THE NUTRITIVE ORGANS OF PLANTS 41 



1. The outline of the root including the tip. 



2. A loose mass of cells covering the lower end of the root which 



make up the roof-cap. 



3. Label root- tip, cells of the root- cap. 



56. The functions of roots. Laboratory Study No. 30. 



A. Roots as organs for holding the plant to the soil. 



Secure a vigorously growing plant in a pot (e.g. a rubber 

 plant) or better try the following experiment on a 

 good sized weed in a field. Attach to the stem just 

 above ground level a spring balance. Pull on the 

 balance until the plant shows signs of letting go its 

 hold on the soil, then note the reading in pounds on 

 the scale. 



1. In your own words describe what was done. 



2. How much force in pounds was exerted on the 



plant? 



3. What important function of roots is shown by this 



experiment ? 



B. Roots as organs for absorbing soil-water. 



(Before proceeding further with the .root study, the osmo- 

 sis experiments, 44-53, should be performed if they 

 have not already been done.) 



Study the diagram of a root-hair in the text-book (Fig. 12) 

 and if possible examine with the low power of the 

 microscope some of the younger (shorter) root- 

 hairs. Each root-hair is an elongated part of an 

 outer cell of the root. 



1. Draw in your note-book a diagram of a root-hair, 



labeling cell-wall, thin layer of protoplasm, cell- 

 sap, and nucleus. 



2. What separates the soil-water from the cell-con- 



tents? 



3. Recall the characteristics of cellular structure as 



given in 42. Now state which is the more dense, the 

 soil-water or the cell-contents. 



