LESS, xxi MULTIPLICATION OF NUCLEUS 213 



fate of the two is shown at once by the node dividing into 

 a horizontal plate of cells while the internode remains 

 unicellular. 



Soon the cells of the new node begin to send out short 

 blunt processes arranged in a whorl : these increase in size, 

 undergo division, and form leaves (A D, / 2 , / 3 ). 



These processes are continually being repeated ; the apical 

 cell is constantly producing new sub-apical cells, the sub- 

 apical cells dividing each into a nodal and an internodal 

 cell ; and the nodal cell dividing into a horizontal plate of 

 cells and giving off leaves, while the internodal cell remains 

 undivided. 



The special characters of the fully-formed parts of the 

 plant are due to the unequal growth of the new cells. The 

 nodal cells soon cease to grow and undergo but little altera- 

 tion (comp. nd l and nd^\ whereas the internodes increase 

 immensely in length, being quite 3,000 times as long when 

 full-grown as when first separated from the sub-apical cell. 

 The leaves also, at first mere blunt projections (A, / 2 ), soon 

 increase sufficiently in length to arch over the growing point 

 and so form the characteristic terminal bud : gradually they 

 open out and assume the normal position, their successors 

 of the next younger whorl having in the meantime developed 

 sufficiently to take their place as protectors of the growing 

 point. 



The multinucleate condition of the adult internodes is 

 also a result of gradual change. In its young condition an 

 internodal cell has a single rounded nucleus (A, int. nd 2 , int. 

 nd B ), but by the time it is about as long as broad the nucleus 

 has begun to divide (D, int. nd* ; c, int. nd 2 ), and when the 

 length of the cell is equal to about twice its breadth, the 

 nucleus has broken up into numerous fragments (c, int. nd l , 

 D, int. nd 2 ), many of them still in active division. This 



