DEVELOPMENT AND FUNCTIONS OP CELLS. ' 51 



nal reproductive cell should make its appearance. Could we 

 but answer these simple questions, we could explain the form- 

 ation of vegetable out of mineral matter, the laws which 

 govern the evolution and special arrangement of cells into the 

 specific forms assumed by plants, and the mechanism of the 

 entire vegetable creation. But, although the subject of cell- 

 development has recently taxed the powers of the ablest 

 minds, it is still confessedly obscure. A more thorough 

 investigation of the simpler forms of vegetation seems to be 

 necessary to the understanding of this important subject. 



59. It would seem, from the facts already brought to light, 

 that there are two methods of cell-multiplication by which 

 growth and reproduction are effected, which are but modifica- 

 tions, of one and the same process of division: 1. The cell is 

 multiplied by the formation of a partition across its cavity by 

 which it is divided into two cells ; one of these cells elongates, 

 and is again subdivided in a similar manner, the original wall 

 of the cell remaining. In this way, a single cell gives rise to 

 a row of connected cells, when the division takes place in one 

 direction, and to a plane or solid mass of cells, when it takes 

 place in two or more directions. This is the ordinary mode of 

 increase in all growing or vegetating parts. 2. The cell is 

 propagated by division of its interior cavity into two, four, or a 

 greater number of free new cells, the original cell-wall being 

 absorbed or perishing in the operation. By this method the 

 reproductive cells of pollen formed in the anthers of all flower- 

 ing plants, and the spores or reproductive cells of flowerless- 

 plants, originate. 



