14 



The Pines 



7. MEXICAN NUT PINE Pinus cembroides Zuccarini 



A low bushy tree of Arizona and adjacent Mexico, occurring on dry mountain 

 ridges at an altitude of about 1900 meters. Its usual height is about 6 meters, 

 with a trunk diameter of 3 dm. It is reported to attain much greater dimensions 

 in Mexico and is variously known as Mexican pinon or pinyon, Nut pine, Pinon 

 and Stone pine; it is recorded as growing also in Lower California. 



The trunk is short, its bushy branches forming a broad round head. The bark 

 is about 12 mm. thick, irregularly and remotely fissured into broad plates which 

 are covered by thin, light reddish brown scales. The twigs are slender, dark yel- 

 low, becoming black; they are covered with pale matted hairs. The large con- 

 spicuous bud-scales soon disappear. The branch-buds are about 6 mm. long, 

 tapering to a sharp point, the scales brown and shining, ovate, acute or long- 

 tipped. Juvenile leaves of this and the other nut pines are produced for the first 

 five years or more, often to the exclusion of all others; they are flat, linear- lan- 

 ceolate, strongly keeled and glaucous, entire, 18 to 25 mm. long, the new ones 

 shorter as the buds of the fascicled needle-shaped leaves develop in their axils. 

 The older leaves are in fascicles of 2 or 3, with a deciduous sheath, dark green, 

 slender, 2.5 to 5 cm. long, much curved, their tips elongated and thickened; they 

 are marked by 4 to 6 rows of stomata on each ventral face and contain 2 dorsal 

 resin-ducts and a single fibrovascular bundle; they are crowded at the ends of 



the branches and persist for three or 

 four years. The staminate flowers are 

 dense oblong or oval, 6 mm. long, the 

 anthers yellow. The pistillate flowers 

 arc lateral and erect on stout stalks, ob- 

 long, about 3 mm. long, their scales 

 thick and dark red. The cones become 

 about 12 mm. long by the end of the 

 first season, growing rapidly the second 

 season, and by autumn have become 

 subglobose, 3 to 5 cm. in diameter, short- 

 stalked, fight reddish brown; the scales 

 are concave, rounded or sharp at the 

 apex, thickened and ridged with a darker 

 central concave knob, that of the lower 

 scales reflexed. The central scales only 

 bear the seeds, the others are sterile 

 and much smaller, those at the base remaining closed and are much reflexed. 

 The seed is nearly cyfindric or slightly triangular, about 8 mm. long, compressed 

 at the tapering apex, full and rounded at the base, dark brown in front, nearly 

 bkick on the back; endosperm sweetish; wing light l)rown, very narrow, remain- 

 ing attached to the cone-scales when the seed falls; cotyledons 9 to 15. 



Fig. 8. Mexican Nut Pine. 



