THE BIOME AS A SOCIAL ORGANISM 21 



rally led to the assumption that the complex of organisms in a par- 

 ticular habitat constituted an entity. It is further evident that the 

 matrix of this entity is composed of the sessile and sedentary individ- 

 uals, which on land are almost exclusively plants, and in the sea, 

 invertebrate animals. On land, this view is supi)orted by the much 

 more intimate connection of plants with the habitat as a consequence 

 of the direct action of the latter upon them and of the universal 

 reaction of plants upon the physical factors concerned. ^Moreover, the 

 food supply of plants is determined by the amounts of energy and raw 

 materials available in the habitat, while all the food of animals is 

 derived directly or ultimately from plants, though in the sea these 

 may grow at a distance. Naturally, these relations had long been 

 known and were to some degree recognized in the general use of the 

 term "biotic factor" by plant ecologists. Nevertheless, the concept 

 involved in this term did not constitute either a logical or natural 

 treatment of plants or animals in a community based also upon the 

 other group of organisms. Such a treatment becomes possible only 

 with the recognition of both organisms as coactors in a complex of 

 effects proceeding from the habitat as the cause. 



The tardy recognition of the biotic formation as the essential 

 entity was naturally due, for the chief part, to the specialized training 

 of biologists as either botanists or zoologists. However, a small share 

 in this must be ascribed to the characteristic motility of land animals, 

 which obscured their inherent connection with the smaller communi- 

 ties, and also to such processes as metamorphosis, seasonal migration, 

 etc., as a result of which many species regularly traverse community 

 limits. 



The Biome as a Complex Organism. One of the first consequences 

 of regarding succession as the key to vegetation was the realization 

 that the community, as noted above, is more than the sum of its 

 individual parts, that it is indeed an organism of a new order (Clem- 

 ents, 1901, 1905). For this reason, it was considered to be a complex 

 organism, bearing something of the same relation to the individual 

 plant or animal that each of these does to the one-celled protophyte 

 or protozoan. The novelty of this proposal naturally evoked criti- 

 cism, but in spite of this the concept has slowly grown in favor, with 

 dynamic ecologists in particular, and by an increasing number has 

 come to be regarded as constituting a new basis for almost unlimited 

 development (Jennings, 1918) . However, it is essential to bear in 

 mind the significance of the word "complex" in this connection, since 

 this expressly takes the community out of the category of organisms 

 as represented by individual plants and animals. With the object of 



