POLYPODIUM. 71 



fronds, and from its lower side chiefly the branching fibrous 

 roots by which it clings to its support. The fronds, if 

 exposed to frost, perish ; but if at all sheltered, they 

 remain green during winter, and until after young ones 

 have been produced, which happens generally towards the 

 end of May. The stipes, or stalk, of the full-grown 

 fronds is usually nearly equal in length to the leafy por- 

 tion ; the entire frond measuring from six to eighteen 

 inches in length. The leafy part of the frond is lance- 

 shaped in outline, but cut in from the margin along both 

 sides nearly as far as the midrib or rachis, and thus 

 becomes what is called pinnatifid. The portions into 

 which it is divided are called the lobes, or segments, or 

 divisions of the frond ; and, in this case they arc usually 

 oblong in form, generally rounded at the end, but some- 

 times tapering to a blunt point, and occasionally notched 

 along the margin. Each lobe has a slightly wavy midvein, 

 producing alternate lateral veins (venules), which generally 

 have about four veinlets or little veins disposed alter- 

 nately ; it is the lowest of these veinlets, on the side 

 towards the point of the frond, which produces the sorus 

 when it is present ; the rest, which are barren, terminate 

 in club-shaped apices, which are very readily seen when a 



