FLOWERING PLANTS INTRODUCTORY 91 



to exercise these functions, the construction of the various organs 

 of the flowering plant can only be understood in the light of a 

 knowledge of their main functions. 



The whole root-system of many flowering plants is developed 

 from the main-root of the seedling. This grows down into the 

 soil, and gives off branches similar to itself. These branches 

 arise at some depth in the main root, and burst through the surface 

 layers of this. They grow obliquely downwards on all sides, and 

 in turn bear finer branch roots. The mass of soil around the base 

 of the plant is thus thoroughly penetrated by the roots of the 

 latter. In the Buttercup no main root can be distinguished. 

 The plant is fixed in the ground by numerous, rather stout, 

 whitish roots springing from the base of the stem. These bear 

 the finer branches. The characteristic features of most roots 

 can be well studied in the root system of a Bean seedling. They 

 need only be briefly mentioned here. The cylindrical shape, 

 the absence of the green colour found in the parts of the plant 

 exposed to the light, and the deep origin of the branches are 

 common to nearly all roots. All the branches are essentially 

 similar, and the root never bears leaves. The roots have to make 

 their way between the particles of soil, and the growing tip of 

 every branch is protected by a little sheath of firmer tissue called 

 the root-cap. The root enters into very close contact with the 

 mineral particles making up the soil, by means of delicate hairs, 

 which grow out in large numbers from the surface. These are 

 called root-hairs, and are found a short distance behind the tip of 

 the root, dying off on the older parts behind. 



All these features are related to the uses or functions of the 

 root. In the first place, the root-system serves to fix the plant 

 firmly in the soil. The growth of the roots in all directions through 

 the soil round the base of the plant, and the close connection 

 between the roots and the particles of soil, fit it admirably for 

 this. The same relations between the root and the soil also 

 enable the root to obtain from the soil a part of the food which 

 the plant requires. A plant takes up no solid food ; all the food 

 materials which it absorbs are taken up in a state of solution 

 or in the gaseous form. By means of the root, water, in which 

 are dissolved small quantities of certain substances of relatively 



