COURSE OF WATER IN STEMS " 45 



WOEK OF THE STEM 

 EXPERIMENT XXII 



Course of water in stems.* * 



A. Cut some short 'branches from an apple tree or a cherry 

 tree, and stand the lower end of each in eosin solution ; try 

 the same experiment with twigs of oak, ash, or other porous 

 wood, and after some hours ^ examine with the lens and with 

 the microscope, using l.p., successive cross sections of one or 

 more twigs of each kind. Note exactly the portions through 

 which the eosin has traveled. Pull off the leaves from one 

 of the stems after standing in the eosin solution, and notice 

 the spots on the leaf scar through which the eosin has trav- 

 eled. These spots show the positions of the leaf traces, or 

 fibro-vascular bundles, connecting the stem and the leaf. 



B. Eepeat with several potatoes cut crosswise through the 

 middle. 



C. Try also some monocotyledonous stems, such as those of 

 the lily or asparagus. 



D. For the sake of comparison between roots and stems treat 

 any convenient root, such as a parsnip, in the same way. 



Examine the longitudinal sections of some of the twigs, the 

 potatoes, and the roots. In drawing conclusions about the 

 channels through which the eosin has risen (those through 

 which the newly absorbed soil water most readily travels), 

 bear in mind the fact that a slow soakage of the eosin will 

 take place in all directions, and therefore pay attention only 

 to the strongly colored spots or lines. 



What conclusions can be drawn from this experiment as to 

 the course followed by the soil water ? 



Refeeences. Detmer-Moor, 9 ; Ganong, 10 ; Strasburger, Noll, 

 Schenck, Karsten, 1 ; Pfeffer-Ewart, 31, I. 



1 If the twigs are leafy and the room is -warm, only from five to thirty minutes 

 may be necessary. The experiment may be performed with a translucent-stemmed 

 plant like Impatiens SuUani, and the course of the eosin watched. See Ganong, 10. 



