MICHIGAN ACADEMY OF SCIENCE. 
4F> 
EFFECT OF SWAYING BY THE WIND ON THE FORMATION OF 
MECHANICAL TISSUE. 
(abstract.) 
Experiments were carried on in the University greenhouse during the 
year 1906-1907 to determine the effect of swaying on the formation of me- 
chanical tissue in normally erect plants. The apparatus was run by an elec- 
tric motor, the motion being constant and regular, and the plants being 
swayed as by the wind back and forth in the same plane. Other plants 
were put in a rocking shelf, run by the same motor, and the whole plant 
was made to rock back and forth, the stems being supported by rods 
thrust into the ground. Control plants subject to the same conditions of 
light, heat, moisture, etc., were set up with those experimented on. A 
variety of plants were used in the course of the experiments, but the com- 
mon garden sunflower, Helianthus annuus, proved most satisfactory. 
Various measurements and tests, also microscopic examinations, were 
made, and a brief summary of the results obtained will be given here. In 
series C, for example, after nine days swaying, the averages obtained were 
as follows: height, experimental plants, 29.2 cm., control plants, 36.8 cm.; 
diameter in plane of swaying, 8.3 mm., excess over the transverse diameter, 
.99 mm., diameter of' controls, 5.7 mm. 
Conclusions: 1. Stems of plants swayed as by the wind are shorter and 
thicker than those not swayed. 
2. The diameter in the plane of swaying is greater than that at right 
angles. 
3. The xvlem in the plane of swaying is greater than that in the trans- 
verse plane. 
4. A greater amount of xylem is produced than in stems of controls. 
5. The rigidity of the stems is increased by the motion. 
6. This rigidity is greater in the diameter in the plane of swaying than 
in the transverse diameter. 
7. The tensile strength is decreased, apparently, though the work on this 
point is not conclusive. 
8. Rocking without tension produces some excentricity, due to geotropism. 
9. Swaying “in the wind” produces greater excentricity, due to the com- 
bined stimulus of strain and gravitation. 
Maude Gilchrist, 
Michigan Agricultural College. 
