WOODY TISSUE. 



47 



thickness and toughness which characterize the liber-cells. Fig. 

 35 represents one of the bast-cells of our Bass-wood 35 & 

 or Linden, with a portion of another ; while Fig. 36, 

 37, represent a few of the cells of the wood from 

 the same stem, and equally magnified ; showing the 

 great difference in the length of the fibre-shaped 

 cells. Being a soft wood, the cells of the latter have 

 thin walls, as is seen on the cross-section of two of 

 them at the top ; while the section of one of the 

 bast-cells shows a thick wall and very small cali- 

 bre. The disproportion in length is still greater in 

 our Leather- wood, which has a bark of extraordi- 

 nary toughness, used for thongs, while the wood 

 itself is very brittle and tender. Its capillary bast- 

 cells measure from an eighth to a sixth of an inch 

 in length, with an average diameter of ^V^ of an 

 inch (so that, if the whole length of a cell, magnified 

 as in Fig. 38, were given, the figure would be from 

 a foot to nearly a foot and a half in length), while 

 those of the wood itself are only the y^ of an inch 

 long. Among the bast-cells are found the longest 

 cells which occur in any tissue. Schleiden says that 

 he has measured those which were four or five 

 inches long. They are of great length in the Milk- 37 



weed Family, and in the Dogbane, or Indian Hemp, 

 the tough bark of which accordingly furnishes the ab- 

 origines a sort of ready-made cordage. In these fam- 

 ilies they are said by Schleiden frequently to exhibit 

 " very delicate spiral fibres, crossing each other. In 

 some spots their cavity becomes entirely obliterated ; 

 whilst in others they are swollen and vesicular, and 

 contain a true milky juice." So that they are the 

 milk-vessels in these plants ; at least in part. The 

 ribs, with the veins and veinlets, that form the fibrous 

 framework of leaves, giving to them the requisite 

 firmness, are chiefly of the same kind of woody tissue as those of 

 the bark. 



FIG. 35. Two bast-cells from the bark of the American Bass-wood, magnified. 



FIG. 36. Some woody tissue from the wood of the same : a, upper end of a spirally-marked 

 duct. 37. A separate cell from the wood. All magnified to the same degree as Fig, 35. 



FIG. 38. Ends of some bast cells from the bark of the Leather- wood (Dirca palustris), highly 

 magnified. 



