THE LIVING STUFF 



23 



With the aid of a microscope we can easily make out the 

 forms of many kinds of cells taken from the bodies of plants 

 and animals. We may 

 note that cells of differ- 

 ent kinds differ from 

 each other not merely 

 in size but in shape 

 as well. Some cells 

 have thicker walls, some 

 thinner walls. Some 

 seem to have various 

 kinds of solid bodies 

 floating about within the 

 covering ; others have 

 few or none of these. 

 Some have smaller and 

 some larger bubbles of 

 clearer liquid. 



In some plant cells 

 the protoplasm can be 

 seen to move about. The 

 cells of certain water 

 plants are especially 

 favorable for showing 

 this movement (Fig. 2). 



36. Nucleus. There 

 is one special portion 

 of the protoplasm that 

 deserves particular no- 

 tice. Near the center, 

 or off to one side, we 

 can generally find a por- 

 tion of the protoplasm 



Fig. 5. Various kinds of plant cells 



/, epidermal, or skin, cells of a leaf, showing the 

 outer wall greatly thickened, and the cuticle ; s, co- 

 lumnar cells, like those of the palisade layer of a 

 leaf pulp ; 3, moving ciliated cells, like those of 

 typhoid bacilli ; 4, swimming spores of a water 

 mold ; J, budding cells, like those of the yeast plant ; 

 6, guard cells inclosing a breathing hole, or stomate^ 

 on the surface of a leaf; 7, a pollen tube growing 

 out of a pollen grain 



that seems to be denser than the rest. This is called the kernel, 

 or micleiis. Because of the transparency of the protoplasm it 



