SINUS-CHARACTERS aT 
Square sinus; one with rectangular corners within; A. Zim- 
icofa, A. Schreberi, some leaves of A. ampliatus and A. roscidus. 
Securiform sinus; one with reéntrant angles within; the cur- 
vature resembling a battle-ax with broad convex, sharp-angled 
blade ; A. securiformis. 
Absence of cordation in radical or basal leaves of the Biotian 
species. This is frequent in sprout-forms and is usual in case of 
the primordial leaf. It is continuous in the plantain-leaf stage of 
any species, and it is therefore occasionally very conspicuous in 
such species as show a strong development of this plantain-leaf 
stage, as in A. decaphyllus or A. roscidus, A. Jusstet, A. viridis and 
A. divaricatus fontinalis. 
Besides the above, absence of cordation occurs sporadically in 
various other species, or perhaps in all. In A. mirabilis perhaps 
cordation may yet be discovered; in A. Hervevi it is but slight 
and often disappears; in A. aucuparius and in A. castaneus it is 
little developed. 
TEETH OF THE LEAF-MARGIN 
Teeth along the leaf-margins of the Biotian species are in gen- 
eral coarser and stronger in the Divaricati. In all the other species 
they are apt to be tipped abruptly with an aculeus; in the Divar- 
icati each tooth is apt to be practically acuminate, the green mem- 
brane continuing nearly to the point, instead of ceasing abruptly 
as in A. macrophyllus. In A. mirabilis, and in slightly less degree 
in A. macrophyllus sejunctus, the ending is a solid, sharp, short, 
triangular, yellowish tubercle instead of a slender, needle-like 
aculeus. In estimating the characteristic form of teeth for a leaf 
the middle of the sides is most reliable ; toward the base the form 
is often varied decidedly, or intermixed, crowded or greatly re- 
duced. Almost all the leaf-borders become gradually entire be- 
fore reaching the apex. Small leaves which are nearly entire 
throughout are not unusual, irrespective of species ; sometimes in 
A. macrophyllus pinguifolius and A. excelsior the teeth are almost 
obsolete, even on very large leaves. 
The form of the teeth on the leaf-margin is quite characteristic 
usually, and among broad-leaved asters is often one of the most 
available single characters to be found. The middle and lower 
