MUSCI. SPHA GNA CEA E. 



181 



The class of Mosses may be distributed into four groups, not however of equal 



value : 



1. Sphagnaceae. 



2. Andreaeaceae. 



3. Phascaceae. 



4. Bryineae, or true Mosses. 



Of the above groups the first has only one genus, the second and third a few 

 genera only, the fourth includes all the remaining very numerous genera. The first 

 two groups have many points of resemblance to the Hepaticae, and this is the case with 

 some genera even of the true Mosses ; there is a certain amount of likeness between 

 the lowest forms of all the groups, but not between the highest ; hence the Mosses 

 form four divergent series, the third and fourth of which may be united into one. 



The Sphagnaceae 1 contain only one genus, Sphagnum. If the spores germinate in 

 water, they produce a branching protonema, on which the leafy buds appear as direct 

 lateral outgrowths (Fig. 133, C) ; on a solid substratum the short protonema first forms 



FIG. 134. Sphagnum acutifoliunt. The flat protonema/r, with a young leafy 

 stem m, magn. about 120 times. After Schimper. 



FIG. 133. Sphagnum acutifolium. A a large spore seen from the apex. B a small spore. C a protonema h ' 

 formed from the spore ; at/r the rudiments of young plants. After Schimper, magnified. 



a branching flat expansion on which the leaf-buds arise (Fig. 134), as is the case 

 in Tetraphis. The leafy stems produce some slender rhizoids only when they are 

 young, and never form a protonema in the copious manner of the true Mosses. 

 The stem in a more advanced stage gives rise to a lateral branch beside every fourth 

 leaf and each branch as soon as formed branches again repeatedly, and in this way 

 tufts of branches are produced arranged regularly and forming a small head at the 

 summit of the stem but further removed from one another lower down. The branches 

 develope in different ways ; one branch, in growth and character like the stem, appears 



1 W. P. Schimper, Versuch einer Entwicklungsgesch. d. Torfmoose, Stuttgart, 1858. 



