Peat-Mosses 



with non-crystallisable cell-contents as in other mosses, one must 

 conclude that the large cells serve other purposes beside that of 

 water carriers. Perhaps they are, when filled with air, a protec- 

 tion to the cells containing leaf-green, serving both as shields 

 against excessive heat and light and as a barrier to excessive 

 evaporation. 



THE DEVELOPMENT OF ORGANS 



Protonema. The large spores germinate in water to form a 

 thread-like protonema ; or, on land, to form a flat plate of cells, 

 from which the moss-plant develops. Several stages from spore 

 to adult plant are shown in diagrams I, 2, 3, 4, 5, 6 and 7. 

 (See also diagrams on pages 118 and 120.) 



Sphagnum acutifolium. Vertica 

 section to show: (or) archegon- 

 ium; (ch) cut edges of perichaetial 

 leaves; (y} involucral leaf. 

 (See page 120.) 



Sphagnum acutifolium. 



Plant (gametophyte^.The cells of the protonema by division 

 at one point form the plant stem, leaves and rhizoids then the 

 protonema disappears. Upon the moss plant are developed the 

 male flowers (aniheridid) and the female flowers (arcbegonid). 

 In Sphagnum acutifolium the male and female flowers mature 

 in late autumn and in winter and may often be found by digging 



under the snow. 



Antberidium.An antheridium has its origin in a cell of the 

 outer wall of a branch. This cell divides to make two, one of 



119 



