LITERATURE 403 



as well as sensitive. Many cryptogams show negative geo- 

 tropism. Many branches and rhizomes show transverse geotro- 

 pism. Among animals, hydroids show negative geotropism. 

 A marked after-effect follows negative stimulation, by means 

 of it we can show that stretching or the geotropic curvature 

 are independent of any control from the tip after once the 

 stimulus has been transmitted to the stretching region. Like 

 other responses to stimuli, geotropism does not occur in the 

 absence of oxygen. 



LITERATURE 



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feuille des mousses. Rev. Gen. de Bot. Ill, 255 et seq. 

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 CiESiELSKi, T. '72. (See Chapter XIV, Literature.) 

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 Darwin, F. '82. On the Connection between Geotropism and Growth. 



Jour. Linn. Soc. XIX, 218-230. 

 Driesch, H. '92. Kritisohe Erorterungen neuerer Beitiage zur theoretischen 



Morphologie. II. Zur Heteromorphose der Hydroidpolypen. Biol. 



Centralb. XII, 545-556. 1 Oct. 1892. 

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der Schwerkraft auf die Pflanzen. Acta Soc. Scient. Fennicse, Helsing- 



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 '80^ Ueber einige horizontal wachsende Rhizome. Arb. Bot. Inst. "Wiirz- 



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Ztg. XXIV, 49-54. 16 Feb. 1866. 

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 Johnson, H. '29. The Unsatisfactory Nature of the Theories proposed to 



account for the Descent of the Radicles in the Germination of Seeds 



shewn by Experiments. Edinb. New PhUos. Jour. April, 1829. 



812-317. 

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Xin, 180-183. 

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XLIX, 175-189. 



