NUTRIENT SOLUTIONS. 251 



4 Equivalents of Potassic chloride 



4 Equivalents of Calcic nitrate 



1 Equivalent of ... Magnesic sulphate (crystallized) 



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 : l 



Gram. 



Potassic chloride .207 



Calcic nitrate 456 



Magnesic sulphate .171 



673. Pfeffer recommends the formula suggested by Knop : 2 



Calcic nitrate 4 parts by weight 



Potassic nitrate 1 part by weight 



Magnesic sulphate (crystallized) ... 1 part by weight 



Potassic phosphate 1 part by weight 



These salts are to be thoroughly mixed and the mixture used 



CJ > 



in the proportions of ^co' ToVo' suo P arts 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. 



674. According to Knop. the first of the solutions mentioned 

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

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

 employed with safety. But the stronger solution should be used 

 as the plant comes into flower. The slight turbidity w^hich is 

 frequently noticed in these solutions "may be disregarded. 



If the solutions become alkaline while in contact with the 

 roots, as they are very 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 every case to renew the solutions frequently, 

 and as a rule to employ 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. 3 



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

 5 three plants. 



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



- Lehfbuch der Agricultur-Chemie, i. 1868, p. 605. 



3 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 



