372 
THE FLORIST. 
which was the costa of the pinna in the once-divided frond, becomes the 
secondary rachis or rachis of the pinna, the pinnules having each a costa 
and veins as before. Fronds that are thus twice divided into separate 
leaflets, are called bipinnate. When the fronds become once more 
divided upon the same plan, they are tripinnate, and they then have 
tertiary rachides and secondary pinnules or Pinnulets, the latter, as 
before, being furnished with costa, veins, &c. Once more divided the 
fronds become quadripinnate, and such fronds, and all that are still 
more divided, are generally called decompound. In all cases both the 
pinnee and pinnules are distinguished as primary, secondary, and so on, 
if need be; and when only the last series of pinnules, in a very much 
divided frond, are referred to, they are frequently distinguished as the 
ultimate pinnules. It will therefore be seen, that the terms costa and 
rachis, apply to different parts in fronds differently divided; and that 
it is to the principal rib of the last series of distinctly formed leaflets 
that the term costa applies. That once settled, the first branches from 
it, are always the veins, the branches out of these the venules, and the 
branches out of the latter veinlets. We may remark, while on this part 
of the subject, that the parts' of pinnated or bipinnated fronds are, in 
some species, joined to their respective rachides by a natural joint, as 
the stipes is, in some species, to the stem, and that the parts so jointed, 
whether pinnee or pinnules, then readily detach themselves after 
maturity is past. The parts in such fronds are said to be articulated 
wtih the rachis. 
We have so far referred only to undivided fronds, and to those 
called pinnate, bipinnate, and so on, i. e., those once, twice, or more fre¬ 
quently divided into distinct separate leaflets. But they may be par¬ 
tially divided, the divisions more or less united at their base, and not 
separated into distinct leaflets. A frond once divided on this plan is 
called pinnatifid, and the divisions are Lobes. It may be twice or thrice 
