7i8 



BOTANY AND PHARAIACOGNOSY. 



aggregates of calcium oxalate in the lower epidermal cells. Crom- 

 well leaves {Lithospcrnuim officinale) have stiff, scythe-shaped 

 hairs with centrifugal thickening of cuticle. Maple leaves {Acer 



Fig. 281. Forms of calcium oxalate crystals: A, transverse section of rheum show- 

 ing rosette aggregates of calcium oxalate in three of the cells and starch grains in some of 

 the others; B, longitudinal section of scilla showing raphides; C, longitudinal section of 

 quillaja showing large monoclinic prisms of calcium oxalate and also some starch grains; 

 D, transverse section of belladonna root showing one cell filled with sphenoidal micro-crys- 

 tals, the remaining cells containing starch. 



Negnndo) have non-glandular and glandular hairs, the latter with 

 2- to 3-celled stalk and large, unicellular head. Meadow-sweet 

 (Spircca Ulniaria) has unicellular, thin-walled, non-glandular 

 hairs, the hasal walls of which are truncate ; the glandular hairs 



