76 SILVA OF NORTH AMERICA. conifers. 



Santa Catalina, Rincon, Santa Rita, Huachuca, and Chiricahua Mountains of southern Arizona at 

 altitudes between six and eight thousand feet above the level of the sea, forming a considerable part 

 of their forests and on the Rincon Mountains a nearly pure forest some twenty-five square miles in area. 1 

 On the mountains of Sonora and Chihuahua it is more abundant and grows to its largest size, ranging 

 through three thousand feet of elevation over the Cordilleras of Chihuahua from the canons and valleys 

 at their base to the highest summits, forming forests of great extent, and filling the place of the more 

 northern Pinus ponder osa as a widely distributed, abundant, and valuable timber-tree. 2 



The wood of Pinus Arizonica produced on the Santa Rita Mountains in Arizona is light, soft, 

 not strong, rather brittle, and close-grained ; it is light red or often yellow, with thick lighter yellow or 

 white sap wood, and contains broad very resinous conspicuous bands of small summer cells, numerous 

 large resin passages, and thin obscure medullary rays. 3 The specific gravity of the absolutely dry wood 

 is 0.5038, a cubic foot weighing 31.40 pounds. In Arizona it is occasionally manufactured into 

 lumber, and in Mexico is often largely used, although it is difficult to obtain from the high and often 

 inaccessible mountain slopes which are the home of this tree. 



Pinus Arizonica was discovered by Professor John T. Rothrock 4 in 1874 on the Santa Rita 

 Mountains of Arizona. 



1 See Tourney, Garden and Forest, x. 153. American Museum of Natural History, New York, cut on the 

 Pinus Arizonica probably also grows on some of the mountain Santa Rita Mountains, is twenty-four inches in diameter inside 



ranges of southeastern New Mexico. the bark and one hundred and twenty-nine years of age, the sap- 



2 See C. G. Pringle, Garden and Forest, i. 430. wood being eight and five eighths inches thick and one hundred 



3 Pinus Arizonica after its first few years grows slowly. The log and two years old. 

 specimen in the Jesup Collection of North American Woods in the 4 See viii. 92. 



EXPLANATION OF THE PLATE. 



Plate DLIX. Pinus Arizonica. 



1. A cluster of staminate flowers, natural size. 



2. A staminate flower, enlarged. 



3. Diagram of the involucre of the staminate flower. 



4. An anther, front view, enlarged. 



5. An anther, side view, enlarged. 



6. Tip of a branch with pistillate flowers, natural size. 



7. A pistillate flower, enlarged. 



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



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



enlarged. 



10. A fruiting branch, natural size. 



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



12. A seed, natural size. 



13. Tip of a leaf, enlarged. 



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



15. A cluster of young leaves with its sheath, natural size. 



