VII.] 



BOTANY. 



29 



side numerous slender branches or root-fibres. 

 Sometimes the tap-root is very insignificant and not 

 easily distinguished from its fibre-like branches ; the 

 whole root is then distinguished as fibrous. Root- 

 fibres are usually so slender that it is not easy to 

 see their nature ; but this can be done in the hyacinth 

 root, the tip of which, if cut down the middle shows 



FIG. 13. Vertical section of tip of Root-fibre of Hyacinth, many times the 

 real size. 



under a microscope that a sheath of soft flattened cells 

 envelops the tip, within which is a mass of denser 

 cells which form the growing point. 



43. Root fibres do not push themselves into the 

 soil as one thrusts a stick into it ; but they push their 

 way through interstices in the soil as they elongate 

 at the point As the root fibre elongates, the front 

 part of the sheath decays, and the back part, which 

 is constantly renewed by the growing point, takes 

 its place ; thus advancing and displacing water in 

 the case of the hyacinth, and earth in other cases. 



In shrubs and trees the root-fibres as well as the 

 tap-root thickens as it grows, becomes woody, and 

 displaces the earth laterally as well as in front ; and 



