Part 2 Classification of the Species 22

Sections, subsections and groups 25

Section Haploxylon 26

Subsection Cembra 26

Group Cembrae 26

Pinus Koraiensis, Cembra, Albicaulis 26, 27 VIII

Group Flexiles 28

Pinus Flexilis, Armandi 28, 30 IX

Group Strobi 30

Pinus Ayacahuite, Lambertiana 30, 32 X

Parviflora, Peuce, Excelsa 32, 34 XI

Monticola, Strobus 34, 36 XII

Subsection Paracembra 36

Group Cembroides 38

Pinus Cembroides, Pinceana, Nelsonii 38, 40 XIII

Group Gerardianae 40

Pinus Bungeana, Gerardiana 40, 42 XIV

Group Balfourianae 42

Pinus Balfouriana, Aristata 42, 44 XV

Section Diploxylon 44

Subsection Parapinaster 44

Group Leiophyllae 44

Pinus Leiophylla, Lumholtzii 44, 46 XVI

Group Longifoliae 46

Pinus Longifolia, Canariensis 46, 48 XVII

Group Pineae 48

Pinus Pinea 48 XVIII

Subsection Pinaster 50

Group Laricionea 51

Pinus Resinosa, Tropicalis 51, 52 XIX

Massoniana, Densiflora 52 XX

Sylvestris, Montana 54 XXI

Luchuensis, Thunbergii, Nigra 56, 58 XXII

Merkusii, Sinensis, Insularis 58, 60 XXIII

Group Australes 62

Pinus Pseudostrobus 62 XXIV

Montezumae 64 XXV

Ponderosa 66 XXVI

Teocote, Lawsonii 68 XXVII

Occidentalis, Palustris 70 XXVIII

Caribaea 70 XXIX

Taeda, Glabra, Echinata 72, 74 XXX

Group Insignes 76

Pinus Pringlei, Oocarpa 76, 78 XXXI

Halepensis, Pinaster 78, 80 XXXII

Virginiana, Clausa 80 XXXIII

Rigida, Serotina, Pungens 82, 84 XXXIV

Banksiana, Contorta 84 XXXV

Greggii, Patula 86 XXXVI

Muricata, Attenuata, Radiata 86, 88 XXXVII

Group Macrocarpae 90

Pinus Torreyana, Sabiniana 90 XXXVIII

Coulteri 93 XXXIX

INDEX 94

INTRODUCTION

This discussion of the characters of Pinus is an attempt to determine their taxonomic significance and their utility for determining the limits of the species. A systematic arrangement follows, based on the evolution of the cone and seed from the comparatively primitive conditions that appear in Pinus cembra to the specialized cone and peculiar dissemination of Pinus radiata and its associates. This arrangement involves no radical change in existing systems. The new associations in which some of the species appear are the natural result of another point of view.

Experience with Mexican species has led me to believe that a Pine can adapt itself to various climatic conditions and can modify its growth in response to them. Variations in dimensions of leaf or cone, the number of leaves in the fascicle, the presence of pruinose branchlets, etc., which have been thought to imply specific distinctions, are often the evidence of facile adaptability. In fact such variations, in correlation with climatic variation, may argue, not for specific distinction, but for specific identity. The remarkable variation in the species may be attributed partly to this adaptability, partly to a participation, more or less pronounced, in the evolutionary processes that culminate in the serotinous Pines.