HISTOLOGY OF ASARUM VIRGENTICUM. 487 



Hypodermal aolleueltij matte tissue beneath the midvein, palisade 

 not interrupted above it. 



Stereome massively developed around the mestome bundles, com- 

 pletely surrounding them, but espeeially strong above and below 

 them, very thick-walled. 



Smilax walteri Pursh. 



Ilygrophile Forest formation. 



Leaf not thick, deciduous, approximately isolateral. 



Epidermis: Cells containing much chlorophyll (espeeially those of 

 the ventral surface), walls — especially the outer — thickish, the radial 

 walls somewhat undulate on the ventral face, not undulate on the 

 dorsal. Stomata few on the ventral face, numerous on the dorsal, 

 about level with the surface, lying in all directions, each bordered by 

 three to four undifferentiated epidermis cells. Hairs, none. 



MesophyU homogeneous through the leaf; palisade none, but inter- 

 cellular spaces rather larger on the dorsal side. 



Smaller mestome bundles entirely surrounded by rather thin-walled 

 stereome. 



Phoradendron flavescens (Pursh) Nutt. 



Ilygrophile Forest formation. 



Leaf isolateral, thick, leathery, glabrous; veins, even the midvein, 

 embedded in the mesophyll. 



Epidermis: Cell walls straight, thick; cuticle thick, smooth. Sto- 

 mata on both faces, lying in all directions, each bordered by a pair of 

 subsidiary cells which are larger than the guard cells. Hairs none. 



Mesophyll perfectly homogeneous, compact, in about ten layers of 

 nearly isodiametric cells without intercellular spaces. 



Groups of stereome adjoin the mestome bundles on both the hadrome 

 and the leptome sides. 



ASARUM VIKGINICUM L. 



Forest (nonhygrophile) formation. 



Leaf thickish, bifacial, smooth, punctate with semi transparent 

 points. 



Epidermis: Ventral, cells rather large in all dimensions, radial 

 walls undulate; l the cuticle delicately wrinkled, thick, smooth, except 

 on the leaf margins. Dorsal, cells smaller, lower, radial walls thicker 

 and less undulate, the walls collenchyniatically thickened beneath the 

 midvein. Stomata confined to the dorsal surface, rather large, level 

 with the surface, lying in all directions, each bordered by four to six 

 ordinary epidermis cells. Rounded secretion cells numerous (one to 



'Solereder states that the cells of the epidermis on hoth faces have pitted walls 

 (Engler's Bot. Jahrk, vol. 10, p. l l -'7). 



23501'— No. 6—01 12 



