182 THE PLANT LIJ-'F. OP MAKYI \\l> 



III. Distichlis association 

 IV. Iva-Baccharis-Panicum association 

 V. Shrubs and trees: Myrica, Rosa, Baccharis, Juniperus, Pinus 

 taeda, etc. 



In places where littoral currents are marked, a sand-bar is built 

 up around the edge of the marsh, and on it are apt to be found 

 Spartina patens, Distichlis, with scattered plants of Ira and Soli- 

 dago sempervirens, and a fringe of Spartina stricta var. maritima 

 in the water at the edge, while in the depressed area behind the 

 bar Scirpus olneyi, Spartina polystachya, or TypTia may predom- 

 inate, according to conditions. 



Transition areas. — In travelling up a tidal stream to regions 

 where saline influences are less and less felt, an interesting succes- 

 sion of plants may be seen, one association replacing another until 

 all traces of halophytic vegetation have disappeared. The degree 

 of saltness which a species w T ill endure varies within wide limits, 

 some species being found only where the proportion of salt is about 

 that of the open sea (3.5%), e. g. Salicornia sp., Limonium caro- 

 linianum, Tissa marina, so that their presence indicates to the eye 

 the nature of the substratum. Other plants will endure only a min- 

 ute amount of salt, for instance, Scofield (loc. cit.) finds that the 

 limit for growth of Zizania aquatica is 0.374% of salt, while speci- 

 mens are only occasional after a concentration of 0.175% is reached. 

 Between these extremes lie most of the plants found in the salt 

 marshes of the region under consideration. From a study of a num- 

 ber of streams and marshes the following list has been made, approx- 

 imately arranged in descending order of salt resisting capacity: 



Salicornia herbacea 

 Limonium carolinianum 

 Spartina stricta var. maritima 

 Spartina polystacliya 

 Aster tenuifolius 

 Atriplex hastata 

 Solidago sempervirens 

 Acnida eannabina 



