133 BOTANY. 



The relation of the intercellular spaces of the leaves to the canals of 

 the petioles may be studied by carefully made longitudinal sections. 



(c) The resin canals of Silphium laeiniatum and 8. perfoliatum, and 

 the turpentine canals of Coniferae, furnish excellent examples of the 

 larger secretion reservoirs, while the smaller ones may be studied in 

 the cavities in the rind of the orange and lemon, the leaves of Dietam- 

 nus, Xantliox'il/um, Rue (Ruta), Hypericum, and many Labiatae. 



