iQ2o] CLAYBERG— UPLAND SOCIETIES 51 



For the foliage layer is coined the name synfolium, and its devel- 

 opment and ecological significance are analyzed. In connection 

 with mortality, it is pointed out that very many saplings are pinned 

 down by debris, and thus actively destroyed instead of passively 

 dying. 



The study of Kent County, Michigan, by Livingston (18) shows 

 five societies, while the writer has distinguished four here. While 

 this might be interpreted as meaning Kent County was not so far 

 advanced, it must be remembered tkat: (1) oak and hickory play 

 more important roles in succession in the Grand Rapids area than 

 at the north end of the southern peninsula; (2) Livingston recog- 

 nizes three societies containing oak, and two with maple; in this 

 region the four primary types tend to be mutually exclusive; 

 (3) Livingston uses herbs as well as trees in definition of his socie- 

 ties, which the author has not felt justified in doing for this region 

 as yet. 



examining 



it 



seems probable that the hypothesis laid down by Livingston 

 holds in large measure, but it may be that this is only for societies 

 enduring rather small differences in moisture retaining power of the 

 soil; for the fireweed society (secondary) is able to endure a wide 



this particular, being 



out. 



Throughout this region the response of the plant societies to 

 interference and changed environment has been adaptive, in so far 

 as their constitution allowed. Some natural societies, such as the 

 blackberry, are fitted to survive in partly wild areas. Others can 

 invade the fields in competition with the crops. Characters 

 required are quick entry, speed of vertical growth, quickness of 

 fruiting after germination, quantity of seed production, and effi- 

 ciency of distribution; for a given society may be here today and 

 gone tomorrow, plowed under. 



The best example of the weed type among the societies previ- 

 ously discussed is the fireweed society, which contains species that 

 are being rigidly selected by man in his fight against them. These 

 plants are likely to survive long after the maple-beech society is 

 banished to the wood lot and city parkway; for evolution is toward 



