Survey of Plant Kingdom 133 



rootlike rhizoids and structures which superficially resemble stems and 

 leaves, they are not true roots, stems, and leaves, because they lack the 

 vascular tissues (phloem and xylem). Each individual consists of a 

 stemlike axis with its small, attached leaflike structures. The sporophyte 

 of most mosses is usually larger than those of liverworts, even though the 

 sporophytes are parasitic in both. There are approximately 13,900 

 species. True mosses are considered in greater detail in a later chapter. 

 Examples: Polytrichum (hairy-cap moss) (Fig. 45) and Sphagnum 

 (peat or bog moss) (Fig. 46) . 



AritheridluYX) 



Jporanqium 

 -Jperr 



Fig. 45. — Common moss (Polytrichum sp.) of the phylum Bryophyta, class 

 Musci. A, Male gametophyte plant with cluster of antheridia at tip; B, tip of 

 male gametophyte enlarged to show antheridia which produce sperm; C, female 

 gametophyte plant with cluster of archegonia at tip; D, tip of female gametophyte 

 enlarged to show archegonia which produce eggs (ova) ; an ovum fertilized by a 

 sperm is shown developing (at the right) into a sporangium (spore-bearing organ) 

 which produces numerous spores; E, spore germinating to form a bud which de- 

 velops into a gametophyte plant (either male or female). 



10. Phylum Tracheophyta (tre ke -of ' i ta) (Gr. tracheia, duct or ves- 

 sel; phyta, plants). — The plants of this phylum all possess a vascular 

 system composed of phloem and xylem tissues whose complexity varies 

 with the various groups. This phylum includes the club "mosses" of 

 the subphylum Lycopsida, the horsetails of. the subphylum Sphenopsida, 

 and the ferns, gymnosperms, and angiosperms (flowering plants) of the 

 subphylum Pteropsida. 



Tracheophytes possess true leaves, stems, and roots, skeletal materials 

 for more or less upright growth, stomata (small openings) for the ex- 



