THE STRUCTURE OF FERNS. 19 



Taking now a retrospective glance, we have seen that 

 the Perns 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. 



The subject of internal structure, or anatomy, is foreign 

 to the purposes of this volume. We may, however, men- 

 tion in general terms, that 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 elas- 

 ticity to the higher orders of plants. The Perns, 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 botany. 



