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VEGETABLE PHYSIOLOGY 



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). 

 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 



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

 Myxomycete. 



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 

 property of the organism, and is used by it in the ordinary 

 course of its life, even in the absence of stimulation. 



Among the lowliest of the Algae or seaweeds some other 



