averaged 42.6 percent of sea salinity in October 1954; four 
averaged 21.7 percent in June 1956; and five averaged 10.1 per- 
cent in August 1956. The drought, with accompanying salinity 
variations, may have affected some plant species adversely 
through 1955, and the increased rainfall of 1955 may have been a 
factor in the increased vegetation coverage of 1956. Little is 
known of the precise effects of rainfall and salinity, or of 
other envirommental factors, singly and in combination, on the 
various species of marsh plants. 
Changes other than weather may have affected the marsh vege- 
tation. The increased number of canals required by the oil in- 
dustry and navigation has changed the drainage patterns in the 
marsh. This and flood control activities have reduced water 
levels on the marsh by drainage and channeling runoff through the 
marsh into the gulf. The marsh has become more accessible to 
gulf water through these channels. In southwestern Louisiana 
increased usage of fresh water for rice farming has reduced 
amounts reaching the marsh. These gradual changes have shortened 
the period of time that rain or runoff water lies on the marsh 
and have increased the number of times that saline gulf water 
covers the marsh. It is fair to assume that such changes modify 
vegetative density and composition. Improperly applied manage- 
ment techniques have also changed plant composition and density. 
Once established, a perennial marsh plant, with its vigorous, 
vegetative reproduction, may persist for some years while conditions 
2g 
