374 THE UNIVERSE. 



quantity of silica. The stalk of the wheat plant contains a 

 pretty large amount, but this substance strengthens the 

 powerful stem of the bamboo in a much more decided man- 

 ner. According to Davy, the latter contains as much as 

 seventy-one parts of silica in a hundred, and, like our flints, 

 strikes fire with the steel. According to De Candolle, anal- 

 ysis demonstrates that other vegetables absorb iron, and 

 even gold. Copper has also been found in coffee and wheat, 

 and a chemist has computed that in France 3650 kilo- 

 grammes (8055 lbs. avoirdupois, omitting grains) of this 

 metal yearly enter into our food through the medium of 

 this cereal. 1 



Seeing the quantity of water that plants absorb every 

 day, Boyle concluded that this fluid was alone used for their 

 nutrition. The opinion of the celebrated English philoso- 

 pher was adopted by Van Helmont, and he thought he had 

 proved it to demonstration when he saw a willow continue 

 to flourish which he only watered with rain-water, at that 

 time considered to be wonderfully pure. 



Science has overthrown these views by proving that dis- 

 tilled water is in no w T ay sufficient to support life in the 

 plant. 



The aerial organs of vegetable life also play a great part 

 in absorption ; watering the leaves of certain plants makes 



1 It is now considered that the inorganic ingredients in plants are as absolutely 

 necessary to their existence as carbon and oxygen. In addition to such well- 

 known elements of tissue as silicon, chlorine, potassium, etc., modern research has 

 shown the presence of zinc, fluorine, caesium, rubidium, and manganese. All 

 food, however, presented to the plant must be oxidized, or the plant cannot take 

 it up. It is even probable that all ammonia becomes oxidized before assimilation 

 by the plant. Tr. 



