1884 P. clausa Vasey ex Sargent, Rep. 10th Cens. U. S. ix. 199.
Spring-shoots multinodal. Bark-formation slow, as in the preceding species. Leaves binate, from 5 to 9 cm. long; resin-ducts medial, or with an occasional internal duct, hypoderm biform when of two rows of cells. Conelets with long tapering acute scales. Cones from 5 to 8 cm. long, reflexed, ovate-conic, symmetrical, persistent, often serotinous; apophyses lustrous nut-brown, elevated along a transverse keel, the umbo forming a triangular persistent spine.
A species of limited range, confined to the sandy coast of Alabama and to Florida. It sometimes attains timber-size, but is usually a low spreading tree of no commercial importance and never seen in cultivation. It is recognized by its smooth branches, binate leaves and numerous, often multiserial, clusters of persistent, often closed, cones. It is associated with P. caribaea and, in the northern part of its range, it grows with the other Southern species. By its close resemblance it may be considered the serotinous form of P. virginiana.
Fig. 288, Three nodal groups of cones of the same year. Fig. 289, Conelet and its enlarged scale. Fig. 290, Leaf-fascicle and magnified leaf-section. Fig. 291, Larger form of the tree.
[Illustration: PLATE XXXIII. P. VIRGINIANA (284-287), CLAUSA (288-291)]
1768 P. rigida Miller, Gard. Dict. ed. 8. 1909 P. serotina Long, in Bartonia, ii. 17 (not Michaux).
Spring-shoots multinodal. Leaves ternate, from 7 to 14 cm. long; resin-ducts medial, or with an occasional internal duct, hypoderm biform. Scales of the conelet abruptly prolonged into a spine. Cones from 3 to 7 cm. long, ovate-conic, symmetrical, persistent, dehiscent at maturity or rarely serotinous; apophyses lustrous tawny yellow, elevated along a transverse keel, the umbo salient and forming the broad base of a slender sharp prickle.
A tree with bright green foliage in spreading tufts. The northern limit of its range is in southwestern New Brunswick, southern Maine, central New Hampshire and Vermont, the Thousand Islands of the St. Lawrence River and central Ohio. It ranges into Pennsylvania and Delaware at low levels and thence over the Alleghanies into northern Georgia. It is associated with P. strobus and P. resinosa and, further south, with P. virginiana. The cones are rarely serotinous, but it is remarkably like P. serotina in many characters, and is therefore placed in this group.