306 THE PLANT COVERING OF OCRACOKE ISLAND. 



Ducts (probably resiniferous) numerous, especially near the dorsal 

 surface, apparently always lying in the plates of water 1 issue, one 

 below the leptome of the midvein. 



Mestome bundles of the larger veins with a narrow (in transverse 



section crescent -shaped) group of comparatively thin-walled stereome 



above the hadrome. 1 



Aster tenuifolius L. 



Leaves narrow, almost vertical, isolateral, thick, with a deep groove 

 on the dorsal surface on each side of the midvein, margins slightly 

 incurved. 



Epidermis: Cells comparatively large, walls not undulate, the outer 

 greatly thickened; cuticle wrinkled and with slight furrows corre- 

 sponding to the radial walls of the epidermal cells; stomata rather 

 few and large, the guard cells slightly sunken, mostly somewhat 

 deflected in direction from that of the leaf axis, bordered by usually 

 3 ordinary epidermis cells; hairs none. 



Hypodennal cullenchyma in a few narrow layers above and rather 

 wide layers below the midvein. 



CMorenchyma consisting of palisade with high, narrow cells, in 

 about L 2 layers on both faces, strongly converging toward the mid- 

 vein, especially on the ventral side. 



Colorless parenchyma (water-storage tissue) occupying the interior 

 of the leaf in small quantity, and surrounding the midvein, where it 

 replaces the palisade. 



Mestome bundles not reinforced by stereome. 



Aster subulatus Michx. 



Leaves wider and thinner than in the preceding, almost vertical, 

 isolateral, Hat, impressed above the midvein, which below is promi- 

 nent, with a furrow on each side of it. 



Epidermis: Cell walls not undulate, thick, the outer very thick, 

 the inner collenchymatic-thickened where hypodennal collenchyma 

 occurs; cuticle wrinkled; stomata, with guard cells lying parallel to 

 the leaf axis, level with the surface; hairs none. 



Hypodermal collenchyma above and below the veins (about 4 layers 

 between the leptome of the midvein and the dorsal epidermis) and in 

 the marginal angles. 



C More n city ma of compact palisade, occupying practically the entire 

 thickness of the leaf except where collenchyma occurs and about the 

 midvein. 



'The leaves of nonmaritime species of Solidago (e. g. , S. petiolaris, S, neglecta, 

 and »9. erecta) exhibit some interesting differences from S. sempervirens. All three 

 have bifacial leaves with compact palisade and open pneumatic tissue (chloren- 

 chyma least differentiated in S. petiolaris). Stomata few (S. erecta, S. neglecta) 

 or none (.S*. petiolaris) on the ventral surface, guard cells slightly prominent on 

 the dorsal surface. Hairs along the veins, especially on the dorsal face in S. petio- 

 laris, IS or J celled sharp-pointed, bent. 



