THE ASH OF PLANTS. 315 



cotyledons is consumed. But if the roots be placed in 

 a nutritive solution suited to water-culture, the stem 

 grows on without injury until the cotyledons are com- 

 pletely emptied of starch, and afterwards continues to de- 

 velop at the expense of the lower leaves. 



The arrest of growth in the stem evidently is due to 

 the absence of some one or more ash-ingredients, and 

 Bohm found in fact that, by withholding lime-salts from 

 the roots, this characteristic malady was invariably pro- 

 duced. Hence he concludes that calcium compounds are 

 immediately concerned in the conversion of starch into 

 cellulose. 



Magnesium. — Von Kaumer,in the paper just referred 

 to {Vs. St., XXIX, pp. 263 and 273), gives his observa- 

 tions on the relations of the magnesium salts to the veg- 

 etative processes. He states that, all other conditions 

 being favorable, the exclusion of magnesium from a nu- 

 tritive solution in which the scarlet-runner vegetates is 

 followed by cessation of chlorophyl-production and of 

 that enlargement of the new-formed cells wherein the 

 act of growth largely consists. Accordingly, in absence 

 of magnesium-supply, the plants, which at first grew nor- 

 mally; after reaching a height of forty inches, began to 

 show signs of disturbed nutrition. The uppermost in- 

 ternodes (joints) of the stems almost ceased to lengthen 

 and became exceptionally thick and hard, their leaves 

 failed to open, and both joints and leaves were white in 

 color with but the faintest tint of green. Soon new up- 

 ward growth ceased altogether, the terminal bud and 

 unfolded leaves dried away, and, while the lower, first- 

 formed and green leaves remained fresh for weeks and 

 the lower stem threw out new shoots, healthy growth 

 was at a stand-still, and the plants gradually wibhered 

 and perished. The normal growth of the bean plants 

 for a month or more in nutritive solutions containing no 

 magnesium is accounted for by the supply of this ele- 



