NUTRIENT SOLUTIONS. 251 



4 Equivalents of Potassic chloride 



4 Equivalents of . . Calcic nitrate 



1 Equivalent of . . Magnesic sulphate (oiystallized) 



One part of the mixture of these salts is to be dissolved in 

 one thousand parts pure water, and then a trace of ferric phos- 

 phate is to be added, and at times during any culture a trace 

 also of potassic phosphate. The proportions of the above salts 

 to a liter of water are given as follows by Bretfeld : ^ — 



Gram. 



Potassic chlori<le 207 



Calcic nitrate ... 4.56 



Magnesic sulphate 171 



673. Pfeffer recommends the formula suggested by Knop : ^ — • 



Calcic nitrate 4 parts by weight 



Potassic nitrate . . . . . . 1 part by weight 



Magnesic sulphate (orybtalUzed) . 1 part by weight 



Potassic phosphate 1 part by weight 



These salts are to be thoroughly mixed and the mixture used 

 in the proportions of ggVir) Tc'cm zhv parts of water. To the 

 solutions, when ready for use, a drop or two of a solution of 

 some iron salt, or a decigram of ferric phosphate, must be 

 added. 



G74. According to Knop, the first of the solutions mentioned 

 above (one half pro mille) is as dilute as can be useful ; and ou 

 the other hand, a five pro mille solution is as strong as can be 

 employed with safet}'. But the stronger solution should be used 

 as the plant comes into flower. The slight turbidity which is 

 frequently noticed in these solutions may be disregarded. 



If the solutions become alkaline while in contact with the 

 roots, as they are ver}' apt to do, a trace of dilute nitric acid 

 may be added with advantage. But it must not be forgotten 

 that it is best in evei-y case to renew the solutions frequentlj-, 

 and as a rule to emplo3' them in tolerably large amounts. 

 Moreover, it is advantageous to pass a current of air occasion- 

 ally through the solutions in which the roots are placed, for the 

 purpose of supplying more oxygen to them.^ 



a manner that 1 ami 2 contained one plant eacli, 3 and 4 two plants each, and 

 5 three plants. 



1 Das Versuchswesen auf dera Gebiete der Pflanzenphysiologie, 1884, p. 120. 



2 Lehrbuch der Agricultur-Chemie, i. 1868, p. 605. 



' For solutions for the cultivation of fungi various formulas have been pro- 

 posed, only a few of which can be here referred to : (1) 3 to 8 grams of sugar 



