144 Proceedings of Indiana Academy of Science. 



the kliiiostiit was used In jniniil or make (iniiiilalcral llic foi-cc of .s,'nivity 

 oil 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 w'ill 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 cylinder which was 

 5 cm. 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 (luantity 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 centrifugiug 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 carried 

 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 i-oots ten mm. long to begin with in two 

 hours 3.3 mn in air when so centrifuged. In water they grew 2.(i5 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 centrifugiug of one. two and up 

 to five days the same effect was seen. The si^ecimen 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 centrifugiug with 2000 g the sixteen phmts averaged 77.2 

 mm in length while the control plants averaged 103.7 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 sutficient to show, however, tlie severe tests which 

 ipfeffer, W, Pflanzenphysiologie, Zweite Auflage, Bd. 2, P. 567. 



