DECEMBER. 
571 
in the Sea Spleenwort, what was before the costa then becomes the 
Rachis, and each pinna has its costa and series of veins, just as in the 
undivided frond. Such once-divided fronds are said to be pinnate. 
Diagram explanatory of Terms applied to the Division of Fronds, Margin, &c.— 
(a), simple frond (indicated by the outer dotted line); (b), pinnatifid apex, the lobes (c) having 
acute apex ( d ), obtuse apex (e), obtuse sinus (/), or acute sinus (g ); (i, k, l, m , w, 6) pinnae ; 
(i), crenulated pinna of pinnate frond, auricled at the anterior, abscised at the posterior base; 
( k ), pinnate pinna=bipinnate frond : (/), bipinnate pinna=tripinnate frond ; (rn), bicrenated 
pinna of pinnate frond; (n), sessile sinuated pinna of pinnate frond, with obtuse apex; 
(o), stalked entire pinna of pinnate frond, with cordate base and acute apex ; (h, p, q, r), 
lobes—(/t), adnate-decurrent biserrated lobe of pinnatifid frond ; p, serrated lobe of pin- 
n itifid' frond ; (q), aristato-serrate lobe of pinnatifid frond; (r(, pinnatifid lobe of pinnatifid frond 
=bipinnatifid frond, the secondary lobes=lobulets; (s), adnate pinnules; ((), pinnulets or 
secondary pinnules. 
Where the pinnae are again divided into separate leaflets, which leaflets 
are called Pinnules, the part which in the undivided frond was the 
costa, becomes the primary rachis or rachis of the frond; and that 
B B 2 
