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Esther Pearl Hensel 



The third cohiniii of the last series, March 8, 190.5, shows very 

 well the negative effect of light. The tent was made of black 

 cambric, which produced so dift'use a light that an exposure of 

 solio paper for five minutes at 3 :oo p.m. on a bright day, Decem- 

 ber I, 1904, resulted in no coloration whatever of the sensitive 

 paper. Here, the flowers close as early as those situated where 

 the light is more intense. 



Following are three instances out of a dozen or more showing 

 the effect of increased temperature : 



The relative light values may be considered here also. On 

 February 25, 1905, at 10:30 a.m., light was o in the north 

 house, and .33 in the south house ; in the former the flowers 

 w^ere still open, while in the latter they were beginning to wither. 

 At T :io P.M. in the north house, the flowers were beginning to 

 close in darkness (o), while in the south house they were nearly 

 closed in a light value of .33. At 5:00 p.m. in the north house, 

 with light o, flowers were nearly, closed, while in the south house, 

 light .01, they were entirely closed. 



On March 6, 1905, at 9:00 a.m., morning glories were open 

 in the north house with light o, in the south house with light 

 ,0[2, and in the open with light .06. At i 130 p.m., they were— 



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