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/ 11 or phases, have, however, changed 

 much in relative size. Whereas in the liverworts and mosses 

 the gametophyte 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 sporophyte 

 is the phase which is usually seen and the only part popularly 

 known. 



69. The gametophyte.- -The vegetative body of this phase 



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, 

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

 strikingly like a thallose liverwort in 



f^ J 



general form, being distinctly dorsiventral 

 and having rhizoids on its under side, 



FIG. 74. Ventral side of . . . . , c , . 



the gametophyte of a which fasten it 111 plaCC. (BCCaUSC OI thlS 



fern, Asple niitni. The ,,,.,,. 



notched end is the an- thalloid form and DCCaUSC it SCCmed to 



terior. Rhizoids near . . 



posteriorend. The small precede the 'real plant a popular 



circles show position of . . 



male organs; the chim- phrase meaning the sporophyte it was 



ney-likeprojectionsnear , ,.. /~v i ,1 



anterior end the female called a promauuim.) Only the central 



organs. Magnified 10 . . r 



diam. After Kerner. part oi the gametophyte consists ot more 

 than one layer of cells. On the under side of this central 



60 



