CHAPTER XXI 



PTEBIDOPHYTES (FERN PLANTS) 



■HY.t. Summary from Bryophytes. — In introducing the Bryo- 

 pliytcs ;i summary from tlie Thalloi^liytes was given (see § 

 GO), indicating certain important things which that groui) 

 has contributed to the evolution of the plant kingdom. 

 In introducing the Pteridophytes it is well to notice certain 

 important additions made by the Bryophytes. 



(1) Al/eni/i/'iun iif (jeneratidus. — The great fact of alter- 

 nating sexual (gametophyte) and sexless (sporophyte) gen- 

 erations is first clearly ex23ressed by the Bryo}iliytes, altliough 

 its Ijeginnings are to be found among tlie Thallopliytes. 

 Each generation produces one kind of si)ore, from wliich is 

 developed the other generation. 



(i) (uiiiietdjilnife the cJihirdiih ifll iji'iieriil Imi. — On account 

 of this fact tlie food is chiefly manufactured l)y the ganieto- 

 phyte, wliich is therefore tlje more conspicuous generatioji. 

 When a moss or a liverwort is sjHiken of, therefore, the 

 gamet(i]iliyte is usually referred to. 



(:!) Hiiinctiiplnjlf inid sjiornjili jile nut liiih'pcinlviii .—'Ww 

 sporojihyte is mainly dependent upon the gametoi)liyte for 

 its nutrition, aiul remains attache(l to it, being commonly 

 called the sporogonium, and its oidy function is to produce 

 spores. 



(4) DiffiTciitiiiHoii (if tlidlhis iiifn sfi'iii mil] Ji'iiri's. — 

 '^riiis a.ppea.rs incompletely in the leafy Liverworts (Jiiiii/rr- 

 miniiiiii forms) and much nuire clearly in the t'rect and 

 radial leafy branch (gametophore) of the Mosses. 

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