386 



In the averages Koninosbergf.h's tables (4) of the light- and daik- 

 growth-response a iTiaxiniiim occiiniiig after dai'keniiig ina^' indeed 

 be found on pages 51, 52 and 53. It occurs after ahont 20 — 30 niin., 

 (circa 25 minutes), but also in connection with further experiments 

 KoNiNGSBERGKH does not consider these reactions as dark-growth- 

 responses. 



In the cases, in which Vogt observed the dark-growth-response, 

 it lies averagelj after 21—24 min., (averagely 22i min.), which is 

 in accordance with our results. Siehp finds his maximum averagelj 

 after 30^ — 35' min. (averagelj 33 min.). But we should beai' in 

 mind, that this investigator did not change the exposure to 320 M.K. 

 to dark, but to a slighter illumination with. 17. 7 M.K. (pag. 699 

 and (following). 



Accordinglj in our experiments both after a previous exposure 

 of 6 and 8 hours, and of 4 and 4è hours, we tound a dark-growth- 

 response with the coleoptiles of Aveiia, contrarj to the light-response 

 of this organ. 



The Light- and Dark- growth-responses of the root of Sinapis alba. 



This organ being much less sensitive to light, 1 deemed it desirable 

 to applj stronger illuminations, \iz. of 3500 M.K. In spite of the 

 insertion of a cooler with running water into the circuit, a gradual 

 rise of temperature fiom 0°.5 — 1°.0 C. in the course of an hour 

 could not lie prevented. On darkening, a fall of temperature could 

 be prevented bj again putting the heating into operation. Then 

 oscillations above 0°.05 — 0°.l C. did not occur. 



The roots were subjected to 4-sided illumination at 21°, 5 — 22°.8 C. 

 for 3 — 5 hours. First the light-growth-respoiise was determined, 

 yielding the following averages: 



We observe a distinct response of growth. The retardation of 

 growth is permanent in all cases also after the new external equi- 

 librinm of growth has been attained. 



