Grossenbacher — Radial Growth in Trees. 
27 
son. The excessive growth at the curve and the accompanying 
“red-wood” was found to have developed on the under or con¬ 
vex side of the curve. This was assumed to indicate that grav¬ 
ity has more influence in the production of “red-wood” than 
longitudinal compression. 
Rubner 46 has given us some interesting observations on ex- 
centrix as well as of more irregularly distributed radial growth 
of trees. He called attention to the fluted or furrowed trunks 
and buttressed trunk-bases so characteristic of certain species. 
He attributed the ridges to excessive and the valleys to subnor¬ 
mal radial growth. In Carpinus the deep, wide grooves in the 
stem were found to occur at places where several compound 
medullary rays are grouped together, while lesser depressions 
or channels occurred along each individual compound ray, but 
these lesser grooves were practically compensated for by the 
greater phloem production so that the outer surface of the bark 
did not show them. In portions of trunks represented by the 
ridges the rays were small and it was assumed by Rubner that 
the distribution of the large and small rays influences the rel¬ 
ative amounts of radial growth of the ridges and valleys in the 
wood cylinder. While Nordlinger 47 assumed that the valleys 
are due to an excessive bark pressure along the large rays owing 
to the development of stone cells or abnormally long phloem-ray 
cells in the bark at such places. He notes the absence of marked 
valleys and grooves in oaks devoid of broad rays, and that on 
very large, old trees the outer rings often have the valleys be¬ 
tween the large rays while the ridges occur along the rays. The 
armpit-like depressions below some branches, according to Rub- 
ner, occur under branches whose leaves elaborate only enough 
food for their own use thereby leaving the region just below 7 the 
branch bases insufficiently supplied, owing to the deflection the 
branch-bases cause in the downward current of food in the trunk. 
These depressions are said to be chiefly confined to epinastic 
species. In the valleys Rubner found the wood to consist main¬ 
ly of thick-walled fibers and the radial arrangement of the cells 
w r as perfect, apparently because the valley-wood is devoid of ves- 
sels. The large “false rays” present in the valleys of Carpinus 
46 Rubner, K. Das Hungern des Cambiums und das Aussetzen der 
Jahrringe. Naturw. Zeit. Forst-u. Landw. 8:212-62 1910. 
47 Nordlinger, H. Wirkung des Rindendruckes auf die Form der 
Holzringe. Centralbl. Gesam. Forstwesen. 6:407-13. 1880. 
