98 



PLAKT STUDIES 



Plants ■\vliicli ordinarily develop soil roots, if Lroiight 

 into i)rop('r -water relations^ may develop water roots. For 

 instance^ willofl's or otlier stream Lank plants may lie so 

 close to the water that some of the root system enters it. 

 In such cases the nnmerous clustered roots show their water 



Fig. 93. An orchid, showing aerial roots. 



character. Smiietimes root systems developing in the soil 

 may I'litcr tile, drains, when water roots will develop in such 

 clusters as to choke the drain. The sarne Ijunehing of water 

 roots may Ijc noticed when a hyacinth liulb is grown in a 

 vessel iif watei'. 



(i'i. Air roots. — In certain parts of the tropics the air is 

 so moist that it is jiossible for some plants to olitaiu sutli- 



