PERIODICAL OPENING AND CLOSING OF FLOWERS. 17 



life through the falling rays, till the moment when insolation 

 commences, after which the number again decreases. At mid-day, 

 with few exceptions, and those of night-bloomers, every flower has 

 opened its cup. 



It is time, however, to institute a similar inquiry into the circum- 

 stances attendant on the cessation of insolation and the setting of 

 the sun. 



Plants whose blossoms close before the end of insolation : 



Sonehus asper, 10 hours before, or — 10 



Lactuca scariola — 8 



Scorzonera laciniata — 7 



5 species — 6 



5 „ — 5 



10 „ — 4 



6 „ — 3 



12 „ — 2 



14 „ — 1 



The number of species increases as the hour approaches at 

 which insolation ceases. No blossom closes before the insolation 

 begins, for even those plants whose cups are closed before mid-day 

 remain for some hours with open cups exposed to the direct rays 

 of the sun. 



Plants whose blossoms close with the cessation of insolation : 

 11 species. 



Plants whose blossoms close after the cessation of insolation : 



2 species 

 2 

 3 



3 „ 

 2 

 2 

 3 



Lychnis vespertina 

 (Enothera biennis 



+ 1 



+ 2 



+ 3 



+ 4 



+ 6 

 + 7 

 + 12 

 + 15 



When insolation, and therewith a higher degree of intensity of 

 light, has ceased, a peculiar apathy, as regards the light which still 

 remains, seems to possess the vegetable kingdom, for though with 

 the rapidly decreasing intensity one might expect a rapid increase 

 in the number of plants which close their blossoms, almost an 

 equal number of cases occurs at every hour after the end of 

 insolation. We must suppose, therefore, that in consequence of 

 many hours' exposure to the influence of the direct rays, their 

 susceptibility towards the far fainter light which is dispersed in 



