HISTOLOGY OF XOLISMA FOLIOSIFLORA. 501 



Kpidenois; Cells alike on both surfaces, rather small, the radial 

 walls somewhat undulate, the tangential (especially the outer) greatly 

 thickened; cuticle thick, delicately wrinkled. Stomata confined to 

 the lower surface, large, lying in all directions, the ridges of entrance 

 slightly prominent, the guard cells with greatly thickened cuticle, 

 each bordered by usually five ordinary epidermis cells which they 

 greatly exceed in size. Hairs scattered over the surface of the mid- 

 vein on the dorsal side of the leaf, short, erect, conical, pointed, very 

 thick- walled, unicellular; also scattered pericellular glands on short 

 pericellular stalks. 



Hypoderm continuous on the ventral side of the leaf, one-layered, 

 its cells nearly iso-diametric, containing chlorophyll. 



Palisade one-layered, very compact, the cells little higher than 

 broad. Pneumatic tissue occupying most of the thicknessof the leaf, 

 very open, with large intercellular spaces, containing scattered crystal 

 cells (calcium oxalate). 



Mestome handle of the midvein strongly compressed in the plane of 

 the leaf. 



Hypodermal coUenchymatie tissue in one layer above and two or 

 three below the midvein. 



Stereome in a thin interrupted supporting band above and below the 

 midvein, also (rather thin-walled) in the leaf margin. 



Xolisma foliosiflora (Michx.) Small. 1 



Hygrophile Forest formation, usually in sunny places. 



Leaf comparatively thin, probably deciduous, bifacial, somewhat 

 shining above. 



Epidermis: Ventral, radial cell-walls somewhat undulate, the outer 

 and cuticle moderately t hickened ; cut icle strongly wrinkled. Dorsal, 

 radial walls strongly undulate; Ihe cuticle thinner and less wrinkled. 

 Stomata only on the lower surface, lying in all directions, about level 

 with the surface, each bordered by four to six undifferentiated epi- 

 dermis cells. Hairs confined to the lower surface, scattered, some- 

 what elongated, pericellular, glandular; also, along the midvein, 

 there are blunt-pointed, unicellular hairs with thick granular wall. 



Palisade in one compact layer of rather low cells. Pneumatic tissue 

 open. 



Hypodermal coUenchymatie tissue in one or two layers above and 

 two or three beneath the midvein. 



Stereome rather thin-walled, forming an almost uninterrupted thin 

 sheath around the larger mestome bundles. 



1 Compare Medenzu's characters for the nearly related Xolixma (Lyania) lignx- 

 trina in Engler's Bot. Jahrb., vol. 11. pp. ISO. 181 (1890). That species is described 

 as having two layers of palisade, the cells high and narrow. Its glandular hairs 

 are figured in t. ./, /. :/. Yesque ( Ann. de Sc. Nat. Bot., ser. 7, vol. 1, p. 235) describes 

 Lyonia pauienlata as having the palisade in two layers, and "the cells of both 

 layers alike are six to eight times longer than wide." 



