98 THE NA TURE-STUD Y RE VIE W [ 2 : 3 ~ M arch, .906 



Your class is thus forced to conclude that the bark is not needed to 

 conduct the sap to the parts above. The bark is removed, the wax 

 obstructs the place previously occupied by the bark. The conclus- 

 ion is inevitable that the upward current is in the wood with a bare 

 possibility that some of it may rise through the pith. An examination 

 of the pith, however, in most cases shows it to be entirely inadequate 

 for water conduction. Further experiments could be made which 

 would prove conclusively that the pith cannot conduct water at all. 

 Thus we are left with the firm conclusion that the sap current rises 

 through the wood and not through the bark. 



Some of your pupils will now ask, " Why is it, then, that if we 

 girdle a tree around its base, the tree dies ?" This is a very different 

 proposition from girdling a single branch on the tree. A full explana- 

 tion of this phenomenon is too long for this present article. We 

 may briefly explain it, however, by saying that there is a downward 

 current of food material through the bark and that the roots receive 

 their supply in this way. If the bark be removed at the base of a 

 tree, the path of food from the leaves to the roots is blocked and the 

 roots as a consequence sooner or later are starved to death. The 

 death of the roots in this fashion of course ultimately brings about 

 the death of the tree top. It will be seen from this, then, that in 

 the experiment we have just outlined, the girdled branch is receiving 

 its sap from the roots, but it is not sending back to the roots any food 

 material whatever. A branch in this condition is partially a parasite 

 upon the rest of the plant. It is receiving but it is giving nothing in 

 return. 



NATURE-STUDY IN CITY PRIMARY SCHOOLS 



BY MARY C DICKERSON 



Formerly of the Rhode Island Normal School 



Author of ' ' Moths and Butterflies ' ' and ' ' The Frog Book ' ' 



I This paper contains the substance of an address before the Primary Teachers 

 of Providence, Rhode Island.] 



During the past few years there has been a great nature movement, 

 and in many of the schools of the country nature-study has been 

 given a place in the curriculum. But even where this has been 

 done it is not always an honored place that nature-study holds 

 on the program in the schools. This is because of very, definite diffi- 



