THE STEM. 21 



stems. Before closing this chapter on stems, let me tell 

 you something of the Cuticle, Eiyidermis, and Barh, 



Sectio:n- II. — Cuticle. 



42. The cuticle is a membranous substance covering the 

 Avhole plant from root to anther-box, with the exception 

 of the spongioles and the stigmatic surface of the pistil. 



43. The epidermis is the exterior layer of the true bark ; 

 it also underlies the cuticle of the leaves, etc. Under the 

 microscope it is seen to consist of layers of flattened cells, 

 sometimes of one layer only, again of many. This mem- 

 brane is full of pores on the under side of the leaf. These 

 mouths are very evidently designed to carry off all super- 

 fluous moisture and unnecessary gases elaborated by the 

 assimilation of sap. Upon the epidermis are found various 

 organs, as Hairs, Stings, Prickles, Gla^^dular hairs. 

 Scurf, and Lenticels. 



44. Hairs are formed of cells proceeding from the epi- 

 dermis. They are covered with the cuticle. 



45. Stings differ from hairs in the fact that they sprii^g 

 not immediately from the epidermis, but from cells rising 

 above it, which cells contain an active poisonous fluid 

 which is sent up the hollow hair and through the orifice 

 at the top by the slightest pressure. Prickles are from the 

 cuticle, and are hooked and stiff. They Ml off as the 

 stem increases, and are therefore found upon new wood, 

 and very rarely upon old. 



46. Scurf is a scaly substance, caused, as some botanists 

 suppose, by the cohesion of many minute hairs. 



42. What is the cuticle ? Where found ? 



43. What is the epidermis? Its appearance under the microscope? What is 

 this membrane full of? How are these pores formed ? Their use ? Mention the 

 names of the organs found in the epidermis. 



44. What are hairs ? With what are they covered ? 



45. What arc stings? IIow do they difler from hairs? What are prickles? 

 Do they adhere permanently ? . 



46. Scurf ? 



