laris 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