Mineral Nutrients 163 



as valuable a fertilizer as potassium chlorid or sulfate. 

 We must regard as one of many types of facts opposed to 

 this view the vast amount of experimental work showing 

 the direct value of particular nutrients, and more espe- 

 cially, of particular nutrients at certain stages of the 

 growth of the crop. The view is of undoubted value 

 in suggesting lines of investigations. Associated with it, 

 usually, is the idea of toxic excreta from plant roots, which 

 is considered in another place. 



90. The paraffined wire basket in nutrition studies. 

 In determining through plant growth certain soil relations 

 by a quick laboratory method it has been the custom to 

 employ tumblers or other similar glazed vessels from which 

 there could be no loss of the materials employed. These 

 are not always satisfactory, since, if drying out proceeds, 

 spaces are left between the soil and the vessels, and under 

 unfavorable conditions, especially, it is in these spaces that 

 the roots grow, thus giving no exact indication of the soil 

 conditions. 



The paraffined basket method is well demonstrated by 

 Figure 48, in which, from left to right, successive stages in 

 the preparation of the culture are shown. As described 

 by Schreiner, the basket is dipped top downward into hot 

 paraffin several times until a rim is made. It is then filled 

 with soil to the rim, and firmly packed near the gauze, 

 the surplus protruding soil being brushed off. The basket 

 is then dipped into the paraffin up to the rim several times. 

 The paraffin penetrates into the soil pores or capillaries, 

 and there is no line of cleavage, as with glazed vessels. 

 The surface of the soil may be covered with paraffined 

 paper, in which slits are made for placing the seedlings. . 



