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ROYAL HORTICULTURAL SOCIETY. 



bananas, coffee, yams and mandiocca, which is conducted by mere 

 irrigation without any animal manure. Darwin has himself visited 

 but few tropical countries where such a cultivation takes place 

 without manure, and has observed even this very imperfectly. He 

 instances the cultivation of maize in Peru and Chili, which is 

 conducted in barren river-sand, without remembering that it is 

 irrigated by rich humous water from the mountains, and in con- 

 sequence receives the richest possible nutriment. [Further he 

 concludes from the cultivation of the oil-palm in Guinea, in the 

 moist sand of the coast, that nourishment takes place from the 

 air. Schleiden, Liebig, &c. have spoken with amazement of the 

 fact that 33,000,000 lbs. of palm-oil are exported every year from 

 Guinea, which contains some 24,000,000 lbs. of carbon, without 

 any animal-dung from which it might arise, and conclude there- 

 fore that dung and soil supply no carbon. Had they known that 

 a single moderate-sized German river, the Elbe, for instance, at 

 Magdeburg, yields daily 1798 cwt., or yearly 64,728,000 lbs. of 

 humous extract, which contains above 40,000,000 lbs. of carbon, 

 their amazement at an exportation of 24,000,000 lbs. from the 

 whole of Guinea would be much diminished, especially since the 

 waters of tropical lands are far richer in diffused liumus than 

 those of colder districts. Darwin and Tschichatschew (' Travels 

 through the Pampas,' 1844) estimate that a proportionate quantity 

 of carbon is afforded, without any manure, by the luxuriant growth 

 of the herbage in the Pampas of Buenos Ayres, from which count- 

 less herds of wild oxen and horses are supported — simply from the 

 skins of these animals, which answer to a weight of 6,000,000 lbs., 

 which therefore must arise from the carbonic acid of the air, and 

 the decomposition of water. "When, however, we consider how 

 rich the water of the soil is in humus, we shall see that the 

 alleged amount of organic matter is nothing in comparision with 

 the carbon which flows yearly into the sea with the humus of the 

 Amazon and Orinoco, into which rivers pour whose waters are 

 almost black, and which is constantly renewed from the soil. 

 According to Darwin's theory, the culture of palms in our stoves 

 could certainly not be accomplished. 



To arrive at a correct judgment of the cultivation of plants 

 without manure in warm climates, great distinctions must be 

 made of different lands and localities. "We may reckon as countries 

 in which, with few exceptions, cultivation is carried on by mere 

 irrigation without the use of manure, — in Asia, Arabia, Persia, 

 Turkistan, Chiwa, Eochara, the East Indies, Siam, Cochin China, 



