24 Mr. R. B. Hiuds on Geographic Botany. 



volea, Spigeliacece, Stylidea, Tropceolea, AmaryllidetE, Hatnodo- 

 racece, Iridece, Restiacece. 



As has been stated^ a considerable number of the natural fami- 

 lies are represented in all the six divisions, and, ceteris paribus, 

 those Avith the largest amount of species maj' be justly supposed 

 to be in this respect the most prominent. With increased num- 

 bers not only are the means of repetition multiplied, but there is 

 greater scope for variety of habit and predilection ; the former 

 displayed in the diversity of herbs, shrubs and trees, and the 

 latter in pecuharity of constitution. Those most distinguished 

 for a large amount * of species, as Crucifera with 990, Myrtacea 

 715, LeguminoscB 3875, Umbellifera 1009, Cinchonacea 1631, 

 CaryophyUec? 759, have the most extensive range. It does not 

 appear that the habitat is influenced by the number of genera, as 

 might at first be supposed, since there are comparatively few in 

 Malvacece, Caryophyllece, Leguniinosce and Geraniacea ; about the 

 average number in Cruciferce, but below it in Cinchonacea. Of 

 the hundred natural groups previously referred to, thirty-three 

 are distributed through all the divisions, whilst 



Europe has representatives of . . 52 



Asia 83 



Africa 76 



North America 81 



South America 83 



Australasia 53 



Confined to a single division . . 9 



The number of genera composing the families varies con- 

 siderably ; those of tropic or sub-tropic regions appear to have 

 more than others of temperate regions in proportion to the spe- 

 cies ; but the tropic families do not abound generally either in 

 genera or species. Leguminosa with 272 genera, Cinc/ionacea 

 215, Crucifera 100, UmbellifercE 160, are among the largest. 

 Some consist only of one or two genera and scarcely more species ; 

 others with a large amount of species have but few genera, as 

 Geraniacea with 490 species and only five genera ; LoranthacecB 

 330 species and fom- genera; Oxalidece 159 species and also four 

 genera. As instances to the contrary are Aurantiacece vriih. forty- 

 four species and twelve genera ; Olacinece seventeen species and 

 eight genera ; Droseracea forty-five species and eight genera ; 

 with Bomhacece, Meliacea, Magnoliacea, Flacourtianea. Taken 

 collectivel}^, the whole amount of natural families possesses an 

 average of upwards of eighteen genera each, or more correctly 



* The numbers stated are obtained from DeCandolle's ' Prodromus Regni 

 Vegetabilis." 



