ON GENERA AND SPECIES. 009 
successive development form a stem (caudex), which is 
either erect or more or less 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 r 
stem, termed sarmenium, 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— 
~ asciculate. This is peculiar to a few Tree Ferns and the 
order Marattiacee, in which the fronds when mature fall 
ee away, leaving marks of rhomboid scars on the stem.* 
... Second — Solitary. This consists of a creeping jie 
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 (squame). It is - 5 
_ 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 |. 
(stipes) is articulate, and there separate on. becoming — : 
mature, leaving the mark of a round, aeuo concave ks 
scar or `. cicatgix. 
_ * See Tribe Cyathee. 
termed swreulum, emitting roots from its under surface, Co 
Special nodes on its sides, with which the base of i te od 1 E 
