term decomposition. All this active life will either be stopped, by closing 

 the soil interstices with water, or be turned to those destructive phenomena 

 of decay, decomposition in the absence of oxygen. Every soil has its my- 

 cological as well as its bacterial flora, which decomposes the organic sub- 

 stances. According to Oudemans and Koning^, these are approximately 

 typical for definite kinds of soil. 



In potted plants it is safe to assume the beginning of stagnation when 

 the vipper surface of the soil is covered with a hard white or reddish colored 

 lime crust, firmly attached to the edge of the pot. From the uncommonly 

 large amount of carbon dioxid developed by the addition of acetic acid, 

 it is evident that the incrustation of the uppermost soil layers in the pot, 

 and at the edges, results especially from calcium carbonate. 



Magnesium carbonate is met with and also ferrous carbonate, which 

 later through oxidation, produces as ferric hydrate dififerent colors in the 

 crust. According to the microscopic examination, the characteristic 

 swallow-tailed crystals of gypsum and the octahedrons of calcium oxalate, 

 as well as the rhombic forms of calcium phosphate, soluble in acetic acid, 

 occur. The presence of the last named salt can not always be demonstrated 

 and never in large amounts. On the other hand, calcium carbonate and 

 probably magnesium carbonate, together with very fine particles of quartz 

 sand, make up the usual substances of the crusts, between which is per- 

 ceptible at first an abundant fungous growth with a formation of conidia on 

 the humus. The production of these crusts may be explained by the fact 

 that the water, given in large quantities in watering, becomes charged with 

 the carbon dioxid, abundantly produced by the process of decomposition 

 within the soil interstices. Hence water is a splendid medium for dissolving 

 the calcium carbonate present in the soil, the magnesia, the ferric phosphate, 

 the ferric silicate, etc. 



The more quickly the superfluous water is drawn away by good drain- 

 age in the pot, the less will the minerals be dissolved and washed away. On 

 the other hand, if the water stands in the pot and once becomes charged 

 with calcium, which is soluble in the form of calcium bi-carbonate, it can 

 only be removed by evaporation from the saturated upper surface of the 

 pot and, when the pores of the pot are not closed by a green, slimy algal 

 growth, this excessive water also evaporates slowly through its sides ; it 

 leaves behind the dissolved substances. The pots "become coated." The 

 calcium remains behind as calcium carbonate just as on the edge of a kettle 

 in which water containing lime has been boiled. 



Thus the usefulness of the two processes, the frequent washing of the 

 flower pots and the breaking up of the upper surface of the soil, is dem- 

 onstrated. 



In the increasing desire to attain our ends by fertilization, dii¥erent 

 fertilizers are added to water soaked plants, but the main need,- — sufficient 



1 Oudemans, C. A. J., et Koning-, C. J., Prodrome d'une flore mycolog-ique obtenue 

 de la terre humeuse du Spanderswoud etc. Extr. Archiv. neerland.; cit. Z. f. Pflan- 

 zenkr. 1903, p. 60. 



