c calyptra; or neck of the archegonium ; ps pseudopodium. E ripe sporangium with 

 operculum, and the remains of the archegonium situated on the pseudopodium which is 

 still surrounded by the perichaetium ; to the left is a barren branch. F Portion of a 

 foliage-leaf seen from above: I perforations; b chlorophyll-containing cells; s spiral 

 thickenings. 



colourless. This anatomical structure is an essential condition for 

 +be formation of peat. The Bog-Mosses grow by preference on 



