458 Gregory: Effects of pressure ox roots of Vicia Faba 



The methods used in the experiments were of the simplest 

 kind. The seeds were germinated and allowed to grow normally 

 for three or four days (roots havuig secondary roots were never 



used). The roots were then placed between two plaster of Paris 

 blocks in order to have the pressure lateral. The blocks were 

 held together by different widths of elastic bands, the amount 

 of pressure depending on the number and the width of the bands 

 used. The roots remained under pressure usually during tw^enty- 

 four hours, the actual time being from one P. M. to one P. M., in 

 which case the roots were fixed during the secondary period ol 

 maximum growth as determined by Kellicott.* Some roots were 

 compressed during twelve hours only ; in this case they were killed 

 at eleven P. M. during the primary period of maximum growth. 

 The roots w^ere fixed in alcohol acetic, sublimate acetic, Flem- 

 ming*s fluid, and chromic acid. Alcohol acetic was found to be 

 the best fixative. Serial sections, 5 n in thickness were made, 

 and stained with iron haematoxylin, which proved to be the most 

 satisfactory stain. Control experiments were carried out under the 

 same conditions, the roots being fixed at the same periods and the 

 sections stained in the same manner. 



Seventeen roots were compressed and sectioned. These may 

 be divided into three groups : 



1. Those least compressed, the pressure varying from 650 to 

 1000 grams. Exp. T, II, VIII, IX, XV ; 



2. Those with a medium amount of compression, the pressure 

 varying from 1000 to 1400 grams. Exp. VII, XII, XIV; 



3. Those with a maximum amount of compression, varying 

 from T400 to 2000 grams, Exp. Ill, IV, V, VI, X, XI, XIII, 

 XVI, XVII. 



The table of measurements shows the number of experiments 

 performed, the time during which pressure was applied, the length 

 and approximate thickness of the roots after compression, and 

 finally the total amount of pressure. This amount of pressure was 

 determined empirically only. The width of the crack between the 

 blocks was measured before the roots were taken out, records 

 being made of the number of strips of pasteboard necessary just to 



*Kellicott, VV. E, The daily periodicity of cell division and the elongation of 

 the root of AUmm. Bull. Torrey Club 3! : 529-550. 1904. 



