4 VEGETABLE PHYSIOLOGY 



exist without any cell-membrane, and may be freely motile, 

 swimming in water by means of cilia. The absence of the 

 cell-membrane can also be observed in certain peculiar 

 fungi, which are to be found creeping over moist surfaces 

 without such appendages (fig. 4). These are known as 

 the slime-fungi or Myxomycetes. In many respects they 

 approach very near to one of the humblest animals, the 

 Amoeba. They have hardly any structure, appearing like 



Fiu. 4. PORTION OF A PLASMODIUM OF A Myxomycete. x 300. 

 (After De Bary.) 



a lump of transparent jelly, the whole mass being called a 

 plasmodium. They have the power of extruding a certain 

 portion of their substance in the form of a blunt process 

 known as a pseudopodium, and by means of these pseudo- 

 podia they can creep slowly over the surface on which they 

 are lying. The naked condition is, however, exceptional 

 in plants. In most of those which are unicellular the 

 living substance is covered by its delicate membrane, and 

 it may either occupy all the space inside the latter, 

 or may have in its interior a cavity or vacuole, which is 



