232 GYMNOSPERMS 



The richest regions in genera and species arc in western North 

 America and in extra-tropical eastern and central Asia. There are 

 not many conifers in tropical and southern Africa. 



In the immense forests, where there is the greatest display of 

 individuals, the number of genera and species is not correspondingly 

 great. 



Piniis, with its 90 species, is the dominant genus of the Northern 

 Hemisphere; while Podocarpus, with 70 species, is just as dominant 

 in the Southern Hemisphere. 



Pseudotsuga taxifolia is the dominant lumber conifer of North 

 America, various species of Pinus coming next. Araucaria hraziliana 

 holds a similar place in South America. Crypioincria japonica is the 

 principal lumber conifer of ya.^'dx\\ Araucaria bidwilli is an important 

 lumber conifer of northeastern Australia; and Dacrydiiim cupressi- 

 num and Agathis australis are the principal lumber trees of New 

 Zealand. Various species of Pinus are the conifer lumber trees of 

 Europe; and the exotic Araucaria hidwilli and Pseudotsuga taxifolia 

 seem likely to become the conifer lumber trees of South Africa. 

 Seeds of Pseudotsuga taxifolia are being exported in great quantities 

 for reforesting in various countries of both the Northern and South- 

 ern hemispheres. 



The great mass of conifers, both living and extinct, belong to 

 extra-tropical northern regions; and in geological times, the northern 

 extension was even greater than at present. 



In the Miocene, Pinus, Taxodium, Sequoia, and Glyptostrohus 

 flourished in Greenland, with Picca and Tsuga also represented. 

 At the same time, Spitzbergen had Pinus, Junipcrus, and Liboccdrus; 

 and Iceland had Pinus, Picea, and Sequoia. Araucaria has been 

 identified in the Rothliegende of France. Pinus and W iddringtonia 

 are known from the Jurassic onward. 



Araucarioxylon arizonicum, of the famous petrified forest of 

 Arizona, goes back to the Triassic; but some question whether it be- 

 longs to the Araucariaceae. However, there is no doubt that Ari- 

 zona, at that time, had a tree with wood very much hke that of 

 Araucaria (fig. 241). 



Although many conifers, in the wild state, are now very much 

 restricted in their distribution, they flourish when planted in far 



