TISSUES. 



157 



tion forming a flbro- vascular bundle. 



399. Woody tissue is made up of slender, lengthened, 

 lignified cells, which taper at the 



ends, and are found in woody 

 plants overlapping each other, 

 and packed in bundles (Figs. 

 502-504). 



400. Bast tissue is composed 

 of elongated cells, with thickened 

 walls, not sufficiently lignified to 

 be hard ; they are flexible and 

 tough, and abound in the inner 

 bark of dicotyledonous trees and 

 shrubs. 



401. Disk-bearing tissue is constituted of length- 



ened cells, which have pits or 

 lens-shaped markings, found in 

 the Pine and other gymnosperms 

 (Fig. 505). 



402. Vessels or ducts are 

 tubes or passages through which 

 the fluids pass from one part of 

 the plant's structure to another. 

 In the formation of these pas- 

 sages elongated cells arrange 

 themselves end to end, become 

 anastomosed ; the walls in the 

 ends -of the cells are ruptured or 

 disappear, and uninterrupted pas- 

 sages are produced. 



403. Spiral vessels are con- 

 505, Lengthwise section of (Scotch structed by the union of spiral 



Pine) Pinus Sylvestris, showing disk- 

 bearing tissue ; <*, Cambium wood-ceiis; cells, in the manner described in 



a, Z>, c, etc., older cells ; t, t', t", bordered 



pits; st, large pits (x225).-Socfts. ^Q ^g^ article (Fig. 506). 



