4 VEGETABLE PHYSIOLOGY 
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 
Ameba. They have hardly any structure, appearing like 
alump 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 protrusion 
Fic. 4,—Portion or 4 Puasmopium oF A Myzxomycete. x 300. 
(After De Bary.) 
known as a psewdopodium, 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 a delicate membrane or 
cell-wall, and it may either fill the space inside the latter, 
or may have in its interior a cavity or vacuole, which is 
filled with a watery fluid. In the multicellular plants each 
chamber during life contains its own protoplast or little mass 
of protoplasm, which is connected, as already mentioned, 
