EELATIONSHIPS WITH THE ELOKAS OF OTHEK REGIONS. 235 



pregnant fact is that the genera are, almost without exception, much more strongly 

 developed in America than they are in Australasia and the Antarctic islands. But if we 

 take the vegetation generally of the southern coldest zone and regions the preponderance 

 of what may be termed American types, in contradistinction to those which are more 

 fully represented in the Australian region, is not so great ; and if the bulk of Antarctic 

 vegetation seems clearly traceable to America, the isolation in South America of such 

 essentially Australasian types as Lebetanthus (Epacrideae) and Leptocarpus (Restiacea?) 

 is not easily explained. . 



FURTHER DETAILS OF THE DISTRIBUTION OF SOME OF THE MORE 



PROMINENT NATURAL ORDERS. 



Undee each natural order and genus and species in the Enumeration some particulars 

 are given of its general distribution, as well as any peculiarities of its distribution that 

 could be expressed in a few words ; and this information is amplified and augmented in 

 the preceding Tables, while the succeeding paragraphs are devoted to a fuller exposition 

 of the general and special features of the leading natural orders in the vegetation of 

 Mexico and Central America. Something of interest might be written respecting the 

 composition and distribution of each natural order, and much more concerning those 

 treated of, but it would be more in place in a work dealing with the phytogeography 

 of the world than here. 



Banunculacece. 

 All the seven genera of this order in Mexico and Central America are of wide range, 

 and there is, perhaps, no other large order of dicotyledons in which so high a proportion 

 of the genera has so wide a range. Of the forty-nine species, twenty-seven are endemic, 

 eighteen others restricted to America, leaving only four that extend to other parts of 

 the world. Two genera, Aquilegia and Delphinium, find their southern limit in 

 America in Guatemala and Mexico respectively. 



Cruciferce. 

 We have of this ubiquitous, mainly herbaceous, order of temperate and cold regions 

 twenty genera, two of them endemic, and five others restricted to America ; and of the 

 remainder eleven are widely diffused and two common to the Mediterranean region. 

 Forty-two out of seventy-six species are endemic, and only four extend beyond America. 

 Sisymbrium is the most numerous in species. 



Cistinece. 



Helianthemum offers one of the most notable connections with the Mediterranean 

 region. It is also represented by one or more species in extratropical South America. 

 Lechea and Hudsonia are peculiar to North America, the former extending southward 



biol. CENTE.-AMEE., Bot. Vol. IV., August 1887. 2 i 



