Water-conductivity in Sycamore Wood. 
2 63 
is traced downwards, this level being about the same as that at the first 
internode of the final segment. The same condition may be inferred from 
Figs. 2 and 10 ; here the rise in the curve at the final internodes of the lower 
segments is due to the fact that the wood widens out at the nodes, and that 
these internodes are very short ; see Fig. 1. The size and numbers of the 
water-conducting elements in these annual rings are illustrated in Fig. 4. 
Curve F shows a maximum for the total number at the first internode of the 
final segment, and a general tendency to decrease in the number, as the 
curve is traced backwards. This may be seen also in Figs. 3 and 10. The 
number of these elements per unit area naturally tends to decrease down- 
wards also, as appears from Curves D, Fig. 4 ; the special provision of 
mechanical elements at the base of the plant, as mentioned by Farmer 
(5, p. 241), is indicated by a comparison of Curves A and D, Figs. 5 and 
4. in this region. With the general decrease in number downwards is 
associated to some extent an increase in average width, as shown in 
Curves E, Fig. 4. The influence of the presence in the second and outer 
annual rings of wider vessels than occur in the innermost ring is apparent, 
and there is a slight increase downwards and outwards apart from this. 
The following table will make this clearer, from the point of view of maxi- 
mum diameters : 
• 
Max . diam. of vessels in [x. Max. diam. of vessels in /x. 
Specimen. 
Annual 
First-year 
Lower 
Specimen. 
A nnual 
First-year 
Lower 
ring of 
segment. 
segments. 
ring of 
segment. 
segments. 
S 2 
’16 
5° 
— 
S 4 
’16 
40 
— 
’17 
50 
57 
’i7 
53 
60 
’18 
50 
67 
’18 
56 
67 
S3 
’*4 
38 

S 5 a 
’17 
60 
— 
’15 
46 
46 
’18 
— 
66 
’16 
40 
47 
S 5 b 
— 
60 
— 
’i7 
50 
53 
S 5 c 
— 
26 
— 
*18 
50 
57 
S 5 d 
— 
57 
— 
S 5* 
— 
48 
— 
Among the figures obtained for average diameters and numbers per 
unit area, in wood of the second and outer rings only, taken separately, the 
limits of variation are as follows : 
Range of values for E in /x 31-35 to 17-04 
» » D 85 „ 247 
These various factors contribute to keep the conducting area, as repre- 
sented by Curves B, Fig. 5, fairly level along its course in each separate 
annual ring, with a maximum generally at the first internode of the last 
segment. This appears also in Fig. 9, but is less clear in Figs. 2 and 12. 
Of course Curve B represents the absolute conducting capacity in its trans- 
verse aspect only ; its fall backwards from the maximum is probably com- 
pensated, and more than compensated, by the greater length and decreased 
