November 30, 1900.] 



SCIENCE. 



837 



jecture that the ancestors of most of these 

 genei-a whose actual history is still undis- 

 closed were thus distributed during Mio- 

 cene time. Very broadly speaking, sev- 



On the other hand, the number of shade- 

 loving tropophytes or mesophytes is de- 

 cidedly greater than in the first category. 

 The plants of the second category are more 



Genus. 



Butneria( Galycanthus] 

 Sarracenia. 



Hydrangea. 



Stuartia. 



Olethra. 



Monotropsit ( Schweinitzia) . 



Leucoihoe. 



Mohrodendron ( Halesia ) . 



Coastal Plain Species. 

 florida. 

 flava. 

 grandiflorus. 



quercifolia 



Carolina ( Gardeni). 



Malachodendron{i>irginica). 



alnifolia* 



Reynoldsim. 



axillaris. 



raeemosa.* 



phyllyreifolia. 



dipterum. 



parviflorum. 



Appalachian Species. 

 fertilis [glauca). 

 flava var. oreophila. 

 inodorua. 

 hirsutus. 

 radiata . 

 cinerea. 

 arborescens. 

 major, 

 pentagyna. 

 acuminata, 

 odorata. 

 Gatcsbm. 

 recurva. 

 floribunda. 

 caroUnum {tetrapiera). 



eral of these genera represent groups 

 which appear to be on the wane, as distin- 

 guished from the dominant and, one may 

 say, aggressive types of presumably neo- 

 tropical origin to which the species of the 

 first category chiefly belong. 



In another important respect the second 

 category differs from the first, i. e., in its 

 ecological character. A majority of the 

 species which it comprises are woody plants, 

 shrubs, lianas or trees ; and this majority 

 becomes a large one if we take into account 

 the list of representative species just given. 

 The first category, as we have seen, con- 

 sists almost wholly of herbaceous forms. 



A considerable number of species of the 

 second category, notably several of the 

 woody plants with thick, more or less per- 

 sistent, leaves is essentially xerophytic in 

 structure. But the xerophilous leaf-struc- 

 ture is here in most cases probably a con- 

 sequence of the long duration of that organ 

 and a protection against winter conditions, 

 rather than an adaptation to the eifects of 

 climate and soil during the growing season. 



* Eanges beyond the northern limits of the Aus- 

 tro-riparian area. 



often scattered among Transition and Car- 

 olinian vegetation, showing generally little 

 tendency to form well-defined Lower Aus- 

 tral colonies. Finally, they are, on the 

 whole, less characteristic of the Austro- 

 riparian area, as distinguished from the 

 Carolinian area, than are many of the spe- 

 cies of our first category. 



Having thus segregated the two principal 

 groups of species which constitute the floral 

 element under discussion, are we in a posi- 

 tion to draw conclusions as to its past 

 history? The answer must be that it is 

 possible as yet to formulate only broad 

 generalizations which are hardly more 

 than pure hypotheses. The paleontological 

 record, during the period which doubtless 

 witnessed the gradual rearrangement of the 

 plant covering of the Southern Appalachian 

 country in its present form, i. e., from the 

 Pleistocene to the present, is fragmentary 

 in the extreme for the region in question. 

 We can get only glimpses of what may have 

 been the course of events. Here and there 

 a headland can be seen, but the trend of 

 the intervening shore-line is only to be 

 guessed at. 



