MANUAL FOB SUGAR GROWERS. 9 



Internally, the structure of tlie root may be 

 briefly described as a mass of cellular tissue through 

 the centre of which passes a heart or core composed 

 of fibro-vascular bundles ; the outside is covered 

 with a layer of somewhat hardened cells forming a 

 kind of bark. 



The function of the root is twofold : it serves to 

 fix the plant in the ground and also to absorb certain 

 food-materials from the soil ; it is in doing this that 

 the root-hairs play an important part. Only plant- 

 food in a state of solution can enter the root, and 

 that almost entirely through the root-hairs ; the older 

 parts of the roots are almost destitute of absorbing 

 power, and thus the extremities of the roots and 

 rootlets are the only parts by which water with 

 plant-food in solution can enter the plant, — a point 

 to be borne in mind in the application of manures. 

 The actual manner in which the root absorbs food 

 is by the process known as osmose ; this may be 

 thus explained : When two fluids are separated from 

 each other by a thin membrane, various substances 

 dissolved in one of the fluids have the power of pass- 

 ing through the membrane and thus appearing in the 

 fluid on the other side, and this transfer of material 

 will go on until the two fluids become of the same 

 strength ; this may be experimentally illustrated by 

 placing some strong solution of salt in a bladder, and, 

 after tying it up securely, placing it for a few hours 

 in a basin of water. On examining the water it will be 

 found to be quite salt, the salt having passed through 

 the bladder by the process of osmose. Only those 

 substances which are capable of crystallising can 



