96 



LEAVES AND FOLIAGE 



Kentucky coffee tree. Remark- 

 able differences in forms are 

 seen by comparing seed-leaves 

 with mature leaves of any plant 

 (Fig. 143). 



202. THE LEAF AND 

 ITS ENVIRONMENT. 

 The form and shape 

 of the leaf often have 

 direct relation to the 



135. Peltate leaves of so-called 

 Egyptian lotus. 



i 





place in which the leaf grows. Floating leaves 

 are usually expanded and flat, and the petiole 

 varies in length with the depth of the water. 

 Submerged leaves are usually linear or thread-like, 

 or are cut into very narrow divisions. Thereby is 

 more surface exposed, and possibly the leaves are 

 less injured by moving water. 



203. The largest leaves on a sun -loving plant 

 are usually those which are fully exposed to light. 

 Compare the sizes of the leaves on the ends of 

 branches with those at 

 the base of the branches 

 or in the interior of the 

 tree -top. In dense foli- 

 age masses, the petioles 

 of the lowermost or 

 undermost leaves tend to 

 elongate to push the 

 leaf to the light (Fig. 144). 



204. On the approach of win- 

 ter the leaf ceases to work, and 

 often dies. It may drop, when it 

 is said to be deciduous ; or it may remain on the plant, 

 when it is said to be persistent. If persistent leaves re- 

 main green during the winter, the plant is said to be 



138. Linear- 

 acuminate 

 leaf of 

 grass. 



137. Short-oblong leaves of box. 



