-2- 
The plant can also tolerate other elements which are not on 
the "essential" list, and it is sometimes convenient to use 
these; for example, in one of the mixtures quoted below, 
calcium is given in the form of calcium chloride, though the 
plant does not need chlorine. 
In preparing a solution for the water culture method, it 
is usual to take first the salts which are required in relatively 
large amounts, and dissolve these in the full quantity of water 
required. Then to this are added small quantities of stock 
solutions containing the trace elements. The trace element 
solutions are made as follows: 
A. water half a gallon 
boric acid 1 teaspoonful 
manganese sulphate 1 teaspoonful 
zinc sulphate 1 teaspoonful 
After dissolving the above, add 1/8 teaspoonful copper sulphate. 
B. water 1 pint 
ferric chloride 4 teaspoonful 
Two teaspoonful of solution A and 4 teaspoonsful of solution B 
are added to five gallons of the main culture solution just 
before use. 
The main culture solution may be made up as follows. To 
five gallons of water add the following salts (measured dry): 
monopotassium phosphate 
teaspoonsful 
calcium nitrate 
4 
do. 
magnesium sulphate 
1 
? 
2 
do. 
ammonium sulphate 
do. 
alternative combination of salts 
is as follows: 
monopotassium phosphate 
1 
teaspoonful 
sodium nitrate 
1 
do. 
magnesium sulphate 
do. 
calcium chloride 
1 
do. 
It should be noted that both calcium nitrate and calcium chloride 
absorb water rapidly from the air and must be kept in tightly 
stoppered bottles. 
But it is not merely necessary to give plants the right 
salts In the right proportions. The solution must have the right 
degree of acidity, and this may vary somewhat for different 
plants. Also, as the roots take up some of the dissolved salts, 
the acidity may change and need correction. This is not ordinarily 
necessary when plants are grown in soil, as the soil has a stabi¬ 
lizing effect. Another and still more important fact is that 
roots need air as well as water. Ordinary soil provides air in 
the spaces between the soil particles. Water will dissolve air, 
but not very much; and the warmer the water the less air it will 
bold. Therefore it is necessary to have some method for aerating 
the water in which the roots are to grow. 
The procedure then for growing plants by the hydroponic 
method is to make up your solution as above specified, and put 
it into suitable vessels (the size naturally varies with the size 
and number of plants you wish to produce). Earthenware vessels 
must be used , as metals corrode and may upset the balance of the 
solution. The top of each vessel must be covered with wire netting, 
and on this is placed a layer of moss, fern roots, or some other 
fibrous material to hold the seeds or young plants in position. 
The seeds are planted in the layer of moss (which is kept moist) 
and as soon as they germinate their roots enter the water, there 
0>rVi° 
