292 



THE PLANT COVERING OF OCBACOKE ISLAND. 



Mestome bandies each inclosed by a mestome sheath (figs. 38, 39, 40) 

 which has small cells with equally thickened walls; parenchyma 

 sheath with large, thin-walled cells containing chlorophyll where they 

 adjoin the palisade; mestome parenchyma in a single layer sepa- 

 rating the hadrome from the leptome of the larger bundles; com- 

 panion cells of the sieve tubes with much thickened walls. 



Fig. 40. —Chloris petraea— three small mnstnme bundles from tho blade. (Letters as in fig. ;j'.i. ) 

 In a the mestome sheath is thick- walled only on tho leptome .side; in b and c the thickening of 

 the mestome sheath is morn distinct and begins to show also on tho hadrome side. The sheath 

 is closed in all of those small bundles and is a true mestome sheath. Scale 500. 



UNIOLA PANIC ULATA L. 1 



Leaf rather thick and hard, more or loss involute when dry, deeply 

 furrowed on the ventral surface, the intervening ridges broad and 

 truncate or but slightly rounded at summit; dorsal surface with very 

 slight corresponding depressions. 



Epidermis: Ventral with cells smaller and thinner- walled than on 

 the dorsal surface, the outer walls more arched, many of the cells, espe- 

 cially on tho sides of the furrows, extended into short, stout, pointed, 

 unicellular, antrorse, prickle-like hairs with cuticle rough and exces- 

 sively thickened (lumen almost obliterated except toward the base); 

 stomata near the bottom of the ventral furrows; bulliform cells in very 

 small groups at the bottom of the furrows. Dorsal with conspicuously 

 pitted walls and very thick, 2 strongly wrinkled cuticle, 1 or sometimes 

 2 or 3 short cells alternating in the same rows with long ones; hairs 

 none; stomata less numerous than on ventral surface. 



Stereome strongly developed (more so than in any other of these 

 strand grasses) ; si rong, flattened subepidermal supports at the sum- 

 mits of the ventral ridges, separated from the mestome bundles by 

 thin-walled colorless parenchyma which also contains small, isolated 

 groups of stereome; narrow, mostly 2-layered subepidermal groups 

 on the dorsal side opposite the ventral furrows; strong subepidermal 

 supports on the dorsal side of each mestome bundle; finally, strong 

 marginal groups. 



Chlorenchyma: Palisade small-colled, radially disposed on each side 

 of each mestome bundle in single layers, which are perpendicular to 



1 Compare Holm, Bot. Gaz. vol. 16, pi JJ,ff. S to 12, 1801. 



4 But much loaa so than in Holm's material from Fort Monroe, Va, 



