88 BIOLOGY: GENERAL AND MEDICAL 



quantitative difference in the weight of the dried 

 residuum of mould secured. 



If we wish to study plant nutrition and discover out 

 of what materials the substance of the growing organism 

 is elaborated, it can be done with exactness by means 

 of a water culture. This consists of distilled water to 

 which are added known quantities of such compounds 

 as are essential to the life processes of the plant, v. d. 

 Crone recommends the following solution which is one 

 of the best: 



Distilled water 1000-2000 c.c. 



Potassium nitrate 1 gram 



Ferrous phosphate 0.5 gram 



Calcium sulphate . 25 gram 



Magnesium sulphate 0.25 gram 



An examination of these ingredients will discover the S 

 in two, P in one, K in one, Ca in one, Mg in one, and Fe 

 in one, thus this solution furnishing all of the electrolytes 

 essential to plant life, a seed or spore moistened with 

 it is able to set in motion those chemical processes by 

 which its integration is effected. Some of the essential 

 elements of the protein of the protoplasm are, however, 

 conspicuous by their absence, Where, for example, 

 are the O, H, and C? There are two sources from which 

 these may be obtained, O from the atmosphere into 

 which the plant grows, H from the water into which its 

 roots extend, and in each of which more or less C0 2 is 

 dissolved and may yield the C. 



Absorbing the H 2 O, the C0 2 , and the O, the germ of 

 living substance, by virtue of the powers it already 

 possesses, with the aid of the electrolytes with which it is 

 supplied in the solution, begins operations by combining 

 these molecules to form more complex compounds, some 

 of which it no doubt immediately carries further through 

 intermediate steps to the actual plant protein, some of 

 which it stores up for time of future need, and some of 

 which it uses for the scaffolding in which its increasing 

 active substance is to be supported and by which it is to 



