1 8 Esther Pearl Hensel 



is in all cases, however, the cause of movement, light and the 

 humidity of the air in no way influencing it except in so far as 

 they are necessary to the .continued growth of the plant. The 

 Composite head acts as the simple flower. 



Experiments shozuiiig that light docs not influence opening 

 and closing. Plants with buds that were ready to open, or that 

 were open for the first time, were at 6:00 p.m. put into shade 

 tents made of black cambric and of sufficient darkness so that 

 there was not the slightest coloration of solio paper at 3:00 p.m. 

 after 5 minutes exposure, when the sun was shining brightly 

 upon the tent. The next morning, the flowers in the shade tents 

 were open as wide as those in normal sunlight. In other experi- 

 ments, the same results were obtained ; in nearly every case, the 

 temperature in the shade tent was the same as in the sunlight, 

 or a little higher. 



Experiments shelving that hiiiiiidity has no direct eifcct upon 

 ■flower nioi'cmeut. Plants with flowers open one day only were 

 used. At 5:00 P.M. after the flowers had closed, one plant, well 

 watered, was placed in a bell jar with the sides of the bell jar 

 wet with water and the pot standing in water. A thermometer 

 was suspended in the jar. Another plant was placed in a bell 

 jar, which had been dried by lying on its side in a very dry room 

 with an air temperature of 23° C. and a relative humidity of 25 

 per cent. The pot was wrapped in rubber cloth so that there 

 could be no evaporation from the pot or soil, and a flat dish filled 

 with calcium chloride placed beside it to absorb any moisture 

 given off. A thermometer was suspended in this jar also. The 

 following morning, both flowers were open at 8:00 a.m., as were 

 those left in normal conditions. The temperature in the dry jar 

 was 27.6° C, in the moist one 25.6° C, and in the normal one 

 21° C. with a relative humidity of 54 per cent. The same results 

 were obtained several times, so that this experiment also seems 

 to prove conclusively that opening i^ not dependent directly upon 

 the humidity of the air. 



Experiments shozving that variations in temperature produce 

 opening and closing. T have been able to open and close dande- 

 lion flowers before the usual time by varying the amount of heat 



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