ADJUSTMENT TO SURROUNDINGS 
143 
136. Correlation among Leaves. On a vertical and 
equally illuminated branch, as of maple, the petioles of 
the lower leaves are longer than those above them, and 
the stalks of opposite leaves are usually about equal in 
FIG. 102. Garden nasturtium (Tropaolum majus), showing leaf- 
mosaic in seedlings. Top view; compare Fig. 95, showing other views of 
the same seedlings. 
length (Figs. 100 and 101). But on horizontally growing 
branches, the attitude of the leaves is profoundly altered. 
The length of the petioles, and their attitude is such as 
to insure the placing of the blades in positions for the 
most favorable illumination. This often results in a 
marked twisting and bending of the leaf-stalks. Blades 
