386 BOTANICAL GAZETTE [OCTOBER 
articles have appeared that are notable, not only for the divergence of the views 
expressed, but also for the decided advance they have made in providing a 
logical system of classified units for the use of students of vegetation. 
Greason® embodies in his article an individualistic concept of ecology, 
contending that all phenomena of vegetation depend upon the phenomena of 
the individual plant. The plant association he conceives to be an area of uni- 
form vegetation developed by similar environmental selection from the immi- 
grants from the surrounding population. is position, while extreme, will 
prove most useful if it serves to focus attention upon the intensive study of 
some of the most important species of a vegetation so as to discover their 
reactions to various environments and to the factors which limit their invasion 
and establishment in plant communities. 
e other extreme is seen in the work of CLEMENTS,’ as expressed in what 
doubtless is the most notable of recent contributions to ecological literature. 
Without attempting to review or criticize his book as a whole, it may be pointed 
out that he selects the formation as the fundamental unit and regards. this 
plant community as an organic entity exhibiting origin, growth, maturity, and 
death. As an organism it is able to reproduce itself and possesses a life history 
which is a complex but definite process. The climax community is the adult 
organism of which all initial and medial stages are but stages of development. 
Thus CLEMENTS would limit the term formation to the climax community, while 
the successional series leading up to the climax formation he calls a “sere.” 
He has provided a complete system of subordinate units for the analysis of 
both formation and the sere, the former being divided successively into asso- 
ciations, consociations, 7 and clans; the latter into associes, consocies, 
socies, colonies, and families. This recognition of a plant community as an 
entity comparable in some extent at least to an organism seems strictly in 
accord with the views of most ecological workers, and if the relationship be 
regarded as one of close analogy rather than homology it will probably prove 
the most stimulating and anGatactory atetale: It Aprents, however, that 
CLEMENTS’ system of subordinate ore elaborate than is required 
to meet the needs of most investigators. 
A somewhat simpler system, introducing but few new concepts or terms, 
recently organized by NicHots,” commends itself to the reviewer as including 
those units and terms dssaienly in. _ past have aig an satisfactory, and 
which now for the first time h combined system. NICHOLS 
* GLE , H. A., The structure and — of the plant association. 
Bull. ans ha Club 44:463-481. 1917. 
9 CLEMENTS, F. E., Plant succession, Carn, Inst. Wash, Pub. 242. pp. xilit-51!- 
pls. 61. 1916. 
* Nicwots, Geo. E., The interpretation and application of certain terms and 
concepts in the ecological classification of plant communities. Plant World 20:305~ 
319, 341-353. 1917. 
