Carbon and vegetables

1159. Carbon, As carbon constitutes nearly one half of every vegetable substance, it is, of course, the most important element in the food of plants. As it is a solid substance insoluble in water, it cannot be taken up by the spongioles of plants in that form: it can only be imbibed by the plants when it is in combination with oxygen, or, in other words, in the state in which it is found in the atmosphere.