POLYPODIUM. 



80 



P. distans, they are cut nearly or quite down to the midrib into toothed or 

 deeply-cleft lobes. In another section of Phegopteris the fronds are small or 

 medium- sized, tri- or quadripinnatifid (three or four times divided nearly to 

 the midrib), a character which is well illustrated in our " Oak Fern," 

 P. Dryopteris ; or the fronds are ample and many times divided, like those 

 of P. punctatum. 



Phlebodium (Phleb-o'-di-um), P. Brown. This very distinct sub-genus 

 comprises but few species. The veins form ample, regular cells, each with 

 two or more distinct free veinlets, which bear the spore masses on their 

 united points, the costal series of cells being always destitute of spore 

 masses. The best-known of the species included in this sub-genus is 

 undoubtedly P. aureum. 



Phymatodes (Phy-mat-o'-des), Presl. This extensive sub-genus, which 

 includes the sections Dipteris and Drynaria, is distinguished by the copious, 

 irregular, fine cells of its fronds, the free veinlets spreading in various 

 directions, as also by the disposition of the spore masses, which vary as to 

 position, but are generally found on the back of the united veinlets. The 

 majority of the species have undivided fronds, such as those of P. longifolium, 

 mostly of a thick texture, with the under- surface of a matted or scurfy 

 nature, as in P. angustatum. Some species, such as P. Billardieri, have their 

 fronds deeply pinnatifid, while in a few of them the fronds are distinctly 

 pinnate (divided to the midrib), a character which is best illustrated in 

 P. juglandifolium. 



The geographical distribution of the genus is very wide, Polypodiums of 

 one section or another being found in nearly every part of the world. It 

 is, however, in Central and in South America that they are most abundant ; 

 a certain number of very distinct species are found throughout India, and a 

 few others are native of Australia and Japan. Eaton, referring to the 

 distribution of the genus, states (" Ferns of North America," vol. i., p. 120) that 

 " the true Polypodia of the United States and Canada are but eight in number. 

 Three of these have veins free : P. plumula [elasticum], fcdcatum [a form of 

 P. vulgar e~], and vulgar e ; two, P. californicum and incanum, have their veins 

 sometimes free, sometimes sparingly reticulated ; and three, aureum, Phyllitidis, 

 and Scouleri, have their veins regularly reticulated, but in three different 

 methods, representing respectively the sections Phlebodium, Campyloneuron, 



