PLATE IV. = 
Fig. 15.—Portion of stem: ft, trichomes; e, epidermis; y, palisade; 
bf, bast fibers. » 325. 
Fic. 16.—Surface view of stem epidermis: s, stoma; h, scar of tri- 
chome. 175. q 
Fic. 17.—Cross section of stem, one year old, showing longitudinal sec- 
tion of a stoma: st, p, palisade; cl, chloroplasts; g, guard cell; 7, air 
chamber; the cuticle is shaded black.  » 475. 
Fic. 18.—Longitudinal section of stem, showing cross section of a 
stoma. 475. 
Fic. 19.—Longitudinal radial section of stem cambium: c, cambiform 
cell of the phloém. x 325. 
