PROMINENT SYSTEMATIC FEATURES OF FLORA. 



461 



Of introduced plants that have become naturalized in the Dismal 

 Swamp region, 96 species were collected or observed, although the 

 total number occurring there is undoubtedly considerably greater. 

 The origin of these species is as follows: 



Europe ' 



Tropical America . _ -. -- J 



Tropical Asia . - 



Eastern extratropical Asia --• - 



Extratropical North America 3 



Total - 96 



In the following table is given a lisl of the families.of Pteridophyta 

 and Embryophyta which are represented in the Hera of the Dismal 

 Swamp region, with the number of genera and species of each which 

 there occur. Owing tit the fragmentary mil uiv of the collections of 

 Thallophyta which were made, if has seemed best to omit these, and 

 likewise the Bryophyta, from the table. It is not to be supposed that 

 nearly the total number of species, or even of genera, which actually 

 occur in the region are here included, lint it is believed that the 

 enumeration embraces a large majority of both the species and the 

 genera in the groups included. Only such species as are certainly or 

 very probably indigenous are here enumerated. 



The object of the table is to present the distribution of the flora by 

 families, so that those which are dominant in the region will at once 

 appear. The twelve largest families are as follows: 



Family. 



Poiiceae (Gramineao)- 



Cyperaceae - 



Compositae 



Viciaceae(Papilionaeeae) 



Fagaceae 



Rosaeeae 



Number 

 of genera. 



Number 

 of species. 



Family. 



Number I Number 

 cif genera, of species. 



k:5 Ericaceae — 



ti9 I Scrophulariaceae 



1)8 Juneaceae 



120 1 1 Orchidaceae- 



15 1 1 Nepetaceao . 



15 J Rubiaeeac- 



- 







■s 



L3 



s 



12 











IS 



11 



8 



11 







11 



The prominence of such families as Fagaceae, Rosaceae, Ericaceae, 

 Juneaceae, Nepetaceae, and, in Cyperaceae, the genus Carex, in the 

 Dismal Swamp region is sufficient evidence that there is a strong 

 boreal element in its flora. On the other hand, there is a great 

 development of other Cyperaceae (notably Oyperus and Ryncho- 

 spora), which belong essentially to the warmer parts of the world; 

 of Viciaceae (chiefly belonging to tribes and even genera which are 

 widely distributed in the tropics); and of Scrophulariaceae (princi- 

 pally in the largely tropical tribes Gratioleae and Gerardieae). In 

 Compositae, the Eupatorieae, a mainly tropical tribe, are abundantly 

 represented, while the Anthem ideae and Senecionideae, which are 

 largely boreal tribes, are almost wanting, the former being represented 

 only by introduced species. Furthermore in the largest family, that 

 of the true grasses, Poaceae (Gramineae), one-half of the indigenous 

 species belong to the two largely tropical tribes Andropogoneae and 

 Paniceae. 



