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 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, 

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

 strikingly like a thallose liverwort in 

 general form, being distinctly dorsiventral 

 and having rhizoids on its under side, 



Fig. 74. —Ventral side of ... _ . . .^ r i • 



the gametophyte of a which fasten it in place. (Because of this 



iem.Asfilenzum. The ,,,.•,,- , t ». j, 



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



terior. Rhizoids near , . , t . . , , , . 



posteriorend. The small precede the "real plant — a popular 



circles show position of . . 



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

 anterior e r nd e ?he°fema?e called a prolhallium.) Only the central 



organs. Magnified 10 r . , . x c 



diam.-After Kemer. part of the gametophyte consists of more 

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



60 



