174 



HUTCHINSON'S POPULAR BOTANY 



obstacle, as well as any difference in the hardness of the soil, and he will 

 turn from that side ; if the earth is damper on one than on the other side, 

 he will turn thitherwards as a better hunting-ground. Nevertheless, after 

 each interruption, guided by the sense of gravity, he will be able to 

 recover his downward course, and to burrow to a greater depth." 



Note, too, how the sensitiveness of the root and rootlets struck Mr. James 



Rod way during his study 

 of plant life in the forests 

 of Guiana: "Roots are 

 undodbtedly able to dis- 

 tinguish suitable from un- 

 suitable food, and though 

 they may be poisoned now 

 and then, this is nothing 

 strange, as the same thing 

 happens to man. Their 

 sensitive tips go wandering 

 in every direction, branch- 

 ing here and there in 

 search of proper food. 

 As long as the soil is 

 uncongenial they press 

 forward, and only when a 

 good feast is discovered 

 do they throw out that 

 broom-like mass of fibres 

 so conspicuous on the 

 banks of rivers and creeks. 

 A barren subsoil is care- 

 fully avoided by keeping 

 to the surface, while in 

 the rich river bottom the 

 sour, water-logged alluvion 

 is equally distasteful. On 

 the sand-reef the tap-roots 



FIG. 218. MAIZE AT A STILL LATER STAGE, 



Showing the primary root which has broken through the coleorhiza (cr). 

 and two adventitious roots growing from the base of the young stem. 



go down fifty feet 



more, and spread most 



evenly to glean every particle of food contained in the water that has 

 percolated to these depths. On the mountain, again, every chink and 

 cranny between the rocks is explored, the roots sometimes .penetrating 

 through narrow crevices into hollows where water has accumulated, and 

 spreading their network of fibres over the roof, down the walls, and 

 into the pools. In some cases it appears as if the roots smell the water at 

 a distance, and move straight onwards until they reach it. Some epiphytes 



