MOISTNESS OF THE SOIL : HYDROTROPISM 257 



soil : hydrotropism. — The tips of roots are sensitive to changes 

 in the moisture of the soil : while growing through the ground 

 they bend towards the parts which are dampest. In consequence 

 of this peculiarity, the roots of plants frequently find their way 

 into drain pipes, wells and water courses some considerable 

 distance away from the place where the stems are growing. 



