no 



Elementary Plant Physiology. 



taste, to determine the nature of the secretion (Figs. 80, 

 81). Make a careful examination to ascertain the manner 

 of extrusion of the secretion. In many instances it will be 



B 



Figf. 80. — A^ glandular hair from stipule of pansy iVzola tricolor) ; 5, glandular 

 hair from scale of ^scultcs hippocastaneum^ covered with excreted substance ; C\ 

 glandular hair from petiole of Primula Sinensis. 



found to be held between the outer walls of the gland and 

 the superficial layer of cuticle, and is only set free when the 

 cuticle bursts. Cypripediuni and Primula will offer interest- 

 ing material for the study of this point. 



119. Secretions serving as a protection. — Many of 



Fig. 81.— >4, glandular hair from inflorescence of the hop iHunmlus') ; B, same 

 after the cuticle has become distended by secretion; C, stinging hair of nettle 

 iUrtica dioica) ; i?, waxy secretion on stem of sugar-cane iSaccharum ojfflcina- 

 runi). 



the secretions formed by external glands are of such a nature 

 as to serve to repulse the encroachments of animals, and thus 

 damage to the body of the plant is avoided. The glandular 



