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 



Experiment to prove that water 

 is given off through the leaves 

 of a green plant. 



The skeleton of a leaf. M.R., 

 the midrib; P., the leafstalk; 

 v., the veins. 



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 hlade^ 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 

 under surface of a leaf seen under the 



