INTKODUCTION 



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 adapt- 

 ability, partly to a participation, more or less pronounced, in the evolutionary processes that cul- 

 minate in the serotinous Pines. 



