EXPERIMENTS ON HEMP. 25 1 



from the green leaves of the plant folding closely about 

 them. Convolvulus ar^vensis, t. 312, Anagallis ar- 

 vensiSj t. 529, Calendula pluvialis, and many others, 

 are well known to shut up their flowers against the 

 approach of rain ; whence the Anagallis has been 

 called the Poor Man's Weather-glass. It has been 

 observed by Linnaeus that flowers lose this fine sen- 

 sibility, either after the anthers have performed their 

 office, or when deprived of them artificially ; nor do 

 I doubt the fact. I have had reason to think that, 

 during a long continuance of wet, the sensibility of 

 the Anagallis is sometimes exhausted ; and it is evi- 

 dent that very sudden thunder-showers often take 

 such flowers by surprise, the previous state of the at- 

 mosphere not having been such as to give them due 

 warning. 



That parts of vegetables not only lose their irrita- 

 bility, but even their vital principle, in consequence of 

 having accomplished the ends of their being, appears 

 from an experiment of Linneeus upon Hemp. This 

 is a dioecious plant, see p. 234, and Linnaeus kept 

 several fertile-flowered individuals in separate apart- 

 ments from the barren ones, in order to try whether 

 they could perfect their seeds without the aid of pol- 

 len. Some few however remained with the barren- 

 flowered plants, and these ripened seed in due time, 

 their sticrmas having faded and withered soon after 

 they had received the pollen. On the contrary, the 

 stigmas v/hich had been out of its reach continued 



