70 



BOTANY 



PART I 



which the secretion has been formed and the walls gradually dissolved. 

 The secretory cavities filled with ethereal oils in the orange and 

 lemon have this origin. 



6. Glandular Cells and Glandular Tissue. Glandular cells, 

 which excrete substances from their protoplasts to the outside or into 

 the intercellular spaces, occur singly or in groups in the epidermis, in 



FIG. 75. Glandular hair from the 

 petiole of Primula sinensis. (x 142. 

 After DE BARY.) 



FIG. 76. Glandular scale from the female inflores- 

 cence of the Hop, Humulus lupulus, in vertical 

 section. A, before, B, after the cuticle has become 

 distended by the secretion. In B the secretion 

 has been removed by alcohol, (x 142. After 

 DE BARY.) 



the parenchyma, and in other tissues. The glandular cells resemble 

 parenchymatous cells, but have as a rule abundant protoplasm and 

 large nuclei as in meristematic cells. The excreted substances are 

 usually end products of metabolism and frequently have an ecological 

 significance. Closely connected glan- 

 dular cells forming a layer constitute 

 a GLANDULAR EPITHELIUM. 



Glandular epithelia or isolated 

 glandular cells are of frequent occur- 



FIG. 77. Sessile digestive gland from the upper side 

 of the leaf of Pinguicula vulgaris. A, In longi- 

 tudinal section. B, Seen from above. (ROTHERT 

 altered from FENNER.) 



FIG. 78. Schizogenous oil-reservoir in a 

 cross - section of the leaf of Hypericum 

 perforatum. S, the glandular epithelium. 

 (After HABERLANDT.) 



rence in the epidermis and are often covered by a porous cuticle. In 

 this situation glandular hairs, the knob-shaped end cell of which is 

 secretory (capitate hairs, Fig. 75), -also occur. Other glandular hairs 

 may be scale-shaped (Fig. 76), and glandular emergences (Fig. 56) 

 are also found. The secretion is very often composed of resinous 



