ABSORPTION OF ASH-CONSTITUENTS 95 



grain. Cultures in water extracts of unproductive soil give but poor growth, 

 but growth is improved proportionally with the dilution of the extract with 

 distilled water (Fig. 64). Addition of hme frequently neutralizes the toxic 

 effect. To secure a good crop in an unproductive soil that contains toxins, it 

 is necessary to find substances that render the soil toxins harmless. 



The effects of water extract from bog-soil and of bog water, upon the 

 development of Vicia faba^ (Windsor or broad bean) are shown in Fig. 65. 

 The addition of calcium carbonate and the adsorptive action of carbon- 

 black have been very effective here. In this case the toxic action of the bog 

 water was probably due to toxins arising from the microorganisms of the soil,'' 

 rather than to toxins emanating, from the bog plants.* 



Toxins of some agricultural soils are Organic in nature, as is indicated by the 

 following experiment.^ Water extract of a soil that had become alfalfa-sick 

 was toxic to this plant, but if the soil was brought to a red heat before making 

 the extract the latter was not toxic. Water extracts of other soils, which had 

 not been in aKalfa culture, had no injurious effect upon the growth of this 

 plant. 



Experiments have also been made to determine the effects of various plant 

 substances upon plant growth. Such substances are sometimes injurious and 

 sometimes beneficial. Watering with a 3-per cent, solution of nicotin, for 

 instance, produces good growth in tobacco, and is likewise beneficial to potatoes.* 



' Dachnowski, Alfred, The toxic properties of bog water and bog soil. Bot. gaz. 46: 130-143. 1908. 



'LiShnis, F., Handbuch der landwirtschaftlichen Bakteriologie. Berlin, igio. 



' Pouget, I., and Chouchak, D., Sur la fatigue des terres. Compt. rend. Paris 14s : 1200-1203. 1907. 



* otto, R., and Kooper, W. D., Untersuchungen uber der BinHuss giftiger, alkaloidfdhrender Ldsungen 

 auf Boden und Pflanzen. Landw. Jahrb. 39 : 397-407. 1910. 



* That bog waters are toxic to ordinary plants (at least, in that they have an acid reaction), 

 has long been suspected. Schimper (Schimper, A. F. W., Plant geography upon a physiologi- 

 cal basis. Translated by W. R. Fisher. Oxford, 1903) considers bogs as physiologically dry, 

 but is not clear as to just what physiological dryness may be due to. Livingston tested the 

 two logical possibilities in this case. He found (Livingston, B. E., Physical properties of bog 

 water. Bot. gaz. 37: 383-385. 1904) that high osmotic concentration of bog water is 

 not a possible explanation of physiological dryness; bog water has a freezing-point no 

 lower than that of water from drained swamps and rivers of the vicinity. By the use of 

 an alga as a physiological indicator, the same author showed very clearly that bog waters 

 usually contain toxic substances. (Livingston, B. E., Physiological properties of bog water. 

 Bot. gaz. 39; 348-3SS. 1905.) It appeared also that this toxicity (for the alga used) was 

 surely not directly related to acidity, the degree of acidity being measured with phenol- 

 phthalein as indicator. It is interesting to note that this first step toward an analysis of the 

 bog-water problem occurred at almost exactly the same time as the general problem of toxic 

 substances in arable soils was opened up (in its modern sense) by Whitney and Cameron (1904) 

 [see note i, p. 93] and by Bedford and Pickering (1903) [see note j, p. 93]. The three 

 lines of work were entirely independent. Transeau also (Transeau, E. N., On the develop- 

 ment of palisade tissue and resinous deposits in leaves. Science, n. s. 19: 866-867. 1914) 

 had shown that bog water is toxic, to Rumex at least, before the excellent studies of Dachnow- 

 ski (cited here in text), and those of Rigg were published. (Rigg, G. B., The effect of some 

 Puget Sound bog waters on the root hairs of Tradescantia. Bot. gaz. 35: 314-326. 1913. 

 Idem, The toxicity of bog water. Amer. jour. bot. 3: 436-437. 1916. Idem, A summary 

 of bog theories. Plant world 10: 310-325. 1916.) It seems probable that microorganisms 

 and lack of oxygen have to do with the production of these bog toxins. — Ed. 



