Pits of the ray-cells small. Cones tenaciously persistent, serotinous in various degrees. Conelets mucronate or spinose. Spring-shoots uninodal. Resin-ducts mostly internal 48. Pringlei Resin-ducts mostly septal 49. oocarpa Spring-shoots multinodal. Cones symmetrical. Leaf-hypoderm not biform. Bark-formation late 50. halepensis Bark-formation early 51. pinaster Leaf-hypoderm biform. Cones with slender spines. Leaves binate. Cones dehiscent at maturity 52. virginiana Cones serotinous 53. clausa Leaves ternate. Cones dehiscent at maturity 54. rigida Cones serotinous 55. serotina Cones with stout spines 56. pungens Cones oblique or unsymmetrical. Cones and leaves very short, not exceeding 6 cm. Cones curved or warped 57. Banksiana Cones straight 58. contorta Cones and leaves much longer, more than 7 cm. Posterior cone-scales gradually larger than anterior scales. Bark-formation late 59. Greggii Bark-formation early 60. patula Posterior cone-scales abruptly larger than anterior scales. Cones with very stout spines 61. muricata Cones with minute or deciduous prickles. Bark-formation late 62. attenuata Bark-formation early 63. radiata 48. PINUS PRINGLEI 1905 P. Pringlei Shaw in Sargent, Trees & Shrubs, i. 211, t. 100. Spring-shoots uninodal, sometimes pruinose. Leaves ternate, from 15 to 25 cm. long; resin-ducts internal or with an occasional septal duct, hypoderm biform, in thick masses, often projecting far into the green tissue and sometimes touching the endoderm. Conelets mucronate. Cones from 5 to 10 cm. long, reflexed on a rigid peduncle, subsymmetrical or more or less oblique, tenaciously persistent, often serotinous; apophyses sublustrous tawny yellow or fulvous brown, convex, the posterior scales often more prominently developed, the mucro usually wanting; seed with a perceptibly thickened wing-blade. A tree with long erect bright green foliage, confined, so far as known, to the subtropical altitudes of western Mexico. As it grows in Uruapan, Michoacan, there are two forms of the cone, large and small, both with the same long rigid leaf. Plate XXXI. Figs. 268, 269. Three cones and seed. Fig. 270, Leaf-fascicle and magnified leaf-section. 49. PINUS OOCARPA