CELLULAR ORGANIZATION OF PROTOPLASM 1 



A. Plant Tissues 



1. Carefully peel off a small piece of the delicate, transparent covering 

 (epidermis) from the upper surface of a green leaf. This can be done by 

 using the point of the scalpel or by tearing the leaf. Mount the epidermis 

 according to the directions for temporary preparations given in the pre- 

 vious section on "Microscopic Preparations" (p. 243). 



2. Examine the epidermis in the temporary preparation just made 

 with both the low and the high power of the microscope. Draw about ten 

 adjacent epidermis cells to show their arrangement and general struc- 

 ture. Each cell should be drawn about one-half inch in diameter. 



3. Examine, with the low power, a permanent preparation of stained 

 sections of an Onion root. Note that some of the sections have been cut 

 parallel to the long axis of the root (longitudinal sections), and some 

 of the sections have been cut across, i.e., at right angles to, the long axis 

 (transverse, or cross, sections). 



4. Study first one of the longitudinal sections under the low power. 

 Draw in outline a portion of the section near the tip of the root. Study 

 the cells in this region with the high power. Note : (a) the cell wall 

 which marks the cell boundary ; (b) the rather faintly stained cytoplasm 

 which forms the cell body ; (c) the central, spherical nucleus embedded 

 in the cytoplasm and frequently containing (d) a tiny nucleolus. Many 

 of the older cells, situated some distance back from the tip of the root, 

 contain (e) a large vacuole which, when the cell is alive, is filled with 

 a liquid, (/) the cell sap. 



5. Make (a) a drawing of a portion of the longitudinal section, lying 

 near the tip, under the low power to show the general arrangement of the 

 cells ; (6) a drawing of a single cell under the high power to show the 

 detailed cell structure. 



6. Study one of the transverse sections under the low power. Select a 

 typical cell and make a drawing of it under high power similar to the one 

 just made in paragraph 5. 



7. Compare the last two drawings of cells in paragraphs 5 and 6. With 

 them as a basis make an outline drawing of a cell in perspective, that is, 

 one which will show the cell as a solid with the three dimensions. 



1 B. pp. 3-8. 

 247 



