302 THE PLANT COVERING OF OCRACOKE ISLAND. 



Sesuvium maritimum (Walt.) B.S.P.^ 



Z/ea/ isolateral, somewhat succulent. 



Epidermis cells with non undulate, radial walls, the outer some- 

 what thickened, some of the cells much larger and probably serving 

 for water storage; cuticle smooth; stomata Ij^ing in all directions, 

 guard cells level with the epidermis, each stoma bordered by 3 to 

 (usually 4 or 5) undifferentiated epidermis cells; hairs none. 



Stereome none. 



Chlorenchyma homogeneous and occupying the entire thickness of 

 the leaf, interrupted by large intercellular spaces, which lie beneath 

 the large (water- storage) epidermal cells. 



Mestome bundles with a small group of collenchyma on the leptome 

 side. 



Stein: Epidermis with cell walls, especially the outer, strongly 

 thickened. Stereome none. Collenchyma in small groups above the 

 leptome of the primary mestome bundles. Cells containing crystal 

 masses in the pith and a few in the cortex. 



TissA MARINA (L.) Britton.^ 



Leaf isolateral, hemicylindric, furrowed, margins sparsely ciliate, 

 especially toward base. 

 Epidermis with cells somewhat elongated parallel to the leaf axis, 

 the radial walls strongly undulate, the outer walls 

 slightly thickened; stomata always parallel to the 

 leaf axis, guard cells slightly prominent, lying usu- 

 ally between 2 ordinary epidermis cells and at right 

 angles to their dividing wall, but sometimes bordered 

 b}^ 3 cells; hairs (on the margins) glandular (fig. 46), 

 capitate, with a 3 or 4 celled stalk. 

 FIG. m.-Tissa mar- Stereome none. 

 ^■na— glandular hair CMorenchyma compact, its cells not elongated. 

 Scale 240^ margin. Colovless parenchyma (water tissue) constituting 



the interior mesophyll. 

 MesUyme bundle of the midvein small, lying deep in the water tissue, 

 with a small group of collench3ana outside the leptome. 



Stem: Epidermis with thick outer cell walls and wrinkled cuticle. 

 Outer cortex separated from the inner by an unbroken, 2-la3^ered ring 

 of stereome, with cell walls (especially of the inner layer) compara- 

 tively thin. 



^ Sesuvium pentandr} nil Ell. — Compare Warming's description and figure of 

 ^. portulacastrum, Halofj^t Studier. pp. 180, 211. 

 ■^ Spergularia salina J. and C. Presl. 



