USEFUL FIBER PLANTS OF THE WORLD. 



DEFINITION OF FIBERS. 



The tissue of plants when viewed under the microscope is seen to be 

 made up of cells which are compacted together as they are formed dur- 

 ing the growth of the plant, thus slowly building up roots, stems, and 

 leaves. The walls of these cells inclose the life germ, or protoplasm, and 

 the substance of which they are composed is known 

 as cellulose, which chemically is very similar to starch. 



Regarding the size ot the cells of which common 

 plants are made up, Dr. Gray states that their ordi- 

 nary diameter in vegetable tissue is between one 

 three-hundredth and one five-hundredth of an inch. 

 The smaller of these sizes would allow as many as 

 125,000,000 cells in the compass of a cubic inch. "All 

 soft cellular tissue, as leaves, pith, and green bark, is 

 called parenchyma, while fibrous and woody plants 

 are composed of prosenchyma, that is, of peculiarly 

 formed strengthening cells." We are also told that 

 those cells that lengthen and at the same time thicken 

 their walls form the proper woody fiber, or wood cells ; 

 those of larger size and thinner walls, which are thick- 

 ened only in certain parts so as to have peculiar mark- 

 ings, and which often are seen to be made up of a row 

 of cylindrical cells, with the partitions between ab- 

 sorbed or broken away, are called ducts, or sometimes 

 vessels. There are all gradations between wood cells 

 and ducts, and between both these and common cells. 

 But in most plants the three kinds are fairly distinct. 

 Wood cells, or woody fibers, consist of tubes, com- 

 monly between one and two thousandths of an inch, 

 in diameter. A highly magnified group of these cells from Button- 

 wood (after Gray) illustrates the manner in which wood cells are put 

 together, their ends pointed and overlapping, thus strengthening the 

 whole. (See fig. 1.) 



Wood cells also occur in the bark, though they are longer, finer, 

 and tougher than those found in the wood. They form the princi- 

 pal part of fibrous bark, or the bast layer, and are called Bast 



9 



Fig. 1.— Woody cells 

 of Buttonwood. 



