

of Mississippi and Louisiana 77 



Chenopodium Berlandieri sometimes occurs. It is possible to point 

 out the limit of the middle beach only in a loose way. For the 

 present we regard the upper beach as occupying the ridge and the 

 area behind it. Here the flora is very diversified, fva fruteseens 

 is the first shrub to make its appearance, and this almost always 

 heavily attacked by Cuscuta Gronovii. In lower places Spartina 

 polystaehya and .S. jimciformis and Sporobolus Virginicus are quite 

 abundant. On the crests of the ridges Dondia maritima and Atri- 

 plex cristata, while here and further back Lyciuin Caroliniamtm,Bor- 

 richia fruteseens, Chrysoma paiiciflosculosa, and Opuntia Opuntia 

 are the chief perennials. Among these Ambrosia artcmisacfolia, 

 Leptilon Canadense, Lepidium Virgiuieum, Elymus Virginicus, 

 Polygonum and Cakile fusiformis form a weedy growth. Creep- 

 ing over these plants are the vines Seutera palitstris, Vigna glabra 

 and Ipomoea sasrittata and /. commutata. 



Salt Marsh Vegetation 

 Muck Mars] i Formation {Plate u) 



The simplest salt marsh condition is to be found on those 

 islands which are small and lie in a protected position so that the 

 sea does not throw up the shell fragments which occur in the con- 

 tiguous waters. An island of such character is a low-lying, al- 

 luvial flat with a surface which is nearly level. The flora is limited 

 to a few species segregated usually in two easily recognizable asso- 

 ciations. These are the grass association, either mixed or pure, 

 and the Batis-Salicornia association. The former is to be found 

 more often near the shore where the surface is a little higher than 

 in the interior and is composed of Spartina (S. patens and S. 

 stricta), which in many places are largely replaced by Distichlis. 

 Other grasses are quite rare. The other association is composed 

 of succulents of two genera, namely, Bads maritima of tropical and 

 subtropical distribution, Salicomia Bigelovii and S. ambigua. The 

 first-named is by far the most dominant plant, forming in some 

 places a pure association covering acres of surface. A striking 

 character of the plant is the strong development of cortical 

 aerenchyma about the roots and the lower part of the stem. The 

 anatomical characters of this and many others of the American 



