BIOLOGICAL PAPERS 12: 



The sandstone cliffs on Rock River are quite in contrast. These 

 cHft's are porous. On their tops stunted pine, cedar and black oak 

 are almost alone. Basswood, maple, hop hornbeam and yew are 

 never present, and the growth is never dense. 



COMPETITIOX AXD GENERAL RELATIONSHIPS 



AMONG THE SUBTERRANEAN ORGANS 



OF MARSH PLANTS. 



Earl E. Sherff. 



The statements and conclusions in the present paper are based 

 mainly upon my work at Skokie ^Marsh. in the years 1910 and 

 1911.^ The marsh itself is closely associated with Skokie Stream, 

 a small, intermittent, meandering stream that begins west of 

 Waukegan. Illinois, and ends west of Glencoe. Illinois. Its 

 vegetation may be described briefly as consisting of reed-swamp, 

 swamp-meadow and true meadow. 



Darwin, in his Origin of Species, pointed out that because two 

 species of the same genus usually resemble each other, the strug- 

 gle between them, if they come into competition, will generally 

 be more severe than between two species of dift'erent genera. 

 Clements has since emphasized the fact that similarit}- in gro^^'th 

 form rather than in systematic position determines the intensity' 

 with which dift'erent species compete. One of the main objects 

 in my investigation at Skokie ]\Iarsh was to ascertain how far 

 similarity in growth form among different species fparticularly 

 in regard to depth of subterranean organs") results in competi- 

 tion : or. conversely, how far dissimilarity" in growth form results 

 in ability to live together harmoniously in a complementary 

 relationship. 



We have here [illustrated on screen] a view of the rhizome 

 interrelationships of the bur-reed (Sparganium eurycarpum), 

 the arrow-leaf (Sagittaria latifolia) and one of the water knot- 

 weeds (Polygonum Muhlenbergii). where the three species occur 

 together in the less hydrophytic parts of the reed-swamp. . . . 

 As shown on the screen, the knot-weed rhizomes and roots lie 

 rather deep. ... It will be seen that the roots of the arrow- 



1 A general and also more elaborate account than here possible will be found in 

 the Botanical Gazette. 53:413-435, 1912. 



