122 EXPEEIMENTS WITH PLANTS 



the root-hair pull the water away from the particles ? 

 It would seem that there must be substauees in the 

 root -hair wliicli attract water, just as the sugar draws 

 the water through a Wahiut-shell or bladder (pages 16 

 and 61) . In some roots we can taste sugar (Carrot, 

 Parsnip, Beets, etc.); by applying chemical tests we 

 find in all roots sugar or other substances capable of 

 attracting water. It appears, then, that the root-hair, 

 which is a long, closed sack (as you may easily see 

 with a good hand-lens or with the low power of a com- 

 pound microscope), contains substances w^hicli attract 

 water. We can easily make an artificial root-hair ^ of 

 any sort of membrane which will allow water to pass 

 through but retain the sugar inside; such are ox- or 

 pig-bladder or parchment paper; perhaps the most 

 convenient is the membrane which lines an egg-shell; 

 empty the contents of the e^g through a small hole at 

 one end ; jilace the shell in a tumbler and cover with 

 weak acid or vinegar; place another tumbler inside 

 the first, to keep the egg submerged. When the shell 

 is dissolved away, fasten the membrane to a glass tube 

 (about one-fourth of an inch in diameter), as shown 

 in Fig. 91; three or four turns of tightly wound string 

 (or, better, of elastic band) fasten it satisfactorily.^ 



1 Artificial root-hairs may be made by hollowing out Carro^^s. using an en- 

 tire eg^, etc., but it seems better to eliminate all living parts from the appa- 

 ratus, that the pui'ely physical features may be emphasized. 



2 It is well to prepare several tubes and then choose the one which gives 

 the best results on trial. 



