8 
GENERAL DESCRIPTION 
of the stem extending on or under the ground, ex- 
tending very far indeed in some ferns, farthest in the 
Common Bracken. When not under ground, these 
creeping stems are generally clothed with hairs or 
scales, sometimes becoming quite shaggy. The rhi- 
zome varies considerably in size, from that of the 
Common Polypody, which is as thick as one’s little 
finger, to that of the Film Ferns, as fine as thread. 
The fronds consist of two parts, — the leafy portion, 
and the stipes , which is the part of the stalk above the 
caudex or rhizome. The farther continuation of the 
stalk, forming in the leafy part a midrib, or midvein, 
which becomes branched when the frond is divided (as 
in the Oak Fern), is called the rachis (rachides in the 
plural). The stipes is generally more or less furnished 
with brownish membranous scales, sometimes only a 
few at the base, sometimes extending along the rachis. 
When the frond is divided quite down to the rachis, or 
midrib, it is said to be pinnate , and each of the leaf- 
like divisions is called a pinna (Latin for a feather). 
When these pinnce are again divided in the same man- 
ner the frond becomes bi-pinnate, or if thrice divided 
tri-pinnate. When the division is nearly but not quite 
down to the rib or midrib the pinnule (or small pinna), 
the pinna, or the frond, is called pinnatijid. 
The True Ferns are developed in a peculiar man- 
ner, coming up in a crozier-like form, having the rachis 
rolled in from the point to the base. In the more com- 
pound ferns the frond-divisions are each again rolled in 
after the same fashion. This is called being circinate. 
