20/ 



currents of air, they begin to wilt in spite of sufficient soil moisture, because 

 the quantity of water evaporating through the leaves cannot be replaced 

 cjuickly enough by the root. To be sure, the supply of water will be in- 

 creased as the temperature rises simultaneously with the increased sunshine. 

 According to De Vries^, imbibition of the cell walls is increased and thereby 

 their ability to conduct water, but the increased supply, nevertheless, cannot 

 make good the loss through evaporation and the leaves must droop. If the 

 pots are then watered, without having been tested, the earth will become 

 sour. 



The same result is found in the so-called New Holland and Cape plants 

 belonging to the families of the Epacrideae, Ericaceae, Papilionaceae, 

 Rutaceae, etc. The loose, fine, sandy, but little decomposed earth, such as 

 heath mould, cannot be pressed very firm into the pots, because the unde- 

 composed pieces of roots and leaves form a very loose consistency ; with too 

 heavy watering, however, the fine grains of sand and clay are first stirred 

 up and then washed down so that only the long, loose fibrous elements re- 

 main at the upper surface of the pot. These naturally retain but very little 

 water and let it run down very- quickly to the bottom of the pot. On this 

 account the upper surface of the pot is always almost half dry. If now the 

 gardener lets himself be led astray and waters the pots under such con- 

 ditions, and if the pots have no good drainage, the very fine roots will decay. 

 (It should be remarked in passing, that the so-called soured pots quite fre- 

 quently show an alkaline reaction. I found with potted plants, whose roots 

 had decayed, that moist red litmus paper turned blue as far as it lay upon 

 the surface of the pot). 



As a means of overcoming this, transplanting into very sandy earth and 

 sinking the soured plants in beds with warm soil has already been recom- 

 mended. As a matter of course the roots must be cut back to the healthy part 

 when transplanted. As a precautionary measure, the pots may be plunged into 

 the ground and similar methods may be recommended. In doing this, how- 

 ever, a stick or a piece of wood, turned like a cone, should be used to make a 

 deep, funnel-like hole, whose upper edge is exactly the size of the edge of 

 the pot. The pot then hangs in the hole. Below the pot the lower part of 

 the conical hole forms a cavity and prevents the earth worms from crawling 

 into the drainage hole in the pot and stopping it up. In flower pots stand- 

 ing in a room, or on flower racks, the soil will not sour if only some little 

 care Is taken. The water content of the soil may be judged easily and com- 

 paratively accurately by tapping the pot. If the earth is full of moisture, 

 the water lies between the individual particles of soil and the sides of the 

 pot and the sound resembles that of a dense mass ; when the amount of water 

 is scanty, however, the pot rings hollow. 



According to the above, therefore, one should consider not only how 

 much to water, but in what way potted plants should be watered. In order 

 to avoid washing away the finest particles of clay and sand and thereby 



Bot. Zeitung-. 1872, p. 781. 



