HOW TO STUDY LEAF HISTOLOGY 301 



pared by making free-hand cross-sections of leaves held between two 

 pieces of pith or cork, and mounting the material in water. Study 

 such leaves as ivy (Hedera helix), begonia, cycas, geranium, and corn. 

 Note the number of layers of palisade cells, the spongy parenchyma, 

 the epidermal layers. Which cells bear chlorophyll? Write a brief 

 description of the tissues of each leaf, and make a drawing of the geranium . 



To study stomates in. cross-section: In the cross-sections of leaves 

 of geranium, corn, ivy, lily, or spider-lily prepared for the above exper- 

 iment, look for the stomates and make a careful drawing from the one 

 you can see best. 



Study of stomates in surface 

 view: From the under surface of 

 leaves of geranium and impatiens, 

 peel bits of epidermis by tearing 

 the leaf. Mount these in water 

 and examine under low power. 

 Are the stomates scattered or in 

 groups? With the aid of a higher W^ 474 . Leaf ^ 10Br of the plane . tree or 



power, draw a few Stomates show- I sycamore. The scar surrounds 



ing their guard-cells and the sur- '** <? ^ which was covered by 



the hollow base of the petiole. 



rounding epidermal cells. Make _^s 



a similar study and sketch of the epidermis torn from the under surface 



of a Begonia sanguinea leaf. 



The openings or pores are known as stomata, singular stoma; also as 

 stomates, singular stomate. 



NOTE ON SCOPE, APPARATUS, AND METHODS. The work outlined 

 in Part III is sufficient, if well done, to occupy one period of the pupil's 

 time each school day for six weeks. These chapters are intended 

 only as laboratory guides. The pupil should work out each structure 

 or part for himself before taking up the succeeding subject. The work 

 in this Part deals with only the elements of the subject, but it is as 

 much as the pupil can hope to take up with profit in an outline course. 

 Apparatus. The apparatus necessary for the work outlined in 

 these chapters on histology may be secured from dealers in micro- 

 scopes and laboratory supplies at a low figure. Schools should obtain 

 catalogues from the following and other reliable dealers: 



Bausch & Lomb Optical Co., Rochester, N. Y. 



Eimer & Amend, New York. 



The Franklin Educational Co., Boston. 



Ward's Natural Science Establishment, Rochester. 



Richards & Co., Chicago and New York. 



