CH.xxii] GEOGRAPHICAL DISTRIBUTION 245 



they haA^e any real right to possess. Of the 32 floral regions 

 accepted in the latest work, 9 are upon islands, and 7 upon small 

 southern areas, and 12 in all are in the south, against only 1 i for 

 the very much larger land masses of the north! 



The work upon Age and Area described above makes it much 

 more clear why these difficulties arise. No two genera, in all 

 hkelihood, will spread about the world at the same rate, so that 

 it is evident that what may be a marked floral region for one 

 genus of plants (or animals) will not be so for another, unless the 

 region has been well isolated for a long time, when it will, as in 

 the case of many islands, contain many endemics of many 

 different families. The whole subject requires a complete re- 

 consideration in the light of the results provided by Age and 

 Area, before it Avill be safe to try to divide up the world In this 

 manner. All that can be safely said at present is that regions 

 with great numbers of endemics in many families can be regarded 



as regions tha"- ^ '' '" ' •■ • • 



tive isolation. 



as reo-ions that have existed for a long time, perhaps in compara- 



Another thing that seems indicated by the work outlined above 

 is that in general the floras of the world, including those of most 

 of the islands, must have reached their present positions over 

 land or narrow straits which would not seriously interfere with 

 the passage of species. The arithmetical, systematic, and other 

 relationships between them, are too complex, and too evident, 

 to ha^e resulted from transport over wide stretches of sea, a 

 process which would sift out a Axry few from a comparatively 

 large flora. 



A way in which Age and Area may proA'e incidentally useful 

 has been indicated above, and in a number of papers (126-134). 

 For example, in New Zealand (127, p. 452) a number of widely 

 distributed species, many more than would be expected, were 

 found in the class of smaHest area. On examination, they proved 

 to be, so to speak, the leavings of the flora. Twelve of 21 were 

 Monocotjdedons, four were from the neighbourhood of Kaitaia, 

 and so on; it was clear that many of them, though they perhaps 

 appeared to be really native, were in fact introductions to 

 the countr}^ Pomaderris apctala pro\-ed to be a xcry marked 

 exception among the plants of the Chathams in regard to its 

 distribution in New Zealand (129, p. 332), and therefore was 

 probably an introduction. The doubtful natives of Jamaica were 



