THE LEAF. 59 



LEAF ARRANGEMENT. 



I. Take branches of basswood, elm, maple, and horse- 

 chestnut, and study the leaf arrangement. In winter the 

 position of the leaves of preceding years may be deter- 

 mined by the leaf -scars. 



Are the leaves placed advantageously as regards expos- 

 ure to light ? Cf .- Lubbock, Flowers, Fruits, and Leaves, 

 pp. 103-114. 



II. Compare other plants, e.g. primrose and fuchsia, 

 dandelion and geranium, with regard to this principle. 



III. Try the effect of putting the leaves of one species 

 on the branches of another, without changing the leaf 

 arrangement. 



MINUTE ANATOMY. 



I. With a pair of fine forceps strip off a portion of the 

 epidermis of a hyacinth leaf. Mount in water and examine 

 under the high power of a compound microscope. Observe 



1. The elongated epidermal cells destitute of chlorophyll. 



2. The stomata, each with two reniform guard-cells con- 



taining chlorophyll bodies. Draw. 



II. Place a small portion of a leaf of the English ivy 

 between two pieces of pith, and, with a keen razor, cut a 

 number of transverse sections. Examine under the com- 

 pound microscope. Select a section that shows all the 

 structural details and draw accurately. Beginning with 

 the upper surface the section shows 



1. The upper epidermis, consisting of a single layer of 

 thick-walled cells, destitute of chlorophyll. 



