ORDERS OF MOSSES 251 



phyte elongates it carries up the remains of the distended 

 archegone as a httle cap (calyptra). 



445. The spores, which are round or angular cells 

 containing protoplasm, chloroplasts, oil-drops, etc., 

 germinate quickly upon moist soil. Each spore pro- 

 trudes a tubular filament, which develops into a conferva- 

 like branching growth of green cells, called the "pro- 

 tonema." Upon this buds are eventually produced from 

 which spring up the leafy stems, thus completing the 

 round of life. 



446. There are three orders of Mosses, including about 

 12,600 species, as follows: (1) Black Mosses (Order An- 

 DREAEALEs), composed of a few small and rare mosses 

 whose spore-cases open by four longitudinal slits; (2) 

 Peat-mosses (Order Sphagnales), composed of large, 

 soft and usually pale-colored plants, with clustered lat- 

 eral branches; they inhabit bogs and swampy places, 

 where they form dense moist cushions, often 

 of great extent. On account of peculiarities 

 in the structure of their leaves they are en- 

 abled to absorb and hold large quantities of 

 water, and for this reason they are exten- 

 sively used for "packing" in the transporta- 

 tion of living plants. They all belong to fig. 127.— 

 the genus Sphagnum, and their spore-cases (Andreaea and 



.,,.,,. , , Sphagnum). 



open by a circular lid, leaving an unguarded 

 opening (without teeth). In this and the preceding 

 order the stalk supporting the spore-ease is an extension of 

 the gametophyte stem and not a part of the sporophyte. 



447. (3) True Mosses (Order Bryales) include the 

 great majority of the species of this class. They are 

 usually bright green (in a few genera brownish), and in 

 most instances live upon moist ground and rocks, or 

 upon the bark of trees; in a comparatively small number 



