76 GENUS PINUS 



XU. mSIGNES 



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 per- 

 sistent, often serotinous; apophyses sublustrous tawny yellow or fulvous brown, convex, the pos- 

 terior 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. 



