248 MORPHOLOGY. 



materials are passed from the gametophyte to the sporogonium. The upper 

 part continues to grow, and finally the upper end differentiates into the mature 

 capsule. 



523. Protonema of the moss. When the spores of a moss germinate they 

 form a thread-like body, with chlorophyll. This thread becomes branched, 

 and sometimes quite extended tangles of these threads are formed. This is 

 called the protonema, that \a> first thread. The older threads become finally 

 brown, while the later ones are green. From this protonema at certain 

 points buds appear which divide by close oblique walls. From these buds 

 the leafy stem of the moss plant grows. Threads similar to these protonemal 

 threads now grow out from the leafy stem, to form the rhizoids. These 

 supply the moss plant with nutriment, and now the protonema usually dies, 

 though in some few species it persists for long periods. 



Classification of the Mosses. 



CLASS MUSCINEJE (MUSCI). 



524. Order Sphagnales.* This order includes the peat mosses. There 

 is but one family (Sphagnaceae) and but a single genus (Sphagnum). The 

 peat mosses are widely distributed over the globe, chiefly occurring in 

 moors, or "bogs," usually low ground around the shores of lakes, ponds, or 

 along streams, but they often occur on wet dripping rocks in cool shady 

 places. Small ponds are sometimes filled in by their growth. As the 

 sphagnum growing in such an abundance of water only partially decays, 

 "ground" is built up rather rapidly, and the sphagnum remains are known 

 as "peat." This "ground "-building peculiarity of sphagnum sometimes 

 enables the plant (often in conjunction with others) to fill in ponds com- 

 pletely. (See Atoll Moor, Chapter LV.) 



The gametophyte of sphagnum, like that of all the mosses, is dimorphic, 

 but the first part (or protonema) which develops from the spores is thalloid, 

 and therefore more like the thallose liverworts. The leafy axis (or gameto- 

 phore) which develops from the thalloid form is very characteristic (see 

 Chapter LV). 



The archegonia are borne on the free end of the main axis, while the 

 antheridia are borne on short branches which are brightly colored, red, 

 yellow, etc. The sporophyte (sporogonium) is globose and possesses a 

 broad foot anchored in the end of a naked prolongation of the end of the 

 leafy gametophore. This naked prolongation of the gametophore looks 

 like the stalk of the sporogonium, but a study of its connection with the 

 sporogonium shows that it is part of the gametophyte, which is only devel- 

 oped after the fertilization of the egg in the archegonium. In the sporogo- 

 nium there is a short columella, and the archesporium is in the form 01 un 

 inverted cup. 



* As subclass in Engler and Prantl. 



