PROBLEM 56 



75 



Find little cores of wood extending out through the cortex into the 

 rootlets. This so-called central cylinder is made up of bundles of 

 tubelike cells. The cells collectively form the fibrovascular 

 bundles. 



In the picture of the cross section (see page 74, Civic Biology) 

 find (1) the cortex, (2) the central cylinder, and (3) the root hairs. 

 How many cells are in a root hair ? From what 

 part of the root do the root hairs grow? 



Place some bean or corn seedlings in red ink. 

 Allow them to remain in the sun for a few hours 

 and then examine the stem and leaves carefully. 

 What has happened? 



Cut a cross section of one of the above stems. 

 Which part of the root and stem shows the pres- 

 ence of red ink? Examine free-hand sections 

 under the microscope. 



Conclusion. By what path do fluids pass 

 up the root and stem ? 



Problem 56: To find out how root hairs 

 absorb soil water. 



Materials. Egg or glass test tube (large), 

 celloidin, sealing wax, glass tubing, thistle tube. 



Method. To make an artificial root hair 

 we may take either an egg, or a celloidin cell, 

 which is made by pouring a little thin celloidin 

 into a clean test tube, revolving the tube 

 rapidly, and then carefully removing the film 

 of celloidin which has been formed within the 

 tube. With care a nearly uniform artificial 

 membrane will have been formed within the 

 tube. This, when removed, may be filled with 

 glucose solution, or any dense material that 

 will dissolve in water. Tie the upper end of 

 it tightly over the wide end of a thistle tube and insert the 

 bag in a dish of water. 



If an egg is to be used, break the shell at one end and remove 



APPARATUS TO SHOW 

 OSMOSIS. 



