52 THE VEGETATIVE FUNCTIONS OF PLANTS 
48. Relation between Root-hairs and Soil. If young, 
active roots are removed from the soil, thoroughly rinsed 
in water, and examined with a compound microscope 
at the zone of root-hairs, it will be seen that tiny par- 
ticles of soil have adhered so closely to the cell-wall of 
FIG. 39. Water-hyacinth (Eichornia crassipcs). Photomicrograph of 
a longitudinal section of a root, showing the mode of origin of lateral roots 
(i.e. endogenous), a, b, c, lateral roots; r. t, root-cap. 
the hair that they were not washed off; in fact, they can- 
not be removed without tearing the hair. They appear 
to be imbedded in the cell-wall (Fig. 42), and are firmly 
held by pectin mucilage, resulting from a transformation 
of the outer membrane of calcium pectate. Since pectin 
is a water-loving colloid its importance here is recognized 
at once, in connection with the absorption of liquids by 
the root-hairs. 
