J 



Notes on the effect of mechanical pressure on the roots of 



Vicia Faba 



. Louise Hoyt Grkgory 



According to the second law of Hertwig,* '' the axis of the 

 mitotic figure typically h"es In the longest axis of the proto- 

 plasmic mass, and division therefore tends to cut this axis at a right 

 angle." Pflugerf and Driesch, | experimenting with sea-urchin 

 eggs, found that Hertwig's law held true even when the eggs had 

 been compressed, and, as a result of the pressure, the long axis of 

 the body was modified. 



Conditions among plants do not always verify this law. 

 Berthold § has shown that the cells of the cambium layer may 

 divide lengthwise, in which case the mitotic figure would lie in the 

 shortest axis of the body. Kny, H from his experiments of pres- 

 sure on the division wall of plants, comes to the conclusion that 

 the orientation of the mitotic figure, and with it the position of the 

 division wall, may be influenced by pressure. 



My work has been done with the purpose primarily of seeing if 

 there is a definite effect of pressure on the mitotic figure, and 

 secondarily of studying the morphological changes that take place 

 in the compressed root-cells. The problem was given me by Pro- 

 fessor H. M. Richards, whom I wish to thank for his helpful 



suggestions. 



The material used in the work was Vicia Faba, whose roots are 

 large and well adapted for experimental purposes. Roots of Zea 

 Mays and Helianthns anmnis were tried, but gave poor results. 



* Hertwig, O. Welchen Einfluss iibt die Schwerkraft auf die Teilung der Zellen ? 



Jenaische Zeitschrift i8 : — . 1884. 



tPfiiiger, E. tJber die Einwirkung der Schwerkraft und anderer Bedingungen 



auf die Richtung der Zelltheilung. Arch. ges. Physiologie 34 : 607-616. 1884- 



X Driesch, H. Entwicklungsmechanische Studien IV, Zeitschrift wiss. ZooXo- 



gie 55; — . 1893. 



\ Berthold, G. Studien iiber Frotoplasmamechanik. Leipzig, 1886. 



11 Kny, L. Ueber den Einfluss von Zug und Druck auf die Richtung der Scheide- 



wande in sich theilenden Pflanzenzellen. Ber. Deut Bot. Gesell. 14: 378-39'- 



1896. 



457 



