2 10 
James Small. 
In this way the velocity of the wind used in each experiment can 
be calculated from the pressure such a wind has upon the disc of 
the anemometer. 
Constants — 
Diameter of Tube=4’5 cms. 
Length of Tube for Dispersal=125 cms. 
Area of Disc of Anemometer=8'55 sq. cms. 
k=-0025 gms. 
Method. 
The essence of the experiments lies in dropping the fruits 
through the hole D in the tube and determining the maximum 
amount of wind which has no effect on the fruit when it has once 
fallen, and also the minimum amount of wind which blows the fruit 
right through the tube. Preliminary experiments showed that the 
relative humidity of the air had an effect on the results, so that the 
R.H. was determined at the time of each set of observations. As 
the general phenomena are very similar for each species one 
example will now be given in detail. 
Taraxacum officinale, Weber.—The same fruit, an average 
one, was used throughout the experiment. It was manipulated 
with tweezers and inserted through the hole into the tube. Two 
or three observations were taken with the tube at each of the 
several distances from the fan, the distance being measured from 
the heavy end of the fruit in each case. The results are given in 
Table X. The Relative Humidity was *77; the pappus spread 
out to form a flat disc-like surface by means of a pulvinus of the 
Lactuca type (see Chap. V, A). The lowest speed of the fan was 
used throughout the experiment. 
In Table X the first column gives the distance from the fan 
of the near end of the tube. From these measurements the pres¬ 
sure on the disc is calculated from the observed pressure of ’16 
gms. at 30 5 cms. (cp. Table IX); this pressure is giyen in gms. per 
sq. cm. in the third column. The velocities calculated from the 
observed pressure, taking k=-0025 gms. in the formula V=p' 
are given in the fourth column. These figures are calculated to 
the second decimal place, but under the conditions of the experi¬ 
ment the accuracy of the results is scarcely of that degree. The 
main point is that they are very much less than would be the case 
if the mechanics were simply those of a body falling in quiet air, 
