24 Esther Pearl Hensel 



OTHER HEMERANTHOUS TYPES 



The flowers of Gentiana parryi, the large blue gentian, open 

 for two or more clays only during the day from 8:00 to 10:00 

 A.M. and close from 5 :oo to 6:00 p.xM. It is very noticeable that 

 they do not open on cloudy, cold, or rainy days and that they 

 close on the approach of rain. Detached flowers will stay open 

 in the house at night but will close out of doors; if brought in- 

 doors they will open in the dark. Gentiana acuta behaves in 

 much the same way, and opens at about the same time. It also 

 stays open for almost the same number of days, possibly a little 

 longer. 



I carried on a few experiments with tulip flowers, but was 

 unable to do much with them as they did not seem -to close at 

 night. They were forced bulbs potted for me by a local 

 greenhouse. I did succeed in opening a few with increased tem- 

 perature but not with J/<° C. difference, such as Pfeffer says is 

 possible; nor was it possible to close the flowers with either a 

 moderate or extreme degree of cold. 



NYCTANTHOUS TYPES 



Experiments zvith Mentselia nuda. The flowers of this plant 

 open from 3:00 to 5:00 p.m. and are closed again the following 

 morning between 5 :oo and 6:00 a.m. This is repeated for 3 to 5 

 days. The sepals do not close around the corolla after once 

 opening, but stay reflexed. When first opened, the flower emits 

 a fragrance which is lacking after a few hours, a fact probably 

 in some way connected with pollination. On rainy days, when 

 it is cool and cloudy, the opening is two hours or more earlier 

 than on bright sunshiny days. The experiments which I was 

 able to carry on were all performed in the fields, in the moun- 

 tains at Halfway, Colorado. The gravel slides on which Ment- 

 zelia grows experience very great extremes of temperature on 

 their surface: during a single day, from 10° C. between 6:00 and 

 7:00 A.M. to as high as 46° C. at 11:00 a.m. or 25° to 35° C. 

 between 2:00 and 3:00 p.m. On account of this fact, I took soil 

 samples of the gravel at the time the flowers opened or a little 



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