LIFE FORMS 49 



taxonomic and biomc forms are the same; this is especially apparent 

 in invertebrates but holds throughout with few exceptions. 



Life forms that bear the distinct impress of a particular habitat or 

 some division of it are known as habitat forms, and those of plants 

 have been termed ecads if they can be produced experimentally. 

 Among animals, a group with a characteristic behavior response has 

 been called a inores (Shelford, 1913, a) ; to avoid certain difficulties, 

 especially as to the plural, it is now proposed to employ the word 

 "mune" {munus, function, role). Of more recent impress and hence 

 of less import are the growth forms and competition forms. However, 

 plants often exhibit striking forms of the latter type, both in nature 

 and in culture, and this is true only to a less extent for animals. 



Bases. The major principles underlying life forms were enunciated 

 by Drude as: (1) the role played by the species in vegetation, and (2) 

 its life history in relation to the habitat, in terms of duration, pro- 

 tection, propagation, and overwintering (1890, 1896). These were 

 later increased to the following five: (1) the basic form, tree, shrub, 

 etc.; (2) form and duration of leaf; (3) protective devices during the 

 resting period; (4) position and structure of the organs of absorption; 

 and (5) reproduction as a single or recurrent process (1913). The 

 system of Warming (1909) took into account three major features, 

 viz.: (1) duration, (2) length and direction of internodes, and (3) 

 position and relations of buds to overwintering; it also took into 

 account five minor ones, namely: (1) structure of buds, (2) size of 

 plant, (3) duration of leaves, (4) adaptation of the green shoot, and 

 (5) capacity for social life (1909). Clements gave more or less equal 

 value to the life period, method of overwintering, conservation of 

 shoots, and success in competition (1920, 1928). 



Systems of Life Forms. The essential similarity of the systems 

 more or less current is readily perceived from the fact that Drude 

 makes trees, shrubs, perennial, and annual herbs the basic life forms; 

 Warming's major division of land plants is into monocarpic and poly- 

 carpic, essentially annual and perennial, while Raunkiaer's largest 

 groups correspond practically to woody plants and perennial and 

 annual herbs. In accordance with this general agreement, Clements 

 has proposed the following as a simple practicable system, embodying 

 the major features of the others: 



1. Annvials 6. Cushion herbs Woody perennials 



2. Biennials 7. Mat herbs 11. Halfshriibs 

 Herbaceous perennials 8. Rosette herbs 12. Bushes 



3. Sod grasses 9. Carpet herbs 13. Succulents 



4. Bunch grasses 10. Succulents 14. Shmbs 



5. Bush herbs 15. Trees 



