Plant World Continued 



217 



2. Andreaeales ( 



108.) 



3. Bryales ( 



). The black mosses. (Fig. 

 ). The true mosses. (Fig. 109.) 



r~ 



Fig. 109. A Common Moss. 



(Catharinea Undulata). 

 Showing the branching leafy moss 

 plants (gametophytes) attached to 

 the rootlike mass of protonemal 

 filaments and bearing sporophytes. 

 (After Sachs.) 



Fig. 110. Sphagnum Acutifolium, Ehrb. 

 A., prothallus (pr.) with_ a young _ leafy 

 branch just developing from it; B., portion of 

 a leafy plant; a., male cones; clu, female 

 branches; C, male branch or cone, enlarged 

 with a portion of the vegetative branch adher- 

 ing to its base; D., the same, with a portion 

 of the leaves removed so as to disclose the 

 antheridia; E., antheridium discharging spores; 

 F.j a single sperm; G., longitudinal section of 

 a female branch, showing the archegonia 

 (ar.); H., longitudinal section through a 

 sporongonium, with dome of sporogeneous tis- 

 sue; ar., old neck of the archegonium; /., 

 Sphagnum squarrosum Pers.; d., operculum; 

 c, remains of calyptra; qs., mature pseudo- 

 podium; ch., perichaetium. (After Schimper.) 



The Sphagnales are the most primitive, and the Bryales the most 

 highly developed. 



Sphagnum (Fig. 107) is a peat moss, growing, as its name implies, 

 in swamps and along the margin of lakes. The peat bogs of northern 

 regions are made up of thick clumps of this plant. Peat mosses are 

 usually light green in color, bordering on white, and sometimes have a 

 slight tinge of red and yellow. 



The plant has certain branches which bear reproductive cells, and 

 other branches which are sterile. (Fig. 110.) 



The gamete plant (the one bearing the gametes or reproductive 

 cells) has an upright stem with a mass of pith in the center. The outer- 

 most portion is called the cortex. The cell walls in the cortex are thicker 

 than those in the center, and often contain pigment. The cortex varies 

 from two to four cells in thickness. The leaves are only one cell in 

 thickness, and never have a midrib or other veins. In other words, 

 there are no fibrovascular bundles in the stem. The lack of fibrovascular 

 bundles is one of the great characteristics which distinguish this whole 

 group of plants from the next higher grouping — the Ferns. 



