22 'history of BRITISH TERNS. 



The Ferns belong to the lowest group of vegetation, 

 ■which is especially remarkable for its loose and often 

 succulent texture, owing to the absence, or nearly so, of 

 those tissues which give firmness and elasticity to the 

 higiier orders of plants. The Ferns, however, are the 

 highest members of this group, and hence we find them 

 possessing, to some extent, both woody and vascular tissue, 

 — matters which, together with cellular tissue, the soft 

 loose material above mentioned, may be found explained 

 in any elementary book on physiological botan}'. 



Taking now a retrospective glance, we have seen that 

 the Ferns are, as regards external structure, flowerless 

 plants, having erect or creeping stems, which bear the leaf- 

 like fronds ; and on some part of the surface of the latter, 

 usually the lower side, but sometimes the margin, are borne 

 the clusters of seeds, which, in the majority of the native 

 species, are, when young, furnished with a membranous 

 scale-like cover. 



