SECRETING CELLS IN GENERAL 



20I 



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. io8, 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. io8,5). 

 The interior globular glands arise by 



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, 

 Fig. 1 10.— Cross-section through leaving an intercellular cavity (Fig. 



a portion of orange peel showing \ .i .• n 



the cavity-of an interior, globular ^^^)^ ^^ ^^ SeCrCting CcUs Hiay 



gland at g; crystals of hesperidin at break doWIl altogether, leaving 



h; calcium, oxalate crystals at fe, , . . 



(After Tschirch and Oesterie.) their sccretions 111 the cavity 



Fig. 109. — Fornmtion of 

 an interior, globular, ly- 

 sigenous gland of the leaf 

 of Dictamnus fraxinella. 



A, g, g and c, mother cells 

 of the gland; c, from the 

 protoderm, and g, g, from 

 the fundamental tissue. 



B, older stage where the 

 cells .have begun to form 

 the secretion. The last 

 stage is shown in Fig. 112. 

 (After Sachs.) 



