2^6 



THE PLANT COVERING OF OCRACOKE ISLAND. 



Croton maritimus Walt. 



Leaf flat, bifacial, both surfaces densely covered with a gray, scale- 

 like pubescence. 



Epidermis: Ventral, cells small, walls not undulate, thin; siomata 

 vei-y numerous, guard cells level with the epidermis, each stoma sur- 

 rounded b}^ 4 epidermal cells, 

 of which 2 are differentiated 

 as crescent-shaped subsidiary- 

 cells parallel with the guard 

 cells; hairs pluricellular, stel- 

 late, consisting of a long cylin- 

 drical stalk rising above the 

 surface and composed of many 

 smaU cells partlj^ of subepi- 

 dermal origin, from the apical 

 cell of Avhich radiate in a 

 nearly horizontal plane nu- 

 merous unicellular, sharp- 

 pointed arms with thick, 

 smooth cuticle, cohering near 

 their bases so as to form a shal- 

 low cup. Dorsal, similar ; cu- 

 ticle thickened and granular 



Fig. 44. — Cro/o?i maritimus— Yisiiv from dorsal leaf 

 surface, o. View from above; &, cross section; Ep, 

 epidermis; P, palisade. Scale 340. 



underneath the large veins; 

 stomata about equally numerous; hairs (fig. 44) with less numerous 

 and thinner-walled arms. 



Hypoderin^ none, except beneath the large veins, where several 

 layers of thin- walled collenchymatic tissue occur. 



Stereome, none. 



Chlorenchyma: Palisade in one layer, comi3act, the cells elongated, 

 interruiDted onh^ by thick-walled, branching, sclerotic idioblasts; 

 pneumatic tissue of roundish cells. •* 



Ilex vomitoria Ait. 



Leaf evergreen, thick, shining and dark green above, bifacial. 



Epidermis: Ventral, cells rather high (but small in their diameter 

 parallel to the leaf -surf ace), the outer wall and cuticle much thick- 

 ened but not nearly so high as the cell lumen, radial walls rather 

 thin, undulate; cuticle smooth; stomata none; erect, short, stout, 

 pointed, often curved, prickle-like unicellular hairs with ver^^ thick 

 walls (lumen almost obliterated) and smooth cuticle along the mid- 

 vein.* Dorsal, cells smaller, thicker- walled (outer wall and cuticle 

 exceeding the cell lumen in height), the radial walls nearly straight, 

 porous; cuticle Avrinkled; stomata very numerous, guard cells slightly 

 depressed; hairs, none. 



' This specie*! is, therefore, an exception to the rule that evergreen leaves have 

 no hairs on the upper or ventral surface. (See Lalanne, p. 117.) 



