348 
ILLUSTRA TIONS. 
Plate XII. 
MORPHOLOGY OF THE LEAF. 
Fig. 65. — A leaf of Viola tricolor showing lamina, petiole, stipules 
and the distribution of the veins. 
Fig. 66. — Transverse section of midrib of leaf of stramonium : 
(EU), upper epidermis; (CO), collenehyma; (PA), 
palisade cells; (0), layer of cells containing rosette- 
aggregates of calcium oxalate; (M), loose mesophyl ; 
(EL), lower epidermis; (OP), prisms of calcium oxalate; 
(OS), cryptocrystalline crystals of calcium oxalate; 
(ST), stoma; (T), ducts; (SU), sieve on upper side of 
ducts; (SL), sieve on lower side of ducts; this 
arrangement of sieve and ducts forming hicollateral 
fibrovascular bundles. 
Fig. 67. — Transverse section through lower surface of leaf of stra- 
monium ; stoma, with guard cells, (G); (N), surrounding 
cells; (A), intercellular cavity usually tilled with cell 
sap or watery vapor; (E), epidermal cells. 
Fig. 68. — Surface section of upper surface of leaf of Viola tricolor 
showing four stomata. 
Fig. 69. — Surface section o( under surface of leaf of Viola tricolor 
showing live stomata. 
Fig. 70. — A section through the margin of the leaf of Viola tri- 
color showing a tooth with three water pores. 
Fig. 71. — A water pore of Viola tricolor in surface section. 
