'////•; I'HVsiof.oav or plaxts 277 



food. If uc burn sonic wood tf> ;i white ;ish and 

 then an.ilyse it, six inorLjanic elements w ill always 

 be found — potassium, magnesium, calcium, iron, 

 phosphorus, and sul|)hur. These substances have 

 been prcjvcd b)- experimental water-culture ' to 

 be indisjjcnsablc to plant-life ; others arc found in 

 larger or smaller quantities, but the)' are not, 

 judging by experimental tests, essential to plant 

 life. These inorganic elements do not enter the 

 plant as such, but in the form of salts dissolved in 

 water ; the phosphorus and sulphur as phosphates 

 and sulphates. l^xactK' how these salts and other 

 elements are absorbed will be best learnt from a 

 simple experiment. 



■ Testing the effect of plant food by water-culture is carried out in 

 the following manner. Six large jars are filled with distilled water. 

 In \o. I all the six elements above mentioned are placed in small 

 quantities, so as to form a weak solution. In No. 2 only five of 

 them are addetl to the water, and in each succeeding jar one 

 element is left out. A seedling plant which has heen germinated 

 on ilamp sand is suspended in each jar in such a manner that the 

 leaves are in the air and the roots in the water without the seed 

 touching the liquid. The growth of the young plants is carefully 

 observed, ind the result is found to be that No. i will grow and 

 flourish, finding all its needful food in the water, whilst the rest of 

 the seedlings will show plainly by their feeble and starved condition 

 that, the food elements Iwing absent, they cannot build up their 

 stenis and leaves, and must eventually perish. 



