THE FERNS 



123 



green tissue enables it to utilize the carbon dioxide of 

 the atmosphere. 



It is not a long step from such a sporophyte as that 

 of Anthoceros to that of the lower Pteridophytes. In 

 the latter, owing to the 

 early development of a 

 root in the sporophyte, 

 the latter soon becomes 

 quite independent of the 

 gametophyte, which is 

 generally short lived, 

 although occasionally it 

 reaches a considerable 

 size and may live for 

 several years, especially 

 where the sporophyte 

 fails to develop (Fig. 

 31, A). 



The sporophyte in 

 even the lowest Pterido- 

 phytes exhibits a com- 

 plexity far exceeding 

 that of the highest 

 moss. This is especially 



the case in regard to the external differentiation. While 

 in all Bryophytes there is very little development of 

 special external members in the sporophyte, in ferns 

 there are very early developed several characteristic 

 external organs, viz., stem, leaf, and root. The foot, or 

 absorbent organ of the embrj'o, is much like the corre- 

 sponding organ in the moss-embryo. 



Corresponding to this development of external mem- 



FiG. 31. — A, gametophyte of a fern 

 (Marattia) , showing a forking of the 

 growing point, and the development 

 of secondary buds, k ; B, gameto- 

 phyte of the same fern, with the 

 young sporophyte, sp, attached ; C, 

 a liverwort, Anthoceros, with several 

 sporophytes, sp, attached to the 

 gametophyte, g. The sporophyte is 

 capable of long-continued growth, 

 but does not develop a root, and 

 hence never becomes entirely inde- 

 pendent. 



