WATER-ABSORPTION AND TRANSPIRATION. 113 



examine the roots of as many plants as possible, wild and 

 cultivated, pulling or digging them up and examining them 

 as directed in Chapter I. for the root of Broad Bean. What 

 characters do nearly all roots appear to possess in common, 

 from your own observations on roots of various plants? 

 What do you think are the chief uses, or functions, of roots ? 

 How could you test your ideas on this subject by simple 

 experiments ? Try any methods that occur to you, before 

 going further. 



* (a) In a Bean seedling grown in sawdust or soil, cut across the main 

 root just below the cotyledons : the plant falls over. Support the 

 plant by tying it to a stick, and keep the soil or sawdust moist around 

 the cut place : notice the new roots formed from the base of the 

 stem. 



* (b) Repeat (a) with another seedling, planted by itself in a pot or 

 box, but after tying it to a stick allow it to remain unwatered. What 

 changes does it show, from day to day, in the colour, shape, and 

 position of the leaves, and in any other respects ? How would you 

 describe these changes, and what ultimately becomes of the shoot? 

 For comparison, allow some uninjured seedlings to remain unwatered : 

 do they show the same changes ? What do these simple observations 

 prove as to the work of the root ? 



* (c) Fix a seedling with its root dipping into water in which some 

 powdered vermilion has been shaken up vigorously. After an hour 

 or two, cut across the root a short distance above the surface of the 

 coloured liquid. Has any of the colouring-matter (which consists of 

 grains suspended in the water) entered the root ? 



* (d) Fix a seedling with its root dipping into red ink (colouring- 

 matter in solution), and after a time (try several seedlings, and give 

 them different lengths of time) cut across the root, to see how far 

 upwards the colour has spread, and in what part of the root it travels. 

 Also cut across the stems of seedlings that have been in red ink for a 

 day or two, and notice the red-stained bundles : how does the liquid 

 travel in the leaves ? 



The root, therefore, fixes the ptant in the soil and also 

 absorbs water and passes it upwards through the stem into 

 the leaves. The water absorbed from the soil is not pure 

 water : it contains dissolved substances of great importance 

 in the nutrition of the plant, as we shall see later. 



Do you know of any plants whose roots have other func- 

 tions besides those of fixing the plant and absorbing water 

 with dissolved salts ? 



s. B. 8 



