216 R. J. STEINHOFF 



Pinus lambertiana Dougl.; Pinus montioola Dougl.; and Pinus strobus var. 

 chiapensis Martinez. The latter variety is covered by H. B. Kriebel, else- 

 where in these proceedings. 1 Three of these species--?, albicaulis, P. 

 flexilis, and P. montioola- -are limited to Canada and the United States. 

 Two, P. lambertiana and P. strobiformis , occur in both the United States 

 and Mexico. Another, P. ayaoahuite , ^.s found from central Mexico southward 

 into the Central American countries of Guatemala, El Salvador, and Honduras. 



SECTION P AERY A 



SUBSECTION BALFOURIANAE 



Foxtail Pine (P. balfouriana) and Bristlecone Pine (P. aristata) 



Foxtail pine has a very limited distribution in two parts of 

 California (Critchfield and Little, 1966; Map 20). Bristlecone pine is 

 more widely distributed in east-central California, eastern Nevada, Utah, 

 Colorado, and northern New Mexico and Arizona (Critchfield and Little, 

 1966; Map 21). When cut for study, one bristlecone pine tree in eastern 

 Nevada proved to be at least 4,844 years old, making it the oldest known 

 tree (Currey, 1965) . Trees of both of these species are very slow 

 growing (3 to 6 inches height per year) and of no commercial value for 

 timber production (Figs. 1 and 2). 



The two species, foxtail and bristlecone pines, have been success- 

 fully crossed at the Institute of Forest Genetics, Placerville, California. 

 Attempts to cross these species with members of Section Strobus have been 

 very limited (Institute of Forest Genetics, Placerville, Calif., unpublished 

 data; and Bingham, Hoff , and Steinhoff , In press) , but it appears unlikely 

 that they will hybridize. Because of their very slow growth these species 

 probably would be of interest only to someone working on trees suitable 

 for watershed protection or avalanche control, although P. aristata 

 appears to be fairly resistant to attack by the blister rust fungus 

 {Cronartium ribioola J. C. Fisch. ex Rabenh.; see Bingham 2 ). 



SECTION STROBUS 



SUBSECTION CEMBRAE 



Whitebark Pine (P. albicaulis) 



This species has a range extending from central British Columbia on 

 the north to the southern Sierra Nevada Mountains in California. In the 

 Rocky Mountains, it extends as far south as central Wyoming (Critchfield 

 and Little, 1966; Map 5). It occurs primiarly near timberline but in the 

 north occasional trees may be found scattered at lower elevations. 



Whitebark pine, as found growing naturally, usually is of limited 

 value for timber production but is important for watershed protection and 

 has considerable esthetic value. Because of their normally exposed 

 habitat, most trees are twisted and repeatedly forked and frequently are 

 somewhat procumbent. The limbs are large, upturned sharply, and often 

 compete with the main stem for dominance (Fig. 3). Under more favorable 



Kriebel 3 H.B. White pines in North and Central America: Pinus strobus 

 and introduced Asian and European species, these vrocee dings . 



2 Bingham, R. T. Taxonomy, cross ability 3 and relative blister rust 

 resistance of 5-needled white pines, these proceedings . 



