472 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



but the fasciculate branches are different from what is found 

 amongst any other mosses. The narrow cells of the leaves are 

 derived from the tissue of the stem, the larger cells being 

 formed independently in the meshes of the net-work. Their 

 outer wall is perforated, which is not the case in those other 

 white-leaved mosses, which agree with them in structure. 

 Another peculiarity is the total absence of roots ; and still 

 another, the resemblance of their globose pedunculate anthe- 

 ridia to those of Jungermannice. Sphagna live in boggy 

 places, where they grow with great rapidity, soon filling up 

 inequalities in the surface, and forming a spongy, almost inde- 

 structible mass, which affords a fitting soil for many Crypto- 

 gams and Phcenogams. The peat, however, which is thus 

 formed, is useless, from its soft spongy texture, for fuel. " In 

 this division," says Mr. Wilson, " the leaves and the fascicles 

 of the branches are disposed around the stem in spirals, so that 

 for every complete spiral, formed by five fascicles of branches, 

 there are eight spirals formed by twenty leaves ; four leaves 

 being inserted between each pair of fascicles. The insertion of 

 the fascicles, like that of the antheridia, is not in the axils of 

 the leaves, but immediately at the side of the leaf, presenting 

 some analogy to Fontinalis." The lid of the sporangium has 

 been observed to be driven off with considerable force, so as 

 to give a distinctly audible report. Sphagna are found both 

 in the north and south hemispheres, but the species of the 

 latter are all found in Europe. 



III. AcROCARPi, Bridel. 



Frait terminating the main shoots. 



523. There are no Cryptogams, ferns excepted, of which the 

 arrangement is less satisfactory than that of Mosses. It is quite 

 useless to propose divisions founded solely on the peristome, 

 for their fallacy will be seen at every step we take. The 

 habit is of far greater importance than the peristome. This, 

 therefore, will be one great guide to affinities, though, as in 

 other cases, its value must be weighed cautiously. The true 

 key will probably be found hereafter in the structure of the 

 young sporangium, which has at present been deeply studied 



