MUSCI. SPHA GNA CEAE. I 83 



round holes like those of the leaves (Fig. 136). These colourless cells both in the 

 leaves and in the cortex of the stem and branches serve as a capillary apparatus to the 

 plant to draw up the water of the bogs in which it lives and convey it to its upper parts ; 

 hence it is that plants of Sphagnum, which are continually growing taller, are filled with 

 water like sponges up to their summits even when their beds are raised high above the 

 surface of the water. 



The archegonia ahd antheridia are formed chiefly but not exclusively in autumn and 

 winter, and on branches of the tuft before mentioned at the summit of the primary stem, 

 while they still belong to it and are therefore still near the summit. Antheridia and 

 archegonia are always on different branches, and sometimes on different plants, and in 

 the latter case the male and female plants grow in large separate patches. If owing to 

 dry weather the primary stem does not elongate during the development of the 





E 



cl 



FIG. 137. Sphagnum acutifolium, A a male 

 branch with some of the leaves removed in order 

 to show the antheridia a. B an antheridium 

 opened and very highly magnified. C a mature 

 motile spermatozoid. After Schimper. 



FIG. 133. Sphagnum acittifolium. A a portion of the surface of a leat 

 seen from above ; cl tube-like cells containing chlorophyll, f the spiral 

 bands, / the holes in the large empty cells. B transverse section of a 

 leaf; of the cells containing chlorophyll, Is the large empty cells. 



sporogonia, the latter are subsequently found still on the terminal tuft ; but if there is 

 a sufficient supply of water and consequent growth in length of the stem, the fertile 

 branches are separated from one another and appear lower down on the stem, and the 

 sporogonia and the older antheridial branches are thus moved further from the summit, 

 though they were close to it when the sexual organs were ripe. The branches that bear 

 the antheridia are distinguished externally by their crowded leaves overlapping one 

 another like tiles, and forming beautiful orthostichies or spiral parastichies ; their colour 

 is often yellow or a bright red, and especially a dark green, and they are thus easily 

 recognised (Fig. 135, a, a). The antheridia are placed beside the leaves on the de- 

 veloped shoot ; as they are never terminal but occur one by the side of each leaf in the 

 middle part of the shoot only, the latter may continue to grow at the summit, and pass 

 into an ordinary flagellate branch. The Sphagnaceae resemble many of the Junger- 

 mannieae in this position of the antheridia, and still more in their roundish form and 

 long stalk ; their mode of opening too recalls the Hepaticae rather than the Mosses 

 (Fig. 137). The archegonia arise on the blunt end of the female branch, the upper leaves 



