832 



SCIENCE. 



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



an elevation of 300 meters (1,000 feet). Be- 

 low that altitude, the flora of the Southern 

 Appalachian Region is mainly Carolinian, 

 and the presence in its midst of numerous 

 Austro-riparian forms would be expected. 

 The occurrence of Lower Austral species at 

 higher elevations, in the midst of a chiefly 

 Transition flora is the phenomenon which 

 demands our attention.* 



Some of the species occurring on Lookout 

 Mountain, but not reported from other sta- 

 tions in the mountains, e. g., Pinus Taeda, 

 Cebatha Carolina ( Cocoulus oaroUims) , Vaccin- 

 ium arhoreum and Spigelia marilandica, also ex- 

 tend farther up the Tennessee Valley. Fin- 

 ally a considerable number of Lower Austral 

 species, which are encountered rather rarely 

 among the mountains, are frequent or com- 

 iQon along the Tennessee River, near Knox- 

 ville (elevation 270 meters) . We may cite : 



Poa Ohapmaniana. 



Arundinaria macrosperma. 



Arundinaria tecta. 



Yucca filamentosa. 



Agave mrginica. 



Centrosema mrginiana. 



Hypericum densiflorum. 



Hypericum mrgatum. 



Callicarpa americana. 



Aster concoCor. 



Tetragonetheca helianihoidee 



Helenium nudiflorum. 



The Austro-riparian species which are 



* Naturally the extent of Lower Austral invasion 

 is greatest along the water-courses of the region. 

 Thus, in the valley of East Tennessee, which is in 

 much of its length fully one hundred miles wide he- 

 tween the Great Smokies southeastward and the 

 Cumherland Eange towards the north and west, there 

 occur at an elevation of 240 to 270 meters not a few 

 typically Austro-riparian species which apparently do 

 not penetrate those smaller mountain valleys which 

 are situated above 300 meters. Examples are' : 



Agrostis Elliotiiana. 



Ampelopsis cordata {Cissus Ampelopsis). 



Gynoctonum Mitreola [Mitreola petiolata). 



Nemopldla microcalyx. 



Lithospermum tuberosum. 



Diapedium hracliiatum {^DicUptera hracMata). 



Eupatorium incarnaium. 



met with in the region thus defined do not 

 always grow scatteringly among Carolinian 

 forms. Not infrequently, in peculiarly 

 favorable localities, such as the diminutive 

 pine barrens which cover sandy river bot- 

 toms and the dry, sunny lower slopes of 

 the hills, they occur in numbers so pro- 

 nounced that a botanist suddenly set down 

 amongst them might be puzzled for a mo- 

 ment as to his zonal whereabouts. Yet a 

 two or three hours' walk would take him 

 through a typical Transition vegetation into 

 that which is almost wholly Canadian. 

 Two colonies of this character with which 

 I am personally familiar are worthy of 

 more detailed description. 



Along the French Broad River below 

 Paint Rock, N"orth Carolina, and just within 

 the limits of Tennessee, the stream is bor- 

 dered by limited strips of flat land, which 

 are mostly covered by a small growth of 

 yellow pine (Pinus ecJdnata or mitis), with 

 frequent clearings among the trees. The 

 altitude of the river-banks is here from 345 

 to 360 meters (1,150 to 1,200 feet) above 

 the sea. In these groves the herbaceous 

 flora is, as it were, a bit of the carpet of 

 the coastwise pine-barrens, which has been 

 laid down intact along the banks of a moun- 

 tain stream. The following list of species, 

 all of which are abundantly represented, 

 indicates the character of this flora. It will 

 be noticed that Graminese, LeguminosSe and 

 Compositse contribute a very large propor- 

 tion. 



Erianthus alopecuroides. 



Andropogon argyrmus. 



Ohrysopogon nutans var. Linnmanus. 



Sporobolus asper. 



Danthonia sericea. 



Oymnopogon ambiguua ( 0. racemosus). 



Triodia Ohapmani. 



Cratmgus uniflora {O. parvifolia). 



Morongia anguslata [Schrankia angusfata). 



Oracca spicata ( Tephrosia spicata) . 



Siylosanthes riparia. 



Rhynchosia erecta. 



Croton glandulosus. 



