CH. V] CAMBIUM. 73 



and from 6 to 15 or more cells in depth ; it will also be 

 seen that the top and bottom edges of the rays end in 

 ridge-like cells, triangular in outline, which give to the 

 rays the form of double-edged blades. 



Cambium. 



To understand the part played by the cambium it is 

 necessary to examine it under a high power. The 

 beginner will not find it easy to prepare sections of the 

 requisite amount of fineness owing to the delicate nature 

 of the tissue. But although he will not be able to see as 

 much as is shown in the figure (fig. 34) taken from 

 Strasburger, yet he ought to be able to make out some 

 of the chief points. The most characteristic feature about 

 the cambium is the radial arrangement of its cells. The 

 arrangement is so regular that it enables us to sketch 



FIG. 34. 

 TRANSVERSE SECTION OF THE STEM OF THE SCOTCH FIB (Pinus sylvestris). 



phi, phloem; s.p, sieve-plate ; m.r, medullary ray; 



c, cambium ; the letter c is opposite to the initial cell i ; the youngest or 

 latest formed cell wall forms the right hand wall of the cell i ; it 

 may be recognized by ending flush against the radial walls. 

 In the xylem, 1, 2, 3 represent stages in the development of the bordered 

 pits which characterize the tracheids of the pine. 

 After Strasburger. 



