304 



THE PLANT COVERING OF OCKAOOKE ISLAND. 



Hypoderm continuous, 1- layered. Outer cortex with rather thick- 

 walled cells, containing chlorophyll; inner cortex gradually becoming 

 thinner-walled and colorless. 



Siereome in a concentric band of isolated groups, lying inside the 

 middle of the cortex. 



Lactiferous ducts few, lying just outside the mestome bundles. 



Mestowe bundles bioollateral, 

 perilepfomatic, the leptome most 

 strongly developed on the outer 

 periphery of the hadrome. 



LlPPIA NODIFLORA Mx. 



Leaf* imperfectly bifacial, usu- 

 ally horizontal, but sometimes 

 vertical. 



Epidermis alike on both sur- 

 faces, cell walls thick, not undu- 

 late; cuticle wrinkled; stomal a 

 (fig. 47) lying in all directions, 

 guard cells almost level with the 

 ventral surface, slightly depressed 

 on the dorsal surface, each stoma 

 bordered by 2 crescent-shaped, 

 chlorophyll - holding, subsidiary 

 cells which are usually at right 

 angles to but often nearly or quite 

 parallel to the guard cells, and of 



«. ,, ,-,.., , ,.,„.« • which one is usually considerably 



a, Stomataon leaf; b, hair and stoma on ventral larger than the other; hairs abun- 

 leaf surface; e. hair on dorsal surface. Scale , „ nij.ii 



340 dant on both faces, parallel to 1 lie 



veins, appressed, lying in slight 

 grooves of the epidermis, each attached by its middle (hence 2-armed) 

 to a short cylindrical foot cell, which is bordered by several wedge- 

 shaped (as seen from above) radially arranged epidermis cells, the 

 free cell with a very thick, warty cuticle. 



Hypodermal coUenchyma (not very typical), in 1 or 2 layers above 

 and 3 or 4 below the principal veins, interrupting the chlorenchyma 

 in full-grown leaves. 



Chlorenvltyma : Palisade 2-layered, the cells rather short; pneu- 

 matic tissue rather compact, not well differentiated from the palisade, 

 but its cells more nearly isodiametric and containing less chlorophyll. 



Mestome bundles (of larger veins), with some stereonie below the 

 leptome and a small group of collenchyma above the hadrome, which 

 finally becomes continuous with the subepidermal group of col- 

 lenchyma, 



■Compare Warming. Halofyt-Stndier, p. £{:{, ami Solereder, Syst. Anat.,p. 71:?, 



Fio. 47. —IJppia uiHh'florn stomata and hairs. 



