THE SCIENCE OF PLANT ECOLOGY. 159 



celience, yet, if one would go far in the line of investigation, he must 

 also be at home in the laboratory and the herbarium. 



But perhaps the mention of some of the specific branches of 

 botanical study which are now considered to be within the province of 

 the ecologist will make the term clearer than any mere generalizations 

 can do. The physical environment of a plant, the conditions of tem- 

 perature, moisture, light, texture and chemical composition of the 

 soil, occasions in it many modifications, gross and minute. These are 

 sometimes simple and obvious, but often complex and obscure. To 

 detect and properly explain such correlation of structure to life con- 

 ditions is an essential task of ecological botany. But besides its ad- 

 justment to physical surroundings the plant comes into contact with, 

 and must adapt itself to the habits of innumerable other vegetable 

 and animal organisms. In other words, it has also a biological en- 

 vironment, which, because of its greater complexity, induces much 

 more profound mutations of structure. Here we are concerned, for 

 example, with the countless wonderful adaptations to fertilization by 

 the aid of insects and birds ; the often striking arrangement looking 

 to the dissemination of seeds by the agency of animals; the means 

 whereby the plants seek to protect themselves against marauders, of 

 which perhaps the most wonderful is the providing of a home for war- 

 like ants which serve the plant as a vigilant police ; the insect-feeding 

 habit of certain forms, which usually inhabit a nitrogen-poor soil, 

 and the adjustment of the parasite to its host. 



One of the most fruitful applications of ecological methods has 

 given birth to a new branch of plant-geography, which turns aside 

 from the study of the distribution of taxonomic forms as interpreted 

 by their geological history, and seeks to understand the distribution 

 of biological form with regard to climate and to soil. To the ecologi- 

 cal plant geographer it is of comparatively little interest that the 

 family Saraceniaccce occurs only in the Western hemisphere and the 

 NepcntJiaccce exclusively in the Eastern ; or that certain genera and 

 species occur only in eastern North America and in eastern Asia. 

 But he is vitally concerned with the fact that the Atlantic slope in 

 North America is naturally a wooded region and that the country be- 

 tween the Mississippi and the Rockies has a climate suited to grassy 

 prairies but not to extensive forests. Likewise with the striking 

 similarity in habit and adaptations to environment of the vegetation 

 on the coast of New Jersey and on the sand hills of Nebraska. The 

 remarkable predominance of evergreen trees and large shrubs in the 

 western Mediterranean region, in southern California, and in parts of 

 South Africa and of Australia awakens his keen interest. He find his 

 belief that like conditions of environment always induce adaptations 



