308 APPENDIX. 



origin certainly, but of what part it is often uncertain ; still we now think some of them, 

 perhaps a considerable number, may have been imported from the Northern States. 



The Vascular Plants under consideration for the whole area number 12,233 species, 

 referred to 1849 genera, belonging to 167 natural orders. 



To begin with the Northern Province, which is the largest of the three, and roughly 

 consists of the extratropical part of Mexico with a southward extension in the table- 

 lands not indicated on our map, and indefinable extensions into Texas, New Mexico, 

 and Arizona, &c, more fully discussed in the paragraphs, page 217 to 227. 



Authenticated from within the Mexican portion of this floral province there are 

 3040 species of vascular plants belonging to 836 genera; and of the former 2930 are 

 flowering plants, constituting a small fraction over a quarter of the number recorded 

 from the whole of Mexico and Central America, yet probably far short of the number 

 actually existing. Thirty-nine of the natural orders in the central and southern 

 provinces are not known to be represented in the northern province. The absent 

 orders are mostly essentially tropical, or consisting of hygrophilous plants. 



The exceedingly sparse representation of the Melastomaceae, Begoniaceae, Passiflo- 

 raceae, Cucurbitaceee, Gesneraceae, Piperaceae, Aristolochiaceae, Scitamineae, Bromeliaceae, 

 OSnidese, and Palmae is also evidently more the result of climatal conditions than the 

 latitudinal position of the country. 



Three orders, the Frankeniaceae, Elatineae, and Santalacese, represented by one 

 species each, are not known to occur in the central and southern provinces. Among 

 orders absolutely or relatively numerous in species are : — Cruciferee, 44 ; Polygalaceae, 

 27; Malvaceae, 53; Malpighiaceae, 21; Leguminosae, 315; Crassulaceae, 16*; Ona- 

 grarieae, 28; Cactaceae, 137* ; Composite, 629 ; Asclepiadeae, 52 ; Polemoniaceee, 22 ; 

 Hydrophyllaceae, 21; Boraginege, 47; Convolvulaceae, 51; Solanaceae, 52 ; Scrophularineae, 

 72; Labiatae, 77; Nyctagineae, 36; Amarantaceae, 33; Chenopodiaceae, 20 ; Polygo- 

 naceae, 25 ; Euphorbiaceae, 129 ; Cupuliferae, 22 ; Coniferae, 25 ; Amaryllideae, 23 *, 

 Liliaceae, 35 * ; Gramineae, 184 ; and there are 100 species of Filices, the majority 

 belonging to xerophilous genera. Against this there are only twelve orchids recorded, 

 and the two or three epiphytal ones among them are almost certainly not from this 

 province ; and thirty-four Cyperaceae, while 170 species are recorded from South Mexico. 



Here in this flora, or fragment of a flora, the Compositae constitute 21 per cent, 

 of the flowering plants; Leguminosae 10 per cent.; Cactaceae 4'6 per cent.; and 

 Euphorbiaceae 4*4 per cent. Noteworthy too is the large number of species of many 

 other gamopetalous orders besides the Compositae; and of such small orders as the 

 Polemoniaceae and Nyctagineae, which find their greatest concentration in this province. 



The number of grasses, though only half that of the smaller area of South Mexico, is 

 proportionally high, forming 6*3 per cent, of the flowering plants, or nearly 2 per cent. 



* As explained above, these orders are probably represented by a considerably larger number of xerophilous 

 members. 



