POSITION OF ECOLOGY IN MODERN SCIENCE 181 



could be based the study of a flora from the evolutionary point of 

 view, and confined climatological considerations within their proper 

 limits. But A. Grisebach in his earlier works had already begun to 

 develop the doctrine that the victories of the all-conquering clima- 

 tological factors find their outward expression in "formations" 

 composed of special forms of the vegetation with which our earth 

 is decked. The cactus alone does not determine the arid character 

 of the desert, nor the Mauritia palm the tropical character of the 

 Amazon region, nor the Lodoicea that of the Seychelles Islands. 

 Mosses and lichens are not the only plant growth on the Siberian 

 and Canadian tundras; and among the conifers the northern 

 larches bear witness to quite different ecological conditions from 

 those designated by the cedars of Lebanon, or the Araucarias 

 which grow in eastern Australia and on the southern shores of the 

 American tropics. With these plants, however, grow other species 

 having the same requirements in regard to light, heat, and moist- 

 ure, and all these together make up a typical formation in their 

 common station. 



Since Grisebach elaborated these fundamental ideas and gave 

 them general expression in his Vegetation der Erde (1872), he may be 

 regarded as the founder of the third period in the development of 

 ecology, just as I regard von Humboldt, with his Essai sur la geo- 

 graphie des plantes, to be the founder of the second and Linnaeus that 

 of the first, which began with the appearance of his Flora lapponica. 



As yet, however, the ability to penetrate the intimate relations 

 existing between climate and plant life was lacking. The discovery 

 of mere outward facts of contiguity furnished only the barest out- 

 line, which still needed the accumulation of important data for its 

 true comprehension. 



Knowledge of the evolution of the earth and of organic species 

 became the aim of scientific research. Darwin's great intellectual 

 achievements bore universal fruit. Such men as Moritz Wagner 

 attempted to extend questions of theoretical evolution so as to in- 

 clude the problem of the distribution of species, until then regarded 

 as something fixed and unalterable, and thus the idea of evolution 

 became involved in the explanation of present conditions. In a sim- 

 ilar attempt, especially in botany, to give formal diagnosis a more 

 natural bent, the mere description of organs was transformed to bio- 

 logical morphology, while anatomy was changed to physiological 

 anatomy. For floristic purposes the attempt was made, by means 

 of the clear and simple methods used originally in experimental 

 physiology, to correlate organs with the physiological factors of the 

 environment. 



While these new tendencies, developed from morphology and 

 physiology, which to-day form the closest connection between the 



