appeared to be taller and more robust than outside, probably account- 
ing for the fewer stems but greater weight inside. Revegetation of 
small openings created by the activities of the nutria produced 
smaller and more numerous stems outside the exclosure. Olney's 
three-square and big cordgrass, both food plants of the nutria, 
showed significantly higher means inside than outside the exclosure 
by analysis of variance. The average number of culms of Olney's 
three-square decreased with time both inside and outside, but at a 
greater rate outside. The average number of culms of big cordgrass 
fluctuated inside the exclosure with time, but decreased steadily 
outside the exclosure. 
Exclosure 2, located in the saltmeadow cordgrass - Olney's 
three-square type of Transect C, was invaded by muskrats late in 
1953. The activities of the muskrats affected the vegetation in 
the exclosure, hence only data for 1953 are given in table IV. By 
July 1953, 5 months after construction of the exclosure, the vege- 
tation appeared denser and taller inside than outside the exclosure. 
Comparison shows that the means per quadrat were significantly 
different at the 5 percent level with the higher mean inside for 
weight of vegetation, total number of stems, and number of culms 
of saltmeadow cordgrass. 
Exclosure 3 was erected in the only dense colony of big cord- 
grass remaining along Transect C in May 1955. The purpose of 
choosing this location was to ascertain if, protected from nutria, 
the big cordgrass would deteriorate as it appeared to be doing 
14 
