[7] 



82 



FLOWERING PLANTS 



Leaves. 



A . Examine the transverse section of the leaf-lamina provided. Make a drawing of the structure, shewing 

 (a) the epidermis and cuticle of the upper surface, (b) the palisade cells of the mesophyll, (c) the spongy tissue of 

 the mesophyll with large intercellular air-spaces, (d) the lower epidermis, its stomata and cuticle. Note also (e) the 

 vascular bundles. 



B. Mount another section in Schulze's solution. Note that the cuticle turns yellow while the cellulose-walls 

 and starch grains turn blue. 



C. Examine the leaf of geranium (Pelargonium) in the glass of coloured solution. Cut across the leaf-stalk 

 and veins and observe that the coloured solution has been sucked up in the wood elements of the vascular bundles. 



D. Strip off a piece of the epidermis from the lower surface of a leaf of Iris ; mount it in water and sketch 

 under a high power (a) a few of the epidermal cells, without chloroplasts, and (b) the guard cells, containing 

 chloroplasts, surrounding the pore of each stoma. Treat the upper epidermis similarly and note that stomata 

 are absent. 



E. Examine a transverse section of the leaf of Iris, and draw a vascular bundle, distinguishing (a) xylem 

 with tracheids, (b) phloem with sieve-tubes and companion-cells, (c) hard bast of fibres. Stain with analine 

 chloride. This turns lignified tissues bright yellow. 



Examine also and draw a stoma in transverse section distinguishing (a) guard-cells with cell cavities containing 

 chloroplasts, (b) cuticle of guard-cells and neighbouring epidermal cells, (c) vestibule, (d) pore of stoma. 



