Grossenhacher—Radial Growth in Trees. 
39 
only the first power of its horizontal diameter. He also con¬ 
cluded that vertical stems may become excentric owing to one¬ 
sided action of wind but that the effect on some trees might be 
different on account of variations in the shape and the conse¬ 
quent distribution of the weight of the top. The crooks in a 
tree trunk are assumed also to be gradually eliminated by the 
distribution of the radial growth in response to strain stimuli. 
The same laws are thought to apply to the radial growth in roots 
but because of the variation in the environing soil they are not 
always so regularly effective. 
Vochting 74 cut the tips from some potted one-year-old savoy 
plants and placed them with their pots in a horizontal position. 
He attached weights to some near their decapitated tips and al¬ 
lowed them to vegetate during some months. The vertical diam¬ 
eter of the stems was markedly increased in the regions of great¬ 
est strain while the stems of the check plants retained their 
cylindrical forms. 
The far-reaching applicability of this wind-gravity hpyothe- 
sis originating with Schwendener and elaborated by Metzger and 
others, according to which tree-trunks and other stem structures 
have a form required of a shaft of equal endurance throughout, 
has recently been questioned by Jaccard. 75 He holds that the 
hypothesis is untenable because measurements and calculations 
made by him on a number of spruce trees resulted in a noncon¬ 
formity of the hypothetical and actual forms of their trunks. 
It was found that the portions of the trunks beginning with 5 
m. above ground and extending to about 9 m. above ground were 
practically of the form and dimensions required of such a shaft 
but above and below that region the trunks were thicker than 
required by the laws of mechanics. In one instance described 
in detail, however, the trunk of a spruce practically conformed 
to the required hypothetical shaft. 
Although much more frequent strong winds are said to occur 
in western Switzerland the trees there were not found to differ 
appreciably from those of eastern Switzerland where strong 
winds are few. Jaccard maintained that during the growing sea¬ 
son the wind is too spasmodic to be a factor in the distribution 
74 1. c. 
76 Jaccard, P. Eine neue Auffassung liber die Ursachen des Dieken- 
wachstums. Naturw. Zeit. Forst-u. Landwirts. 11:241-79. 1913. 
