| Outer walls of the leaf-endoderm thick. | |
| Cones large, attaining 12 cm. or more in length. | |
| Prickles of the cone inconspicuous. | |
| Bark-formation late | 37. pseudostrobus |
| Bark-formation early | 38. Montezumae |
| Prickle of the cone conspicuous | 39. ponderosa |
| Cones small, 7 cm. or less in length | 40. teocote |
| Outer walls of the leaf-endoderm thin. | |
| Spring-shoots mostly uninodal. | |
| Prickle of the cone slender, sometimes deciduous. | |
| Cones mostly oblique | 41. Lawsonii |
| Cones symmetrical | 42. occidentalis |
| Prickles of the cone stout and persistent | 43. palustris |
| Spring-shoots multinodal. | |
| Resin-ducts internal | 44. caribaea. |
| Resin-ducts mostly medial. | |
| Prickle of the cone stout | 45. taeda |
| Prickle of the cone slender. | |
| Bark-formation late | 46. glabra |
| Bark-formation early | 47. echinata |
37. PINUS PSEUDOSTROBUS
- 1839 P. pseudostrobus Lindley in Bot. Reg. xxv. Misc. 63.
- 1839 P. apulcensis Lindley in Bot. Reg. xxv. Misc. 63.
- 1842 P. tenuifolia Bentham, Pl. Hartw. 92.
- 1846 P. orizabae Gordon in Jour. Hort. Soc. Lond. i. 237, f.
Spring-shoots uninodal, conspicuously pruinose. Bark-formation late, the cortex of young trees smooth. Leaves in fascicles of 5, sometimes of 6, from 15 to 30 cm. long, drooping; resin-ducts medial, hypoderm variable in amount, often in very large masses, the outer walls of the endoderm thick. Conelets mucronate. Cones from 7 to 14 cm. long, ovate or ovate-conic, symmetrical or oblique, deciduous and often leaving a few basal scales on the trees; apophyses rufous or fulvous brown, flat, elevated or, in one variety, prolonged in various degrees, the prolongations nearly uniform or much more prominent on the posterior face of the cone, the mucro usually deciduous.
A species of the subtropical and warm-temperate altitudes of Mexico and Central America. Its range includes both eastern and western slopes of the northern plateau. Its northern limit is in Nuevo Leon, and it probably reaches in Nicaragua the southern limit of pines in the Western Hemisphere. It is distinguished from all its associates by the smooth gray trunk of the young trees, by their long internodes, and by their drooping gray-green foliage.
Some cones of this species develop protuberances of all degrees of prominence up to the curious cone collected in Oaxaca by Nelson (var. apulcensis, Shaw, Pines Mex. t. 12, fig. 8). There is also a remarkable difference in the amount of leaf-hypoderm. On many trees of the western part of the range this tissue forms septa across the green mesophyll. Such partitions are sometimes met in other species, P. Pringlei or P. canariensis, where the hypoderm is abundant. But in P. pseudostrobus they appear in some leaves of weak, as well as of strong hypoderm (var. tenuifolia, Shaw, Pines Mex. t. 13, ff. 2, 4, 5, 7, 8).
Fig. 211, Cone. Fig. 212, Two cones of var. tenuifolia. Figs. 213, 214, Two cones of var. apulcensis. Fig. 215, Magnified section of 3 leaves of var. tenuifolia. Fig. 216, Magnified section of 2 leaves of the species. Fig. 217, Bud destined to produce staminate flowers. Fig. 218, Ten-year old branch showing smooth cortex. Fig. 219, Young and mature trees in open growth.