THE PLANT WORLD. 21 



3. Two peculiar genera occur in North America, Sequoia and 

 TaxoiVnmi , one at the west, the other at the east. 



5. The great dominant genus Pmus, with its 70 species, constitutes 

 about one-third of the northern coniferous flora, and one-fourth of 

 the coniferous flora of the globe. This genus is followed in import- 

 ance and wide distribution l)y Jnnijperm^ Ahies, Picea^ Larix, and 

 Taxm; in the order given. 



The distribution of the southern forms is modified by the fact 

 that temperate conditions occur in three great isolated areas, although 

 this has not resulted in the corresponding separation of genera that 

 niiffht be expected. The general facts may be grouped as follows: 



1. Podocarpm^ With its 40 species easily the second genus of 

 Conifers, is distributed throughout the temperate region of the South- 

 ern Hemisphere. 



2. South America and Africa are each generically paired with 

 Australia, Araucaria being common to Australia and South America, 

 and CaUltrls common to Australia and South Africa. 



3. The Australian region is the notable coniferous region of the 

 Southern Hemisphere, containing six peculiar genera. 



■i. Two peculiar genera occur in South America, and nine in 

 Africa. 



In considering this very distinct segregation of the Conifers into 

 two groups, separated by the tropics and containing diflferent genera, 

 one is tempted to question whether there is also a difl'erence of age, 

 but the present evidence is opposed to such a view. That the two sets 

 of forms were once associated in a general distrilnition throughout the 

 Northern Hemisphere seems to be clear, but whether there was a simi- 

 lar association in the Southern Hemisphere remains to be discovered. 

 In any event, conditions at the north for s niie reason became uncon- 

 genial for the genera now restricted to the Southern Hemisphere. 



The Proceedings of the Biological Society of Washington (Vol. 

 xiii, pp. 109-121) contains an article by Mr. F. V. Coville, on the 

 botanical explorations of Thomas Nuttall in California, about which 

 there has been much misinformation current. Everv movement of Nut- 

 tall is carefully traced, and there is also given a full list of the princi- 

 pal new species based on NuttalFs Californian collections, that must 

 prove of much value to students of that flora. 



