--33-- 



It is interesting in this connection to note Holt and Lee's 

 ) conclusions as to the vole of the intensity factor in phcto- 

 tropis . They ntate that, "T'n^re is no evidence t/iat 







respond to any other property cf li^ht than its intensity. All 

 phototatio response in ^xplainea by the ii tensity of the 11,-^rt, and 

 the direction fro;a wai ^Ji it -lornes. 11 But my experiments 'Vith Volvox 

 show oonolu'9ively t/iac for Any Driven intensity the blu3 and violet 

 wave lengths tire --test stim luting effioienoy, but tliat by 



increasin-; th-j duration of the exoosure the same effect is produced 



L n d tlie otlir BCte^naJ and "by , aity of the 



other colors they oan be made to produce an equally rapid re ponse. 

 This is in in or a i . 1 -.c-'t's ( '^'7 ) Conclusions that photo- 



tropio resp'-na-jB are net entirely in ependent of intensity. 



