542 
Andropogon furcatus -—--~---e-- -+2++ ¢e0++-4> eevee +----- -~->> Poa pratensis 
---7 
Panicum _virgatum ,. ---~ 
Spartina Mfthauxiana | -- ~ 
Carex spp.-- ---- ----=-- --- ------- 2 -> Carex-Juncus-Iris 
Scirpus fluviatilis ....-.~. - ae cece cre eesteenes eee ee eeeeee--> Typha latifolia 
Unpastured Pastured 
Morainal depression, 
Fic. 5. Diagram showing the plant associations and hydrarch succes- 
sions in morainal depressions. The dotted lines indicate the changes 
brought about by grazing. 
to a mixture of blue grass with timothy and red top and allowing a few 
years for the blue grass to establish itself and crowd out the other 
grasses, except in low places where red top is a dominant pasture 
grass. On fertile loamy soil this succession will occur within three or 
four years, but on clay soils a somewhat longer time is required. 
With the foregoing associations and their successional relationships 
in mind it is of interest to compare them with the associations found 
on the more extensive shallow depressions of the ground moraine. This 
can be done at present only by having recourse to the relic patches of 
prairie plants along railway rights-of-way and fence-rows (Plates LXV— 
LXX). When this comparison is made, the same general associations 
frequently interspersed with patches of coarse herbs and cultivated grasses 
are met with again in the same order from lowlands to upland. This 
comparison also shows that most of the prairie areas of the older gla- 
ciated regions of the state had reached the Andropogon furcatus stage 
before they were disturbed by man, while large areas in the Wisconsin 
