346 



SPONTANEOUS MOVEMENTS IN PLANTS. 



to the vibratile cilia of animals, especially those of the polygastric 



animalcules ! In Conferva 



vesicata, the vibratile cilia 



are found to occupy one 



end of the spore (Fig. 475). 



In other species, they are 



likewise restricted to some 



one part of the surface, but 



are only two or three in 



number. 



661. In Oscillaria (Fig. 

 66, p. 66) the fully devel- 

 oped plant exhibits occa- 

 sional writhing movements, 

 so well marked that the 

 vegetable character of the 

 genus was once question- 

 ed. The Closteria (Fig. 

 77) and other minute Des- 

 midiaceous plants exhibit 

 well-marked spontaneous 



movements of translation from time to time : and the nearly allied 

 Diatomacea3 the lowest and most ambiguous of plants were 

 long referred to the animal kingdom, on account of the energetic 

 motions they exhibit. The lowest tribe of plants, in this as in 

 other respects, makes the closest approach to the lowest tribes of 

 animals. 



662. Not only, therefore, do many, if not all, plants manifest 

 sensitiveness to external agents, and more or less decided, though 

 slow, movements ; but many species of the higher grades exhibit 

 certain vivid motions, either spontaneous or automatic, or in conse- 

 quence of extraneous irritation ; while the lowest tribes of aquatic 

 plants, as they diminish in size and in complexity of organization, 

 habitually exhibit, at some period of their lives at least, varied 



FIG. 467. Fruiting end of a plant of Vaucheria geminata (after Thuret) ; one of the branches 

 still containing its spore. 463. Moving spore just escaped from the apex of the other branch; 

 the ciliary apparatus seen over the whole surface. 469. Spore in germination. 



FIG. 470-473. Successive steps in the germination of Conferva vesicata. 474. The plant 

 developed into a series of cells, four of which display the successive steps in the formation of a 

 spore. 475. The locomotive spore with its vibratile cilia (copied from Thuret). When the 

 movement ceases, and it begins to germinate, it appears as in 470. 



