THE FLORA OF JAPAN. 133 



nearly peculiar to two regions furnishes evidence of similar 

 nature and of equal pertinency with representation by identi- 

 cal species, will hardly be doubted. Whether or not suscep- 

 tible <5f scientific explanation, it is certain that related species 

 of phaenogamous plants are commonly associated in the same 

 region, or are found in comparatively approximate (however 

 large) areas of similar climate. 1 Remarkable exceptions may 

 indeed be adduced, but the fact that they are remarkable goes 

 to confirm the proposition. Indeed, the general expectation 

 of botanists in this regard sufficiently indicates the common, 

 implicit opinion. The discovery of a new Sarracenia or of 

 a new Halesia iu the Atlantic United States, or of a new 

 Eschscholtzia, Platystemon, or Calais west of the Rocky 

 Mountains, would excite no surprise. A converse discovery, 

 or the detection of any of these genera in a remote region, 

 would excite great surprise. The discovery of numerous 

 closely related species thus divided between two widely sepa- 

 rated districts might not, in the present state of our knowl- 

 edge, suggest former continuity, migration, or interchange ; 



1 The fundamental and most difficult question remaining in natural 

 history is here presented — the question whether this actual geographi- 

 cal association of congeneric or other nearly related species is primordial, 

 and therefore beyond all scientific explanation, or whether even this may 

 be to a certain extent a natural result. The only noteworthy attempt at 

 a scientific solution of the problem, aiming to bring the variety as well as 

 the geographical association of existing species more within the domain 

 of cause and effect, is that of Mr. Darwin and (later) of Mr. Wallace, — 

 partially sketched in their short papers " On the Tendency of Species 

 to form Varieties, and on the Perpetuation of Varieties and Species by 

 natural Means of Selection," in the " Journal of the Proceedings of the 

 Linnsean Society," vol. iii. (Zoology), p. 45. The views there suggested 

 must bear a prominent part in future investigations into the distribution 

 and probable origin of species. It will hardly be doubted that the ten- 

 dencies and causes indicated are really operative ; the question is as to the 

 extent of their operation. But I am already disposed, on these and other 

 grounds, to admit that what are termed closely related species may in 

 many cases be lineal descendants from a pristine stock, just as domesti- 

 cated races are ; or, in other words, that the limits of occasional variation 

 in species (if by them we mean primordial forms) are wider than is gener- 

 ally supposed, and that derivative forms when segregated may be as con- 

 stantly reproduced as their originals. 



