A YEAE IN SCIENCE 87 



is a thin skin, the epidermis, one layer of cells thick. 

 Make a cross section of the carrot and identify the 

 parts. Make a drawing of both the cross and the 

 longitudinal sections. 



To determine the paths of liquids through roots, 

 place the cut end of a carrot in eosin solution for a 

 number of hours. Make a cross section and examine. 

 Indicate in the drawing of the cross section the region 

 through which the liquid passed. 



Exercise 58. External Structure of Stems. 

 Object: ,To study the external characteristics of 



stems. 



Apparatus 



Box elder twi;s Dissecting microscope 



Scalpel 



Directions: Procure a twig of box elder about two 

 feet in length. Examine it carefully, noting the gen- 

 eral characteristics of the bark. At intervals on the 

 twig notice the small blister-like elevations, the lenti- 

 cels. These are openings through the bark of young 

 stems for the interchange of gases. On a twig of this 

 season's growth, how are the leaves arranged? On 

 the older portions of the stem note the leaf scars. Do 

 you find any buds on the stem ? What relation do they 

 bear to the leaves or to the leaf scars? Do you find 

 rings of narrow scars on the stem? What difference 

 in the appearance of the stem above and below these 

 rings? Prom what were these rings of scars caused? 



