46 



THE ELEMENTARY STRUCTURE OF PLANTS. 



of the discs, or thin spots, has just been explained (45). On ac- 

 count of their markings and unusually large size, and because in 

 the Pine Family they make up the wood without any admixture 



of ducts, these peculiar wood-celfs 

 have been thought to be rather a 



&,\/tf eff ifo/ form of vascular tissue. But in the 



lHxl3H9l Star- Anise the same kind of mark- 

 ings is found on undoubtedly genu- 

 ine woody tissue (Fig. 33). In the 

 Yew, on the other hand, where the 

 discs are few, delicate spiral mark- 

 ings appear (Fig. 34), showing a 

 perfect transition between the prop- 

 er woody and the vascular tissues; 

 as is seen by comparing the figure 

 with that of a spirally marked duct 

 of Bass-wood, Fig. 36, a. 



55. Bast Tissue, or Woody Tissue of the Liber. The bast or 

 bass, fibrous inner bark, or liber, as it is variously termed, of those 

 plants that have a true bark separable from the wood of the stem, 

 is principally pleurenchyma, consisting of much longer, very 

 thick-sided, and usually tougher, but more soft and flexible cells, 

 than those of the wood itself. These properties are " probably 

 given them that they may possess the strength, combined with flex- 

 ibility, which their position near the circumference of a branch 

 renders necessary." These especially adapt them to the useful 

 purposes they so largely subserve for clothing and cordage. 

 The textile fibres of flax, hemp, &c., are all derived from this 

 woody tissue of the bark, separated from the brittle cells of the 

 wood itself, and freed from the surrounding thin-sided parenchy- 

 ma by maceration (which soon decomposes the latter) and me- 

 chanical means. Cotton differs from linen in many respects ; it 

 consisting of hairs, or long tubular cells, growing on the seeds, 

 with very thin walls, which collapse so that they twist variously, 

 which gives them a peculiar adaptation to be spun, or drawn out 

 together by torsion into a thread. But the walls have none of the 



FIG. 33. Magnified woody tissue of Ulicium Floridanum (longitudinal view), marked with 

 large dots, like the discs on the wood-cells of the Pine Family. 



FIG. 34. Magnified woody tissue from the American Yew (longitudinal view), showing 

 delicate spiral markings ; some of the cells also showing the disc-like markings or dots of ordi- 

 nary Coniferae. Across the base is seen a portion of a medullary ray. 



