830 



SCIENCE. 



[N. S. Vol. XII. No. 309. 



2. There are at least 11 dorsal vertebrse, 

 perhaps two or three more. 



3. The great comparative and absolute 

 length (21 feet) of the cervical series, a 

 striking analogy to that exhibited in the 

 struthious birds. 



4. The actual number of dorsals in Diplo- 

 docus seems to be 11, but cannot be defi- 

 nitely determined from our skeleton, and 

 we must await further discoveries for its 

 solution. 



J. B. Hatcher. 

 Caenegik Museum. 



PLANT GEOGRAPHY OF NORTH A3IEBICA. 

 III. 

 THB LOWEB AUSTRAL ELEMENT IN THE FLORA 

 OF THE SOUTHERN APPALACHIAN RE- 

 GION. A PRELIMINARY NOTE.* 



In that portion of the United States 

 which lies south of the Potomac and Ohio 

 Elvers and east of the Mississippi, three 

 principal orographical areas are readilj' dis- 

 tinguishable. These are generally known 

 as the Pine Barren or Low Country (Coastal 

 Plain), the Piedmont or Middle Country 

 and the Mountains or Upper Country. 

 Their respective characteristics — climatic, 

 physiographical and biological — have been 

 BO often described in popular and scientific 

 writings that to enumerate them here would 

 be superfluous. So obvious are their dis- 

 tinguishing features, that no observant 

 traveler fails to take note of them as he 

 crosses the southeastern States. 



The altitudinal limits of these three areas 

 coincide roughly with those of three great 

 continental life zones, i. e. , the Lower Aus- 



*In the matter of nomenclature, in this paper, I 

 have followed that employed by Britton and Brown 

 in their 'Illustrated Flora of the Northern United 

 States and Canada.' But in order to be understood 

 by readers who are not familiar with that nomencla- 

 ture, I have added, in parentheses, the synonym gen- 

 erally current among American botanists before the 

 adoption of the ' Rochester Code, ' wherever a change 

 has been made under that code. 



tral Zone in its humid or Austro-riparian 

 Area ; the Carolinian Area of the Upper 

 Austral, and the AUeghanian Area of the 

 Transition Zone.* 



The Coastal Plain, presenting but scant 

 diversity in its orography, is occupied al- 

 most exclusively by a Lower Austral fauna 

 and flora. In the Piedmont Region the 

 surface of the country is less uniform and 

 we encounter within its general boundaries 

 many scattered localities where conditions 

 permit the occurrence of Lower Austral or 

 of Transition colonies amid the prevailing 

 Carolinian life. But in the Mountain Re- 

 gion there exists such a variety of condi- 

 tions that all the life zones from Lower 

 Austral to Hudsonian are represented in 

 places, although their limits are here very 

 ill-defined, and the precise location of them 

 presents many intricate problems. 



Thus along the higher Smoky Mountains 

 and the Blue Ridge, we find a typically Can- 

 adian forest of firs (^Abies Fraseri), accom- 

 panied by such trees and shrubs as the 

 yellow birch (Betula lutea), mountain ash 

 (Sorbiis americana), mountain maple (Acer 

 spicatum), red elder (Sambuciis racemosa) and 

 wild red cherry (^Prunus pennsylvanica) . 

 Other characteristically Canadian species 

 like the striped maple (^Acer pennsylvani- 

 cum), hemlock (Tsuga canadensis), white 

 pine (Pinus Strobus) and the arbor vitse 

 ( Thuya occidenialis) descend to much lower 

 elevations (900 meters or less). Along the 

 crest of the highest mountains of this 

 region, usually at an altitude of 1,800 meters 

 (6,000 feet) or upwards, a sparse Hudsonian 

 flora is encountered. The green alder {Alnus 

 viridis), and, of herbs, Arenaria groenlandica, 



* For a definition and description of these zones see 

 Merriam in Nat. Geogr. Mag., 6 : pp. 220-238, Maps, 

 1894. Also, 'Life Zones and Crop Zones of the United 

 States ' ; Bull. Div. Biol. Survey, U. S. Dept. Agric, 

 10 : pp. 18-33, Map, 1898 (with a correction of the 

 temperature data), in Scienob 9 : No. 212, p. 116 

 (1899). 



