Now, herbaceous and all other green plants stand alone among terrestrial natural bodies, in so far as, under the influence of light, they possess the power to build up, out of the carbonic acid gas in the atmosphere, water and certain nitrogenous and mineral salts, those substances which in the animal organism are utilised as work-stuff. They are the chief and, for practical purposes, the sole producers of that vital capital which we have seen to be the necessary antecedent of every act of labour. Every green plant is a laboratory in which, so long as the sun shines upon it, materials furnished by the mineral world, gases, water, saline compounds, are worked up into those foodstuffs without which animal life cannot be carried on. And since, up to the present time, synthetic chemistry has not advanced so far as to achieve this feat, the green plant may be said to be the only living worker whose labour directly results in the production of that vital capital which is the necessary antecedent of human labour.* Nor is this statement a paradox involving perpetual motion, because the energy by which the plant does its work is supplied by the sun--the primordial capitalist so far as we are concerned. But [156] it cannot be too strongly impressed upon the mind that sunshine, air, water, the best soil that is to be found on the surface of the earth, might co-exist; yet without plants, there is no known agency competent to generate the so-called "protein compounds," by which alone animal life can be permanently supported. And not only are plants thus essential; but, in respect of particular kinds of animals, they must be plants of a particular nature. If there were no terrestrial green plants but, say, cypresses and mosses, pastoral and agricultural life would be alike impossible; indeed, it is difficult to imagine the possibility of the existence of any large animal, as the labour required to get at a sufficiency of the store of food-stuffs, contained in such plants as these, could hardly extract from them an equivalent for the waste involved in that expenditure of work. * It remains to be seen whether the plants which have no chlorophyll, and flourish in darkness, such as the Fungi, can live upon purely mineral food.