54 



LABORATORY AND FIELD EXEECISES 



a. Low-power study. Are all the cells of the epidermis 



alike in structure and form ? Do they have chloro- 

 plastids as a part of the cell contents ? Do they differ 

 in this respect ? 



b. A high-power study. 



Study the color- 

 less and the green 

 cells of the epi- 

 dermis very care- 

 fully with a high 

 power. Note the 

 shape and struc- 

 ture of each kind 

 of cell. How many 

 green cells are 

 grouped together ? 

 Are they separated 

 by a solid wall or 



is there a pore _, 



IIG. lo. Transverse section of a leaf 



e, e lt upper and lower epidermis with 

 thick outer wall (c) and stomate (st) ; p, 

 palisade cell layer with intercellular space 

 (o) below the stomate; sp, spongy pa- 

 renchyma with intercellular spaces (i) ; 

 ph, phloem ; x, xylem of a vein in section. 

 After Prantl 



between them ? 

 c. Drawing. Draw a few 

 cells of the epider- 

 mis of the leaf ac- 

 curately, indicating 

 the detailed struc- 

 ture of thestomataand the surrounding epidermal cells. 

 2. Leaf sections of a fresh leaf. Study transverse sections of 

 leaves cut from fresh material. Locate the main tissue 

 layers of the leaf in such sections and note their gen- 

 eral character. Use low power and dissecting lenses 

 in the study of these thick sections. Is the green 

 tissue favorably placed for receiving light rays? Do 

 you find the veins and the epidermis ? 



