426 PHARMACEUTICAL BOTANY 
these empty cells are elongated narrow cells containing 
chloroplasts. 
OrDER 2.—ANDREAALES Or Rock Mosses consisting of one 
family, Andreeacee with the single genus Andreea, of xerophytic 
habit, occurring on siliceous rock. ; 
OrpDER 3.—BRYALES, or true mosses, comprising the most 
highly evolved types of bryophytes. Examples: Polytrichum, 
Funaria, Hypnum, and Mnium. 
LirE History oF PoLyTricHuUM CoMMUNE (A TypicaAL TRUE 
Moss).—Polytrichum commune is quite common in woods, forming 
Fic. 317.—Protonema of a Moss. A, Early stages of germinating spores: v, 
vacuole; w, rhizoid; s, spore wall or exosporium. B, Developed protonema 
about three weeks after germination; 4, primary filament; k, bud and w, rhizoid. 
The bud develops into a gametophytic plant. (After Sachs from Small.) 
a carpet-like covering on the ground beneath tall tree canopies. 
It is dicecious, the plants being of two kinds, male and female. 
Beginning with a spore which has fallen to the damp soil, we 
note its beginning of growth (germination) as a green filamentous 
body composed of chloroplast-containing cells arranged end to 
end. This is called a protonema. ‘This protonema soon becomes 
branched, giving rise to hair-like outgrowths from its lower por- 
tion called rhizoids and lateral buds above these which grow into 
leafy stems bearing rhizoids at their bases and which are com- 
monly known as ‘‘moss plants.” At the tips of some of these 
leafy stems antheridia (male sexual organs) are formed while on 
others archegonia (female sexual organs) are developed. The leafy 
