Dec. 1, 1919 Effect of Salts and Organic Extracts on Citrus Seedlings 269 



The organic matter extracted from upland peat is decidedly acid, but 

 the degree of acidity varies greatly in diflferent samples. In the upland 

 peat employed in this work, i gm. of the soluble material extracted 

 with 3 per cent ammonium hydrate, after being evaporated to dryness 

 to remove the ammonia and again dissolved in water free from carbon 

 dioxid, required 0.088 gm. sodium hydroxid to neutralize it, using phenol- 

 phthalein as an indicator. The acidity is therefore about 8 per cent of 

 an hydrochloric acid solution of the same concentration by weight. 

 Since the root elongation was stimulated in the most concentrated 

 organic extracts used (1,000 parts per million), it appears that at least 

 in the presence of the other constituents of the peat extract the growth 

 of the citrus seedlings is not inhibited by the organic acids present in 

 concentrations equivalent to 80 parts per million hydrochloric acid.^ 



The figures in Table I, showing the root elongation, are not to be 

 considered as representing accurately the relative stimulation of the 

 various peat concentrations. Often a solution of 10 parts per million 

 of peat would give as good plants as a solution of higher concentration. 

 No attempt was made to find the amount of organic matter needed for 

 maximum growth. Neither potassium chlorid nor sodium nitrate in 

 water cultures stimulated the growth of the seedlings, so the action of 

 the organic matter is not to be attributed to the addition of these nutrient 

 salts. 



STIMULATING ACTION OF CALCIUM CARBONATE AND BICARBONATE 



Calcium carbonate was found to have as pronounced an effect as 

 organic matter in stimulating the root elongation of citrus seedlings. 

 This is shown in the following table, the figures representing the total 

 root growth of 10 seedlings in eight days. About o.i gm. of calciuni 

 carbonate was added to each culture flask, which contained about 250 cc. 

 of solution. 



Table II. — Stim-ulation of root growth of citrus seedlings by calcium, carbonate 



' The nature of the organic adds present in the upland peats of the United States does not appear to have 

 been specifically investigated. Some of the organic acids and other substances of definite chemical com- 

 fKJsition which have been isolated from alkaUne extracts of soils are listed in a paper by Shreiner and Shorey, 

 who state that the vegetable acids of the hydroxy-fatty series which are added to the soil with the plant, 

 residues apparently soon break down into simpler compounds. (SchreinER, Oswald, and Shorey, 

 Edmund C. chemicai, nature op soil organic matter. U. S. Dept. Agr. Bur. Soils Bui. 74. p. 13. 1910.) 



