PLANT BOOTS 185 



look like fuzzy white threads. Touch the root hairs with the point 

 of a pencil. They cannot, like the rest of the root, stand being dis- 

 turbed. On what part of the root do the root hairs grow ? As the 

 blotting paper dries, what happens to the root hairs? 



Plant roots are prepared particularly by the little root 

 hairs, which were examined in Experiment 90, to take the 

 film of water which surrounds the soil particles and ca'rry 

 this water to the stem and, through it, to the leaves. The 

 water which the roots take from the soil is a dilute solu- 

 tion containing the plant food substances. Not only do 

 roots absorb the water from the soil, but they secrete 

 weak acids which aid in dissolving the mineral substances 

 which the plants need. This can be seen where plant 

 roots have grown in contact with polished surfaces, such 

 as marble. These surfaces are found to be etched. 



Experiment 91. Cut a potato in two. Dig out one of the halves 

 into th^ shape of a cup and scrape off the outside skin. Fill the potato 

 cup about | full of a strong solution of sugar. Mark the 

 height of the sugar solution by sticking a pin into the inside 

 of the cup. Place the cup in a dish of water. The water 

 should stand a bit lower than the sugar solution in the potato 

 cup. After the cup has stood in the water for some time, 

 notice the change in the height of the denser sugar solution. 



Experiment 92. Bore a f -inch hole 3 or 4 inches deep in 

 the top of a carrot. Scrape off the outside skin and bind 

 several strips of cloth around to keep the carrot from split- 

 ting open. Fit the hole with a one-hole rubber stopper 

 having a glass tube about 1 meter long extending through 

 it. Fill the hole in the carrot with a strong sugar solution 

 colored with a little eosin and strongly press and tie in the F . g3 

 stopper. The sugar solution will be forced a short distance 

 up the tube by the insertion of the stopper. Mark with a rubber band 

 the height at which it stands. Submerge the carrot in water and allow 

 it to stand for a few hours. Mark occasionally the height of the column 

 in the tube. Taste the water in which the carrot was submerged. 

 There has been an interchange of liquids within and without the 

 carrot. 



