20 THE PLANT WORLD. 



GEOGRAPHICAL DISTRIBUTION OF CONIFERS. 

 By John M. Coulter. 



NO group furnishes a better illustration of geographical diversity 

 than do the Conifers. They belong to temperate regions, and 

 a general map indicating their distribution would show a 

 heavy north temperate massing and a lighter south temperate massing, 

 the two separated from one another by the broad tropical belt, traversed 

 only in the East Indian and Andean regions. 



These northern and southern masses contain what are regarded as 

 different generic types. The only exceptions are the dominant south- 

 ern genus Podocarpus, which reaches the China-Japan region by way 

 of the East Indies, and the northern Lihocedrus, which reaches Aus- 

 tralia by the same route, and also extends far into temperate South 

 America by way of the Andes. Aside from these two lines, and these 

 two genera, there is no crossing of the tropics, all the other genera 

 being exclusively northern or southern. 



It is worthy of remark that the greatest display of Conifers in 

 genera and species is that which borders the Pacific Ocean, the chief 

 centers being the China- Japan region, Australia, and Western North 

 America. 



The Pinoidccp, that is, the forms with true cones, or at least with 

 ovules concealed, are characteristically northern, the two great divis- 

 ions Ahletine/B and Cajyr^^ssinecB being entirely northern excepting the 

 Araucarians, the peculiar Tasmanian Artkroiaxis. and the Actinostro- 

 hince. 



Among the Taxoidew^ on the other hand, the Podocarphxec^ are 

 all southern excepting the few species which reach China, and the 

 Taxinem are all northern excepting the Australian Pliyllocladus. 



Of the four great groups of Conifers, therefore, AMetineCB, Cu- 

 pressmece, and Taxinem belong to the north, although each one has a 

 small southern contingent; while Podocarpinece belong to the south. 



Certain facts connected with the distribution of the northern 

 forms seem noteworthy: 



1. A number of genera are common to the China- Japan region and 

 Western North America, six being in common besides those which 

 extend broadly over both hemispheres. 



2. The number of genera restricted to the China-Japan region 

 is no less than seven, and most of them are monotypic. 



