1020] SWINGLE, NEW SPECIES OF PISTACIA 109 



National Herbarium No. 332516, E. W. Nelson^ No. 4445, "Road over mountain 

 between Victoria and Jaumave Valley, altitude 800-2500 ft.," Tamaulipas, Mex,, 

 May 31, 1898, two fruiting branches. 



The species probably occurs not only along the Rio Grande, but also along 



its tributary streams, both in Texas and in the Mexican states of Coahuila, 

 Nuevo Leon and Tamaulipas, wherever the soil conditions are suitable. 



In March, 1907, Mr. F, B. Headley visited the Rio Grande Valley near 

 the mouth of the Pecos River and sent specimens and photographs, adding 

 the following notes on the species: 



"A characteristic of . . • this species is that as fast as the old trunks die out new 

 ones shoot forth from the same base. The majority of the trees observed were stam- 

 inate. More trees are found growing in rocky than in silt soil. It may be that the 

 pistache is crowded out from those soils and locations where it enters into compe- 

 tition with other trees. It is evidently highly drought-resistant, for it grows out of 

 rocky soils at an altitude of from 200 to 300 feet above the river level. It also grows 

 in moist locations, but most of the trees observed and photographed were growing 

 out of the rock bottom of cafions which are periodically swept by floods. I found 

 many trees having neither staminate nor pistillate blossoms. Goats seem to be fond 

 of the leaves and it is probably for this reason that there are at present no young 

 pistaches in this location." ^ 



Prof. S. C. Mason's notes on an unusually large tree read as follows: 



"Along the pond below the Hinojose spring I located what I believed to be the 

 largest pistache tree yet recorded. . . . This was in a rich . . , alluvium and its roots 

 doubtless penetrate to permanent moisture. The main old trunk is fourteen 

 inches in diameter, besides several large sprouts from the ground seven or eight 

 inches in diameter, others smaller; the entire tree having a spread of thirty-nine feet 

 and a height of about thirty feet." * 



On the second trip by Professor Mason, April 7, 1910, this tree was found 

 to be staminate and already out of bloom; but on his third trip, March 17, 

 1911, this tree was in full bloom and from it the male syntype was collected 

 as well as many additional specimens (merotypes). 



The larger trees in the alluvial plain of the Rio Grande near the mouth 

 of the Pecos River are nearly all male. Professor Mason, w^ho visited this 

 region in March, and again in April, 1910, expressly to study this Pistache, 

 reports as follows: 



**0n Saturday morning ... I made a tramp alone of twelve or fifteen miles, go- 

 ing to the big bend of the Rio Grande six miles above our camp [near the Big Spring 

 on Hinojose's ranch]. Just below this I discovered two large groves of pistache in 



the old alluvium at the front of the bluffs facing the river. ... In all of these groups 

 the pistillate trees were in very small proportion, not over ten per cent. This is a 

 difficult matter to offer an explanation for. Another point may be merely acci- 

 dental, but without exception the large trees are staminate. In no case did we find 

 an unusually large tree to be pistillate. . . . 



The recuperative power of this tree is remarkable. Parts of a stool that are old 

 and dead at the top will send up most vigorous shoots, so that the top is renewed and 

 kept vigorous. The growth is slow, a stem of apparently average growth, 4^ inches 

 in diameter, showing 33 annual rings. This stick shows on a radial measurement, 

 1^ inches of yellow-brown heart wood to one inch of sap wood. The sap wood is 



1 Frank B. Headley, letter to Walter T. Swingle, dated San Antonio, Texas, April 1, 1907. 

 * Letter to Walter T. Swingle dated San Antonio, Texas, March 7, 1910. 



