24 



LABORATORY AND FIELD EXERCISES 



c. Draw two or three cells greatly magnified (half an inch 

 in diameter), to illustrate the parts of plant cells as 

 seen under a high power. Label all of the parts of 

 one cell carefully. 



CELL-WALL THICKENING AND CELL DIFFERENTIATION 



1. Sections of celery, corn, or a similar plant. 



a. Cell differentiation. Observe the entire section with 



the low power of a compound microscope. Are 

 the cells in different parts of the section of uniform 

 size and form ? Why 

 should one expect to 

 find different kinds of 

 cells in the cell col- 

 ony which makes up 

 the structure of any 

 stem, leaf, or root ? 

 Observe any definite 

 order or grouping of 

 similar kinds of cells. 

 Explain such group- 

 ings on the basis of 

 use, or function, in 

 a celery or corn stalk. 

 The regular oval cell 

 masses are vascular 

 bundles, which con- 

 duct water and foods up and down the stem. 



b. Make an outline sketch of the entire section as it ap- 



pears to the naked eye or with a hand lens. Shade 

 in the areas showing thick- walled cells, and outline 

 the vascular bundles. Consult Fig. 7. Label. 



FIG. 9. Epidermis and collenchyma 



ep, epidermis; col (collenchyma), the 

 thick-walled cortex cells; th, thick- 

 walled portion of collenchyma cell 



