CORRELATION OF DISTRIBUTIONAL FEATURES. 575 



marked climatic difference is shown between these two areas on the 

 chart for P (plate 57, figs. 16 and 23). 



Turning now to the more detailed vegetation charts, the area 

 occupied by Pinus palustris (plate 6) nearly corresponds to the south- 

 eastern humid province, as shown by P (plate 46, figs. 2 and 21). 



Pinus divaricata (plate 7) occupies about the same area as the north- 

 eastern humid province, as shown by E (plate 53, figs. 3 and 22) ; its 

 area also somewhat nearly corresponds to the same province on the 

 charts for P/E and H (plates 57 and 65, figs. 16 and 23, 17 and 24). 



Bulhilis dactyloides (plate 11) shows an area of distribution nearly 

 corresponding with the eastern subdivision of the semiarid province 

 and the most arid portion of the eastern subdivision of the semihumid, 

 as shown by P/E and H. The fine from Hudson Bay to the Gulf of 

 Mexico passes nearly through the north-south axis of its area. 



Pinus edulis (plate 14) occupies nearly the arid province, as shown 

 by E. 



Picea sitchensis (plate 14) occupies about the northwest humid 

 province, by P/E, and Tsuga heterophylla (plate 14) covers about the 

 northwestern humid and semihumid provinces by the same index. 



Quercus falcata (plate 18) has an area of distribution nearly corre- 

 sponding to the southeastern humid province, as shown by P. Less 

 satisfactory agreements with this same province are exhibited by 

 Sapindus marginatus (plate 19) and Itea virginica (plate 23). In all 

 these cases the distribution area extends farther north in the Missis- 

 sippi Valley than does the climatic province as shown. 



Populus halsamifera (plate 19) occupies the northern part of the 

 eastern subdivision of the humid province, by E. It extends farther 

 south than this climatic area, as shown by P/E. The climatic charts 

 are not sufficiently detailed in the Northwest to show a correspondence 

 to the northwestern area of the species. 



Decodon verticillatus (plate 23) has an area of distribution nearly 

 conforming with that of the eastern subdivision of the humid province, 

 together with all but the most arid portion of the eastern subdivision 

 of the semihumid province, as shown by P/E or H. 



Phorodendron juniperinum (plate 29) has an area of distribution 

 roughly corresponding to the arid province, by P/E and H. 



Oxybaphus nyctagineus (plate 33) occupies the more humid part of 

 the eastern semiarid province and the more arid part of the eastern 

 semihumid province, as showTi by P/E, the distribution area of this 

 form being much like that of Bulhilis dactyloides (plate 11). 



The schematic presentation on page 576 shows the relations just 

 described, for the individual species considered. 



