254 THE LIFE OF THE PLANT 



Tradescantia (see fig. 15) or the stinging hairs of the 

 nettle, and also in the cells of the flesh of fruit, as, for 

 instance, the large cells visible to the naked eye making 

 up the ripest parts of a water melon. We have but 

 to take some of these cells with a needle and place them 

 under a microscope to notice this curious streaming 

 movement of the protoplasm in every one of them. 

 Thus the protoplasm in these cells is in continuous 

 movement. This movement is spontaneous : it is not 

 provoked by any external physical agents, although 

 such agents as heat or electricity may affect it, accelerat- 

 ing, retarding, or even entirely arresting it. So many 

 and such varied illustrations of this movement are 

 known to us, that it seems most likely it is character- 

 istic of the protoplasm of all cells, at all events at a 

 certain period of their existence. 



Sometimes this movement of the protoplasm mani- 

 fests itself in a still more curious way, and so strongly 

 as to be seen even with the naked eye. There is a 

 group of organisms so peculiar that for a long time 

 scientists wondered whether they were to be con- 

 sidered plants or animals. Even nowadays some 

 people reckon them as a separate third kingdom, 

 although it might be more reasonable to range them 

 among the simplest plants, along with the fungi. These 

 organisms are called slime fungi, because during the 

 greater part of their existence they present but a mass 

 of protoplasm without any structure whatever, without 

 any cell-walls, and therefore like slime, colourless, or of 

 a brownish or bright yellow colour. These organisms 

 appear on the surface of decaying wood, leaves, etc. 

 One such organism specially well known occurs on 

 the piles of bark accumulated in tanneries. It appears 

 in masses without any definite shape, looking like thick 

 cream, only yellow in colour, penetrating amongst the 

 pieces of bark in thin filaments, or collecting on their 

 surface in variously branched or compact masses. If 



