tern
Illinois. It is extensively manufactured into material of all kinds
that enters into the construction of buildings. It differs from P.
virginiana in its longer leaves, brittle branches, and much greater
height, from P. glabra in its rough upper trunk, and from both by the
frequent presence of trimerous leaf-fascicles.

Of the six or seven pines of the southeastern United States, this
species covers a larger area and ascends the slopes of the Alleghany
Mountains far enough to meet the northern species, P. virginiana, P.
rigida, and P. strobus. Unlike the western members of this group, P.
echinata and its associates are not variable. Their characters are
singularly constant, as their limited synonymy and total lack of
varietal names attest.

Plate XXX.

Fig. 260, Cone. Fig. 261, Leaf-fascicle and magnified leaf-section
from a ternate fascicle. Fig. 262, Magnified leaf-section from a
binate fascicle. Fig. 263, Multinodal branchlet bearing lateral and
subterminal conelets and a ripe cone. Figs. 257, showing mucronate
scales of the conelet, and 259, showing dermal tissues of the leaf,
are applicable also to this species.

[Illustration: PLATE XXX. P. GLABRA (256-259), ECHINATA (260-263), TAEDA
(264-267)]

=XII. INSIGNES=

Pits of the ray-cells small. Cones tenaciously persistent, serotinous in
various degrees. Conelets mucronate or spinose.

Spring-shoots uninodal.
Resin-ducts mostly internal 48. Pringlei
Resin-ducts mostly septal 49. oocarpa
Spring-shoots multinodal.
Cones symmetrical.
Leaf-hypoderm not biform.
Bark-formation late 50. halepensis
Bark-formation early 51. pinaster
Leaf-hypoderm biform.
Cones with slender spines.
Leaves binate.
Cones dehiscent at maturity 52. virginiana
Cones serotinous 53. clausa
Leaves ternate.
Cones dehiscent at maturity 54. rigida
Cones serotinous 55. serotina
Cones with stout spines 56. pungens
Cones oblique or unsymmetrical.
Cones and leaves very short, not exceeding 6 cm.
Cones curved or warped 57. Banksian