212 APPENDIX. 



No. VII. 



THE LEAF. 



i. Imbed in pith a piece of Hellebore leaf preserved in 

 alcohol: cut sections at right angles to the midrib of the leaf 

 and mount in dilute glycerine. Shew on your sketch : 



a. epidermis of the upper surface; the cells contain 

 protoplasm and a nucleus but no chlorophyll-corpuscles ; 



6. palisade cells of the mesophyll ; 



c. spongy tissue of the mesophyll ; 



d. epidermis of the lower surface similar to a., but 

 with stomata whose guard cells contain chloroplasts. 



ii. Strip off a piece of the lower epidermis of a fresh 

 living leaf and mount in water. Shew on your sketch : 



a. epidermal cells with sinuous outlines, containing 

 no chloroplasts; 



b. stomata, each with two kidney-shaped guard cells, 

 containing chloroplasts. 



iii. Place the lamina of a living leaf of Ranunculus 

 ficaria, Limnocharis Humboldtii, or Arum maculatum in 

 a glass of water ; then suck at the end of the leaf-stalk 

 (petiole) watching the lower surface of the lamina. As the 

 sucking proceeds, the leaf appears sodden, the darkening 

 in colour being due to the entrance of water into the 

 intercellular spaces. 



iv. Examine a branch of Groundsel (Senedo vul- 

 garis) to observe the phyllotaxis or order of succession of 



