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A TEXT-BOOK OF BOTANY. 



the cells (Fig. 134, c). Pores are rare, but when present they 

 are annular or slit-like. Collenchyma occurs near the surface 

 of plant organs, as herbaceous stems, when they form ribs, as 



FIG. 136. Various forms of stone cells: A, epidermis of hyoscyamus seeds; B, 

 pericarp of pimenta, containing brownish tannin masses; C, seed-coat of coffee; D, seed-coat 

 of almond; E, transverse section of seed-coat of white mustard showing beaker cells; F, 

 surface view of beaker cells of seed-coat of white mustard; G, transverse section through 

 stone cells of endocarp of olive, the lumen containing air; H, a stone cell from the periderm 

 of calumba, containing numerous monoclinic prisms of calcium oxalate; I, various forms 

 of stone cells isolated from pericarp of star anise. 



in the Umbelliferae. It is also found in leaves and in fruits, as in 

 the Umbelliferae. 



SCLERENCHYMA CELLS include all of those cells which have 

 more or less uniformly thickened walls composed of lignocellulose, 



