538 
Andropogon furcatus_ <<—£———————— Poa pratensis 
Poa compressa 
an 
Panicum virgatum Agrostis 
a canadensis Silphium-Cacalia 
Spartina Michauxiana 
Carex stricta 
Scirpus fluviatilis 
Fic. 4. Diagram showing the successions of the principal associations on 
the old lake-bed of Lake Chicago, including those of cultivated grass- 
es. See Plates LI, LIV-LXIV 
state. Their presence today is the result of their introduction and use in 
cultivation. The blue grasses were apparently introduced from Europe. 
Waller (30) finds that the early settlers of Virginia and Kentucky looked 
upon Poa pratensis as a dangerous introduced weed and some of them 
prophesied that it would some day drive the farmers out of the country. 
A wealthy plantation owner, fearful lest the blue grass would ruin his 
pastures, ordered his slaves to dig it out and burn it. The early settlers 
of Illinois say that blue grass came into the state following the destruc- 
tion of the native grasses by cultivation and grazing. The prominence 
of these cultivated grasses on the, Chicago praitie is, indicative of dis- 
turbance by man and raises the question as to how far this prairie may 
