MR. G. BEKTHAM OS EUPHORBIACEiE. 251 



special means of dispersion. Of the 176 species, 105 are given 

 as exclusively American, 68 as confined to the Old World, and 

 only 3 as amphigeous : there are, however, some others so closely 

 representative of each other in the two continents as to 

 be considered identical by some botanists. The preponde- 

 rance is American ; and one of the almost constant characters, the 

 petal-like appendages to the involucral glands, is, as we have seen 

 in other sections, specially American. It is, however, well marked 

 m many Old- World (especially Australian) species of limited 

 areas. Again, when we come to consider the connexion of the 

 tribe with other groups of the genus, we find evidence on both 

 sides. Of the species where there is no petaloid appendage, five 

 are maritime plants of the Pacific islands, and a sixth is the am- 

 phigeous E. pilulifera. The few Anisophylla which assume the 

 habit of other tribes are American ; and some American Adeno- 

 petala (Zygophyllidia) approach very near to Anisopliyllum in all 

 respects. The probability is that the type was very early estab- 

 lished in both continents, that it became more readily developed 

 in America than in the Old World, and that there have frequently 

 been casual interchange of species between the two, many of them 

 having long continued and still continuing to produce local varie- 

 ties to be gradually differentiated into species. 



2. Stenolobe^:. 



The eminently geographical character of the small tribe Steno- 

 lobeae has been already exhibited under the head of systematic 

 arrangement (above, p. 204). Of the G6 species limited to Aus- 

 tralia, only three are tropical, including a common weed,Poranthera 

 microphylla, spread all over the territory, but not extending 

 beyond it ; and the Chilian Dysopsis is the only extra-Australian 

 species to be added to the 66. Whether the constancy of tho 

 marked exceptional but essential character derived from the 

 embryo can be taken as absolute proof of community of origin, 

 or whether it may be supposed that Euphorbiacea? of different 

 tjpes, when establishing themselves in Australia, assumed one 

 special character unknown elsewhere, cannot now be decided. 

 It is certain that some Stenolobeae show in other respects some 

 slight affinities with Phyllanthe«,whilst others tend rather towards 

 Crotonea? ; but no one genus is closely allied to any one in either 

 of these tribes ; and it may well be generally conjectured that 



