PLANTS MAKE FOOD 



85 



carefully, it would be seen that the 



colored fluid is confined to collections 



of woody tubes immediately under the 



inner bark. Water evidently rises in 



that part of the stem we call the wood. 

 Water given off by Evaporation from 



Leaves. Take some well-watered 



potted green plant, as a geranium or 



hydrangea, cover the pot with sheet 



rubber, fastening the rubber close to 



the stem of the plant. Next weigh 



the plant with the pot. Then cover 



it with a tall bell jar and place the ap- 

 paratus in the sun. In a few minutes 



drops of moisture are seen to gather 



on the inside of the jar. If we now 

 weigh the pot- 

 ted plant, we 

 find it weighs 

 less than be- 

 fore. Obvi- 

 ously the loss 

 comes from the 



water lost, and evidently this water escapes 

 as vapor from either the stem or leaves. 



The Structure of a Leaf. In the ex- 

 periment with the red ink mentioned 

 above we will find that the fluid has gone 

 out into the skeleton or framework of 

 the leaf. Let us now examine a leaf 

 more carefully. It shows usually (1) a 

 flat, broad blade, which may take almost 

 any conceivable shape ; (2) a stem which 

 spreads out in the blade (3) in a number 

 of veins. 



The Cell Structure of a Leaf. -The 



V., the veins. under surface of a leaf seen under the 



Experiment to prove that water 

 is given off through the leaves 

 of a green plant. 



