204 



STRUCTURE AND LIFE HISTORIES 



Fi. 147. Diagram of life-cycle of sphagnum. 



189. Other Mosses. The so-called "true mosses," 

 with which we are perhaps more familar than with 

 sphagnum, cannot be studied here in detail, but it may be 

 said that, in broad outline, their life histories are closely 

 similar to that of sphagnum. The protonema does 

 not produce a thallus, but the leafy branches, or moss- 

 plants, arise directly from the filamentous protonema 

 (Fig. 148). They are both monoecious and dioecious. In 

 the "true mosses" no pseudopodium is formed, but the 

 stalk of the sporophyte (so very short in Sphagnum), 

 elongates to form a seta, often over i inch in length. In 

 the spore-case, or capsule, there is much less sporogenous 

 or fertile tissue, in proportion to sterile tissue, than in 

 Sphagnum. Moreover, at the base of the capsules, in 

 the true mosses, occur functional stomata, opening into 

 intercellular spaces, and surrounded by chlorophyll- 



