NATURE IN LITTLE 



enemies as we do, their youth, their maturity, their 

 ripe old age. 



How curious it is that the air-plants should be 

 able to get their mineral elements from the air as if 

 this all but impalpable fluid were a soil full of lime 

 and magnesia and silica, and the plant pushed in- 

 visible roots into it! In Florida how often I used 

 to pause and regard them when I saw them growing 

 upon gate-posts or dead tree-trunks and flourishing 

 so luxuriantly! I burned some of them up to see if 

 they left any ashes and was surprised at the amount. 

 Is this semi-tropical air, then, so loaded with all these 

 mineral elements? How much I wished to see the 

 mechanical or chemical devices by which the plants 

 seized it or strained it out of the air! A Russian 

 chemist says that "if a linen surface moistened with 

 an acid be placed in perfectly pure air, then the 

 washings are found to contain sodium, calcium, 

 iron, potassium. Linen moistened with an alkali 

 absorbs carbonic, sulphuric, phosphoric, and hydro- 

 chloric acids." The presence of organic substances 

 in the air can be proved by similar experiments. 

 The cosmic dust in the air from the wear and tear 

 of the vast sidereal machinery, not detectable by 

 any of our human senses, may also be a source of 

 some of the mineral elements in the air-plants. It is 

 evidently by the aid of the acids in the leaf that 

 these plants trap and appropriate the iron and 

 the potassium. The ^atmosphere, then, seems like 

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