CHAPTER VI. 



FERNWORTS AND SEED-PLANTS. 



Fernworts. 



Among the still more complex plants, the ferns and their 

 allies, the same "alternation of generations" can be seen. 

 The two "generations," or phases, have, however, changed 

 much in relative size. Whereas in the liverworts and mosses 

 the gametophytc is much the larger and more conspicuous, as 

 well as the longer-lived, among fernworts the sexual phase is 

 so much smaller that it is seldom seen ; and in some species 

 it is almost microscopic. On the other hand, the sp(iro|)hyte 

 is the jihase which is usually seen anil the only part ]io]iularly 

 known. 



69. The gametophyte. — The vegetative body of this jjhase 

 of the fernworts in its best developed forms 

 is a small, flattened, green body of oblong, 

 orbicular, or cordate outline, commonly 

 less than half- a centimeter in diameter, 

 rarely as much as 2 cm. (fig. 74). It is 

 strikingly like a thallose li\"erwort in 

 general form, being distinctlv dorsi\entral 

 and having rhizoids on its under side. 



Fig. 74. — ^^-1ll^al side nf . . 



the gametophyte of a which fastcu it lu [ihice. ( ISecause of this 



fern, As/>h'ii!um. The ,,,.,,. , , . , 



notched end is the an- thalloid form and becausc it seemed to 



terior, Rhij^oids near i i , , 



posteriorend. Thesmaji precede the "real plant — a popular 



circles show position of . 



male organs; the chim- plirase meaning tlie s|)orophyte — it was 



ney-likeprojectionsnear 7 ,,■ \ 



anterior end the female called a />r()//li!//ll/ //I .) Ollh' the Central 



organs. Magnified 10 ' , 



diam.— After Kcrner. ]'avt of tlic gaiiictopli V te cousists ot iiiore 

 than one layer of cells. ( )n the under side of this central 



60 



