168 ANIMALS AND PLANTS. 



The great majority of conspicuous plants are. as 

 everybody knows, green ; and this arises from the abun- 

 dance of their chlorophyll. The few which contain no 

 chlorophyll and are colourless, are unable to extract the 

 carbon which they require from atmospheric carbonic 

 acid, and lead a parasitic existence upon other plants; 

 but it by no means follows, often as the statement has 

 been repeated, that the manufacturing power of plants 

 depends on their chlorophyll, and its interaction with the 

 rays of the sun. On the contrary, it is easily demon- 

 strated, as Pasteur first proved, that the lowest fungi, 

 devoid of chlorophyll, or of any substitute for it, as they 

 are, nevertheless possess the characteristic manufacturing 

 powers of plants in a very high degree. Only it is 

 necessary that they should be supplied with a different 

 kind of raw material; as they cannot extract carbon 

 from carbonic acid, they must be furnished with some- 

 thing else that contains carbon. Tartaric acid is such 

 a substance; and if a single spore of the commonest 

 and most troublesome of moulds Penicillium be sown 

 in a saucerf ul of water, in which tartrate of ammonia, 

 with a small percentage of phosphates and sulphates is 

 contained, and kept warm, whether in the dark or ex- 

 posed to light, it will, in a short time, give rise to a thick 

 crust of mould, which contains many million times the 

 weight of the original spore, in protein compounds and 

 cellulose. Thus we have a very wide basis of fact for 

 the generalisation that plants are essentially character- 

 ised by their manufacturing capacity by their power 



