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 asa 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? 
(4) 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- 
aeeaneign late wise by a strong midrib and that many so- 
Ny ase yey called veins run from this to the margin. Are 
ase re these veins parallel? Hold the leaf up towards 
the light and see how the main veins are con- 
nected by smaller veinlets. 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 
Fic. 59. Netted Vein- glass and look for hairs distributed on the 
ing (pinnate) in Leaf surfaces. Describe the manner in which 
of Foxglove. the hairs are arranged. 
EET 
acy 
Ry SO 
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 Plants, Vol. I, pp. 623-637. 
