290 



THE PLANT COVERING OF OCRACOKE ISLAND. 



form cells. Dorsal as in S. patens, the short cells usually single, 

 hero and there rounded, with strongly thickened walls, almost form- 

 ing papilla 1 ; stnmata none; hairs none. 



Hijpodermal colorless parenchyma in a single layer beneath the 

 dorsal epidermis, 1 interrupted by subepidermal stereome. 



Stereome not strongly developed, a small subepidermal group on 

 the dorsal side of each mestome bundle; flattened supporting strands 

 (1 or 2 layers) at the summit of each ventral ridge, not decurrent 

 along its sides; also in the leaf margins. 



Chhrenchyma consisting of small palisade cells in a single layer, 

 radially arranged on each side of each mestome bundle and extend- 

 ing immediately beneath the epidermis to the stereome at the summit 

 of eacli ventral ridge; each 2 neighboring layers of palisade, between 

 each two nerves, either adjoining or separated by a few, large, color- 

 less parenchyma cells; chlorophyll also in most of the cells of the 

 parenchyma sheath. 



Mestome bundles with mestome sheath and mestome parenchyma 



much as in S. patens. Parenchyma sheath (around the mestome 



sheath) of large cells, those adjoining the palisade layer containing 



Chlorophyll, the sheath occasionally interrupted on the dorsal side of 



2 c the bundle by a few 



Be y^gs^7\Tm?>^cT-r>^^_. cells of tlie subepider- 



mal stereome. Large 

 parenchyma cells, in 2 

 or 3 layers, occupying 

 the thickness of the 

 ventral ridges and ap- 

 pearing to be an exten- 

 sion of the paren- 

 chyma sheath; when 

 in 3 layers, the middle 

 one colorless. 2 



FlG.87.— Chloris petraea— leaf blade. Transverse section, show- 

 ing tho midrib in the keel, covered by layers of colorless tis- 

 sue and a group of bulliform colls (BO on tho ventral sur 

 face; be, a small group of bulliform cells between two mestome 

 bundles. Tho mestome bundles are indicated by their paren- 

 chyma sheaths and by the stereome, which forms small sub- 

 epidermal groups. The thick walled mestome sheath is drawn 

 only in the two largo bundles. Scale 84, 



Chlorispetkaea Sw. 3 



Leaf (fig. 37) becom- 

 ing conduplicate when 



1 The .specimen figured by Duval-Jouve, loc.cit., has 2 or 3 layers. 



"Spartina stricta maritima (Walt.) Scribn., the common form elsewhere along 

 our Atlantic coast, is practically identical in leaf anatomy with S. stricta from 

 Ocraeoke, except in the following particulars: The epidermis cell walls on the 

 dorsal surface are thinner and less porous and show less of the wavy thicken- 

 ing; the short cells are more often in pairs, and, when single, are more often 

 papilliforin; stereome is somewhat more strongly developed, as would be expected 

 from the larger size of the plant and the greater length of the leaves. The mate- 

 rial examined was from Lynnhaven Bay, Virginia. 



'Figured by Duval-Jouve. Histotaxie, p. 355, j>l. 18, f. 1. For an example of 

 similar leaf structure compare the same author's paper, "Etude histotaxique des 

 Cyperus de France." Mem. de l'Acad. de Montpellier, tome T pi. 22, f. 6. 1874. 



