3o6 



In regard to the action of magnesia, Loew and May^ have expressed 

 the opinion that a definite quantitative proportion between soluble calcium 

 and magnesium compounds is necessary for favorable growth (corres- 

 ponding approximately to their molecular weights, i. e. 5 to 4). Magnesium 

 in the soil in great excess over calcium is injurious. Plants which in so far 

 lack magnesium, as that calcium is present in excess, exhibit symptoms 

 of starvation. A small excess of calcium arrests the poisonous action of the 

 magnesium. In the use of fertilizers containing magnesium, calcium should 

 also be given at the same time. This advice should be taken to heart. Even 

 if plants can well endure magnesium, and even actually need it, any excess is 

 certainly injurious, as has also often been proved in fertilization with raw 

 potassium salts. 



f. Changes Duk to a Lack of Chlorine. 



It should perhaps be assumed that chlorine and calcium arc antagonistic 

 in plants. Mayer's conclusion, mentioned under potassium, that the action 

 of potassium chlorid is weakened by calcium and, conversely, would indicate 

 this. In the same way Knop- found that less calcium is taken up when the 

 nutrient solution contains chlorine, and the calcium did not appear to be 

 represented in any corresponding way by potassium or any otlier base. Thus 

 the chlorine compounds (by the retention of the calcium) cause an essential 

 increase in the acid content of the plant sap. Since, among the acids ab- 

 sorbed, the phosphoric acid predominates, Knop thinks it permissible to 

 ascribe to this acid the greater fertility with a use of nutrient solutions con- 

 taining chlorine, which was observed by Nobbe. Accordingly one would 

 like to explain the process thus, — the chlorine which accumulates^ in greatly 

 dififerent quantities in the plant body, according to the amounts offered the 

 roots, can increase the transportability of the phosphoric acid, since it 

 decreases the absorption of calcium and thus prevents the appearance of the 

 phosphoric acid in the slowly soluble form of calcium phosphate. If t'^c 

 phosphoric acid, co-operating in the formation of the proteins, reaches 

 very easily the meristematic areas of the growing tips, an abundant forma- 

 tion of cytoplasm occurs together with cell increase and, in connection with 

 this, a plenteous streaming of the carbo-hydrates for the protein regenera- 

 tion. Accordingly, vigorously growing shoots with but little stored up reserve 

 substances will necessarily be found in plants, fertilized with chlorine. 

 Actually, the many fertilization experiments show a decrease in starch ard 

 reserve sugar in the luxuriantly growing cultivated plants. 



1 Loew, O., and May, W., The relation of lime and magnesia to plant growth. 

 U. S. Departm'-nt of Asric. Bull. I. cit. Bot. Jahresber. 19'^]. H n. 141. 



2 Chemisch-physiolog-iscne Ilntersuchung-en ijber die Ernahruner der Pflanze 

 von Knop and Dworzak. Aus Berichte d. Kgl. sachs. Gesellsch. d. Wissensch. vom 

 23. April, IST,"^. Cit. Jahresber. f. Agrikulturchcmie. 1875. p. 267. 



3 Pag-noul, Sur le role exerc# par les sels alcalin sur la vegetation de la b-^tter- 

 a,ve et de la pomme de terre. Compt. Rend. 1875. Vol. LXXX, p. 1010. Fertilizing 

 experiments carried on for five years with chlorids showed for beets a fliurtuation in 

 contents from 1 to 50. In potatoes, the smallest yield in tubers coincided with the 

 least amount of potassium carbonate in the ash but with the greatest amount of 

 chlorides. 



