34 SILVA OF NORTH AMERICA. 



CONIFERS. 



red and their bases dark dull red. The seeds are broadly ovate, slightly compressed, half an inch long 

 and about a third of an inch wide, with a thin dark red-brown coat produced into a narrow margin, 

 and are furnished with thin dark rounded wings about an eighth of an inch in width. 



Pinus strobiformis is scattered over the rocky ridges and the sides of the canons of the Santa 

 Catalina, Santa Rita, and Chiricahua Mountains of southern Arizona, and of the Sierra Madre of 

 Chihuahua, at elevations of from six to eight thousand feet above the level of the sea, never forming 

 groves and usually growing singly along the lower margin of the forests of Pinus Arizonica. 



The wood of Pinus strobiformis is hard, although light, not strong, and close-grained ; it is pale 

 red, with thin nearly white sapwood, and contains thin inconspicuous bands of small summer cells, large 

 resin passages, and numerous obscure medullary rays. 1 The specific gravity of the absolutely dry wood 

 is 0.4877, a cubic foot weighing 30.39 pounds. The rarity of this tree and the inaccessibility of the 

 places where it grows in the United States prevent the use of its wood, which is as valuable as that of 

 the other western White Pines. 



Pinus strobiformis was discovered by Dr. F. A. Wislizenus 2 in Chihuahua in October, 1846, 

 and was first found in the territory of the United States by Dr. J. T. Rothrock 3 in 1874 on the Santa 

 Rita Mountains of Arizona. 



1 Pinus strobiformis, considering the dryness of the region it in- only one hundred and seventy-nine years old, with an inch and five 



habits, appears to grow with comparative rapidity. The specimen eighths of sapwood showing forty-seven layers of annual growth, 



from the Santa Rita Mountains in the Jesup Collection of North 2 See vi. 94. 



American Woods in the American Museum of Natural History, 3 See viii. 92. 

 New York, is thixty-one inches in diameter inside the bark, and is 



EXPLANATION OF THE PLATES. 



Plate DXLrV. Pinus strobiformis. 



1. A branch with staminate flowers, natural size. 



2. A staminate flower, enlarged. 



3. Bract of a staminate flower, enlarged. 



4. Diagram of the involucre of the staminate flower. 



5. An anther, front view, enlarged. 



6. An anther, side view, enlarged. 



7. A branch with pistillate flowers, natural size. 



8. A pistillate flower with its peduncle, enlarged. 



9. A scale of a pistillate flower, upper side, with its ovules, enlarged. 



10. A scale of a pistillate flower, lower side, with its bract, enlarged. 



11. Tip of a leaf, enlarged. 



12. Cross section of a leaf, magnified fifteen diameters. 



Plate DXLV. Pinus strobiformis. 



1. A portion of a fruiting branch, natural size. 



2. A cone-scale, upper side, with its seeds, natural size. 



3. A cone-scale, lower side, natural size. 



