RISE OF WATER 63 



What light does the structure throw on the results of the preceding 

 experiment ? 



Eefekences. Detmer-Moor, 9 ; Ganong, 10. 



EXPERIMENT XXXIX 



Passage of water from stem to leaf. Place a freshly cut leafy- 

 shoot of some plant with large, thin leaves, such as Hydrangea 

 Hortensia, in eosin solution for a few minutes. As soon as the 

 leaves show a decided reddening pull some of them off and 

 sketch the red stains on the scars thus made. What does this 

 show ? 



EXPERIMENT XL 



Rise of water in leaves.* * Put the freshly cut ends of the 

 petioles of several thin leaves of different kinds into small glasses, 

 each containing eosin solution to the depth of one quarter inch or 

 more. Allow them to stand for half an hour, and examine them 

 by holding up to the light and looking through them to see into 

 what parts the eosin solution has risen. Allow some of the leaves 

 to remain as much as twelve hours, and examine them again. 

 The red-stained portions of the leaf mark the lines along which, 

 under natural conditions, water rises into it. Cut across (near the 

 petiole or midrib ends) all the principal veins of some kind of 

 large, thin leaf. Then cut off the petiole and at once stand the 

 cut end, to which the blade is attached, in eosin solution. Eepeat 

 with another leaf and stand in water. What do the results teach? 



EXPERIMENT XLI 



Does the leaf vary in its starch contents at different seasons ? Collect in 

 early summer, at the close of a sunny day, some leaves of different kinds of 

 trees and shrubs and preserve them in alcohol. Collect other leaves of 

 the species as they are heginning to drop from the trees in autumn and pre- 

 serve them in the same way. Test some of each lot for starch, as described 

 in Exp. XXXII. 



What does the result indicate ? 



