POSITION OF ECOLOGY IN MODERN SCIENCE 179 



By the word "ecology" we understand the vital phenomena 

 exhibited by plants and animals in the struggle for space, under 

 conditions enforced by the climate and the physiography of a 

 country. "Struggle for space" is Ratzel's appropriate version of 

 Darwin's proverbial phrase, "struggle for existence," whose pur- 

 port, however, remains unchanged. In the struggle for space each 

 organism requires a place in which he can fulfill his career ; that is, 

 secure nourishment, and leave behind him descendants capable of 

 occupying a similar location. Each organism is closely associated 

 with its environment; each plant, each animal, lives, like mankind, 

 in a special world of its own. 



These considerations show us that ecology is the borderland to 

 which the sciences of biology and geography can both lay claim. 

 Thus the ecologist, persuaded of the importance of the various vital 

 problems which here cover common ground, must have a com- 

 plicated equipment for his varied work; he must be as familiar 

 with the use of the balance, photometric and thermometric instru- 

 ments, as with the absolute dominion of lifeless nature. In order 

 not to be betrayed into forming hasty conclusions, he must work in 

 the herbarium as a florist, with the microscope as a physiological 

 anatomist, and also bear constantly in mind the geological develop- 

 ment of present conditions. 



Yet until now botany and zoology have held aloof from one an- 

 other in this new scientific departure, although it is just here that 

 victories common to both have been achieved, as, for instance, 

 in the biology of the flower whose form shows adaptation to the 

 needs of the insect world ; or in cases where there is mutual de- 

 pendence between plant and animal, the one affording domicile, 

 the other protection, as in the case of the Imbauba trees of Brazil, 

 w r hich furnish food and lodging to armies of ants, who in turn protect 

 the trees from the devastating hordes of leaf-cutting ants. In this 

 connection, too, has been brought to light the usefulness of the 

 modest earth-worm and the versatility shown by plants in the 

 methods used for protection from the voracious assaults of snails 

 and caterpillars. The dire need of animals struggling to obtain 

 their scanty nourishment is often revealed at the same time as 

 the silent efficacy of the protective forces of the plant kingdom. 



We can readily understand how through all ages the effect of large 

 troops of Herbivora has been harmful to the plant world, while the 

 effect of their enemies, the Carnivora, has been beneficial, and how 

 these two influences must have produced various changes in the 

 formations. 



In determining the dependence of organic life upon the physio- 

 graphic character of a country, the science of botany is naturally 

 of the utmost importance, since the individual plant is found actually 



