98 



ESSENTIALS OF BOTANY 



careful sketch of its under surface, about natural size. Label the 

 broad expanded part the blade, and the stalk by which it is attached 

 to the twig, leaf-stalk or petiole. 



Study the outline of the leaf and answer these questions : 

 (a) What is the shape of the leaf taken as a whole ? (See Appen- 

 dix.) Is the leaf bilaterally symmetrical, i.e., is there a middle line 

 running through it lengthwise, along which it could be so folded that 

 the two sides would precisely coincide ? 



(h) What is the shape of the tip of the 

 leaf? (See Appendix I.) 



(c) Shape of the base of the leaf? (See 

 Appendix I.) 



(d) Outline of the margin of the leaf? 

 (See Appendix I.) 



Notice that the leaf is traversed length- 

 wise by a strong midrib and that many so- 

 called veins run from this to the margin. Are 

 these veins parallel ? Hold the leaf up towards 

 the light and see how the main veins are con- 

 nected by smaller veinlels. Examine with your 

 glass the leaf as held to the light and make 

 a careful sketch of portions of one or two 

 veins and the intersecting veinlets. How is 

 the course of the veins shown on the upper 

 surface of the leaf? 



Examine both surfaces of the leaf with the 

 glass and look for hairs distributed on the 

 surfaces. Describe the manner in which 

 the hairs are arranged. 



Fig. 59. Netted Vein- 

 ing (pinnate) in Leaf 

 of Foxglove. 



The various forms of leaves are classed and described 

 by botanists with great minuteness, ^ not simply for the 

 study of leaves themselves, but also because in classify- 

 ing and describing plants the characteristic forms of the 

 leaves of many kinds of plants form a very simple and 

 ready means of distinguishing them from each other and 



1 See Kerner and Oliver's Natural History of Pla7Us, Vol. I, pp. 623-637 



