LEAVES — STRUCTURE OR ANATOMY 9I 



Suggestions. — To study epider7nal hairs : 75. For this study, 

 use the leaves of any hairy or woolly plant. A good hand lens will 

 reveal the identity of many of the coarser hairs, A dissecting micro- 

 scope will show them still better. For the study of the cell structure, 

 a compound microscope is necessary. Cross-sections may be made 

 so as to bring hairs on the edge of the sections; or in some 

 cases the hairs may be peeled or scraped from the epidermis and 

 placed in water on a slide. Make sketches of the different kinds of 

 hairs, 76. It is good practice for the pupil to describe leaves in 

 respect to their covering : Are they smooth on both surfaces ? Or 

 hairy? Woolly? Thickly or thinly hairy? Hairs long or short? 

 Standing straight out or lying close to the surface of the leaf ? 

 Simple or branched? Attached to the veins or to the plane surface? 

 Colour? Most abundant on young leaves or old? 77- Place a 

 hairy or woolly leaf under water. Does the hairy surface appear 

 silvery ? Why ? Other questions : 78. Why is it good practice 

 to wash the leaves of house plants? 79. Describe the leaf-scars 

 on six kinds of plants : size, shape, colour, position with reference 

 to the bud, bundle-scars, 80. Do you find leaf-scars on mono- 

 cotyledonous plants — corn, cereal grains, lilies, canna, banana, 

 palm, bamboo, green brier? 81, Note the table on page 88. 

 Can you suggest a reason why there are equal numbers of stomates 

 on both surfaces of leaves of tradescantia and flag, and none on 

 upper surface of other leaves? Suppose you pick a leaf of lilac 

 (or some larger leaf), seal the petiole with wax and then rub 

 the under surface with vaseline ; on another leaf apply the vaseline 

 to the upper surface ; which leaf withers first, and why? Make a 

 similar experiment with iris or blue flag. 82. Why do leaves and 

 shoots of house plants turn towards the light? What happens 

 when the plants are turned around? 83. Note position of leaves 

 of beans, clover, oxalis, alfalfa, locust, at night. 



