1899] 



VEGETABLE ANIMATION 



J 95 





resistance. It is very interesting to observe, if one gives close 

 attention to the appearance of the pale spots at the base of the 

 leaflets, that a flush of dull green passes over them at the moment of 

 movement. This is most easily seen by holding the stimulated leaflets 

 back. The same change of colour is observed in the cushions of the 

 leaf-stalks. 



It is evident that, whatever the nature of the route along which 

 the force of stimulus is conveyed, there must be few obstacles. If it 

 is the case that cell is connected with cell by delicate threads of proto- 

 plasm which pass through the cell-walls, means of uninterrupted passage 

 is afforded when the signal to contract or relax is shot along the tissues 

 of the cushion. 



It is not generally known that the cotyledons of Mimosa pudica 

 also respond to touch. They originally form 

 almost the whole bulk of the seed, and, in 

 germination, rise as fleshy, oval, green leaves. 

 In a warm temperature they move upward 

 fairly quickly, through a considerable angle, 

 when touched. It is of more than passing 

 interest to find sensitiveness exhibited by em- 

 bryonic structures, especially when they differ 

 so greatly from the adult ones in form. 



While the leaflets of the Sensitive Plant 

 rise to meet each other when irritated, in Oxalis 

 (Biophytum) sensitive/, (a plant occasionally grown 

 in greenhouses) they fall. The leaves of this 

 species are pinnate, not trifoliate, as in our 

 native one, wood sorrel. 



The purpose served by the movements de- 

 scribed is to secure the protection of the foliage. 

 In Dionaea and Aldrooanda, two of the series of 

 " Insectivorous Plants " studied so minutely by Darwin, the closure of 

 the leaf-blades is to effect the capture respectively of insects and aquatic 

 animals. It may be mentioned as a practical matter that Aldrovanda 

 is not easily kept healthy for long, unless in water free from lime. 



To many, familiar with the irritability of the Sensitive Plant, the 

 discovery of visible movement in other organs than leaves may not 

 excite much astonishment. If we cautiously examine the flower of any 

 kind of barberry, the columnar pistil will be seen in the centre, with 

 six stamens around it leaning backward, close to the petals and sepals. 

 If the point of a pencil, or the like, be inserted, as if to reach the 

 nectar glands near the base of the petals, there is every likelihood of 

 at least two of the stamens suddenly falling forward against it. After 

 a short interval the stamens gradually fall back and resume their 

 former position, and become ready to repeat the movement when 

 touched. A very few experiments show that the stamen differs from 



P 



/• 



Seedlings of Mimosa pudica. 



Fig. 1. — Undisturbed. 



c, cotyledon. 



Fig. 2. — Touched (nat. size). 



