6 The Vegetation in the 



Grisebach's botanical provinces are much more natural than Pick- 

 ering's quite artificial divisions in U. S. Bxpl. Expeditions, XV; but in 

 regard to the causes that efEected the distinct floras, he is rather one-sided ; 

 exeluding'all geological causes, admitting of recent agencies of migration 

 only, and refuting the theory of transmutation of species, he adheres to 

 the obsolete belief in general revolutions of the globe and new creations. 

 As some other prominent scientists, he seems to be influenced by heredi- 

 tary religious prejudices. However his arrangement of botanical provinces 

 may partly be retained, as far as new discoveries in less thoroughly 

 examined countries will not demand some changes, as proposed by A. 

 Engler, in his Essay on a History of Evolution of the Vegetable World 

 (1879-82), and by 0. Drude (Florareiche der Erde 1884), who both differ 

 from Grisebach in their argumentation acknowledging transmutation of 

 species and geological agencies. 



The limitation, not only of species but of whole genera, and even 

 orders within continents or certain parts of the same, created the idea of a 

 plurality of primitive centres of creation and of a phytogeographical sig- 

 niflcance of endemismus and of monotypes. This view, and the denial of 

 a genetical connection of the species through all geological periods agrees 

 perfectly well with a dualistic conception of cosmogony, the hypothesis of 

 an arbitrary power, that created highly organized beings by an immediate 

 will and placed each kind at a certain locality of our globe. 



A more probable hypothesis is the modern monistic biological 

 theory: By an unknown compulsive force are uninterruptedly produced 

 new forms out of older ones, and more perfect ones, beginning with the 

 most simple organizations, so that the recent forms, by convenience called 

 species, are genetically connected with the extinct. 



Species become extinct in certain localities and are preserved in others; 

 only that way we can understand the co-existence of one and the same 

 species in widely disjoint countries, f. i., of our Phryma leptostachya in 

 North America and the Himalayas; for nobody would believe that this 

 plant has a double origin, and the only explanation of this fact is that the 

 plant had formerly a wider distribution, and became extinct in countries 

 between the actual habitats. Several species of Liriodendron are found in 

 the Miocene formation of Greenland, and, besides, in Germany and Italy 

 when now only one species exist in North America; so the Taxodium 

 distichum, another North American tree, was found in the bituminous 

 slate-clay of Spitzbergen. Therefore, quite properly Bentham proposed, 

 instead of centre of creation, the term centre of preservation. 



The above mentioned species show that endemismus has nothing to 

 do with origin, but only preservation, and that only in that sense it is of 

 any value in phytogeography. Monotypes are very often the arbitrary 

 make of systematies, and depend of their proneness to narrower or wider 

 limitation of species and genera. Hepatica triloba is a monotype as soon 

 as we separate it from Anemone, and as soon as we unite with it the other 



