obtain this effect. On th^day after s-ich illumination examin- 



ation showed that the rhizoids of th_; cultures behind t 



sharply 

 blue and violet filters were all turned away from the light, 



tff/ltr 



behind -3d*- t. 1 '.^ filters continued in the direction in which the 



jtAAJSs *SQ -4^~~tt 



had started, .anqpoaring no different thair-&aa control in dark- 



* 



ness. Therefore the wave IS-ngths responsible for the neg- 



ative phototroplsm ffi////jiin white lighyare those 

 of the blue end of the spectrum. It should be remembered that -Hi 

 there is no question of a difference in intensity entering here 

 because each screen was placed at such a distance from the arc 

 that the quantity of light in each box qas the same. These re- 

 sults are summarized in the following table 



.. KELIOTROPI S M 



Filter^ COLOR TAV^ L^CGTH? DISTANCE FROM 

 , LIGHT CULTUPES NO. I + J 



70 red 6600-7JOQ A.U. T& <~ . 



71 orange 62^0-6800 ' bff - 

 orange 5900-6200 -rt - 



yellow 5600-5900 fe>2. - 



green 5200-5600 70 



blue 4800-5200 (* % " 



violet 4000-4700 * " + -f 



white tfo<Jo -7000 -/- 



^L. 



T Ke s e 



A Dlmilar experiment was triedVrth sunligTit; as" the source 



of illumination. The young plants were exposed behind the fil- 

 ters all day in a south window. The same results were obtained 

 as when the arc was used. Then the experiment w :s repeatedwith 

 diffused light. The boxes were placed in an east window fir eight 



hours_ --- 10 A.M. to 6 P.M. --- on March 28. Again the rhizoids 



/i^txz^-d-vt/e-*- 

 in the blue and violet light showed the frrMffiisrii, but in addition 



a considerable but much smaller portion ware affected in the same 



jP J // fJui. c+Ts*s*h<^^> f <*s<-*-<^ -* 



behind the green filter. &******[< , ->J"Jr<7L /' / 

 L ^JLtZ^^eu^^*^ +*&* **^J^* 



waj 



These experiments 'ndicate that the light of wave length 



* 



4ooo-520CWImgstrom yUnitaVf^ responsible for the phenomenon, 



but that some rhizoids, more sensitive, will respond to those of 



5200-5600. It seems very possible in view of the results on 



