AGRICUT.TURAL BOTANY, CHEMISTRY AND PHYSIOLOGY OF PLANTS I759 



as the carbonates, chlorides, and sulphates, served as sources of the arti- 

 ficial forms. Increasing amounts of the various forms were used, also a 

 variance in the ratio of calcium to magnesium was employed. The earlier 

 applications varied from o.i to 0.6 per cent of magnesium added in magne- 

 sium carbonate and in magnesite. I^ater the following amounts were em- 

 ployed : 2,6, and 10 per cent of magnesium in magnesite ; 10 and 12.7 per 

 cent in dolomite; 0.1,0.01, and o.ooi per cent of magnesium in the carbo- 

 nates, chlorides, and sulphates. 



Eaithen pots 6.5 ins, in diameter by 7.5 ins. in depth were used. Each 

 pot contained 13.2 lbs. of sand, while in the soil series each contained 8.8 

 lbs. of blown silt loam. Sand and soil were used as mediums of control, 

 and to these two materials were added the various forms and amounts 

 of calcium and magnesium. 



Various methods were pursued in extracting the sand. At first dilute 

 hydrochloric acid was kept in contact with the sand for 48 hours, but 

 this failed to remove all the calcium and magnesium. Later the sand was 

 extracted with stronger acid (1350 cc of concentrated hydrochloric acid 

 with 1000 cc of distilled water) for periods of from 9 to 14 days. Sand 

 was also digested on a steam bath for 4 days with this same strength acid. 

 None of the aVjove processes were able to remove all the calcium and ma- 

 gnesium from the sand. After treatment it still contained : 



Calcium Magnesium 



Extraction with dilute acid for 2 days 0.0142 per cent 0.016 per cent 



" " strong " " 4 " 0.0128 " " 0.0089 " " 



At intervals varying from 10 to 14 days^ nutrient solutions were added 

 to the pots and evei}^ 10 days the pots were brought to st«.ndard weight 

 by watering with distilled Wc:ter. The experiments were run in greenhouses 

 and the principal crops used were : wheat (Triticum spp.), alfalfa [Medi- 

 cago sativa), soybeans {Soja max) and cowpeas {V igna sinensis) . Oats {A vena 

 sutiva), clover {Triiolitim pratense), timothy iPhleum pratense), and sweet 

 clover {Mdiloius alba) were also used to test the effect of artificial carbonates 

 upon germination. 



The experiments reported here extended over a period of three years 

 (1912 to 1915) and include approximately 300 pot cultures and upwards 

 of 300 duplicate determinations of calcium and magnesium. 



I>ifficalty was experienced in finding a medium that was free from 

 calcium and magnesium, and which woitld still approach soil conditions. 

 Attempts were made to grow plants in aluminium turnings but without 

 success, probably due to the formation of some aluminium salts when the 

 plant foods were added. 



Wheat and cowpeas grown in granular parafiin without the addition 

 of calcium and magnesiiun showed in tlie total ])lant onh' an amount 

 equal to that furnished by the seed. 



The difference in the medium in. which the plants were grown caused 

 different effects upon the plants. Brown silt loam was a better medium 

 than sand when treated with chemically pure magnesium carbonate, even 



