564 
Holmes.—A Study in the A natomy of 
Curve D. The figures for curves B and C were found by counting 
and measuring the vessels and tracheides in a measured area, and these 
relations are shown in two more curves. Curve D represents the number 
of water-conducting elements per sq. mm. in the transverse section of the 
wood at different levels in the stem. The figures calculated range from 
115 to 4,000 per sq. mm. The curve begins with a gradual rise and ends 
with a very rapid rise, and it will be seen that the change from the gradual 
to the steep ascent corresponds with the similar change in curve C. This 
shows that the rapid increase in specific conductivity in this region is due to 
