THE LIGHT RELATION 47 



leaves on the Norway maple, which is photographed in Fig. 

 79, he would find that leaves which are not on the outside 

 lengthen their leaf-stalks in order to get the light. See Fig. 

 157. Norway maple is common on lawns and roadsides. 



109. We have seen (85) that a large part of the leaves 

 of any one year are packed away in the buds of the previous 

 winter. It is almost impossible that these leaves should be 

 packed away hit or miss. They are usually arranged in a 

 mathematical order. We can see this order when the shoot 

 has grown. We can see it by studying the buds on recent 



81. Rhubarb grown in the dark. The leaf-blades do not develop. 



shoots, since there was a leaf for each bud. The leaves (or 

 buds) may be opposite each other on the stem, or alternate. 

 (Fig. 84.) 



110. When leaves are opposite, the pairs usually alter- 

 nate. That is, if one pair stands north and south, the next 

 pair stands east and west. See the box-elder shoot, on 

 the left in Fig. 84. One pair does not shade the pair beneath. 

 The leaves are in four vertical ranks. 



111. There are several kinds of alternate arrangement. 

 In the elm shoot in Fig. 84, the third bud is vertically above 

 the first. This is true, no matter which bud is taken as the 



