494 BOTANICAL SURVEY OF DISMAL SWAMP REGION. 



the surface, each bordered by five to seven undifferentiated epidermis 

 cells. Hairs densely covering the dorsal surface of the young leaf, 

 especially along the veins; long, weak, flexuous, blunt-pointed, thin- 

 walled, unicellular. 1 



Palisade in one layer, the cells high, forming more than one-half 

 the thickness of the mesophyll. Pneumatic 1 issue with small Inclines. 



Sacs containing a milky fluid occur in the pneumatic tissue- and iu 

 the leptome of the veins. 



Veins prominent beneath, the larger reenforced above and below 

 by strongly developed, hypodermal eollenchymatic tissue. Mestome 

 bundles surrounded by a sheath of stereoine. Thin-walled, colorless 

 parenchyma in a few layers beneath the larger veins, lying between 

 the sterome and the eollenchymatic tissue. 



Bkrchemia scandens (Hill) Trelease. 



Hygrophile Forest formation, climbing high. 



Leaves ombrophobia thin, bifacial, veins very prominent beneath, 

 leaves not punctate. 



Epidermis: Ventral, cells large, high (i. e., extended at right angles 

 to the surface), the outer wall and the granular cuticle thickened, the 

 other walls thin, not undulate. Dorsal, cells similar, but with thinner 

 outer walls (except under the large veins). Stomata on the lower 

 face only, lying in all directions, level with the surface, each bordered 

 by usually four or five undifferentiated epidermis cells. Hairs none. 



Palisade in a single layer, very compact. Pneumatic 1 issue rather 

 open. 



Subepidermal coUenchyma in several very narrow layers above, and 

 several wide layers beneath the larger veins. 



Stereome rather thin-walled, weakly developed adjacent to the 

 hadromeand leptome of the larger veins, that beneath the leptome 

 separated from the subepidermal coUenchyma by several layers of 

 thin-walled, colorless parenchyma. 



Mucilage in the cells of the epidermis" and in one or two layers of 

 the colorless parenchyma beneath the mestome bundles of the midvein. 



1 "Several-relied glandular hairs in all species [of Acer] except A. distylum."— 

 Solereder, Syst. Auat., p. 271. I did not detect them in A. rubrum, even on quite 

 young leaves. 



- Heretofore known to occur in the mesophyll of Acer only in A. campestre.— 

 Solereder, Syst. Anat., p. 271. 



"Volkens (Flora der Aegyptisch-Arabischen Waste, p. 115) says of Zizyphus 

 itpinacrinti: "A great part of its extraordinarily high epidermis cells is filled 

 with cellulose slime. " 



Berchemia is one of the genera of Rhanmaceae in which there are no special 

 mucilage reservoirs, such as occur in Rhamnus, Ceanothus, and other genera of 

 this family, where they are found in the mesophyll, and in the primary cortex 

 and pith of the stem. U-uignard et Colin, Bull. Soc. Bot. de France vol 35 pp 

 88ft-827. ' 



Blenk ( Flora, vol. (17, p. 356 ) states that he docs not find mucilage in the epidermis 

 cells of any Rhanmaceae which have crystals of calcium oxalate in the palisade. 



