ABSORPTION OF ASH-CONSTITUENTS 87 



solution when experimenting with plants whose relation to chlorine is not under- 

 stood; potassium chloride is best for this purpose. Observations of agri- 

 culturists favor the idea that chlorine influences the translocation of carbo- 

 hydrates under natural conditions. Potatoes grown in soil rich in chlorine 

 contain less starch than those cultivated in soil deficient in this element. So, 

 when potatoes with the highest possible starch content are desired chlorine 

 fertilizers are to be avoided. 1 



Zinc is one of the less common ash-constituents. It is contained in a 

 variety of violet (Viola calaminaria or V. lutea var. multicaulis) , which grows 

 exclusively in soils containing zinc. The differences by which these " calamin " 

 violets are distinguished from the ordinary Viola tricolor are probably due to 

 the effect of the zinc salt/ Also, Raulin used zinc in his nutrient solution 

 (see page 47) for Aspergillus niger. Rikhter's 2 investigations showed that zinc 

 promoted growth and the accumulation of organic substances during the 

 earlv period of development of this mould, but prevented the formation of 

 spores. Kostychev 3 also found that zinc influenced metabolism in moulds. 



Aluminium occurs in plant ash rather infrequently. It influences the 

 color of the flowers in Hydrangea (H. hortensis). i Gardeners had long since 

 noticed that the ordinary reddish-flowered hydrangea bore blue flowers when 

 grown in certain soils, such as some forest and moor soils. Tests of many 

 different substances showed that blue flowers always appeared if the soil con- 

 tained soluble aluminium compounds. At first ordinary alum (made up of 

 aluminium and potassium sulphate, AI0SO4 + K 2 S0 4 + 24H2O) was used, 

 being introduced into the soil in pieces varying from the size of a pea to that of 

 a hazel-nut, and blue flowers were always obtained. In another series of experi- 

 ments, some plants were treated with aluminium sulphate and others with 

 potassium sulphate. The cultures with potassium sulphate gave the usual 

 red color, while those with aluminium sulphate always produced blue flowers, 

 and the color appearing with this salt was more intense than that obtained by 

 the alum treatment. The alum therefore produced the blue color because of 

 the presence of aluminium, the potassium being without influence. This case 

 shows clearly how the presence of a non-essential element may influence 

 metabolism in a specific manner. 



Researches in recent years have shown that various elements, such as 

 manganese, boron, rubidium, etc., are more or less favorable to plant growth. 



1 Budrin, Die kunstlichen Diingemittel mit besonderer Berucksichtigung der Stickstoffdiinger. War- 

 saw. 1888. (Russian.)* [See aso Tottingham, Wm. E., A preliminary study of the influence of chlorides 

 upon the growth of certain agricultural plants. Jour. Amer. Soc. Agron. 11: 1-32. 1919.] 



2 Richter, Andreas, Zur Frage der chemischen Reizmittel. Die Rolle des Zn und Cu bei der Ernahrung 

 von Aspergillus niger. Centralbl. Bakt. 77, 7: 417-429. 1901. 



3 Kostytschew, S., Der Einfluss des Substrates auf die anaerobe Athmung der Schimmelpilze. Ber. 

 Deutsch. Bot. Ges. 20: 327-334. 1902. 



4 Molisch, Hans, Der Einfluss des Bodens auf die Bluthenfarbe der Hortensien. Bot. Zeitg. 55: 49-61. 

 1897. 



1 But the studies of Hoffmann appear to controvert this statement. According to this 

 author the calamin violet is the same whether grown with or without zinc, and Viola tricolor 

 does not take the calamin form when supplied with zinc. See: Hoffman, H., Culturver- 

 suche. Bot. Zeitg. 33: 601-605, 617-628. 1875. Idem, Untersuchungen liber Variation. 

 Ber. Oberhess. Ges. Giessen 16: 1-37. 1877. — Ed. 



