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VEGETABLE PHYSIOLOGY 



and not excited by any stimulation from without. The 

 phenomenon is often spoken of as ciliary motion. 



Of a somewhat similar character is the curious creeping 

 movement of the Myxomycetous Fungi. In a few cases the 

 zoospores of these organisms are furnished with cilia or 

 flagella, resembling those of the zoospores already men- 

 tioned, but more frequently each consists of a minute mass 

 of naked protoplasm, which makes its way over the 

 surface of its substratum by putting out blunt processes 

 of its own substance, known as pseudopodia (fig. 148). 



FIG. 148. STAGES IN CONSTRUCTION OF THE PLASMODIUM OF A 

 Myxomycete, 



After a while a number of these zoospores become fused 

 together to form a large jelly-like mass, known as a 

 plasmodium. This colony of protoplasts then makes its 

 way slowly over its substratum by similar pseudopodial 

 movements. Each pseudopodium is a protrusion of the 

 ectoplasm, and the more fluid endoplasm is in some way 

 drawn into the different protrusions, so that the rest of 

 the cell or of the plasmodium follows the extension of the 

 pseudopodium and is dragged after it. Which part of 

 the operation corresponds to the act of contraction is 

 disputed, but it seems probable that it is the second, and 

 that the first protrusion is of the nature rather of relaxa- 

 tion. The movement, like that of ciliary action, is a 



