SPECTRUM, HELIOTROPIC REACTIONS 



TABLE 12 



Experiment 9: Eudendrium exposed to light of 

 4820 Aai. (blue) 



35 



With the same material an experiment with long exposure 

 (five and a half hours) in the region of shorter wave lengths, 

 3750 to 4700 A.u. (namely, from the blue to extreme violet) 

 was carried out. In all, 52 h3'droids out of 66 (i.e., 79 per cent) 

 were bent forward. There was not much difTerence in the vari- 

 ous regions, probably due to the long exposure. 



III. CONCLUSION AND SUMMARY OF RESULTS 



These experiments have shown that the most efficient region 

 in the spectrum for the production of heliotropic curvatures in 

 the hydroid Eudendrium is situated in the blue at -X ~ 4735 A.u. 

 This region coincides approximately with the one found by 

 Blaauw for the seedHngs of oats namely X -^ 4780 A.u. 



The regions in the red, orange and yellow are practically with- 

 out effect in both Eudendrium and Avena. 



The heliotropism of the sessile animal Eudendrium and that 

 of the sessile plant Avena are therefore identical even as regards 

 the most efficient wave length. 



We expect to discuss the effects of different wave lengths upon 

 the hehotropic reactions of motile animals and plants in another 

 paper. 



