3 5 THE LEAF 



if the reticulations of the smaller veinlets are noted. 



Then, too, it must be observed that in a pinnately parallel- 

 veined leaf the secondary veins do 

 not separate from the midrib in such 

 sharp, clear-cut angles as we see in the 

 beech and elm, but seem to flow into 



59. straight-veined leaf j t an( j mingle gradually with it, so that 

 the midrib has the appearance of 



being made up of the overlapping fibers of the smaller 



veins, as in Figure 56. 



41. Use of the Veins. Hold up a stiff, firm leaf of any 

 kind, like the magnolia, holly, or India rubber, to the light, 

 having first scraped away a little of the under surface, and 

 examine it with a lens. Compare it with one of softer tex- 

 ture, like the peach, maple, grape, cotton, clover, etc. In 

 which are the veins closest and strongest ? Which is most 

 easily torn and wilted ? Tear a blade of grass longitudi- 

 nally and then crosswise ; in which direction does it give 

 way most readily ? Tear apart gently a leaf of cotton, 

 maple, or ivy, and one of elm or other pinnately veined 

 plant ; in which direction does each give way with least 

 resistance ? What would you judge from these facts as to 

 the office of the veins ? 



42. Effect upon Shape. By comparing a number of 

 leaves of each kind, it will be seen that the feather-veined 

 ones tend to assume elongated outlines (Figs. 16, 33, 53), 

 while the palmate veining produces more broad and rounded 

 forms (Figs. 25, 55, 61). Notice also that the straight, 

 unbroken venation of parallel-veined leaves is generally 

 accompanied by smooth, unbroken margins, while the 

 irregular, open meshes of net-veined leaves are favorable 

 to breaks and indentations of all kinds. 



43. Veins as Water Pipes. Examine a leaf that has 

 stood in red ink for two or three hours. Do you see evi- 

 dence that it has absorbed any of the liquid ? Cut across 

 the blade and examine with a lens. What course has the 



