i9o8.] OF THE SAND DUNE PLANTS OF BERMUDA. 107 



Conocarpns erectiis. — The leaves of this small tree, which is a 

 true mangrove plant, but which has adapted itself to growth on the 

 sand dunes in Bermuda, are thin and thick. The thin leaves are 

 found on the branches that are placed above the surface of the sand, 

 or in more or less protected positions, w^hile the thick, succulent 

 leaves occur near the surface of the sand, or in exposed, unshaded 

 positions. There is a considerable difference in the anatomical struc- 

 ture. The cuticle in the thin leaf is thickened and the stomata on 

 both sides are hardly if any sunken below the surface. The upper 

 leaf surface shows long palisade cells, while the palisade cells of the 

 lower side are shorter. The loose parenchyma cells form a broad 

 band in the center of the section. A diplophyll (Fig. 13, Plate III.). 

 The thick, succulent leaf has three rows of epidermal cells and 

 three rows of palisade cells, the cavities of which are filled with a 

 gummy, resinous material (not tested) of a brown color. This 

 gummy material is found in the lower palisade as well as in the 

 upper palisade in both the thin and thick leaves and also in some of 

 the loose parenchyma cells of the thick leaf. The stomata in the 

 thick leaves, by the increase in the thickness of the cuticle, are 

 sunken below the surface with an hour-glass atrium or passage out- 

 side of the thick-walled guard cells. The parenchyma cells of the 

 leaf center are arranged in the direction of the palisade cells. A 

 typical staurophyll (Fig. 13 A, Plate III.). 



Sccevola Plumicri. — This plant belongs to the family Goodeniaceae 

 and forms dense clumps on the dune slopes (Fig. 2, Plate I.). 

 Its leaves are alternate, elliptical, short petiolate and obtuse. They 

 are noted for their succulency. The epidermal cells on the upper 

 surface have a thick cuticle with numerous thick walled, sunken 

 stomata. The epidermal cells on the lower surface are of the same 

 thickness as on the upper surface, the stomata being likewise sunken. 

 The palisade cells on the upper and lower sides consist in each of 

 three or four row^s of cells, while the loose parenchyma is arranged 

 parallel to the palisade tissue. Only a single row of central cells 

 are not so disposed. The leaf shows, therefore, partly a staurophyll 

 and partly a diplophyll arrangement of cell (Fig. 14, Plate III.). 



Borrichia arhorescens. — This species of the family Compositae 

 exists in two distinct forms, if they are not good species. One form 



