ON GENERA AND SPECIES. 9 



successive development form a stem (caudex), which is 

 either erect or more or Isss decumbent. The caudex varies 

 in size, according to the normal nature of the species. It 

 is often very short, even consisting of a bud only, scarcely 

 rising above the surface of the ground such is termed 

 acaulose or it forms a low stem a foot or more in height 

 (arboroid), or it assumes the height of a tree (arborescent). 

 Second Uniserial. This consists of a creeping rooting 

 stem, termed sarmentum, which progresses by the succes- 

 sive evolution of single fronds from its apex, each succeed- 

 ing frond being produced from the base of the preceding 

 one, at more or less distance in advance. It either con- 

 tinues simple or branches, and varies in thickness from 

 that of a thread to an inch or more in diameter, and is 

 either epigeous, hypogeous, or epiphytal. 



Articulate vernation also presents two forms. First- 

 Fasciculate. This is peculiar to a few Tree Ferns and the 

 order Marattiacece, in which the fronds when mature fall 

 away, leaving marks of rhomboid scars on the stem.* 

 Second Solitary. This consists of a creeping stem, 

 termed surculwn, emitting roots from its under surface, 

 by which it adheres to the earth or other bodies, but 

 generally trees (epiphytal), rarely hypogeous. It varies in 

 size from short and thick to long and slender, and when 

 young is densely covered with scales (squamcp). It is 

 either simple or branching, and is distinguished from the 

 sarmentum by its apex being always in advance of the 

 forthcoming fronds. These are produced singly from 

 special nodes on its sides, with which the base of the frond 

 (stipes) is articulate, and there separate on becoming 

 mature, leaving the mark of a round, slightly concave 

 scar or cicatrix. 



* See Tribe Cyatheae. 



