26 Wisconsin Academy of Sciences, Arts, and Letters. 
tree-trunks had a greater radius on the side toward which they 
slant and also have 4 'red-wood’ 7 present on the side with the 
longest radius. In one instance a tree on the west edge of a for¬ 
est and therefore having most of its branches on the west side 
was found to have a longer radius as well as abundant 4 4 red¬ 
wood ’ ’ on the east side. In another case trees along the western 
edge of a forest had the typical excessive growth and 4 4 red¬ 
wood ” on the east side of the trunks up to the age of about 80 
to 90 years, after which the new rings showed a lesser excentric- 
ity and a smaller amount of 44 red-wood.” The change seemed 
to have resulted from the presence of a new planting on the west 
side which had attained some size by that time. Hartig con¬ 
cluded that the mechanical or swaying effects of wind not only 
causes excentric radial growth but also induces the formation of 
44 red-wood” on the side of trunks subjected to longitudinal com¬ 
pression. An instance is also cited in which the leeward side of 
a tree-trunk is excessively thickened from the base up but which 
was devoid of 4 4 red-wood ’ ] near the ground although it was abun¬ 
dant farther up. A case is described where the distal part of a 
young spruce stem had been bent into a complete turn and had 
grown in that position during 27 years. Sections cut at various 
points of the curve showed the occurrence of the greatest radial 
growth and of 44 red-wood” on the sides where gravity and lon¬ 
gitudinal compression resulting from the top-weight and wind 
action would require it. The excentricity of large spruce 
branches and the accompanying 44 red-wood” was found to ex¬ 
tend only about four meters out from trunks. 
According to Hartig 44 red-wood” has comparatively large 
intercellular spaces and the cells seem not to be very firmly at¬ 
tached since they frequently fell apart in sections. The tra- 
cheids are said to have especially thick walls the innermost thick¬ 
ening layers of which are arranged spirally. 
In a more recent summary of his investigations of wood Har 
tig 45 claims to have proved the relative influence of gravity and 
longitudinal compression in inducing the formation of 4 4 red¬ 
wood.” Spruce trees planted in large tubs were suspended in 
an inverted position in a greenhouse and the distal part of the 
stems were bent upward and allowed to grow during one sea- 
45 Hartig, R. Holzuntersuchungen. Altes und Neues. Berlin. 1901. 
pp. 99. 
