SOME REMARKABLE WAYS OF PLANTS 161 



certain particular class is known by the name of 

 " Sensitive Plants," because of their especially rapid 

 response. 



With one kind, a gentle wind blowing on the leaves, 

 a few drops of rain, or even the touch of a finger, will 

 cause a hurried folding together and drooping ; much as 

 other leaves will do slowly at the approach of night. A 

 particular species, growing in India, is so excessively 

 sensitive, that even a touch is not needed. 1 It is enough 

 for a man simply to come near ; and the slight stir of air 

 caused by his movements will make the leaves shrink 

 and fall, as if in alarm. 



Years ago I saw in Kew Gardens a singular example. 

 It was the Telegraph Plant from Bengal, 2 a small thing 

 in a pot, with slim pointed leaflets. Outward touch 

 had no effect, but as we stood looking one leaflet here 

 or another there would suddenly drop, like a railway 

 signal falling to announce a train. Then, I was told, 

 each would gradually rise to its old position soon to 

 drop again. No cause was known to which these move- 

 ments could be traced, but they were found to be more 

 frequent with greater heat. 



Many sensitive plants grow in tropical countries, 

 and one of them, a Mimosa, has delicate leaves, which 

 respond prettily on the smallest provocation. First the 

 leaflets droop, then with speed the whole leaf-stalk falls 

 limply. In such cases we do not find the slowness of 

 movement common in plant-life. 



By far the greater number of these curious growths 

 belong to foreign countries. But the little Wood-sorrel 



1 Oxalia sensitiva. 2 Desmodium gyrans. 



