162 



PHYLUM BRYOPHYTA: 



about 300 species that appear to be ecologically in- 

 fluential, especially in localized floras. However, they 

 are most abundant in the tropics and their secondary 

 distribution center is in the temperate zone. 



Moisture generally influences their range. One 

 genus, Riella, is the only completely submerged, 

 fresh-water aquatic. Forms like Riccia are floating 

 aquatics. Others are found in marshes, swamps, and 

 bogs. Many occur on moist, shaded, steep slopes of 

 clifTs or ravines. Still others are in forests on tree 

 trunks, decaying logs, or the ground. Especially in 

 California, a few may live in semiarid areas. Here, 

 they are active during the moist season but all struc- 

 tures, except the growing region and asexually repro- 

 ductive structures, die during summer drought. 

 Apparently none are parasites. The Genus Cryplo- 

 Ihallus is the only bryophyte known to lack chloro- 

 phyll. These liverworts apparently gain nutrients 

 from an intimate association with a fungus (mycor- 

 rhiza). 



Further information on liverworts is included in 

 the discussion of mosses. Liverworts often are found 

 with mosses and display similar ecological reactions. 



CLASS MUSCI (Mosses) 



Diagnosis: spores develop into protonema (a sim- 

 pler protonema occurs in some leafy liverworts), and 

 protonema usually forms one or more leafy gameto- 

 phores (generally the conspicuous part of the plant); 

 gametophore leaves typically develop in three (rarely 

 two) rows, but growth regularly causes leaves to be 

 spirally arranged; protonema and usually gameto- 

 phores anchor to a substrate and absorb materials 

 from the substrate by multicellular hairs (none in 

 Sphagnales); protonema anc^ gametophore constitute 

 two phases of the gametophyte generation; gameto- 

 phores resemble lycopsids (see Figures 11.8 and 

 11.10), but lack vascular tissues and roots (Figure 

 10.5). 



mosses XI 



sphagnum or peat moss XI 



Figure 10.5 Moss types; sizes as indicoted 



