CHLOROPHYLL. ii 



establish itself, on account of the almost universal presence 

 of its food, than is the case with the fungus. In the nature 

 of its food the moss may be regarded as typical of the 

 great majority of plants, in fact of all those that are green ; 

 this colour, called chlorophyll, being inseparably connected 

 with the assimilation of inorganic food ; but it is important 

 to bear in mind that although all green plants agree with 

 the moss in requiring carbonic dioxide as one food con- 

 stituent, yet all are not equally indifferent as to the nature 

 of the food substances absorbed in solution in water, an 

 unusual and sparsely-distributed substance being in some 

 instances an indispensable food constituent, consequently 

 we find that the nature of the soil, or the geological formation 

 of a given district, determines to a great extent the nature 

 of its own flora. The fungus, in the nature of its food, 

 is characteristic of all those plants not furnished with 

 chlorophyll, agreeing with the members of the animal 

 kingdom in requiring organic matter as food. But in the 

 fungi we find that food determines to some considerable 

 extent the distribution of the species. Many kinds of fungi, 

 so far as can be ascertained, have no marked partiality for 

 any particular kind of food ; other conditions being favour- 

 able, so long as organic matter is present, such fungi 

 generally appear. On the other hand, some kinds of fungi 

 are so restricted in the matter of food that they are 

 confined to being parasitic on the leaves of one particular 

 species of plant ; consequently, in such instances the limits 

 of distribution of the fungus is necessarily influenced by the 

 range in space of the plant upon which it is dependent for 

 food. 



{b) Moisture.^The manifestation^ of life in the active 

 state is absolutely dependent on the presence of water in 



