CHAPTER IV 



CYTOLOGY 



THE anatomist, as we have seen, deals with the cells 

 of the plant as they are grouped in tissues. To him 

 the tissues (which are themselves composed of numer- 

 ous cells) are the units with which he works. The 

 cytologist deals with the ultimate unit of the plant 

 body the individual cell. 



The body of a plant, like that of an animal, is ulti- 

 mately composed of innumerable minute cells, which in 

 the plant are each enclosed in a cell wall, and, together, 

 they form a kind of honeycomb. The differences be- 

 tween the cells of the various tissues are principally, 

 differences in the nature of their cell walls. Within, 

 the fundamental living cell is extraordinarily uniform 

 tliroughout the whole plant world. And even more 

 remarkable is the likeness between the cells of plants 

 and animals. In their fundamental and essential 

 features, particularly at that critical time of division 

 and reproduction, the likeness between the plant and 

 the animal cell amounts almost to an identity. This 

 branch of botany and this branch of zoology still remain 

 under the old heading of biological science, for it is 

 impossible to go deeply into cytological work without 

 using both plants and animals as illustrations of funda- 

 mental facts. 



The typical cell consists of a mass of protoplasm, 

 with a central kernel the nucleus ; in plants this is 



