VII 



THE HISTOLOGY OF THE CELL 



Formation of New Cells. It is necessary that new 

 cells should be produced so as to ensure growth and also to 

 continue the life of the plant. The mode in which new cells 

 are produced will depend upon 

 the kinds of organs in which the 



FIG. 117. Diagram to 

 illustrate cell division. 



FIG. 1 16. Starch grains from Potato. The left-hand figure shows a spurious 

 compound grain ; the middle a true compound grain ; and the right-hand, figure 

 ordinary starch grains. 



division takes place. Cell-formation goes on in two different 

 sets of organs, viz., vegetative and reproductive. 



The vegetative parts of a plant are those portions which 

 arc of service to the life of the individual, such as root, stem, 

 branches and leaves. The method of 

 cell-formation in all these organs is by 

 simple division. In this case the nu- 

 cleus first divides into two, the protoplasm 

 then separates into two parts, and a cell- 

 wall is formed between the newly formed 

 nuclei. Two cells are thus formed. These 

 cells are at first only half the size of the 



parent cell, but they grow and become as large as the cell from 

 which they were formed. In this method of cell formation 

 there is only a portion of the cell-wall of the new cell which is 

 new, the remaining portions belonging to the parent cell. 



The reproductive parts of a plant are those portions which 

 are concerned in the propagation of the species. They are a 

 tax on the individual which bears them, for such individual 

 must find the whole of the material necessary to give the off- 

 spring a start in life. In all the higher plants this is done by 

 the production of seeds, which produce new individuals, and so 

 keep up the continuity of the species. Cell-formation in 

 reproductive organs is characterised by a rounding off of the 

 protoplasm : and no portion of the parent cell-wall aids in the 

 formation of new daughter cells. 



