LEAVES— STRUCTURE OR ANATOMY Cjt 



Suggestions. — To study epidermal 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 the plane surface? 

 Color? 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, color, 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. 



