592 



6. Two or more species may live together in harmony because 

 (i) their subterranean stems may lie at different depths; (2) their 

 roots may thus be produced at different depths; (3) even where roots 

 are produced at the same depth, they may make unlike demands upon 

 the soil; (4) the aerial shoots may have unlike growth-forms; or 

 (5) even where these growth- forms are similar, they may vegetate 

 chiefly at different times of the year. According as one or more of 

 these conditions control the floristic composition of a given com- 

 munity the community may be called complementary. 



7. The root depth having been determined by various factors 

 for the different species in a community, the specifically different root 

 systems then function in a complementary or a competitive manner 

 as the case may be. But even if the root systems be complementary, 

 the community may be competitive because of marked competition 

 among the aerial parts. Likewise, competitive root systems may render 

 competitive a community otherwise complementary. 



8. Through the ability of certain species to utilize different strata 

 in the soil, the aerial portions of these plants are brought into a 

 closer competition. And with closer competition, the chances in the 

 past for further adaptation of similar aerial shoots to dissimilar 

 growth conditions must have been greatly increased. Hence com- 

 munities formerly complementary in a purely edaphic way, may have 

 been largely instrumental in the evolution of completely complemen- 

 tary communities. In so far as they have been thus instrumental, the 

 fact deserves great emphasis, especially when we consider the far- 

 reaching changes in form and anatomical structure necessarily de- 

 veloped as a prerequisite to living in a completely complementary 

 community. 



Annotated List of Plant Species 



As a matter of taxonomic interest to botanists in the future, it 

 seems worth while to present here an annotated list of all the species 

 of the Pteridophyta and Spermatophyta found growing to any extent 

 in Skokie Marsh. Stray species (especially weeds), occasionally ob- 

 served, have not been included in the list, except where evidence in- 

 dicated that they were regular inhabitants. Also, many weeds which 

 occur along the roads traversing the marsh and which do not prop- 

 erly belong to the marsh flora, are omitted. As the following list 

 stands, then, it includes only the established species found in the reed 

 swamp, swamp meadow, and meadow of Skokie Marsh proper. 



