42 STRUCTURAL BOTANY 



base. These buds, though their first origin takes place 

 very early, only develop into branches at a much later 

 time, and often not until the upper part of the leaf 

 has died off. Few branches are formed in this particular 

 Fern. 



Ferns vary very much as regards their branching ; 

 in some, as in the Bracken Fern, the stem forks at the 

 apex ; in a few, as in some Filmy Ferns, the branching 

 is axillary like that of flowering plants, while in others, 

 as in some of the Tree Ferns, the stem does not branch 

 at all. 



The roots which we find on an ordinary full-grown 

 plant are all adventitious, for the original main root 

 of the embryo dies away very early. The adventitious 

 roots, which arise at the bases of the leaves, usually 

 three below each leaf, are very slender and much 

 branched. An old stem is densely clothed with a 

 matted growth of adventitious roots (see Fig. 17). 



B. KEPRODUCTIVE ORGANS 



The ordinary Fern plant, such as we have described, 

 is purely asexual. Like Selaginella, it bears, at this 

 stage, sporangia only, but, unlike that genus, its 

 sporangia and the spores which they contain are all 

 of one kind. The sporangia of the Male Fern and of 

 most other Ferns are borne on the lower surface of the 

 ordinary foliage leaves, so that here there is no difference 

 between vegetative leaves and sporophylls. In this 

 respect such Ferns are on a lower level, as regards the 

 physiological division of labour, than any plants which 

 we have yet considered. 



If we examine one of the fertile leaves in summer, 



