Xlviii IXTRODUCTIOIV. 



** MuSCOIDEiE. 



A distinct axis, but no vascular system. 



Theca closed by an operculum - - - - 2G7. Musci. 



Theca dehiscing without an operculum . - - 268. HEPATiCiE. 



Theca indehiscent, deciduous. Branches leafless and verticillate 269. CharacejE. 



*** Aphyll.t.. 



Neither distinct axis nor vascular system. 



Aerial ; always growing exposed to the air. 



Sporules lying in superficial receptacles - - 270. Lichenes. 



Sporules internal . . - - - 271. Fungi. 



Aquatic ; always growing under water - - - 272. A\.OJZ. 



