474 



A TEXTBOOK OF THEORETICAL BOTANY 



as they are called, for example, turpentine in the Pines ; or they may 

 produce mucilage, another common secretion. 



Sclerotic sheath 



Epithelium 



Fig. 464. — Pitius sylvestris. Transverse section of schizo- 

 genous resin canal with lining epithelium and sclerotic 

 sheath. 



Fig. 465. — Euphorbia splendem. Latex tubes in 

 stem cortex. 



A peculiar type of internal secretion is that known as latex. This is also 

 formed in extensive canal systems throughout the tissues of those plants in 

 which it occurs, but these canals are not intercellular spaces but are greatly 

 elongated cells, inside which the secretion is formed (Fig. 465). Frequently 



