THE LEAFY MOSS PLANT 297 



(Fig. 265, C). The development of the asexual spores in the 

 spore case ends the life history of the moss plant, which may 

 be formulated as follows : 



. / protonema and \ ^ sperm ^ 

 Gametophyte (^ ^ ^ < [ ^ . - Sporophyte 



asexual spore Gametophyte, etc. 

 This in abbreviated form becomes 



G< S > -S-sp- <*> -S-sp-G, etc. 



e 



This formula is identical with the general life-history formula 

 presented for the bryophytes in Sec. 285, and it is clear that 

 gametophyte and sporophyte alternate with one another. 



295. The leafy moss plant. The leafy moss plant is, of 

 course, the conspicuous part of the gametophyte phase of the 

 life history. It consists of an upright stem, branching in some 

 forms, with the leaves almost always distributed spirally. The 

 symmetry of the plant is therefore radial instead of having an 

 upper and a lower side (dorsiventral) as in the leafy liverworts. 

 The leaves consist for the most part of simple plates of cells, 

 which in some forms can become dry and still retain their 

 vitality, freshening up with the next rain. 1 The moss plant is 

 fastened to the earth by filaments of protonema (Fig. 263), 

 which grow out from the base of the stem and form a dense 

 network underneath the moss plants (Fig. 261). This proto- 

 nema becomes brown with age and serves as a system of root-like 

 filaments, or rhizoids, by which the moss plant obtains water 

 from the soil. The growth of the stem normally ends with the 

 production of a terminal group of sexual organs, both of which 

 (antheridia and archegonia) are found on the same plant in 

 some species and on different plants (male and female) in 

 others. Male plants are generally smaller than the female ones 



1 The cells of the moss leaf are excellent subjects for study and have 

 been described in Sec. 196 and illustrated in Fig. 169. 



