58 BOTANY FOR BEGINNERS CHAP. 



wort. This plant can be distinguished from the common Buttercup, 

 because 



(i) Its leaves are cordate and perfect ; in the Buttercup the leaves are 

 very much divided, and the segments are lobed. 



(ii) The petals vary in number from eight to ten ; in the Buttercup 

 there are only five. Examine the roots and note the swollen fibres ; 

 these are used for storing up reserve materials. These are tubercular 

 roots. 



Uses of Boots. Roots perform various functions which 

 can be arranged in a tabular form. 



1. Roots fix the plant in the soil. The roots can anchor a 

 tree like the Oak so that the strongest wind cannot blow it over. 

 In many cases the roots of grass-like plants are used by 

 engineers, to bind together the soil along an embankment, 

 and so keep it from falling, as on the West Coast of Lancashire 

 and in North Italy. 



2. Roots obtain nourishment from the soil. The roots parcel 

 out the soil so that nutritive materials can be extracted from 

 every part by the root-hairs. All the water given out by the 

 leaves of a plant is obtained by the root-hairs from the soil. The 

 roots make good the loss of water which takes place through 

 the leaves. 



3. Roots may be used as a store-house for material to enable 

 the plant to produce flowers and seeds during the next season. 

 In this case the roots are swollen and large. 



4. Roots may be used for climbing, floating, or to enter a host 

 plant. The shape, size, and method of growth of roots will 

 depend upon their function. 



EXPT. 45. Obtain any plant growing in a plant pot. Cover over 

 the soil, either with card-board or tin-foil, to prevent evaporation 

 from the pot. Place the plant beneath a glass globe, and expose to 

 light in a window sill. Note that the inside of the glass is soon covered 

 with moisture. This is given out by the leaves, and the loss can only be 

 made good by the water taken in by the roots. 



Movements of Roots. The younger portions of the roots 

 are all in a constant state of motion. When the radicle leaves 

 the seed it commences to move, and so long as life lasts the tip 

 of the root will go on moving round and round in search of 

 certain substances or conditions. The force exerted by a young 

 radicle when growing is very great ; in twenty-four hours it 

 causes a downward pressure equal to lifting a weight of a 



