FOEMATION OF WOOD 261 



phosphorus, and other elements in minute 

 proportions. 



We have already . mentioned that the cells at 

 the growing point are to all intents precisely- 

 similar to one another, that is to say they exhibit 

 no difierentiation ; as we pass from the growing 

 point to the older parts of the stem we cannot 

 fail to observe that there is a differentiation of 

 the cells and that there are several groups of 

 cells or tissues, totally unlike one another in 

 structure, but all designed to serve some special 

 purpose. 



How are these tissues formed 1 They arise 

 from meristematic tissue, that is to say tissue 

 whose cells are capable of division to form new 

 cells. The first signs of this meristem appear 

 very near the growing point, in fact almost at 

 that point it is possible to distinguish three 

 distinct kinds of tissue, and this tissue has been 

 formed by the meristem of the growing point.- 

 Let us try to make the point a little clearer. 

 The cells of the gro-wing point, which so closely 

 resemble one another, are not permanent ; they 

 constantly divide, by means of a wall which is 

 formed across each one. As a consequence new 

 tissue is formed continuously, and this new 

 tissue differs from the tissue from which it was 

 formed by the fact that all its cells are not 

 ahke. There is a central core of tissue, just 



