28 PLANT LIFE. 



stalk bends entirely over, so that rain passes over the 

 back of the petals or flower stalks. In the garden 

 Kniphofias (or Tritomas), the stalk also shows the most 

 extraordinary curvature. Thus, in October, the apex 

 was observed to be doubled over and pointing downwards 

 at lo a.m., whilst it had become nearly straight at i p.m. 



In some of the Compositae, the head of flowers closes 

 altogether at night, or in bad weather. This is well 

 seen in Daisies, or in the Carlina acaulis, of which 

 Kerner gives a beautiful figure. On the other hand, 

 for some reason, (perhaps the attraction of insects,) the 

 white ray petals of the garden Pyretlmim, and Yarrow 

 or Milfoil {^Achillea inillefoliunL) hang vertically down- 

 wards at night. 



Such protection is scarcely required in the case 

 of Spurrey {Spergula), in which the flower only lives 

 for five hours, and probably only opens in good 

 weather, nor in that of Rosa arvensis, which only 

 remains open two days. But in the Foxglove (six days) 

 and Cyclamen (ten days), in the cases of the Buttercup 

 (seven days) and Crocus (twelve days), movements of the 

 petals and stalk are obviously necessary to prevent 

 wastage of the pollen. , 



It is also interesting to find that the opening seems 

 to be regulated by the temperature. Hemerocallis 

 flava is open for one day only in summer time, but 

 remains open for two days in September and for three 

 days in October. The number of insects will be much 

 less numerous in the latter months, as their appearance 

 is also regulated by the temperature. 



It has been shown by direct experiment that the 

 pollen is of a hardy and resisting nature in those 

 flowers in which it is naturally exposed, such as 

 Poppies, Lilies and Water Lilies, whilst it is very sensi- 



