CH. Ill] ENDEMISM, AGE AND AREA 31 



Baptisia, Nemopanthus, Ceanothus, Dirca, Dionaea, Hudsonia^ 

 Rliexia, Ptelea, Decodon, Houstonia, Symphoricarpus, etc., many 

 of which are fossil in the Old World. As they also include most 

 of the woody endemics of North America, and as each of them 

 belongs to a different family, it is highly probable, if not certain, 

 that they are relics. But, as already pointed out, they are lost in 

 the crowd when considered in connection with their own families, 

 especially as most of them are but small genera. And though 

 they may be relics of a previously more woody vegetation of 

 North America, we have no reason to suppose that they are being 

 killed out by superior species — they have probably been much 

 reduced by change of climate and are not quite so well suited to 

 the conditions that now exist. In warmer countries one com- 

 paratively rarely finds endemics of this kind; the endemics, as 

 has already been pointed out (Age and Area, pp. 91, 165; and 

 p. 26 above), occur chiefly in the large and "successful" genera, 

 like Ranunculus or Poa in New Zealand, or Eugenia in Ceylon or 

 in Brazil. 



Among these just quoted relics there occurs Ceanothus, with 

 forty species in North America only, a genus that must be 

 counted as large for that country. In a recent discussion, Arto- 

 carpus, the jak and breadfruit genus, which is the third largest 

 genus in the large family of the Moraceae, and has over sixty 

 species scattered over Indo-Malaya and China, was quoted as a 

 relic, on the ground of the occurrence of fossils outside its present 

 area. This kind of definition of relic seems to the writer something 

 of a begging of the question. We can no longer be sure that any 

 plant is not a relic. The whole British flora must evidently consist 

 of relics, except perhaps the very local species farthest from the 

 land that has been submerged, and yet the flora is in reality a 

 very young one in its present position. If a change of conditions 

 affect a country, it is in the highest degree improbable, except in 

 a case like the coming of the ice, that it will kill out all the former 

 flora — it will be gradually and partly replaced by newcomers 

 that better suit the newer conditions, and if the conditions change 

 back again, these may be in turn replaced by the older flora, and 

 gradually things may become much as they were before the first 

 change. 



One reason, perhaps, for the unpopularity of age and area was 

 the realisation that it was incompatible with the current view of 

 the way in which evolution had gone on. If we follow it to its 

 logical conclusion, it is clear that as the family in general occupies 



