258 Holmes . — -A Contribution to the Study of 
branches, of various lengths. This circumstance introduces irregularities 
into the curves, beyond those due to differences in the sizes of the leaves. 
About the latter no information can be given for these specimens ; but 
to represent the number of leaves borne along the shoot during each season, 
another line, G, has been introduced into some of the graphs ; the height of 
this line at the position representing each internode indicates the number of 
leaves on the stem above that internode. 
In all cases where the stem cut was more than one year old, the data 
were worked out for each annual ring separately, and the figures were also 
combined to furnish statistics representing the condition of the wood 
as a whole at the end of each year’s growth. From these figures it is 
possible to draw a line representing quantitatively the extent of develop- 
ment of a particular character, for a particular annual ring as far as it 
extends along the stem, or for the whole of the wood present at the end of 
a particular year. Considering the curves which come into the latter 
category, it is evident that those representing the areas of the wood along 
the same stem at the end of each year of its growth, A, or the areas of the 
lumina of all the water-conducting elements, B, or the numbers of these 
elements, F, may be drawn without interference between the same co-ordi- 
nates ; this is sufficiently true in practice of the other curves also, represent- 
ing specific rather than absolute data. But the curves which belong to the 
former category may interfere in this sense, so that separate diagrams 
to illustrate these have been introduced in some cases. Thus for specimen 
S3, which is five years old, there are five lines for each of the seven 
