244 



ELEMENTS OF BOTANY, 



FERNS. 



303. Structure, Form, and Habits of Ferns. — The structure 

 of ferns is much more complex than that of any of the groups 

 of cryptogamous plants discussed in the earlier portions of 

 the present chapter. They are possessed of well defined 

 fibro-vascular bundles, they form a variety of parenchymatous 

 cells, the leaves have a distinct epidermis and are provided 

 with stomata. 



Great differences in size, form, and habit of growth are 

 found among the various genera of ferns. The tree ferns of 



Fig. 208. — Prothallia of a Fern (Aspidium Filix^mas). 

 A, lower side of prothallium ; ar, archegonia ; an, antlieridia ; rh, root-hairs ; 

 B, protliallium producing a young fern plant ; 6, the first leaf ; «', the root^ 

 (Magnified about 8 diameters.) 



South America and of many of the islands of the Pacific 

 ocean sometimes rise to a height of forty feet, while the most 

 minute species of temperate and colder climates are not as 

 large as the largest mosses. Some species climb freely, but 

 most kinds are non-climbing plants of moderate size, with 

 well developed rootstocks, which are often, as in the case of 



