196 EXPERIMENTS ON HEMP, 



during a long continuance of wet, the sensibility of the 

 Anagallis is sometimes exhausted ; and it is evident that 

 very heavy thunder-showers often take such flowers by 

 surprise, the previous state of the atmosphere not hav- 

 ing been such as to give them due warning. 



That parts of vegetables not only lose their irritabil- 

 ity, but even their vital principle, in consequence of 

 having accomplished the ends of their being, appears 

 from an experiment of Linnaeus upon Hemp. This is 

 a dioecious plant, and Linnaeus kept several fertile- 

 flowered individuals in separate apartments from the 

 barren ones, in order to try whether they could per- 

 fect their seeds without the aid of pollen. Some few 

 however remained with the barren-flowered plants, 

 and these ripened seed in due time, their stigmas hav- 

 ing faded and withered soon after they had received 

 the pollen. On the contrary, the stigmas which had 

 been out of its reach continued green and vigorous, as 

 if in vain expectation, nor did they begin to fade til! 

 they had thus lasted for a very long while. Since I 

 read the history of this experiment, I have found it 

 easy in many plants to tell by the appearance of the 

 stigma whether the seed be fertilized or not. The 

 above experiment is the more important as the abbe 

 Spallanzani has recorded one made by himself upon 

 the same species of plant, with a contrary result. 

 But as he has said nothing of the appearance of the 

 stigmas, his experiment must yield to that of Lin- 

 naeus in point of accuracy ; and even if his account 

 be otherwise correct, the result is easily explained. 

 Hemp, Spinach, some Nettles, &c. naturally dioecious, 

 are occasionally not completely so, a few latent barren 

 or fertile flowers being frequently found among those 

 of the other sort, by which provision is made against 



