102 



EXPERIMENTS WITH PLANTS 



a few moments in five per cent formalin and then 

 rinse in clean water; heat the moist earth in the pan 

 (which should be covered during the operation) so 

 that it steams for ten or fifteen min- 

 utes; allow it to cool and then place 

 the seeds upon it. While the root- 

 hairs are growing, the glass cover 

 should not be disturbed. 



Does the amount of moisture affect 

 the luxuriance of growth of the root- 

 hairs? Use a series of pans, with 

 the soil varying from wet to fairly 

 dry. The seeds should be well 

 soaked when placed in the pans; the 

 moisture in each pan can be regu- 

 lated by lifting the glass cover so as 

 to permit greater or less circulation 

 of air. 



What is the use of the root-hairs ? 

 The absorptive surface of the root is 

 increased many fold by the root- 

 hairs. The long, feathery root-hairs 

 which develop on the roots of cut- 

 tings of the Wandering Jew placed 

 in water (Fig. 85) increase the root 

 surface from fifty to seventy - five 

 times; to get so much surface with- 

 out the device of root -hairs each 



S5. Cutting of Wander- 

 ing Jew in water, show- 

 ing root -hairs which 

 increase the absorbing 

 surface from fifty to 

 seventy -five times; in 

 order to get an equal 

 surface without root- 

 hairs each of these 

 roots would have to be 

 from one to six inches 

 in diameter. 



