GENERAL ASPECT OF THE FLORA. 11 



Michx., Thalictrum ckii-atum DC. Near the base of the monnt- 

 iiin, on limestone ledges, (Jatesia kdevirens Gray, Callicarpa 

 Americana L., Triosfeum perfoliatum, L., Silphium brachiatum 

 Gattiiiger. The Cumberlands excel the Alleghanies in a greater 

 variety of ferns. Besides all species of the latter, we also find 

 here Aspleniuin Bradleyi Eat., A. pinnatifidum Nntt., Lygodium 

 palmatu.m Swartz., Scolopendriuni mdgare Sm\t\i , and Tiichomanes 

 f idicans Swartz. 



The third division embraces the valley of East Tennes-ee 

 and the entire area of Middle Tennessee. Contour of surface 

 and geological structure result in East Tennessee from the com- 

 bined processes of folding and erosion, whereby heterogeneous 

 strata are ])laced in juxtaj)osition, the whole valley being an often- 

 repeated series of synclinals and anticlinas of calcarious and 

 siliceous rocks, while in Middle Tennessee erosion alone had 

 been at play. 



A great fault connected with the upheaval of the Pine and 

 Grab-orchard mountains, and in a line south of it, an eroded 

 anticlinal, the Sequatchee valley, designate in the Cuniberhiiid 

 mountain region the western terminus of those (convulsions 

 which involve the problem of the stratographv of the Alle- 

 ghanies in so great difficulties. West of this line spread out 

 the horizontal strata of the Cumberland table-land, which ter- 

 minates with an abrupt descent of about one thousand feet u])on 

 the highlands of Mifhlle Tennessee. These in turn overreach 

 and encircle the floor of the basin of Middle Tennessee by five 

 to six hundred feet, either in a bluff or through a gradual descent. 



The succession of strata is normal throughout: u])permost 

 subcarboniferous limestone and chert, followed by the Devonian 

 shale, lastly the lower silurian. 



Increase in annual range of temperature and greater dry- 

 ness of air, as compared with the former regions, cause the 

 mountain flora to disappear and to yield to other designs in 

 nature's garb. A close botanical inquiry into the array of spe- 

 cies soon discloses the fact that different assemblies of species 

 congregate in the limestone and argillaceo-siliceous region. The 

 former includes the glades, the latter the barrens of Middle Ten- 

 nessee. 



Glades are thinly wooded, unarable lands, with shallow soils, 

 fit only for pastures. They ought to remain in their natural 

 state, undistui'bed by cultivation. To clear them is to convert 

 them into deserts. In some parts they are exclusively occuj)ied 

 by the cedar, with a small percentage of deciduous trees inter- 

 mingled. In other places prevails the Ohio buckeye, (^sculus 



