144 Proceedings of Indiana Academy of Science. 
the klinostat was used to annul or make omnilateral the force of gravity 
on growing stems and roots. 
The effect of very high centrifugal force on plants has been investigated 
by only a few persons and with them the length of time the experiments 
were carried on was very short. I first began the study of the effect of very 
high centrifugal force on the growth of plants in Pfeffer’s' laboratory in 
Leipzig and since then have concerned myself with the subject in general. 
It might be supposed that very high centrifugal force varying from 3,000 
to 5,000 gravities would bring about a cessation of the growth of plants 
and probably kill the specimens. A careful study of this subject, however, 
has shown that this is not the case. The following remarks will give some 
data to show that the plant activities of the kind mentioned did not stop 
but actually continued although less actively. This was shown in the 
following way: Seedlings of Cucurbita pepo were grown until their roots 
were 3 cm. long. Four of these seedlings were then placed through a strong 
cork so that their roots projected into a strong glass eylinder which was 
5 em. long and 28 mm. in internal diameter. The cork rested on the open 
end of the cylinder by a shoulder-like projection and four places in this 
cork were hollowed out to receive the seeds. A small quantity of water 
was put in the bottom of the glass cylinders to retain the moisture neces- 
sary. Gypsum was poured over the part of the seed that projected: from 
the cork and also around the seeds to hold them in place. In all these ex- 
periments when necessary gypsum was used to hold the specimens firmly in 
place, This method of using gypsum in plant experimentation was first used 
by Pfeffer and in the year 1892. I centrifugated the above mentioned 
specimens two hours using 4400 g. The plants were not killed, as stated, 
by this severe treatment but the growth was retarded. In those experiments 
where 4400 g. was used and centrifuging took place in air the amount 
of growth was decreased from 3.5 mn under normal conditions to 2.5 mn, 
When so centrifuged in water the roots grew on the average 2.1 mn, In 
the same way decreases in the rate of growth were observed in Pisum and 
Helianthus when a force of 4400 g. were used. In the same way I earried 
out experiments on other seedlings but sometimes using less force, as low as 
2000 g. for periods first of two hours and then one, two, and in many cases 
as long a period of time as five days. In these experiments longer glass 
cylinders were used than in the first case. For example Zea mays grew on 
the average of sixteen plants with roots ten mm. long to begin with in two 
hours 3.3 mn in air when so centrifuged. In water they grew 2.65 mm. 
in two hours while the controls in sawdust grew 3.8 mn in the same time. 
With a higher centrifugal force of 5000 g. they grew about one-third less 
in the same time. For longer periods of centrifuging of one, two and up 
to five days the same effect was seen. The specimen centrifuged in water 
was killed by the water pressure at the end of the second day in this ex- 
periment. In some other experiments of this kind this did not occur, At the 
end of five days of centrifuging with 2000 g the sixteen plants averaged 77.2 
mm in length while the contre! plants averaged 105.7 mn. Arrangements 
for changing the moisture and air in the cylinders was provided. These 
experiments might be carried on for a much greater length of time if prop- 
erly arranged. This is sufficient to show, however, the severe tests which 
1pfeffer, W, Pflanzenphysiologie, Zweite Auflage, Bd. 2, P. 567. 
