86 OBJECTIONS TO THE HYPOTHESIS [pt. i 



also enables dispersal to be more rapid, and so on. The two cases 

 are quite incomparable. But if the ten Compositae be compared 

 with ten other nearly alUed Compositae, then the effects of the 

 "other" factors will be much the same, and age, which is always 

 pulling alike upon all species, will show its effects clearly. The 

 greater the number of allied forms taken, and the greater the 

 length of time considered, the more clearly will the effects of 

 age show. 



Other objections come under the head of comparison of un- 

 allied forms. For example, it has been objected (16) that herbs 

 must be older than trees, because they occupy greater areas, 

 but that all probabihty is against this, (17) that Age and Area 

 shows that new species must have been formed more rapidly 

 among trees (because there are more of them among the endemic 

 forms), and that this also is against probability, (18) that local 

 endemics are usually unrelated to the wides that grow beside 

 them, and are often very unlike them, and so on. What has just 

 been said about comparing groups of allied forms only really 

 covers most of these, and a reference to such works as Hooker's 

 Flora ofNexv Zealand, or other systematic works, will show that 

 a great deal too much has been made of the supposed differences 

 between the endemics and the wides that accompany them. In 

 the great majority of cases the two are allied, and if they were 

 unrelated, it would be a very remarkable thing that they should 

 show the numerical relationships that we have seen to exist. 

 There are a considerable number of endemic forms, especially 

 within the range of the last glacial period, for example in 

 temperate North America, which are not related to the wides 

 beside them, but when groups of tens are taken, these are quite 

 lost in the crowd, or in some cases can not find a crowd to which 

 they can be attached. There are, however, at most about 400 

 such cases in North America^, and the endemics of most of the 

 world, especially the countries south of the Tropic of Cancer, 

 are to be counted by tens of thousands. Only very rarely, again, 

 will one find a group of ten allied herbs, with a group of ten 

 allied trees closely related to it. In such a case, which Avill very 



1 Sinnott (95) instances as endemics of this class Canja, Plancra, Madura, 

 Garrya, Sassafras, Xanlhorhiza, Baptisia, Ncmopanthus, Ceanothus, Dirca, 

 Dionaea, Hudson ia, Rhexia, Ptdea, Dccodon, Ilouslonia, Sijmphnricarpus,. 

 etc., pointincr out that many occur as fossils in the Old World, and that they 

 include most of the woody endemics of north temperate America. In 

 dealing with such, one must, as already pointed out, include the "fossil"' 

 area, and in any case they are lost in the crowd when not considered singly. 



