244. 



V. -- Pho tot rop isms ci Volvox in Mono chro 'na tic 

 Light of Equal Intensity. 



Oltraanns ( /?<fR ) , Holmes ( J<p3 ) and Mast have reported in detail 

 the reactions of Volvox to li^t stimuli. No one, however, has studi- 

 ed its response to monocnroraatic illumination. The purpcs of the 

 present study is a comparison of its phototropisrne in different spectral 

 re -ions for which the intensity is made equal. 



The recent article by Mast (l?'7) suns up in a table the litera- 

 ture on the reactions of plants and ini^als to colored light so cc - 

 pletely and so concisely that there is no necessity for a repetition 

 here. ite summarizes briefly results jiven in the table as follows: 



"For seedlings < f gr 5 n plants, plumules and radicles, the 

 region in the spectrum of maximum stimulating effect ia in the blue 

 or violet. For the fungi it is somewhat nearer the red. For Bac- 

 terium pho tour? tri cum it is in the infra-red and the orange. For 

 Oscillaria and Piraiaeoium bursaria is it questionable, activity and 

 aggregation being probably determined by cuemioal changes in the solu- 

 tion associated with the colors. For Chlp.mydomonas it is in the 

 green; for all r ther unicellular forms tested it is in the blue, as 

 it is also for the co^l^nterates and vermes and for a few of the 

 molluscs an.-" 1 Arthropods. >ut for most of the molluscs and arthropods 

 it apcears to be in the ,^re ^n or yellow." 



T -)t tb ? -:if<st effective wave lengths -ir* 3 not the erii.ie for even 

 related forms in the lowr organisms iB furt)ir borne cut by lias Us 

 ( l^l"[) results. u e found that the maximum efficiency is near 483 

 for 3uglena, Tra^relomonas, Phacus, Gonium, Arenicola and Lumbric.s; 



