CAMBRIDGE
PRINTED AT THE RIVERSIDE PRESS
1914

REPRINTED 1958 BY THE MURRAY PRINTING COMPANY
FORGE VILLAGE, MASSACHUSETTS

CONTENTS

PagePlate
PART 1 CHARACTERS OF THE GENUS[1]
Cotyledon, Primary Leaf, Bud and Branchlet[1], [2][I]
Secondary Leaves[2][II]
External Characters[4]
Internal Characters[4]
Flowers and Conelet[7][III]
Cone[8][IV]
Phyllotaxis[12][V]
Cone-tissues and Seeds[12]-[16][VI]
Wood[17][VII]
Bark[18]
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.