November 30, 1900.] 



SCIENCE. 



835 



though the answer must be largely specu- 

 lative, it is hardly a pure assumption that 

 both cases may be true in part. In study- 

 ing this floral element, one soon reaches the 

 conclusion that it comprises two categories 

 of species which are markedly different not 

 only in their systematic relationships, pres- 

 ent distribution in the region and probable 

 past history, but even, to a considerable 

 degree, in their ecological constitution. 

 But, in some cases, it is almost impossible 

 to decide-to which of the two groups a given 

 species should be referred. 



1. Plants of probably neotropical origin 

 which have in all likelihood made their 

 first appearance in the Appalachian region 

 in geologically very modern times, probably 

 after the close of the so-called Glacial 

 Epoch. The following list embraces spe- 

 cies which, from their distribution else- 

 where, or from their affinities, are most 

 likely to have had this history :* 



Brianthus alopecuroidea. 



Erianihus brevibarbis. 



Erianthus contortus. 



Andropogon argyrmut. 



A7idropogon Elliottii. 



Ghrysopogon nutans var. Linnmanua. 



Paapalum longipedunculatum. 



Paapalum purpuracens. 



Panicum gibbum. 



Panieum angustifolium. 



Panicum longipedunculatum. 



Panicum viscidum. 



Muhlenbergia capillaris. 



Sporobolus asper. 



Oymnopogon ambiguus. 



Triodia Ohapmani. 



Oyperus echinatus (C. Baldwinii). 



J^jru communis. 



Oommelina erecta. 



Commelina kirtella. 



Yucca filamentosa. 



Agave mrginica. 



Pogonia dinaricata. 



Phoradendron flavescens. 



Asimina parviflora. 



Oebatha Carolina ( Oocculus). 



Morongia angustata [Schrankia). 



Cracca spicata {TepJirosia). 



Stylosanthes riparia, 



Bradbury a virginiana ( Genlrosema ) . 



cut aria mariana. 



Bhyncliosia erecta. 



Crotonopsis linearis. 



Ascyrum stans. 



Hypericum densiflorum. 



Hypericum Drummondii, 



Hypericum virgaium. 



Bhexia mariana. 



Jussice.a decurrens. 



Gelsemium sempermrens. 



Gynoctonum Mitreola {Miireola petiolata). 



Spigelia marilandica. 



GalUcarpa amerieana. 



Oratiola splicer ocarpa. 



Qratiola viscosa. 



Bignonia crucigera (B. capreolata). 



Yatesia Icete-virens ( Gatesia). 



Diodia mrginiana. 



Melothria pendula. 



Elephaniopus iomentosus. 



Eupatorium album. 



Eupatorium aromaticum. 



Lacinaria graminifolia {Liatris). 



Ghrysopsis graminifolia. 



Ghondrophora virgata, 



Pluchea petiolata. 



SilpJiium Asteriscus. 



SilpMum compositum. 



Tetragonotlieoa helianthoides. 



Helianthus angustifolius. 



Helianthus atrorubens. 



Coreopsis major ( G. senifolia). 



Coreopsis aurioulata. 



Marshallia lanceolata var. platyphylla. 



Helenium nudifiorum. 



By far the greater number of species in 

 the above list belong to groups, whether 

 genera, tribes or families, which are chiefly 

 tropical in their present distribution. Thus 

 of the three most largely represented fami- 

 lies, the Graminese belong chiefly to the 

 tribes Andropogonese and Paniceae; the 

 Leguminosse to Mimosse and Phaseolse ; and 

 the Compositse to Eupatorise and Helian- 

 thoidese. This category is furthermore re- 

 markable in consisting almost entirely of 

 herbaceous species. Most of them are of 

 distinctly xerophy tic structure, loving a dry 

 sandy soil and much light and heat. 



