CHARACTERS OF TRIBES AND GENERA. 155 



With such a wide range many species have been described 

 by authors on very slight characters, chiefly in difference 

 in size, for instance, in Moore's Index 55 names are recor- 

 ded, of which only twenty-one are adopted as true species, 

 and these in the "Synopsis Filicum" are reduced to sixteen. 

 In many Aspleniece, plants while young and small produce 

 fructification, and have been considered as distinct species, 

 such is the case with Antrophyum nanum, Fee (A. obtusum, 

 BL}, which is described as not more than an inch in length, 

 but on collating numerous sets of specimens it is impossible 

 to come to any other conclusion than that the intermediate 

 sizes, even from the smallest to 2 feet in length, are only 

 the graduations of a single species, the difference being 

 consequent on age and climatic influences. The principle 

 of creating species of Antrophyum upon difference of size, 

 might with equal justice be applied to the common Harts'- 

 tongue Fern (Scolopendrium officinarum), fronds of which 

 may be found in fructification from a little more than an 

 inch to two feet in length. 



The species vary in the sporangia being immersed or 

 superficial, of which the following are examples. 



* Sporangia immersed. 



A. lineatum, Kaulf. (v v.) (Polytcenium, Desv.) ; A. im- 

 mersum, Bory. ; A. plantagineum, Kaulf. ; A. Cumingii, 

 Fee (A. latifolium, Reinw. non Bl.) ; A. reticulatum, Kaulf. ; 

 A. semicostatum, Bl. 



** Sporangia superficial or slightly immersed. 



A. ensiforme, Hook. (Ic. PI., t. 394, Second Cent. t. 70) ; 

 A. lanceolatum, Kaulf. (v v.) ; A. Cayennense, Kaulf. (v v.) ; 

 A. latifolium, Bl. ; A. Boryanum, Kaulf. ; A. giganteum, 

 Bory. 



