110 ORGANIC CONSTITUENTS OF PLANTS. 



in a great measure by the atmosphere, although they subsequently 

 derive inorganic matter from the rocks, to which they are attached. 

 Air plants, as Bromelias, Tillandsias, and Orchidacese, and many species 

 of Ficus, can grow for a long time in the air. In the Botanic Gar- 

 den of Edinburgh, a specimen of Ficus australis has lived in this con- 

 dition for upwards of twenty years, receiving no supply of nourishment 

 except that afforded by the atmosphere and common rain water, con- 

 taining, of course, a certain quantity of inorganic matter. The follow- 

 ing analysis was made of the leaves of this plant, in 1847, by my 

 pupil, Mr. John Macadam : 



Organic. Inorganic. 

 In 100 -parts. In 100 parts. 



Petiole of former year's growth, including midrib, 82'98 ... 17 - 02 



Three leaves of former year's growth, 86 - 24 ... 13'76 



Petiole of present year's growth, with midrib, 92'65 ... 7'35 



Seven leaves of present year's growth, 92-28 ... 7*72 



All were dried at 212 Fahrenheit. 



In the experimental Garden of Edinburgh, Mr. James M'Nab has 

 cultivated various plants, as Strelitzia augusta, currants, gooseberries, 

 &c., without any addition of soil, and simply suspended in the air, with 

 a supply of water kept up by the capillary action of a worsted thread. 

 Some of the plants have flowered and ripened fruit. These experiments 

 show that the atmosphere and rain water contain all the ingredients 

 requisite for the life of some plants. Boussingault, from observations 

 made on the cultivation of Trefoil, was led to the conclusion, that under 

 the influence of air and water, in a soil absolutely devoid of organic 

 matter, some plants acquire all the organic elements requisite for growth. 

 Messrs. Wiegman and Polstorf took tine quartz sand, burnt it to destroy 

 any organic matter, digested it for sixteen hours in strong nitro-muriatic 

 acid, and then washed it with distilled water. Various kinds of seeds, 

 as barley, oats, vetch, clover, and tobacco, were then sown in it, and 

 watered with distilled water, and all grew more or less. 



218. The elementary bodies already mentioned, in various states of 

 combination, constitute the great bulk of plants. They occur in the 

 form of binary compounds, as water and oily matters ; ternary, as 

 starch, gum, sugar, and cellulose ; quaternary, as gluten, albumen, 

 caseine, and fibrine. The latter compounds seem to require for their 

 composition, not merely the elements already noticed, in the form of a 

 basis, called Proteine (C 40 H 31 N 5 O 12 according to Mulder, or C 48 

 H 36 N 6 O 14 according to Liebig), but certain proportions of sulphur and 

 phosphorus in addition ; thus, albumen = 10 Pr. + IP-f IS; fibrine 

 = 10 Pr. + 1 P + 2 S; caseine = 10 Pr. + 2 S. The tissues into the 

 composition of which these proteine compounds enter, are tinged of a 

 deep orange-yellow, by strong nitric acid. These compounds are highly 

 important in an agricultural point of view, and the consideration of 

 them will be resumed when treating of the application of manures. 



