314 THE FOLIAGE LEAF 



the vestibule and of the walls of the guard cells, and that the 

 latter bulge into the adjacent epidermal cells. Note the inter- 

 cellular spaces and the mesophyll cells below the stoma. 



Examine also in the same section and draw a vascular 

 bundle in cross-section, distinguishing (a) xylem with vessels and 

 tracheids, including the narrow protoxylem elements at the 

 extremity of the bundle, (b) phloem with sieve iubes and companion 

 cells, (c) fibres. Treat with aniline chloride or aniline sulphate. 

 The lignified tissues stain bright yellow. 



(6) Cut the end of the leaf stalk of the floating leaf of Limnocharis 

 across with a sharp knife, place the blade in water, and suck the 

 end of the stalk vigorously. Dark patches appear in the leaf 

 blade owing to water being sucked in through the stomata and 

 filling the large intercellular spaces which communicate with 

 those of the leaf stalk. 



(7) Examine the shoots of Gorse ( Ulex) . Note the arrangement 

 of leaves, branches and buds. The leaves are narrow and 

 spinous, but not so rigid as the branch spines. 



(8) Examine any other examples of needle-shaped, bristle- 

 like, folded or rolled leaves that may be available, both on the 

 plants and in section. 



