CH. Ill] 



MERISTEM. 



39 



region M about the centre of the limiting line, that new 

 cells are being manufactured to replace the ones that are 

 lost. Not only is the region M the manufactory of root-cap 

 cells, but it is also the manufactory of cells which go to form 

 part of the main body of the root. Thus if we were to 

 examine a longitudinal section of a root, and if we carried 

 our observation along the centre line RMC in fig. 14, we 

 should discover this remarkable state of things : well- 

 grown differentiated cells at R, and again at C differentiated 

 root-cap cells, and between them at .M" a small quantity 

 of meristematic tissue, minute, delicate, simple undiffer- 



in 



c 



FIG. 15, 



DIAGRAM ILLUSTRATING MERISTEMATIC (OR MERISMATIC) TISSUE. 

 I. a meristematic cell ABGD. II. a cross-wall db has appeared. 



III. AabB has grown and again equals ABGD in size, while aCDb has also 

 grown. 



IV. AabB has been divided by a cross- wall cd. 



V. AcdB has again grown, it equals ABCD in size and is ready again 



to divide. Meanwhile cabd and aCDb have increased in size con- 

 siderably. 



