190 ELEMENTS OF STRUCTURAL HnTAXY. 



337. Plants with these common characteristics constitute- 

 a group called Pteridophytes or Vascular Crypto- 

 gams, " cryptogam " being a general term applicable 

 to all plants which do not produce true flowers, as 

 " phanerogam " applies to all those which do. 



CHAPTER XXII. 



EXAMINATION OF A MOSS AND A LIVERWORT. 



338. Mosses. Fig. 239 is a representation of the 

 common Hair-Moss (Polytrichum commune), which may 

 be found in early summer almost anywhere. It grows in 

 dense masses, and upon examination it will be found 

 that while many of the stems resemble that shown in 

 Fig. 239, the upper extremities of others form rosettes, 

 as in Fig. 240, whilst others again terminate in ordinary- 

 vegetative buds. 



339. Let us first examine a specimen as represented 

 in Fig. 239. There is, it will be observed, a well-marked 

 stem, or leaf-bearing axis, upon which the crowded 

 minute leaves are sessile. In the Mosses they always 

 are so, and they are found, upon examination with a 

 good microscope, to consist as a rule of only one layer of 

 cells, being therefore much simpler in structure than 

 those of the plants we have so far been engaged upon. 

 It is also to be noticed that the leaves of Mosses are 

 without stomata. 



340. Observe now that our Moss has no true roots. 

 It is, however, fixed to the soil upon which it grows by 

 numerous root-hairs or rhizoids. 



