THE TISSffES OF PLANTS. 



S5 



43. Two varieties of fibrous tissue may be distinguished, 

 viz., (1) Bast (Fig. 15, B), and (3) Wood (Pig. 15, A). 



n 



B 



Fig. 15.—^, wood-flbres of Silver Maple isolated by Schulze's macera- 

 tion ; B, bast-fibres ; &, &. portions of fibres more highly magnified. 



The fibres of the former are usually thicker-walled, more 

 flexible, and of greater length than those of the latter. In 

 both forms the fibres are sometimes observed to be par- 

 titioned. 



Practical Studies. — (a) Split a young maple-twig, then with a 

 very sharp knife start a thin longitudinal radial section, completing 

 it by tearing it off. Mount in water. The torn end will show good 

 wood-fibres. 



(i) Make a very thin cross-section of the wood of the same twig. 

 Note the angular shape of the wood-fibres in this section. 



(fi) Make a cross-section of the bark of the same twig and note the 

 white bundles of bast-fibres, each fibre having greatly thickened 

 walls and a very narrow cell-cavity. 



(d) Now make several longitudinal sections of the same twig so as 

 to cut through one of the bundles of bast-fibres. Note the great 

 length of the bast-fibres. 



(e) Make cross-sections of the wood of various trees, as oak, hick- 



