SILVA OF NORTH AMERICA. 



PINUS. 



Flowers naked, monoecious, the staminate involucrate, fascicled ; stamens indefi- 

 nite, anther-cells 2 ; the pistillate lateral or subterminal, solitary or clustered, their 

 scales spirally disposed ; ovules 2 under each scale. Fruit a woody strobile maturing 

 in two or rarely in three years. Leaves dimorphic, the primordial scattered, the 

 secondary fascicled, persistent. 



Pinus, Duhamel, Traite des Arbres, ii. 121 (1755). — Adan- Pinus, Linnaeus, Gen. 293 (in part) (1737). — Endlicher, 

 son, Fam. PI. ii. 480. — Link, Abhand. Akad. Berl. 1827, Gen. 260 (in part). — Meisner, Gen. 352 (in part). — 



157. — Bentham & Hooker, Gen. iii. 438. — Engelmann, Baillon, Hist. PI. xii. 44 (in part). 



Trans. St. Louis Acad. iv. 161. — Eichler, Engler & Apinus, Necker, Elem. Bot. iii. 269 (1790). 



Prantl Pflanzenfam. ii. pt. i. 70. — Masters, Jour. Linn. Cembra, Opiz, Seznam, 27 (1852). 



Soc. xxx. 37. Strobus, Opiz, Lotos, iv. 94 (1854). 



Trees, or rarely shrubs, with deeply furrowed and sometimes laminate or with thin and scaly 

 bark, hard or soft heartwood often conspicuously marked by dark bands of summer cells impregnated 

 with resin, pale nearly white sapwood, stout branches and branchlets, large terminal and axillary 

 branch-buds formed during summer and covered with numerous loosely imbricated scarious usually 

 chestnut-brown thin ovate acute accrescent scales, the outer empty and persistent on the growing 

 branch, the inner inclosing the leaf-buds, 1 and fibrous rootlets. Primary leaves subulate from a broad 

 base, flat, keeled above and below, usually serrulate, stomatiferous on both surfaces, scarious or hyaline, 

 marcescent, spirally disposed in many series, on some species occasionally produced on vigorous stump 

 shoots and branches ; 2 secondary or foliage leaves clustered, the clusters borne on rudimentary 

 branches in the axils of primary leaves or of bud-scales, and surrounded at the base by sheaths of 

 two lateral keeled scales and from six to ten inner accrescent scales more or less united by their 

 thin edges, inclosing the leaf-clusters in the bud, persistent with the leaves, or loose, spreading, and 

 deciduous during the first season ; leaf-clusters composed of two, three, or five, or rarely of six or seven 

 leaves, or of a single leaf, the number usually definite in each species, or on a few species regularly 

 variable, deciduous during their second season or persistent for many years ; leaves acicular, elongated, 

 acute, spinescent, or occasionally somewhat obtuse and entire at the apex, generally sharply serrulate 

 on the margins and on the keel of the upper surface ; in two-leaved clusters, semiterete, convex below, 

 flat above, in clusters of three or more, triangular and more or less keeled above, or terete when 

 solitary ; stomatiferous, the stomata disposed in longitudinal bands on one or on both surfaces ; fibro- 

 vascular bundles solitary or in pairs ; resin ducts peripheral or parenchymatous or internal, often 

 varying in number in the same species ; hypoderm or strengthening cells scattered under the epidermis, 

 usually at the angles and keel of the leaf, and occasionally also in the fibro-vascular region. Flowers 



