of Mississippi and Louisiana 79 



vium of the marsh so as to make a looser soil which is less homo- 

 geneous and better aerated. It happens also that the area may be 



better drained. 

 nodiflora, LithopJdla 



ate (Lippia 

 Salicor/iia, 



one species of which has plagiotropous shoots. With these there 

 was found on Bird Island a single plant of Citrullus vulgaris, a 

 plant mentioned also by Kearney as occurring in a feral state on 

 Ocracoke. Limoninm Nashii grows usually in such a soil, and is 

 to be found for the most part on the lee margin of the shell dune. 



' Sand Marsh Formation 



On the larger islands the sand covering of the lee part of the 

 island is sometimes so thin that the alluvial foundation is hidden 

 by only a few centimeters. In limited areas, however, the depth 

 of the sand may be greater. In these two ways the conditions 

 for a sand marsh are set up in which the plants may be rooted in 

 pure sand or partly in the underlying alluvium. . The latter con- 

 dition is especially favorable for the formation of a reed marsh in 

 which species of Juncus are the chief factors. Marshes of this 

 kind are sometimes of large area. When the sand covering is 



very thin, as is the case in parts of Breton Island, the sand marsh 

 takes something of the character of the muck marsh, and Batis 

 and Salicornia may occur. When the depth of sand is greater, 

 which happens more frequently at a point more remote from the 

 influence of the salt water an association of plants grows up in 

 which Xyris serotina, Utricularia subulate and Olden/a ndia uniflora 

 are prominent members. The more shoreward stretches of wet 

 sand are either naked or bear a sparse growth of small plants. 

 Among the number are Siphonychia corymbosa, Polypremum pro- 

 cnmbens, Gratiola subulata and Diodia Virginiana. 



■ The Mud Lumps 

 The top soil of these islands is very thin, overlying a dense, 

 sticky clay. The usual marsh and aquatic plants are almost 

 wholly wanting, as are also pines and oaks. The more abundant 

 grasses are Spartina stricta and Capriola Dactylon. The only large 

 trees are melias which have doubtless been introduced. On one 

 of these islands a dense growth of a trailing Rubus not observed 



