+ 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 Myzomycetes. In many respects they 
approach very near to one of the humblest animals, the 
Ameba. They have hardly any structure, appearing like 
Fiu. 4.—Portion oF a PLasmopium or 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 
