Mil. a. BB NT II AM ON EITPHORBIACEiE. 253 



Pachysandra, and further on into the very distinct North-Ameri- 

 can species of that genus. The other two genera of Buxeae, the 

 monotypic Californian Simmondsia and the tropical Andine Sty- 

 loceras with three very distinct species, are* so completely detached 

 and of such limited areas as to afford us no grounds for forming 

 any but the wildest guesses as to their early history, beyond the 

 belief in their remote antiquity. 



4. Phyllanthe^;, G-aleabieje, and Cbotone^j. 



There is not sufficient distinctness in these three tribes, nor suffi- 

 cient unity in each, to warrant us in considering them as primary 

 branches of one stock ; for many an early-differentiated race may 

 have been the common parent of genera now technically separated 

 m the two great tribes Phyllantheae and Crotonese. In consider- 

 ing their geographical distribution, we must regard them all as 

 one tribe, to which may be applied the general views given above 

 of the whole Order, and for further details take successively : 



(1) The genera now existing in the two continents iu identical 

 or nearly allied groups of species. 



(2) The races represented in the two continents by nearly allied 

 but perfectly distinct genera. 



(3) The genera absolutely restricted either to the New or to 

 the Old World, without any near connexions in the other. 



Ic will be observed that for this geographical review, I have 

 thought it necessary occasionally to assign different limits to the 

 genera, from those given to them in the systematic arrangement 

 for practical use. I would also note that the number of species 

 assigned to each genus is often approximative only and sometimes 

 necessarily uncertain, and even the number of genera sometimes 

 indefinite, owing to our imperfect knowledge of so large a number 

 of tropical Euphorbiacese. 



1. Genera common to the New and the Old World. 

 Phyllanthus >, taken in its typical form common to the two con- 

 tinents, must be considered as including Securinega, which is a 

 purely artificial genus, and excluding Glochidion and Synostemon, 

 which may be considered as primary deviations from the type. 

 This typical Phyllanthus includes seven of the sections into which 

 the genus may be fairly divided, of which two, Cicca and Euphyl- 

 fonthns (including Paraphyllanthus), are common to the two con- 

 tinents, with about 114 American and 108 Old- World species, 



*-INX. JOUBK. BOTANY, VOL. XVII. U 



