268 



THE CELL 



447. While a true cell must have cytoplasm and a nucleus, 

 the word cell is applied to the unit structures that make up 

 the plant body. Many of these cells are dead. The wood of 

 trees consists largely of dead wood. The pith of stems also 

 may consist largely of dead cells. The cells of bark are largely 

 dead cells. 



448. Multiplication of Cells. — Every cell owes its origin 

 to some previous cell, and all go back eventually to the germ- 



443. Nuclear and cell division in the root of corn: cell with prominent resting nucleus 

 (a): prophases of nuclear division, spirem (6) and chromosome (c) stages; bipolar 

 spindle (d) ; early (e) and late (/) anaphases; telophases ig) and first evidence 

 of cell-plate; location of cell-wall clearly defined (h). (After Curtis.) 



cells. The method whereby cells are produced is complex. 

 The process is at first internal, and consists in the formation 

 of definite aggregates of protoplasm derived from the nucleus, 

 called chromosomes. In the course of the formation of these 

 chromosomes, intricate changes occur in the cell nucleus 



