. 331 (not Balfour).

Spring-shoots glabrous or temporarily pubescent. Leaves from 2 to 4 cm.
long, persistent for many years; stomata ventral only; resin-ducts
external. Scales of the conelet prolonged into long slender bristles.
Cones from 4 to 9 cm. long, subcylindrical or tapering to a rounded
apex, short-pedunculate; apophyses terracotta or purple-brown, tumid,
the long bristles of the umbo often partly or wholly broken away; seeds
with a long articulate wing.

A bushy tree, similar in foliage to the preceding species, growing at
the timber-limit from Colorado through Utah, central and southern
Nevada and northern Arizona into southeastern California, but
separated from the nearest station of P. Balfouriana by an arid
treeless desert. Engelmann (in Brewer and Watson, Bot. Calif. ii. 125)
considered it to be a variety of P. Balfouriana.

Plate XV.

Fig. 143, Cone. Fig. 144, Seed and enlarged cone-scale. Fig. 145,
Leaf-fascicle and magnified leaf-section. Fig. 146, Conelet.

[Illustration: PLATE XV. P. ARISTATA (143-146), BALFOURIANA (147-150)]

DIPLOXYLON

Bases of the bracts subtending leaf-fascicles decurrent. Leaves
serrulate; fibro-vascular bundle double; stomata dorsal and ventral.
Cones with a dorsal umbo, the phyllotaxis complex. Wood hard, with dark
resinous bands, the annual rings clearly defined.

In this section there are a few species combining the essential
characters of Diploxylon with important characters of Haploxylon. A
subsection, Parapinaster, is established for these exceptional
species.

c. Parapinaster Species with the fascicle-sheath or seed-wing of
Haploxylon.
d. Pinaster Sheath persistent, seed-wing articulate, effective.

=Parapinaster=

Sheath of the leaf-fascicle deciduous VII. Leiophyllae.
Sheath of the leaf-fascicle persistent.
Seed-wing of the Strobi VIII. Longifoliae.
Seed-wing of the Gerardianae IX. Pineae.

=VII. LEIOPHYLLAE=

Sheath of the leaf-fascicles deciduous.
Leaves short, erect, the fructification triennial 20. leiophylla.
Leaves long, pendent, the fructification biennial 21. Lumholtzii.

20. PINUS LEIOPHYLLA

1831 P. leiophylla Schlechtendal and Chamisso in Linnaea, vi. 354.
1848 P. chihuahuana Engelmann in Wislizenus, Tour. Mex. 103.

Spring-shoots uninodal. Leaves in fascicles o