THE ORIGIN AND GROWTH OF PLANT COMMUNITIES 



593 



TABLE XI 



Range of Values for Criteria Applied to the Anatomy and Physiology 



of the Plant Community. The Value Given at the Right-Hand Side 



of the Table is Considered Usual in a Climax Community. 



relatively reduced; several dispersal types are well represented; its 

 ecological determinants are not extreme but moderate; and it exploits 

 the resources of the ecosystem to the full, whereas it betrays little evi- 

 dence of succession. 



Table XII grades the 14 stands previously considered according to 

 the scale proposed in Table XI. It will be seen that the first three 

 stands, as well as the Acereto-uLmetum laurentianum and the Alnetum 

 rugosae, have a high cumulative index, mostly due to a high percentage 

 of 3's and only an exceptional 1, whereas the Solidaginetum, the Poae- 

 tum, the Spiraeetum, and the Lythretum have practically no 3's and 

 a good number of Is. 



Ecosystematic fitness of populations. The individuals belonging to 

 a single interfertile population have been characterized above in sev- 

 eral respects: floristic element, valence, fidehty, frequency, constancy, 

 life form, layering, spacing, coverage, periodicity. In a previous essay 

 on "the varieties of evolutionary opportunity" ( 1952a ) I argued that the 



