VEGETATION OF SALT MARSH POOLS. 483 



Pleiirosiguia angulatum, Melosira nummuloides and a species of 

 NaviciiJa and Synedra. With the retreat of the water and the dry- 

 ing up of the pools, these alg?e and diatoms form crusts, or matted 

 masses (Plate XII., Fig. 2), mixed with the dried leaves of Zostera 

 marina and the remains of other plants. In one pool pieces of news- 

 paper were found stuck together by the mat of blue green algse. 

 The mats of partially dry algse and diatoms (algal paper) assist in 

 the further disintegration of the peaty surface of the pool bottom, 

 but a limit is reached beyond which the process of decay is checked. 

 With a change in drainage of the salt marsh, some of the pools 

 are only occasionally filled with salt water, and the algse begin to 

 die and disappear, leaving a barren soil, which in very dry 

 weather may sun crack, as shown in the photograph of such a 

 pool in the salt marsh back of Atlantic City, New Jersey (Plate 

 XIII., Fig. i). Such denuded areas are now invaded by typic salt 

 marsh species. One such pool investigated was tenanted by a 

 pioneer plant, Atriplcx patida, while an old crescent-shaped de- 

 pression was completely invaded by Triglochin maritimum in pure 

 association, and another area with Pluchea camphorata, Plantago 

 maritima Solidago sempcrvirejis. Still another bare area was in- 

 vaded by Spcrgularia marina, Plantago maritima and a few weak 

 plants of Solidago sempcrvirens. 



An extensive area completely denuded of vegetation by the 

 smothering action of drift material and completely riddled with 

 the burrows of the fiddler crabs, Gelasimus pugnax (Plate XIV., 

 Fig. i), was found occupied by a pure association of the samphire, 

 Salicornia europcca, which is frequently the pioneer species on such 

 mud flats (Plate XIII., Fig. 2). Not all of the areas in our eastern 

 salt marshes are due to the smothering action of the drift material, 

 which consists largely of the dried remains of Spartina glabra and 

 Zostera m^arina, but occasionally, we find a sloping gravel bank, as 

 at Cold Spring Harbor, Long Island, where a fresh-water spring 

 controls during a large part of the day the soil conditions, and 

 where the gravel soil is so hard as to preclude the growth of the 

 usual salt marsh species (Plate XIV., Fig. 2). Under such condi- 

 tions Lilceopsis lincata grows. It is an interesting little umbellif- 

 erous plant with fleshy spatulate leaves, a running stem, and a 



