INTRODUCTORY REMARKS. 
Y 
cipal data for characterizing genera. Even with flowering- 
plants however, modern botanists do not entirely exclude 
habit from generic descriptions. An eminent botanist re- 
marks, that “ in a Natural Order so extremely simple as the 
Liliacece the differences between the genera are necessarily 
very slight, and here we find that such groups as Scilla , 
Ornithogalum , Allium , G-agea , Urginea , and many more, 
are distinguished as much by habit as by an absolute varia- 
tion of structure.”'* This view being applicable to many 
families of plants, induces me to be more confident that 
habit is of importance in defining the natural affinities of 
Eerns. In following up my observations, I find that Ferns 
present two distinct modes of growth : the first, which I 
have named JEremobrya ,f is characterized by the fronds 
being produced singly from nodes on the side of a fleshy, 
surculose rhizome, which has its apex of extension always 
in advance of the nascent frond ; the latter, after having 
arrived at maturity, separates from the node by a special 
articulation. In the following pages JEremobrya is cha- 
racteristic of the genera numbered from one to twenty, 
nearly the whole of which agree with the technical cha- 
racter of the genus Eolypodium , as originally characterized 
by Linnaeus and other early authors. The second and more 
general mode of growth, named Desmobryct, J differs from 
* Bindley, in ‘ Botanical Register.’ 
t Seemann’s ‘Botany of the Voyage of H.M.S. Herald,’ p. 
226. J Ibid. 
