1912] SHERFF—SKOKIE MARSH. 431 
Ludwigia, and Penthorum are very similar throughout in growth- 
form and they constitute mutually a competitive community. But, 
even though mutually competitive, they form with Boltonia and 
Callitriche a community that may properly be called comple- 
mentary. 
\\ 
Fic. 9.—a, Asclepias incarnata; b, Poa pratensis; c, Agrostis alba; d, Equisetum 
arvense; e, Acalypha virginica; f, Eleocharis palustris; July. 
As has already been stated, the flora of the meadow is highly 
diversified. A very large number of definite interrelationships, 
similar to those detailed for the reed swamp and the swamp meadow, 
are found to exist, but lack of space precludes more than a brief 
description of a few examples. In the moist parts of the meadow, 
the soil at a depth of 3-12 cm. frequently contains the tuberous 
thickened roots of Cicuta maculata and Oxypolis rigidior, also the 
