182 FIELD OATS. 



a. The pitted fibrous cells, tracheides y which constitute 

 most of the bundle. 



b. The one or two pitted vessels. 



c. Draw, showing both vessels and tracheides. 

 Mount about one centimeter of the tip of a root from 



plants that have been grown upon blotting paper. Exam- 

 ine with a low power, and note 



11. The root-hairs. Observe their relative length. 



12. The root-cap ; the outer cells sloughing off. Draw. 

 Study the root-hairs with a high power. Notice 



13. The shape, mode of attachment and contents. Draw. 

 Cut a median longitudinal section of the tip of a root, 



including the root-cap. 7 Treat with potash, examine with 

 a high power, and note 



14. The blunt, or even notched tip of the root proper. 



15. The sharp conical root-cap. Note the shape of the 

 cells near the root-tip, and the changed shape near the 

 periphery. 



1 6. The growing point, a cluster of small cells, just back of 

 the root-cap, in the middle of the root-tip. 



17. A short distance behind the tip of the root, the slight 

 differentiation of the tissues into three regions : 



a. A central one, the plerome. 



/;. An outer one, consisting of a single row of cells, 



the dermatogen. 



Between the plerome and dermatogen, the periblem. 



Trace these three regions down to the growing 



point, and notice their relations there. 



7 This is very difficult to do if fresh roots are used, but easier by using 

 roots that have been kept for a few hours in alcohol. The student should 

 cut a series of sections through the whole root. The median one can then 

 be selected. 



