8 
Transactions of the Royal Society of South Africa. 
The determination of the leaf area of the Pine presented greater diffi- 
culties. The most hopeful method seemed to be to find an expression for 
the area involving the length of the leaf and the diameter of its flat side. 
As a first step towards this, sections were cut from various portions of a leaf 
and camera lucida drawings made of these sections. Measurement of the 
perimeter of the curved surface and of the diameter of the flat surface 
showed that the relation between the two was fairly constant and averaged 
1-8, e.g.— 
Leaf No. 1. 
Length, 16 7 cm. 
Position of section. 
Diameter. 
Curved surface. 
C/D. 
Base 
1-39 mm. . 275 mm. 
1-99 
2*1 cm. from base 
1-69 „ 
314 „ 
1-86 
4-2 „ 
1-69 „ 
3-07 „ 
1-82 
63 „ 
1-62 „ 
2-89 „ 
1-78 
8-35 „ 
1-58 „ 
2-86 „ 
1 81 
10-5 „ 
162 „ 
3-02 ., 
1-86 
12-6 „ 
1-50 „ 
259 „ 
1 73 
147 „ 
1-39 „ 
242 „ 
1 75 
157 „ 
115 „ 
2 05 „ 
1-78 
16-2 „ 
107 „ 
16-6 „ 
054 „ 
0-57 „ 
9)16-38 
Average . . . . . 1*8(2) 
Two other leaves, one 16 9 cm. long, the other 101 cm. long, gave as the 
average ratio C/D 1*77 and 1-84 respectively. In the case of nine other 
leaves of varying length the diameter and circumference of the mid-section 
were measured, and the average ratio of C/D in these cases proved to be 
177. The value of C/D was taken as the average of these four values, 
i. e. 1-8. 
The next step was to measure as accurately as possible the area of the 
flat surface of the leaf. This was effected by cutting sections of a leaf at 
intervals from the base and plotting on squared paper the diameter of these 
sections against their distance from the base. In this way one obtained a 
magnified drawing of the flat surface of the leaf, and measured its area by 
counting the number of squares it contained. Knowing the magnification, 
the actual area of the flat surface was then readily calculated. The total 
area of the leaf was then taken as — 
Area of flat surface x (C/D +1) 
i. e. Area of flat surface x 2*8. 
