2i 8 BOTANICAL GAZETTE [SEPTEMBER 



in radius, but was occasionally, noted where it amounted to 38 mm 

 (i.5 in ). Such a constriction is often seen on individual trees in 

 nearly any stand, but in no other case was it found to be a stand as 

 characteristic as it was near Servilleta. 



Pifion is also resistant to severe climatic conditions, since it will 

 succeed over severely exposed slopes where the average annual 

 precipitation is less than 33 cm (i3 in ) and where evaporation and 

 transpiration are high because of the semi-arid climate, the large 

 amount of sunshine, and the prevalence of winds. In this respect 

 it is undoubtedly the most resistant pine in the southwest. However, 

 it prefers a slightly greater precipitation and areas less exposed to the 

 wind. An example of the unfavorable influence of strong winds and 

 a close-textured soil was noted in the vicinity of Fort Stanton, New 

 Mexico, where a level plateau of nearly 8 km (5 miles) in length did 

 not support a single tree, while similar plateaus on all sides, with less 

 wind sweep and a "coarser soil, showed luxuriant growth of both the 

 pinon and the juniper. The tree does not live as long as the junipers, 

 and in general is less resistant to unfavorable climatic conditions. 

 In the drought which occurred in New Mexico from 1889 to 1904, 

 pinon suffered considerably more than the junipers. Many mixed 

 stands were observed in New Mexico and southern Colorado in 

 which 75 to 95 per cent, of all dead trees were pinon. In the frost 

 which occurred in April, 1907, pinon was affected, while the junipers 

 resisted practically all injury. In the wet freezing snow of October, 

 1906, which caused immense damage to the forests of the southwest, 

 fewer branches were broken from the pinon than from the brittle 

 junipers. 



The tree is also more resistant to disease than most of the conifers 

 with which it associates. It is much less affected by the so-called 

 false mistletoe (Razoumofskya) than is the western yellow pine and 

 the junipers. It has fewer insect enemies than the western yellow 

 pine, and is not affected by the witch's broom as is often the case 

 with Douglas fir in the southwest. 



TOLERANCE AND FORM 



Pifion is distinctly an intolerant tree. During its seedling stage 

 it prefers a moderate shade, and hence reproduces best under the 



