Grossenbacher—Radial Growth in Trees. 
41 
the last ring but in a more recent study Jahn 77 made it appear 
that the entire alburnum may be more or less active in water 
conduction although perhaps as much as half or more of the 
water is thought to be carried up the last ring. 
Some evidence of the fact that wind is both a formative and 
a limiting factor in plant growth is afforded by several scat¬ 
tered papers on the influence of wind on vegetation, a few of 
which might be briefly noted in this connection. 
While making an experimental study of the effects of wind 
on vegetation Bernbeck 78 obtained some interesting results. 
He found that both shoots and leaves of plants subjected to 
wind of 14 m. or less per second were injured in proportion to 
the amount of swaying and bending induced and that even del¬ 
icate leaves of shade plants are not injured by the wind if they 
are firmly held to prevent swaying or bending during the ex¬ 
posure. It was found that the production of organic food was 
reduced in leaves exposed to wind as . compared to that accum¬ 
ulating in protected leaves. 
Gilchrist 79 reported that potted plants of Helia/nthus annuus 
subjected to artificial wind swaying and rocking did not grow 
as tall as the checks while the diameter of their stems exceeded 
that of the check plants. Some more recent observations by 
Cavara 80 show a similar effect of wind exposure on the struc¬ 
ture of Iresine, Coleus, Aster, Zinnia, and Sempervivum. 
Esbjerg 81 found that protecting various herbaceous plants 
from strong winds by means of screens resulted in an increased 
yield. An increase of 16 to 31% above that of the checks was 
secured in the yield of grain from rye; the yield of ruta-baga 
roots was increased from 7 to 17% and of mangels from 3 to 
18%, while clovers and grasses showed a gain of from 4 to 23% 
as a result of wind protection. 
77 Jahn, E. Holz nnd Mark an den Grenzen der Jahrestriebe. Bot. 
Centbl. 59:257-67; 321-29; 356-62. 1894. 
78 Bernbeck, O. Der Wind als pflanzen-pathologischer Faktor. In¬ 
augural Dissert. Bonn. 1907. pp. 116. 
79 Gilchrist, M. Effect of swaying by the wind on the formation of 
mechanical tissue. Report Mich. Acad. Sc. 10:45. 1908. 
80 Cavara, F. Some investigations on the action of wind on plant 
growth. Expt. Sta. Record. 25:224-25. 1912. 
81 Esbjerg, N. Experiments with windbreaks. Expt. Sta. Record 
23:435. 1910. 
