340 FERN FRONDS. PART n. 



trunks of tree ferns, which rise sometimes sixty or eighty 

 feet high, are formed. The common Lady Fern, Athy- 

 rium Filix-foamina, furnishes an example of the ordi- 

 nary herbaceous caudex; as also does the Male Fern, 

 Lastrea Filix-mas. In the Hart's-tongue, or Seolopen- 

 drium, the caudex is generally compact, and increases 

 by the formation of new crowns or centres of growth 

 around the older one, till the whole becomes an almost 

 spherical mass of considerable size. 



The stipes or leaf-stalk of a fern is often of consider- 

 able length, and in its upper part, called the rachis, 

 which bears the leafy portion, is commonly more or less 

 branched, as well as furrowed on its upper surface. 

 The fronds, or parts analogous to leaves, are sometimes 

 simple, as in the Hart's-tongue, the rachis of which has 

 a symmetrical limb or wing on each side, so as to 

 form a long, even-margined, narrow, tongue-shaped 

 frond. If the limb on each side of the rachis be deeply 

 divided, as in the Polypodium vulgare, the frond is said 

 to be wing-cleft, or pinnatifid, and the divisions are 

 called segments or lobes. In most ferns, however, the 

 frond is once, twice, or three times winged or pinnate, 

 and in such cases the first divisions are called pinnae, and 

 the secondary or subsequent ones when present, pinnulse 

 or pinnules. The leafy portion, whether simple, pinna- 

 tifid, or pinnate, is always traversed by veins arranged 

 on some definite plan, a most important circumstance, 

 since the sori or fructification of the ferns is always 

 produced in connection with the veins. 



The fertile fronds, in certain groups, differ in form 

 from the sterile, generally by the greater or less con- 

 traction of their parts. In most ferns the full-grown 

 fronds are flat, that is, with all their parts lying in one 

 plane ; but, during their vernation, that is, when they 

 first rise from the stem^ they are circinate or curled in- 

 wards, like a crosier. 



