INTRODUCTION. 15 
the stipes is articulated with the stem, that is to say, it is furnished 
with a natural joint or interruption of the woody fibres, so that in 
age it separates spontaneously. This is not frequently the case with 
the caudiciform kinds. When the firmer tissues of the stipes are 
continuous at the base with those of the caudex, so that the fronds 
do not separate spontaneously, the fronds, or stipites, are said to be 
adherent to the-stem; but when there is a natural articulation or 
joining, so that, when its functions cease, the frond separates and 
falls away, leaving a clean scar on the rhizome or caudex, the fronds 
or stipites are said to be articulated with the stem. The continuation 
of the stipes upwards constitutes the costa or rachis, to which further 
allusion will be made. The stipes and rachis may be either green, 
or of some distinct colour ; if the latter, it is usually a dark purplish 
brown, or blackish purple. 
The upper leafy portion, or lamina of the frond, is that to 
which the name of frond is most frequently and especially given, 
irrespective of the stipes, which really forms part of it. This part 
affords great variety in the mode in which it is divided. A certain 
and by no means inconsiderable number of Ferns, have undivided 
fronds; these are called simple. , When they are partially once 
divided they are pinnatifid, and when quite once divided, that is 
divided down to the rachis, they are pinnate. When partially twice 
divided they are bipinnatifid, and when thoroughly twice divided, 
bipinnate. So, when partially or thoroughly thrice divided, they 
are tripinnatifid or tripinnate; or, if four times divided, quadri- 
pinnatifid and quadripinnate. Many Ferns are once pinnate and 
then pinnatifid; such a mode of division is called pinnato-pinnatifid. 
The divisions of the pinnatifid frond are called segments ; those of 
the pinnate frond, pinne. In the bipinnate frond, the first series 
of divisions are pinne, the second pinnules, or little pinne; in 
the tripinnate frond, the first series are pinne, the second series 
primary pinnules, the third series secondary pinnules, and so on with 

