84 HARSHBERGER— LEAF STRUCTURE OF [April 23, 



shaped, coarsely toothed, or the upper leaves entire. The upper 

 epidermal cells have a considerably thickened outer wall with a 

 warty cuticle. Stomata occur on both leaf surfaces with their 

 guard cells not depressed below the surface. Palisade chlorenchyma 

 of two rows of cells extends to the centrally placed bundles of the 

 leaf and it is rather openly arranged. The loose parenchyma with 

 large spaces shows its cells generally directed in a vertical manner, 

 suggesting a staurophyll, but the bifacial structure is clearly recog- 

 nizable, so that we may classify the leaf as a diphotophyll. The 

 lower epidermis of thin-walled cells shows a roughened outer cell 

 wall surface. 



Ampelopsis quinquefolia (Plate IV, Figs. 20 and 20a). — The 

 Virginia creeper with a compound leaf with five leaflets is an ele- 

 ment of the dune flora of New Jersey. It begins to ascend forest 

 trees, and if these trees are surrounded by drifting sand, the vine 

 spreads out over the sand surface. In other places, it grows on 

 the surface of the dunes and helps to bind the wind-blown sand. 

 The sand-grown plants have leathery leaves in which the upper 

 epidermal cells are compact with the outer wall thickened and its 

 surface rugose. Two rows of palisade cells may be found and the 

 loose parenchyma occupies the other half of the leaf below the 

 midrib and the veins. Tlie stomata are not sunken, and the leaf 

 is a typic diphotophyll. 



Salt Marsh Plants. — The plants of this group are all of them 

 true halophytes, and at the conclusion of the description which fol- 

 lows of the histology of their leaves, a comparison will be drawn 

 between their leaf structure and that of the leaves of the sand 

 strand plants previously described. 



Spartina stricta maritima {=S. glabra) (Plate V, Figs. 21 and 

 21a). — The salt marsh grass is a tall species 0.6-2.4 m. high, leafy 

 to the top and growing along the shore in pure salt water. The 

 leaves are 5-7 dm. long, 1-1.5 cm. wide, usually flat, but sometimes 

 involute. The lower epidermal cells are strongly cuticularized, and 

 where the bundles occur they are reinforced with hypodermal scler- 

 enchyma. The upper leaf surface is raised into ridges, which are 

 covered with small cuticularized epidermal cells without hairs, while 



