INTRODUCTION 



§ 1. The natural family of Ferns comprises cryptogamic, 

 mostly perennial, plants, the leaves or fronds of which are, in 

 the early stage of their growth, coiled up in a particular way, 

 so as to represent a scroll. Their fronds show a great variety 

 of form and texture, and generally bear on the veins of the 

 under surface, or along their edges, the organs of the 

 fructification. 



§ 2. These consist of capsules or spore-cases (sporidia), 

 which burst in various ways, and are either continuous, 

 spread about irregularly, grouped together in heaps (sort), 

 or more rarely collected into spikes or racemes, formed by the 

 contraction of part of the frond. 



§ 3. These capsules are one-celled, stalked or sessile, gene- 

 rally surrounded by an articulated elastic ring, and discharge, 

 when mature, the spores, or minute seeds, which they contain. 

 The sori or clusters of sporidia are, in a great many genera, 

 protected by a peculiar membrane, or scale, called the 

 indusium or involucre, which is deciduous or persistent, 

 derives its origin from the epidermis of the frond, and covers 

 the sori entirely or in part ; while in other cases, the borders 

 of the frond, being dilated and reflexed, perform the function 

 of that membrane. 



§ 4. The Ferns arise from a subterraneous root-stock 

 (rhizome), which for the most part is creeping and of a 

 woody nature. Their stem, or that portion of the rhizome 

 which rises above ground (caudex), is almost ever upright and 

 simple, and but rarely climbing ( Stenochkena Meycriaiia), or 

 hvvLiiQ\iQ^{Gleicheniaceai). It is very short, and nearly wanting 



B 



