EXERCISE 78 

 WHAT IS THE PATH OF WATER IN PLANT STEMS? 



Materials. Freshly cut leafy stems of both soft and woody plants ; red ink or water which 

 has been colored by addition of eosin or other coloring material. 



Directions. Stand freshly cut leafy stems in a colored solution. Very leafy stems, if placed in 

 a sunny location with good circulation of air, may be ready for examination in half an hour. In 

 many cases it will be well to allow the material to stand until the next day. 



Examine the stems by cutting across the stem at intervals or by peeling off the surface. If 

 blanched celery, yellow coleus, or other light-colored plants are used, the stems will be sufficiently 

 transparent to show the red color without cutting. Can the course of the solution be traced into 

 the leaves ? Are there definite tissues through which the solution passes ? Diagram a cross section 

 of the stem and a surface view of a leaf to show any point observed regarding definite tissues 

 through which water passes. 



Additional problem. How would the passage of water in a woody plant be affected if a ring of bark were 

 removed from the stem ? What would be the effect if the ring included the bark and all of the new wood ? 



[Ill] 



