754 A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



report on the North American forests (1884), and Christ's book on the Swiss 

 vegetation (1879). Indeed, from almost the earliest days there had been a slowly 

 increasing concern with ecological problems in plant geography, until shortly 

 before the first World War the literature of ecology had grown so great that 

 it became desirable to establish special periodicals to accommodate it, a stage 

 it which we may perhaps consider the subject to have passed, for the time being 

 at least, beyond the purview of this paper. 



The end of the nineteenth century marked also the centenary of the depar- 

 ture of von Humboldt and Bonpland on their travels in tropical America. Readers 

 will find an interesting account of the development of plant geography up to 

 1900 in Engler's contribution to the Centenary volume of the Berlin Geographical 

 Society (1899), in which he first traces the beginnings of the subject from the 

 earliest times and then its gradual growth on the fioristic side, region by region. 



The double deflection, or apparent deflection, of interest which followed the 

 turn of the century, on the one hand toward more narrowly taxonomic work and 

 on the other toward ecology, for a time left the middle stream of plant geography 

 a somewhat feeble one. In this direction, at any rate, the fifteen years or so 

 preceding the war were not among the most remarkable. This diversionary 

 tendency was intensified also by one of the most considerable advances of that 

 time, the growth of the subject of genetics, for, as will be seen, it was not until 

 considerably later that the underlying unity between genetics and plant geog- 

 raphy became perfectly realized. 



Nevertheless these years were far from being entirely barren. In particular 

 the German school continued to demonstrate its leadership in its chosen fields by 

 the continuation or launching of such great projects as Engler and Drude's Die 

 Vegetation der Erde (1896 — ) — among the volumes of which Harshberger's 

 Phytographical Survey of North America is conspicuous — and Karsten and 

 Schenk's V egetationshilder (1903 — ) which presents so much of interest and 

 importance in the international language of illustration; by such books as those 

 of Solms-Laubach (1905) and Schroter (1912); and by innumerable shorter 

 publications, notably in Engler's Botanische Jahrhiicher. Most of these are on 

 the border line between historical and taxonomic plant geography, but an impor- 

 tant direct contribution to the former was the comparison by Engler of the 

 floras of tropical Africa and of tropical America, a subject which was later to 

 become much more topical. 



In addition, these years saw the earlier writings of several whose major con- 

 tributions to plant geography were to come after the war, among them Fernald, 

 Merrill, Skottsberg, and Willis, but one of the most important series of writings 

 came from H. B. Guppy. Guppy was not a biologist by professional training ex- 

 cept in so far as he began his career as a naval surgeon, but he was that much rarer 

 thing, a born naturalist and observer, and he made good use of the fortune which 

 took him for many years to what are some of the most interesting parts of the 

 world from the point of view of plant geography. His larger works, namely. 

 Observations of a Naturalist in the Pacific (1903-1906), Studies in Seeds and 

 Fruits (1912), and Plants, Seeds and Currents in the West Indies and the 

 Azores (1917), are perhaps a little voluminous and prolix for ordinary reading 

 but they are unquestionably the work of a mind possessed of unusual descriptive 

 and analytical powers. The second volume of the first-mentioned work, which 



