98 PLANT STUDIES 
Plants which ordinarily develop soil roots, if brought 
into proper water relations, may develop water roots. For 
instance, willows or other stream bank plants may be so 
close to the water that some of the root system enters it. 
In such cases the numerous clustered roots show their water 
FIG. 93. An orchid, showing aerial roots. 
character. Sometimes root systems developing in the soil 
may enter tile drains, when water roots will develop in such 
clusters as to choke the drain. The same bunching of water 
roots may be noticed when a hyacinth bulb is grown in a 
vessel of water. 
66. Air roots. In certain parts of the tropics the air is 
so moist that it is possible for some plants to obtain sum- 
