14 



TREES OF NORTH AMERICA 



1. Sheaths of the leaf-clusters deciduous ; leaves in S-leaved clusters. 



13. Pinus Chihuahuana, Eiigelm. Yellow Pine. 



Leaves slender, pale glaucous green, marked by G-8 rows of conspicuous stomata 

 ou each of the 3 sides, 2^-4' long, irregularl}- deciduous from their fourth season, 

 their sheaths deciduous. Flowers : stamiuate yellow; pistillate yellow-green. Fruit 



ovate, horizontal or slightly 

 declining, long-stalked, l^'-2' 

 long, becoming light chestnut- 

 brown and lustrous, maturing 

 at the end of the third season, 

 with scales only slightly thick- 

 ened, their ultimately pale um- 

 bos armed with recurved de- 

 ciduous prickles ; seeds oval, 

 rounded above and pointed be- 

 low, about ^' long, with a thin 

 dark brown shell, their wings 

 ^' loilg and broadest near the 

 middle. . 



A tree, rarely more than 

 40-o0 high, with a tall trunk 

 sometimes 2 in diameter, stout slightly ascending branches forming a narrow open 

 pyramidal or round-topped head of thin pale foliage, and slender bright orange- 

 brown branchlets, soon becoming dull red-brown. Bark of old trunks f'-l^' thick, 

 dark reddish brown or sometimes nearly black, and deeply divided into broad flat 

 ridges covered with thin closely appressed scales. Wood light, soft, not strong but 

 durable, light orange color, with thick much lighter colored sapwood ; occasionally 

 used as fuel. 



Distribution. Mountain ranges of southern New Mexico and Arizona, usually at 

 elevations between 6000 and 7000 ; not common ; more abundant on the Sierra 

 Madre of northern Mexico and on several of the short ranges of Chihuahua and 

 Sonora, and of a larger size in Mexico than in the United States. 



2. Sheaths of the leaf-clusters persistent. 



* Leaves in 3-leaved clusters (3 and 2-leaved in 15, 17, and 21, 5-leaved in IJf). 

 -i- Cones subterminal. 



14. Pinus Arizonica, Engelm. Yellow Pine. 



Leaves tufted at the ends of the branches, in 5-leaved clusters, stout, rigid, dark 

 green, stomatiferous on their 3 faces, 6'-7' long, deciduous during their third season. 

 Flowers dark purple: staminate in short spikes; pistillate on stout peduncles, usually 

 in pairs. Fruit oval, horizontal, 2'-2|^' long, becoming light red-brown, with thin 

 scales much thickened at the apex and armed with slender recurved spines ; seeds 

 full and rounded below, slightly compressed towards the apex, \' long, with a thick 

 shell, their wings broadest above the middle, about y long and \' wide. 



A tree, 80o-100 high, witli a tall straight massive trunk 3-4 in diameter, thick 

 spreading branches forming a regular open round-topped or narrow pyramidal head, 

 and stout branchlets orange-brown when they first appear, becoming dark gray- 



