188 FIRST TEAR SCIENCE 



entire root extension of over 150 feet. This seeking of 

 the roots for water sometimes causes the roots of trees to 

 grow into drain pipes and stop them up. For this reason 

 the planting of certain trees near sewer pipes is often 

 prohibited. 



Experiment 94. Boil some water so as to drive out the air and after 

 it has become cool fill a 2-quart fruit jar half full. Dissolve in this 

 all the necessary plant food as was done in Experiment 88, making 

 the solution the same strength. Place in this a slip of Wandering 

 Jew. Pour over the surface of the water a layer of castor oil or sweet 

 oil. Place this jar alongside the slip in the other complete food solu- 

 tion, Experiment 88. Both slips have the same conditions except 

 that the oil keeps out the air from the roots of one of them. Does 

 the absence of air affect the growth of the slip ? 



As the tips of the roots are delicate, it can be readily seen 

 that if they are to grow readily the soil around them must 

 be mellow. It was also seen in Experiment 94, that if 

 roots are to grow they must have air, another reason for 

 keeping the soil mellow. 



Roots are, however, not simply absorbers of water and 

 dissolved food. Some of them act as storehouses for the 

 food that the plant has prepared for future use. Beets, 

 carrots, parsnips, turnips and sweet potatoes are examples 

 of roots which store food ready for the rapid growth of 

 the next year's plant. 



93. Stems. Experiment 95. Examine a corn stalk. Notice 

 how and where the leaves are attached to the stem. Do the alternate 

 leaves come from the same side of the stem ? Cut a cross section of 

 the stalk. Notice the outside hard rind, the soft pithy material and 

 the small firmer points scattered about in the pith. Cut a section 

 lengthwise of the stalk and notice how these small firmer points are 

 related to the lengthwise structure of the stem. 



Cut off a young growing corn stalk and place the cut end in^ water 

 colored by eosin or red ink. Allow it to stand for some time and 

 then cut the stalk off an inch or two above the surface of the water. 

 How have "the firmer points " been affected? If possible, make the 



