THE SHAPES OF BRANCHES. 149 



all round; while those of the other, which spread laterally, 

 bear their leaves on the two sides. In trees with better- 

 developed leaves, the same principle is more or less manifest 

 in proportion as the leaves are more or less enabled by their 

 structures to maintain fixed positions. Where the foot-stalks 

 are long and slender, and where, consequently, each leaf, 

 according to its weight, the flexibility and twist of its foot- 

 stalk, and the direction of the branch it grows from, falls 

 into some indefinite attitude, the relations are obscured. But 

 where the foot-stalks are stiff, as in the Laurel, it will be 

 found, as before, that from the topmost and upward-growing 

 branches the leaves diverge on all sides; while the under- 

 most branches, growing out from the shade of those above, 

 have their leaves so turned as to bring them into rows hori- 

 zontally spread out on the two sides of each branch. 



A kindred truth, having like implications, comes into view 

 when we observe the relative sizes of leaves on the same 

 branch, where their sizes differ. 20s 



Fig. 205 represents a branch of a 

 Horse-chestnut, taken from the 

 lowermost fringe of the tree, where 

 the light has been to a great extent 

 intercepted from all but the most 

 protruded parts. Beyond the fact 

 that the leaves become by appro- 

 priate growths of their foot-stalks 

 bilaterally distributed on this droop- 

 ing branch, instead of being distributed symmetrically all 

 round, as on one of the ascending shoots, we have here to 

 note the fact that there is unequal development on the upper 

 and lower sides. Each of the compound leaves acquires a 

 foot-stalk and leaflets that are large in proportion to the 

 supply of light; and hence, as we descend towards the bot- 

 tom of the tree, the clusters of leaves display increasing 

 contrasts. How marked these contrasts become will be seen 

 on comparing a and b, which form one pair of leaves that 



