216 



APPENDIX. 



Judging from the scanty data available for comparison, the proportion of monotypic 

 genera in Mexico and Central America is exceptionally high, amounting to 228, or 

 12-3 per cent., of all the genera of vascular plants. One hundred and twenty-seven of 

 these monotypes are endemic; 101 extend to other parts of America, and twenty-one 

 have a wider range. In Australia about 10*8 per cent, of the genera are monotypic. 

 Our monotypic genera are distributed among seventy natural orders, and they are specially 

 numerous in the Compositae, Orchideae, and Gramineae, though they are proportionately 

 more numerous in some of the smaller natural orders. One point this Table specially 

 brings into prominence is the extension of the North-Mexican flora into western North 

 America. Thus, of the 101 monotypic genera which extend to other parts of America, 

 thirty have a north-western extension only, and twelve of those having a wider range 

 also occur in western North America. Of course, those of the latter category 

 possess no particular significance ; but those of the former category constitute an 

 important addition to the evidence bearing upon the natural boundaries of the flora of 

 North Mexico and the contiguous countries. In addition to these thirty monotypes, 

 there are fifty-five genera, belonging to twenty-two natural orders, which are common to 

 Mexico and the North-west only ; and twenty-one of them are Compositse. 



It may be of interest to insert here a list of the natural orders with the number of 

 genera represented in Mexico and Central America by only one species. Including 

 the monotypes already dealt with, they number no fewer than 660 genera, or 35*7 per 

 cent, of the total, belonging to 120 orders. In the Compositae the disproportionately 

 large number of eighty-two genera belong to this category, and in America north of 

 Mexico there are within nine of the same number of indigenous genera of Compositae 

 represented by only one species. Mueller * states that there are 550 genera in 

 Australia, represented by only one species each. 



Number of Genera represented by only one Species. 



Ranunculaceae 



1 



Brought forward 



26 



Dilleniaceae . . . 



1 



Bixineae . . 



4 



Anonacese . . 



2 



Vochysiaceae . 





1 



Menispermaceae . 



3 



Frankeniaceae 





1 



Nymphaeaceae . 



2 



Caryophylleae 





2 



Papaveraceae . 



2 



Portulaceae 





4 



Fumariaceae . . 



. 1 



Elatineae . 





1 



Cruciferae . 



. 8 



Guttiferae . 





3 



Capparideae . . 



4 



Ternstrcemiaceae 





4 



Resedaceae 



. 1 



Malvaceae . 





9 



Violarieae . 



. 1 



Sterculiaceae . 





. 4 



Carried forwarc 



I 26 



Carried forw 



arc 



[ 59 



Brought forward 



59 



Tiliaceae . . 



3 



Malpighiaceae 



6 



Zygophyllaceae . . 



2 



G.eraniaceae . . . 



2 



Eutaceae . . . 



9 



Simarubaceae . 



5 



Ochnaceae . 



1 



Burseraceae . . 



1 



Meliaceae . . . 



1 



Chailletiaceae . 



. 1 



Carried forward 90 



* ' Lecture on the Flora of Australia,' 1883, p. 11. 



