LEAF-CHARACTERS 39 
of the same leaf in the same exposure may be smooth and rough 
either while living or after drying. 
VEINS 
Veins are much alike, but of some diagnostic importance ; 
in 4. carmesinus, A. obolarius, A. castaneus, A. axillaris, and 
perhaps others, they are remarkably succulent and stand out as 
slender ridges beneath, little confluent with the leaf-membrane ; 
as if an aftergrowth, applied to the leaf. In A. castaneus they 
are apt to be depressed above and therefore retain dust and show 
as pale dusty lines over the dark green leaf. In A. biformis and 
in “ pale-streak ” forms of A. multiformis the same is true, per- 
haps aided by some glandular hair. 
Direction of veins: in some cases diagnostic, forwardly curved 
like Cornus and Doellingeria infirma, in coriaceous forms of A. 
divaricatus, in A. castaneus, etc. ; curved directly toward the mar- 
gin in the dcech-twig form of A. divaricatus, in A. ulmarius, etc. ; 
strongly outcurved in A. rupicola ; upward-curved in most species. 
Trinervate leaf-bases characterize all deeply cordate Macro- 
phyli and Multiformes, with the sinus bordered on each side of 
the petiole by three veins, one primary bounding the sinus toward 
the petiole, its lower branch bordering the outer corner of the 
sinus, and a branch from that bordering the side of the sinus, at 
least for a short distance. 
Usually there are three pairs of primary veins given off quite 
close together just above the leaf-base ; sometimes only two; the 
two or more remaining pairs are quite remote. 
WINGs 
Winged petioles are common among many forms of the Dr- 
varicati as well as among the glandular species. Strap-wings, 
long broad wings of uniform breadth like straps, occur often in Æ. 
divaricatus apricensis and are occasional elsewhere. Undulatiform- 
wings, i. e., dilated gradually to a very broad base as in A. undu- 
latus, are frequent throughout ; A. curvescens is particularly subject 
to them. Half-wings, i. e., petioles winged along one side only 
or chiefly, form a singular prevailing feature of one form of A. 
divaricatus and are of sporadic occurrence in most species. But 
