110 JOURNAL OF TIIE ARNOLD ARBORETUM [vol. n 



nearly wliite witli a pale yellowish cast. Both sap and heart wood show small, fine, 

 medullary rays. The wood is rather tough, strong, compact, fine-grained, and 

 weighs approximately GO pounds to the cubic foot. It shows only a moderate tend- 

 ency to check in seasoning and little inclination to warp. The wood could only be 

 procured In short and small samples, seldom more than three or four feet long, and 



from six to eight inches in diameter, but for small articles, as in turnery, and pos- 

 sibly for blocks for wood engraving, it has valuable qualities. 



It is a thin-foliaged species, highly intolerant of shade, cleaning up its stem and 



small branches very rapidly." ^ 



The true Pistacia mexicana is a tree having a single w^ell-marked trunk, 

 not branched at or near the surface of the ground. This is shown clearly 

 by photographs taken near Tehuecan, Puebla, by Dr. J. N. Rose and Mr. 

 C. A. Purpus, and now filed in the National Herbarium, and by a photo- 

 graph taken in the same region by Dr. D. T. MacDougal, now filed in the 

 herbarium of the New York Botanical Garden. The Texas Pistache, on 

 the contrary, almost never develops a single trunk. Prof. S. C. Mason 

 says of the individuals of this species: 



"All show a strong tendency to produce several trunks from the ground or to 

 sprout low down, rather than to form a single stem. In the thickets in the rich soil 

 along the river front (the alluvium of an ancient river flood plain, high above the 

 present) these divergent stems are so highly curved and interlocked as to make the 

 groups almost impenetrable. There is no sign of sprouting from the roots, or what 

 may be termed suckering, nor any indication of surface roots. Deep penetration 

 of the roots seems to be the rule." ^ 



The smaller branches of P. mexicana are smooth and light brow^nish gray, 

 while P. texana has rather rough, dark brownish gray branches, never 



silvery. 



Possible Economic Uses: At first I feared the American Pistaches were 

 so different from the old-world species that the Pistache-nut tree {Pistacia 

 vera L.) could not be grafted on them. However, it has been found by Mr. 

 Eugene May, Jr., that the Pistache-nut tree can be budded readily on P. 

 mexicana, and in view^ of the close affinity of the Texas species it is highly 

 probable that it also can be used as a stock on which to grow the true 



Pistache-nut. 



The Texas Pistache as it grows in the limestone country near the mouth 



of the Pecos, forms compact, rounded clumps, with dark, evergreen foliage. 



In early spring the new growth shows a beautiful wine-red color all over 



the clump. It is a handsome tree, well worthy of trial as an ornamental, 



especially in warmer parts of the southwestern United States. 



Bureau of Plant Industry 

 Washington, D.C, 



September 18, 1920 



* Letter to Walter T. Swingle^ from San Antonio, Texas, April 15, 1910. 



