growths on the 5-foot sample transects (table IT and 
figures 2-9). Nonvegetated ground was used since the effect 
of nutria on the vegetation was expected to be manifested in 
open areas. 
2. The percentages of large openings for Transects A and C 
were derived from measurements along the whole transect 
(table II). 
3. Percentage of various combinations of the principal species 
of plants was calculated from the sample transect measure- 
ments (figures 2-9). For this purpose the relative abun- 
dance of each species of plant in each clump or patch of 
vegetation was estimated visually and considered as "dominant" 
if it formed 50 percent or more of the vegetation and “sub- 
ordinate” if it formed less than 50 percent of the vegeta- 
tion. These calculations gave a good index to changes in 
the density and frequency of plant species. 
Changes in the vegetative pattern of the transects will not be 
discussed in detail. The tables and figures give the detailed in- 
formation. 
Overall, Transects A, B, and C showed a small decrease in the 
extent of nonvegetated ground (open space ) from 1954 to 1955 and a 
greater decrease from 1955 to 1956 (table II). There were some 
variations in this respect from 1954 to 1955 among the vegetative 
types of Transects A and C (figures 2-9). Nonvegetated ground in- 
creased from 1954 to 1955 on the first two vegetative types of 
