PINUS. ROOT. 153 



2. The Pericambium, with its secondary products 

 arranged thus : 



a. Externally a thin band of Cork, the cells of which 

 are arranged in radial rows. 



b. The Cork-cambium, the cells dividing by tangen- 

 tial walls. 



c. The remainder of the original pericambium in a 

 quiescent state. 



3. The Phloem, forming, according to the age of the 

 root, a more or less complete ring. The constituents 

 resemble those of the phloem of the stem, and are often 

 distorted by external pressure. 



4. The Cambium, as in the stem. 



5. The Xylem, in which may be recognised, near 

 the centre 



a. The primary xylem groups, arranged in the form 

 of a Y, and each having, as before, a resin-passage in 

 the fork. 



I. The masses of secondary xylem, more or less 

 fan-shaped, and alternating in position with the groups 

 of primary xylem. The number of the latter, and of 

 the masses of secondary xylem, varies in the lateral 

 root, four being the average number. The constituents 

 of the secondary xylem resemble those of the stem in 

 structure and arrangement. 



IV. Cut, and mount as before, transverse sections of 

 a root about one-eighth of an inch in diameter. 



The arrangement of tissues will be as before, but the 

 fan-shaped masses of secondary xylem will have joined 

 laterally, so as to form a complete ring. Annual rings 

 may also be seen in fact, the structure at the periphery 

 of the root now closely resembles that of the stem. 



