PLATE XVIII. 



Fig. 23. Tangential section of bleached leaf of X. globosum, showing 

 relation of trichomes to veins, x 43. G, veins; H, trichome. 



Fig. 24. Large trichomes from leaf of X. americanum. x 193. /, 

 cells at base of hairs ; J, stoma ; K, epidermal cells ; L, basal cell of hairs. 



Fig. 25. Diagram of cross section of stem of X. americanum. x 11. M, 

 collenchyma; N, resin duct; O, bast; P, phloem; Q, xylem; R, pith; S, 

 parenchyma of pericycle. 



Fig. 26. Diagram of cross section of stem of X. pennsylvanicum. 

 X 11. T, collenchyma; U, parenchyma of pericycle; V, resin duct; W, 

 bast, X, phloem; Y, xylem; Z, pith. 



Fig. 27. Diagram of cross section of stem of X. globosum. x 11. A, 

 epidermis; B, collenchyma; C, parenchyma of pericycle; D, resin duct; E, 

 bast; F, phloem, G, xylem. 



