HISTORICAL DEVELOPMENT 3 



by virtue of which all other lines of botanical inquiry languished. This 

 tendency had spent itself to a certain degree by the opening of the 19th 

 century, and both plant distribution and plant physiology began to take 

 form. The stimulus given the former by Humboldt (1807) turned the 

 attention of botanists more critically to the study of vegetation as a field 

 in itself, and the growing feeling for structure in the latter led to Grise- 

 bach's concept of the formation, which he defined as follows : "I would 

 term a group of plants which bears a definite physiognomic character, such 

 as a meadow, a forest, etc., a phytogeographic formation. The latter may 

 be characterized by a single social species, by a complex of dominant species 

 belonging to one family, or, finally, it may show an aggregate of species, 

 which, though of various taxonomic character, have a common peculiarity; 

 thus, the alpine meadows consist almost exclusively of perennial herbs." 

 The acceptance of the formation as the unit of vegetation took place slowly, 

 but as a result of the work -of Kerner (1863), Grisebach (1872), Engler 

 (1879), Hult (1881, 1885), Goeze (1882), Beck (1884), Drude (1889), 

 and Warming (1889), this point of view came tc be more and more preva- 

 lent. It was not, however, until the appearance of three works of great 

 importance, Warming (1895), Drude (1896), and Schimper (1898), that 

 the concept of the formation became generally predominant. With the 

 growing recognition of the formation during the last decade has appeared 

 the inevitable tendency to stereotype, the subject of ecology in this stage. 

 The present need, in consequence, is to show very clearly that the idea of 

 the formation is a fundamental, and not an ultimate one, and that the proper 

 superstructure of ecology is yet to be reared upon this as the foundation. 



5. Plant succession. The fact that formations arise and disappear was 

 perceived by Biberg as early as 1749, but it received slight attention until 

 Steenstrup's study of the succession in the forests of Zealand (1844 prox.). 

 In the development of -formations, as well as in their recognition, nearly all 

 workers have confined themselves to the investigation of particular changes. 

 Berg (1844), Vaupell (1851), Hoffmann (1856), Middendorff (1864), 

 Hult (1881), Senft (1888), Warming (1890), and others have added much 

 to our detailed knowledge of formational development. Notwithstanding 

 the lapse of more than a half century, the study of plant successions is by 

 no means a general practice among ecologists. This is a ready explanation 

 of the fact that the vast field has so far yielded but few generalizations. 

 Warming (1895) was the first to compile the few general principles of de- 

 velopment clearly indicated up to this time. The first critical attempt to 

 systematize the investigation of succession was made by Clements (1904), 

 though this can be considered as little more than a beginning on account of 



