100 



EXPERIMENTS WITH PLANTS 



the roots diverge from their course more than is ab- 

 solutely necessary to avoid the obstacles? Do they 

 resume their original course as soon as they have 

 passed the obstacles ? 



Study, as far as is practicable, the rootlets which 

 spring from the side roots in the same way in which 



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83. Radish seedlings grown on moist sand, showing root-hairs. 



you have studied the main root and the side roots. 



From the main root, the side roots and the rootlets, 

 spring root-hairs; these can be seen in great profusion 

 if we sow Radish seeds on moist earth in a pan_ (Figs. 

 83 and 84), and cover it with a piece of glass to 

 retain the moisture. Sometimes the roots become 

 covered with mould, w^hich may at first be mistaken for 

 root- hairs. The best way to obviate this is to obtain 

 clean seed; if this is not possible, rinse the dry seeds 



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