20 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



According to Wiesner's '^'^ investigations etiolated seedlings are 

 capable of much more delicate phototropic reactions than others 

 grown in diffuse light. He also believed to have confirmed the con- 

 clusion that light retards growth, finding that such effect was exer- 

 cised even by intensities insufficient to act as phototropic stimuli. 

 The retarding effect was attributed to the entire spectrum, and was 

 quite as great in intense yellow as in blue light. The retarding in- 

 fluence of light was ascribed to the action of the rays not only on the 

 peripheral layers of protoplasm, but also on the wal., as well as upon 

 turgidity. 



A decade later Godlewsky"^ reviewed the entire subject and, after 

 a masterly discussion of the established facts of etiolation, concluded 

 that the theories of self-nutrition and that etiolation was a pathological 

 phenomenon, were inadequate. He proposed instead that such reac- 

 tions were purely adaptive in their nature and are designed to bring 

 the reproductive and food forming organs up into light as rapidly 

 as possible, the food and energy of the plant being directed to the 

 development of the members which would accomplish this purpose. 

 The same theory had been proposed in a general form by Boehm ^^ 

 three years previously. 



In some later investigations by Godlewsky plants kept in dark- 

 ness until II A. M. were found to exhibit a minimum rate at 9 A. 

 M., and after illumination at 11 A. M. the rate was below the normal. 

 The elongating zones were found to be longer in etiolated than in 

 normal green plants, but the turgidity was no greater. Godlewsky 

 affirms that the ductility of etiolated and normal stems is about the 

 same. Maximum ductility in any given cell is maintained longer 

 in etiolated plants however. The illumination of an etiolated plant 

 is followed by a decrease of ductility and elasticity of the older cells 

 of the growing zone. Light was supposed to check the superficial 

 expansion of growing cells, and retard elongation. 



^^Wiesner, J. Die heliotropischen Erscheinungen im Pflanzenreiche. II. Th. 7. 

 1880. 



s' Godlewsky, E. Ueber die biologische Bedeutung der Etioliriingsercheinungen. 

 Biol. Centralblatt, 9: 4S1. 1889. 



Godlewsky, E. Ueber die Beeinflussung des Wachstums der Pflanzen durch aeus- 

 sere Factoren. Anzeig. d. Akad. d. Wiss. z. Krakau. Resumes, p. 206. 1890. 



Godlewsky, E. Die Art und Weise der Wachstumsretardirenden Lichtwirkung 

 und die Wachstumstheorien. Anzeig. d. Akad. d. Wiss. z. Krakau. Resumes, p. 166. 

 1890. 



6^ Boehm. Die Nahrstoffe der Pflanze. 1886. 



