36 THE VOYAGE OF H.M.S. CHALLENGER. 



ORDERS, GENERA, AND SPECIES OF VERY RESTRICTED AREAS. 



For purposes of comparison, a few particulars concerning some continental types of 

 different grades of very restricted areas may be introduced here, if only to show that, 

 from some cause or causes, such exist. We have not space to discuss the possible causes, 

 but it is probable that these types are either dying out or are of comparatively recent 

 origin. From the particulars given below, it appears that inability to produce abundance 

 of good seed is not the cause, in some cases at least. 



ORDERS RESTRICTED TO ONE CONTINENTAL AREA. 



The number of Natural Orders restricted to one region or one continent is considerable 

 even as the orders are circumscribed in Bentham and Hooker's Genera Plantarum ; aud 

 taken in the more limited sense adopted by De Candolle (Geographie Botanique, p. 1158), 

 the number would be about double. Thus, taking the former work as a basis, the Treman- 

 dreae are peculiar to Australia ; the Vochysiacese to Tropical America ; the Chlsenacere to 

 Madagascar ; the Cactacese (except Rhipsalis) to America ; the Calycerege to Extratropical 

 South America ; the Bruniaceas to South Africa ; the Nepenthacese to the tropics of the 

 Old World, excluding continental Africa; the Bromeliaceas to America, the Mayacese to 

 America, the Cyclanthacere to Tropical America ; but the number peculiar to smaller 

 areas is barely half-a-dozen, and, as might be expected, they comprise very few genera and 

 species. Moreover, some of them have perhaps less claim to rank as independent orders 

 than some groups that are reduced to suborders or tribes, and no more claim to the same 

 rank than some of the anomalous genera ; but as connecting links are wanting they are 

 given the superior rank. There is one such order, the Balanopsese, restricted to New 

 Caledonia, and consisting, as far as at present known, of one genus and six or seven 

 species. Another order, the Leitnerieae, comprising only one genus and two species, is 

 peculiar to Florida and Texas. The Colli melliacefc, one genus and two species, are 

 restricted to the Andes of Ecuador and Peru ; while the singular Lennoaceos, consisting 

 of three genera and four or five species, inhabit only Mexico and California. Another 

 small order, the Rapateacese, consisting of five genera and about twenty species, is 

 limited to Guiana and Tropical Brazil. As an instance of a small order occupying 

 distant, separated areas, the Sarraceniacese may be named. This order comprises three 

 genera : Sarracenia, of which there are several species inhabiting Eastern North 

 America ; Darlingtonia, a monotypic genus inhabiting the mountains of California; aud 

 Heliam/phora, also monotypic, which is only known from the mountains of British 

 • riiiana. 



