BRANCHED LEAVES 37 



absorbed liquid followed ? What use does this indicate for 

 the veins, besides the one already noted ? 



We thus see that the veining serves two important pur- 

 poses in the economy of the leaf ; first, as a skeleton, or 

 framework, to support the expanded blade ; and second, as 

 a system of supply pipes, or waterworks for conveying 

 the sa.p out of which its food is manufactured. 



The microscope shows us that the veins are made up of 

 clusters or bundles of woody fibers, mixed with long, tubu- 

 lar cells that serve as vessels for conducting the sap; hence 

 they are called fibrovascular bundles ; which means bun- 

 dles composed of fibers and conducting vessels. In this 

 way the veins get both their hardness and their water- 

 conducting power. The tough, stringy threads that pro- 

 trude from the petiole of a plaintain leaf when broken are 

 made of fibrovascular bundles that supply the leaf blade. 



PRACTICAL QUESTIONS 



1. In selecting leaves for decorations that are to remain several 

 hours without water, which should you prefer, and why : Smilax or 

 Madeira vine (Boussingaultia)! Ivy or Virginia creeper? Magnolia 

 or maple? Maidenhair or shield fern {Aspidiuni)! (41,43.) 



2. Should you select very young leaves, or more mat are ones, and 

 why? 



3. Can you name any parallel-veined leaves that have their margins 

 lobed, or indented in any way? 



4. Which are most common, parallel-veined or net-veined leaves? 



5. Why do the leaves of corn and other grains not shrivel length- 

 wise in withering, but roll inward from side to side? (41.) 



6. Can you name any pahnately-veined leaves in which the secondary 

 veins are pinnate? Any pinnately-veined ones in which the secondary 

 veins are palmate? 



7. Account for the difference. 



BRANCHED LEAVES 



MATERIAL. Lobed and compound leaves of various kinds. Many 

 good examples can be found among the weeds growing on vacant lots 

 in cities. 



44. Lobing. Compare the outline of a leaf of maple 

 or sweet gum with one of oak or chrysanthemum. Do 



