between tide and elevation and the amount of inundation to which a parti- 

 cular area is subjected (Johnson and York, 1915; Hinde, 1954; Adams, 1963). 

 Reed (1947) pointed out that individual S. alt erni flora plants reached 

 their best development halfway between the low and high tide levels and 

 decline in height and luxuriance both seaward and shoreward. Bourdeau 

 and Adams (1956) found that salinity increased markedly from the tall to 

 the short height zone. Results of a greenhouse study by Mooring, Cooper, 

 and Seneca (1971) conducted with North Carolina plants indicated no 

 differences in seedling response to various levels of substrate salinity 

 due to height form of the parent plant. Based on seedling biomass and 

 height response, these researchers postulated that differences in height 

 forms were not genetic and may result from exposure to environments 

 differing in salinity. Biochemical evidence based on total soluble proteins 

 and enzyme patterns, along with field transplant studies of tall and short 

 height forms from Connecticut, also led Shea, Warren, and Niering (1972) 

 to conclude that the two height forms were due to environmental conditions 

 at a given site and not to genetic differences. 



In established stands, the primary means of reproduction is vegetative 

 by means of extensive belowground hollow cylinders of stem tissue called 

 rhizomes. Along intertidal creeks and in newly established stands of the 

 grass, sexual reproduction often occurs. In these areas, the aboveground 

 stems, which are often called culms in grasses, reach their tallest height. 

 Flowers emerge at the terminal end of culms to form elongate flowering 

 heads or inflorescences. Flowering (anthers available for pollination) 

 occurs earlier in more northern populations along the Atlantic coast, often 

 in July, and becomes progressively later in southern populations (Seneca, 

 in press). Pollen is usually transported by the wind, and following 

 fertilization, seed development proceeds. Seeds reach maturity from 

 September to November depending on latitude, and they shatter shortly 

 thereafter. 



The plant can grow in a wide range of substrate textures, from coarse 

 sands to silty-clay sediments. The grass appears well-adapted to the 

 anaerobic substrates characteristic of most salt marshes, because of its 

 oxygen transport system. Large, hollow, air-filled tissue called 

 aerenchyma extend from openings (lacuna) in the leaves down the shoot to 

 the rhizomes and roots (Teal and Kanwisher, 1966; Anderson, 1974). Thus, 

 belowground tissues in the anaerobic substrate are able to receive necessary 

 supplies of oxygen. 



Although S. alterniflora does not usually reach its maximum growth in 

 higher salinity (35 parts per thousand) areas, it is well-adapted to and 

 can outcompete most other flowering plants in these regularly flooded 

 saline habitats. The plant tolerates salinity by taking salt up through 

 its roots and excreting it through special structures in the leaves called 

 salt glands. Because the species can tolerate salt but is not restricted 

 to highly saline areas, it has been termed a facultative halophyte. In 

 some brackish to freshwater tidal marshes S. alterniflora and a related 

 species, S. eynosiwoides (L.) Roth (giant cordgrass) , occur together but 

 can be distinguished by the occurrence of a prominant midrib on the leaf 

 of the latter species and its total absence on S. alterniflora. 



13 



