4 TRANS. ST. LOUIS ACAD, SCIENCE. [164 
entire or mostly fringed on the edges, more or less persistent. or 
mostly deciduous, sometimes articulated above their base. 
The sECONDARY LEAVES constitute the foliage of the tree: 
they are borne on an undeveloped branchlet in the axils of pri- 
mary leaves or mostly of bracts, and are surrounded at base by a 
sheath of bud-scales (Wieder blactter). These consist of 2 short, 
rigid, strongly-keeled, lateral bracts, anda number (6-10 or more) 
of longer, thinner inner ones, which generally are woven together 
by the delicate fringes of their edges, and are then persistent with 
the leaves, though in time worn off at the ends; or they are loose, 
at last spreading and deciduous at the end of the first season. 
This is the case in all the species of the section S¢rodus, in the 
nut-pines, and in a few others: ?. Balfouriana, Gerardiana, 
Bungeana, Chthuahuana, and usually also in P. decophylla. 
The secondary leaves generally occur in definite numbers, 1 to 
5, in a bunch, or their number is slightly variable: some species 
have regularly 2 and 3 leaves (P. mztis, P. Eiiivttic), ties 
vary with 3 to 5 leaves (P. Montezume) ; species with regularly 3 
leaves have occasionally 2 or 4, such with 5 leaves are sometimes 
found with 6 and even 7 leaves. Where we have one (only in 
P. monophylia), the leaf is terete ; where there are two, the leaves 
are semi-terete, convex on the lower surface and flat on the upper 
one when fresh, or channelled when dry. ‘Those leaves that 
grow in bundles of 3 or more are triangular, the upper surface 
being more or less elevated and keeled ; ternate leaves are gener- 
ally somewhat flatter, and quinate ones higher and regularly 
triangular. Thus the shape of the leaf and especially its trans- 
verse section is mostly sufficient to determine the number i in which 
they occur. 
he leaves are in most species minutely but sharply serrulate 
on tRe edges, and mostly also on the keel of the upper surface. 
These serratures are closer together, or more distant, coarser or 
more delicate, but are absent only in a very few West-American 
species: the ceméroid or nut-pines, P. Balfouriana, and most 
forms of P. flexélés. The tips of the leaves are generally entire, 
acute, or acuminate, rarly obtusish; but in all the species of the 
section Strobus they are in the young and fresh leaves finely 
denticulate. 
The stomata are usually distributed in longitudinal rows over 
