ESTABLISHMENT OR ECESIS 63 



also moved northward two hundred miles or more from Indiana into 

 Michigan. Both of these extensions are due probably to the release 

 of territory, change of vegetation, reduction of enemies, or other activ- 

 ities of man. Extension of range in insects is likewise frequent. The 

 boxelder bug moves northeastward from Oklahoma to southern Michi- 

 gan every decade or so, and frequently becomes domiciled, until a 

 winter with prolonged low minima destroys the invaders. 



ESTABLISHMENT OR ECESIS 



By this term is understood the process of making a new home, 

 involving the adjustment and often the adaptation of organism or 

 community to a new place or habitat. It is both more comprehen- 

 sive and more concrete than acclimatization or naturalization, but 

 differs little in essence. It embraces the widest range of adjustment, 

 from the slight movement of a rhizome in practically uniform condi- 

 tions to the establishment of invaders in a bare area or the advance 

 of forest or prairie along an ecotone. It is a much simpler and surer 

 process when a single medium is concerned, as water or soil, in which 

 migration and ecesis are nearly synonymous. Ecesis in land habitats, 

 with the necessity of adjustment to two media of great variety, be- 

 comes correspondingly complex and difficult. However, this statement 

 applies much more fully to plants than to animals, owing chiefly to 

 their direct dependence upon the ece but also in some part to their 

 sessile nature. It is applicable in varying degree to animals, being 

 fairly simple and direct in wide-ranging species, and more complex 

 in sedentary ones or those with narrow limits as to physical factors 

 or choice of food. By contrast with plants, ecesis in animals involves 

 adjustment not only to the new place or habitat but also to a new 

 group of coactions. 



Ecesis in Plants. Differences in the manner and success of ecesis 

 are determined by several elements, namely, the plant or part con- 

 cerned, the medium, and the habitat. In free aciuatic forms the in- 

 dividual itself often migrates and ecesis consists merely in its continu- 

 ing to grow and reproduce, a result more or less assured by the greater 

 uniformity of aquatic habitats. For the offshoots of land plants, espe- 

 cially underground ones, conditions are rather similar, and continued 

 growth and multiplication are certain within the limits set by exces- 

 sive competition. However, in the vast migration of seeds and fruits, 

 ecesis requires successful germination, growth, and reproduction, dur- 

 ing which seedling and plant must often withstand unfavorable ecial 

 factors, intense competition, or injurious coactions. As a consequence, 

 a migrule may meet one of four fates: (1) it may never germinate; 



