SECRETING CELLS IN GENERAL 



2OI 



sisting of a more or less globular group of 

 cells; and the interior tubular type in the 

 form of a tube or canal. Glands belonging 

 to the first type, commonly known as 

 glandular hairs, arise by the tangential 

 division of a protoderm cell producing 

 a multicellular hair, the apical cell of 

 which enlarges and becomes the secreting 

 cell (Fig. 1 08, A), or a group of secreting 

 cells may compose the gland at the apex. 

 Nectaries are usually of protodermal 

 origin and their cells are frequently 

 elongated radially in the form of papillae 

 (Fig. 108,^). 



. ill l J u protoderm, and g, g, from 



The interior globular glands arise by the fundamental tissue. 



the division of a cell or group of cells, 



usually of the. ground meristem, and 



where these glands lie near the surface 



the protoderm may by cell-division con- 

 tribute cells to their formation (Fig. 

 109); or sometimes the protoderm 

 alone gives rise to the gland. Glands 

 of the globular type are found in 

 the clove, rind of orange and lemon, 

 etc. (Fig. no). 



An intercellular cavity into which 

 the secretions of the glandular 

 cells are excreted is formed in one 

 of two ways: The secreting cells 

 may split apart at the center of 

 the group and then draw or grow 

 away from the line of separation, 

 leaving an intercellular cavity (Fig. 

 in), or the secreting cells may 

 break down altogether, leaving 

 their secretions in the cavity 



Fl<;. 109. Formation of 

 an interior, globular, ly- 

 sigenous gland of the leaf 

 of Dictamnvis fraxinella. 

 A, g, g and c, mother cells 

 of the gland ; c, from the 



B, older stage where the 

 cells have begun to form 

 the secretion. The last 

 stage is shown in Fig. 112. 

 (After Sachs.) 



FIG. no. Cross-section through 

 a portion of orange peel showing 

 the cavity of an interior, globular 

 gland at g; crystals of hesperidin at 

 h; calcium oxalate crystals at k. 

 (After Tschirch and Oesterle.) 



