230 HISTORY OF BRITISH FERNS. 



used among the rockwork may have in addition a portion 

 of the sandstone pounded and intermixed with it. That 

 used for inundatum in the lower part of the case will not 

 require this intermixture, and, in fact, will be the better 

 as it approaches the unctuous texture just referred to, 

 which the presence of a good supply of water will soon give 

 to it. 



All parts of the soil should be kept rather moist than 

 otherwise, by the application of fresh water occasionally ; 

 but as the confinement of the atmosphere in the damp state, 

 in a close case, might tend to produce decay in some parts 

 of the vegetable tissues, the little door or hinged sash may 

 from time to time be left open for a few hours, in order 

 that the stagnant moisture may be carried off, when a fresh 

 supply will be doubly grateful to the plants. 



It must be recollected, that the soil will be exposed to 

 very slight drying influences, and can, therefore, never 

 require to be very copiously supplied at any one time ; the 

 proper course being, rather to ventilate frequently, say 

 once a week, in order to carry off the accumulated damp- 

 ness, and then by a moderate fresh supply to produce a 

 continued change of the watery element. For the same 

 reason, and to prevent the souring of the soil, which always 



