Australian Flowering Plants. 191 



From tropical America it spreads more sparingly into North 

 America and extratropical South America, and from tropical 

 into Southern Africa, and eastward into tropical and sub- 

 tropical Asia, forming in each of these outlying districts more 

 or less local groups. More than three-fourths of the genus 

 belong to the section Lepidaploa. ... At least four-fifths 

 of its species are tropical American, but it includes also the 

 North American ones, a portion of those from Africa, and five 

 or six Asiatic species." 13 



Vernonia itself is not indigenous in Australia, but Pleuro- 

 carpa'a, close to Vernonia, is in Australia, and is a monotypic 

 genus. 



Xanthoxylum. (Fagara) Trees mainly of luxuriant type, 

 about 150 species in all tropics and in 5 sections. The first 

 section, with about 115 species, extends over all tropics, with 

 a few outliers in North America, Paraguay, Argentina, the 

 Andes, Japan, China, Korea, Manchuria, and other places. 

 The second section is monotypic from Juan Fernandez. The 

 third section with about 12 species is from the West Indies 

 with the trees luxuriant in habit, while the fourth named 

 Blachburnia, and at one time classed as a distinct genus, is 

 confined to Australia and Hawaii. A fifth section, or, probably, 

 a genus, consists of about 10 species in North America and 

 temperate east Asia. 



Around this great type are gathered many genera both 

 tropical and temperate, but mainly tropical trees with large 

 luxuriant and pinnate leaves. 



Around the group or tribe of Xanthoxylse, however, are 

 gathered three large tribes, namely Boroniese (xerophytes con- 

 fined to Australia), Diosmese (xerophytes confined to South 

 Africa and mostly shrubs), and Cuspariese (confined to tropi- 

 cal America). 



A study of Psychotria (700 species in the Benthamian sense) 

 and its allies, Hibiscus (150 species approximately), Ficus 

 (600 species), Piper (600 species), Phyllanthus (500 species 

 approximately), Peperomia (500 species), Solanum (900 spe- 

 cies), Euphorbia (700 species), Bauhinia (150 species), 

 Hedyotis (in the Benthamian sense), and other vast tropical 

 genera, show a very similar distribution to that here outlined 

 for Cassia, Vernonia, Xanthoxylum., and Acacia, or better still, 

 for Mimosa, in the Linnean sense. 



This peculiar distribution suggests a connection of some 



13 G. Bentham, Composite, Jour. Linn. Soc. London, Botany, vol. xiii, 

 p. 393, 1873. 



