32 



JACQUES LOEB AND HARDOLPH WASTENEYS 



with shorter exposure of the polyps to the spectrum, namely, . 

 four and three minutes. 



The exposure of three minutes is the minimum from which a 

 result can be obtained, and the results of table 6 are difficult 

 to account for. The time of exposure is so short that slight 

 differences in the sensitiveness of various stems make tliemselves 

 felt. Both experiments agree in their result with the previous 

 ones, namely, that the region around 4735 A.u. (in the blue) 

 is the most efficient. 



It was to be expected that in a longer exposure polyps would 

 bend to the light in both indigo-blue and in green but not in 

 yellow and red. Table 7 gives the result of an experiment 

 with an exposure of fifteen minutes. 



Unfortunately, no record of the total number of polyps formed 

 in the yellow and red was preserved ; the number, however, was 

 large. 



The experiment confirms that the blue and indigo are the most 

 efficient rays while the green are markedly less efficient. The 

 yellow and red rays are inefficient. The longer exposure brings 

 out the heliotropic effects in the extreme violet which do not 

 show with shorter exposure. 



In the following experiments an attempt was made to ascer- 

 tain the influence of longer exposure. The first question was 

 whether by making the duration of exposure considerably 

 longer we should be able to induce heliotropic curvatures in the 

 yellowish-green, yellow and red. Second, we wished to find out 

 whether solarization effects might be observed in the case of 

 too long an exposure. 



