DEVELOPMENT. 



II 



conferva, may be seen forming a velvety mass on the 

 ground in the neighbourhood of mosses ; and if a portion 

 of such masses is examined with the microscope, all the 

 stages of growth may frequently be seen. In most mosses 

 the protonema is short-lived, perishing before the moss- 

 plant is fully grown ; but in some of the lower' forms, as in 

 Phascum serratum (fig. 3), it lasts throughout the plant's 

 lifetime. This moss may be found in fallow fields in 

 autumn and spring. The gemmae before mentioned ger- 

 minate much in the same way as the spores, forming first 

 the thread-like protonema, upon which the leafy stem is 

 developed. 



FIG. 3. Phascum (Ephemerum) serratum. i, plant enlarged ; i a, capsule : i b 

 protonema. 2, leaf enlarged, showing loose cellular tissue (areolation). 



The stem varies in length considerably ; in some mosses 

 it is imperceptible without a lens, as in Phascum serratum^ 

 but in many others it is very apparent. It may be erect, as 

 in Polytrichum ; or prostrate, as in some of the Hypnums, 

 or feather-mosses ; simple, as in Pottia (fig. 4) \ or branched, 

 as in Hypnum (fig. 5). In some of the terminal-fruited 

 mosses it branches by what are termed innovations ; these 

 are extensions of the stem, often arising at the top of the 

 old stem, and such branching is usually forked, each fork 

 representing a year's growth. This mode of branching may 

 be seen in many Bryums and other mosses ; a convenient 



