130 ' CHARLES B. LIPMAN 



ample, it is noticed that in wheat plants grown in solutions which 

 are rich in magnesium, or even in potassium, the color of leaves is 

 always a dark green, whereas in the calcium-rich solutions, it is 

 a yellowish green. A similar thing has also been noticed by the 

 reviewer in bean plants treated with an excess of magnesia and 

 lime. Hansteen points out that the damage done to plants in 

 calcium-free solutions consists in the great swelling of the cells 

 of the roots to the point of final bursting and disintegration, 

 making a soft spongy mass of the feeding roots. Here we have, 

 therefore, another example merely of the essential nature of cal- 

 cium to plant growth, showing perhaps different phases of the 

 manner of its functioning in plant life, but no evidence of the 

 necessity of certain ratios of calcium to magnesium for the wel- 

 fare of the plant. 



It should also be pointed out here that Hansteen calls atten- 

 tion to the publication after the preparation of his manuscript, 

 of a paper by Krefting in which some light is thrown on the cal- 

 cium relationships of the brown algae, and namely that the in- 

 tercellular substance of the brown algae consists of an acid named 

 by Krefting "Tangsiiure," and which has the following composi- 

 tion by elements: carbon 39%, hydrogen 5%, oxygen 56%, and 

 which is to be regarded as one of the pectin acids. Krefting 

 shows that with calcium, barium, and strontium ''Tangsaure" 

 makes insoluble compounds, while with potassium, sodium or es- 

 pecially with the alkali metals, and also with magnesium in cold 

 and warm water, it forms soluble compounds. It is also be- 

 lieved by Krefting that double salts are produced by this acid 

 with potassium and sodium, for example, or with other metals 

 in a similar way, magnesium also being included in that group. 

 These double salts are all easily soluble, whereas for example, 

 on the other hand, those double salts which it makes with po- 

 tassium and calcium or with sodium and calcium, or with mag- 

 nesium and calcium, are very difficultly soluble. The signifi- 

 cance of these investigations may be great in the modification 

 of the present established and widely accepted views of Loew 

 with reference to the role of calcium and magnesium which we 

 have above discussed. The reader of this paper will perhaps 



