CHAPTER I. 



ON THE INDIVIDUALITY OF THE CELLS. 



Every plant, germinuting from the seed or spore, is sub- 

 ject from tlie commencement of germination to the close of 

 its allotted period of life) to certain definite laws of develop- 

 ment which are impressed on the cells of which that seed 

 or spore consists. 



If we consider the cells collectively as associated together 

 in masses, constituting definite organs, the regularity and 

 fixity of form assumed by those organs, shows that a certain 

 definite number of cells must be developed to form them, 

 and that these cells must attain a determinate amount of 

 expansion; for growth, or the enlargement of the organs of 

 plants, certainly appears to be as much the result of the 

 expansion of cells already existing, as of the formation of 

 new cells. 



But the cells themselves, regarded individually, exhibit 

 a series of phenomena which prove that they are subject to 

 laws of development, as rigid and invariable as those which 

 govern them collectively. The primitive form of all cells, 

 whether animal or vegetable, is that of a closed spherical 

 vesicle or utricle. There is no plant, or organ of a plant, 

 which is not at the commencement of its growth, fabricated 

 exclusively of cells which approach more or less to that of 

 a sphere in form. If we examine a bud, a young leaf or 

 rootlet, with the ^microscope, in the first stages of growth, 

 we shall find that cells which retain in a great measure 

 their primitive sphericity, and present the same uniform 



