96 



Gravitation sensitiveness not confined 

 to apex of root 



By 



Frederick C* Newcombe, 



Ann. Arbor, U. S. A., Univ. of Michigan. 



With plate III and 6 figures in the text. 



From the time that Charles and Francis Darwin 1 ) in 1880 

 published their experiments on the behavior of decapitated roots 

 toward gravitation down to the year 1895 when Czapek 2 ) pub- 

 lished his results obtained by the employment of glass caps, the 

 contest waged over the question of the perceptive region of the 

 root, a contest accompanied by numerous polemics and thousands 

 of root-decapitations. With the publication of Czapek's work, how- 

 ever, the botanical world seems to have accepted the matter as 

 ended, and has apparently given adherence to the view that only 

 the apical one or two millinieters of the root-tip acts as the per- 

 ceptive organ for gravitation. Earely an author, as in the case 

 of Richter 3 ) and Jost 4 ), states that the proof is still lacking. 



Now it can be shown that neither Czapek's method nor any 

 other method so far employed has or can prove the restriction of 

 the perceptive region to the apical two millimeters of the root. 

 And this demostration can be given without farther experiment, as 

 a matter of logical reasoning. 



Part I: Lack of evidence of localization of geotropic 

 sensitiveness. 



As is well known, most roots, when two millimeters of the 

 apex are excised, show no farther response to gravitation. This 

 result however has not been accepted as demonstrating restriction 



*) Power of movement in plants. London. 



2 ) Untersuchungen über Geotropismus. (Jahrb. wiss. Botanik. XXVII. 

 1895. 243.) 



3 ) Zur Frage nach der Funktion der Wurzelspitze. Inauguraldiss. Frei- 

 burg i. Br. 1902. 



4 ) Review of papers by Richter, Darwin and Massart. (Bot. Zeit. 

 61. 1903. Abt. II. 23.) 



