CONCERNING NOMENCLATURE. 295 



POLYPODIACE^E. 



Sporangia stalked, borne on the back or 

 margin of the frond, opening transversely ; 

 ring vertical and elastic ; rootstock short 

 or extensively creeping ; fronds scattered 

 or clustered ; prothallia green, not subter- 

 ranean. 



TRIBES AND GENERA. 



TRIBE I. POLYPODIES. GENUS. Polypodium. 



TRIBE II. GRAMMITIDES. GENUS. Notholcena. 



TRIBE III. PTERIDES. GENERA. Adiantum, Pterts, Chei- 



lanthes, Pellcea, Cryptogramma. 

 TRIBE IV. BLECHNES. GENUS. Woodwardia. 

 TRIBE V. ASPLENIES. GENERA. Asplenium, Athyrium, Scolo- 



pendrium, Camptosorus. 

 TRIBE VI. ASPIDIES. GENERA. Phegopteris, Aspidmm, Poly- 



sttchum, Cystopteris, Onoclea, Struthiopteris. 

 TRIBE VII. WOODSIES. GENUS. Woodsia. 

 TRIBE VIII. DICKSONIES. GENUS. Dicksonia. 



In the early days of botany, plants were named in a 

 very loose and haphazard manner and several more or less 

 descriptive words were usually combined to form the 

 name of each species. These cumbersome titles were 

 in common use until the time of Linnaeus, but that 

 acute naturalist perceiving the advantage of shorter and 

 more exact names originated a system of naming both 

 animals and plants in which the name of each kind 

 consists of but two words; the first or group name 

 standing for the family and the second or individual 

 name standing for the species. 



Linnaeus was not the first to have a clear conception 

 of genera and species, nor yet the first to give a double 



