194 WILD FLOWERS. 



in this way, it becomes slightly acid, and is much 

 valued by the Norwegians and Swedes as an article 

 of food. 



The butter-wort, in common with many marsh 

 plants, curiously exemplifies the interesting subject 

 of vegetable irritability. If the flower-stalks be 

 rudely touched or struck, the heads, which from their 

 own weight have drooped forward, gradually and 

 with a perceptible movement, erect themselves until 

 at length they sometimes actually lean backwards. 

 So sensitive under some conditions is the whole 

 plant, that if a flower be gathered, all the remain- 

 ing stalks bend backwards and form the " segment 

 of a circle/' and the leaves close down, forming 

 almost a ball ; yet this extreme irritability does not 

 always exist, as I have frequently, and in vain, tried 

 to produce the last phenomenon. It is, however, 

 attributed to it by botanists. 



