THE INNER LIFE OF PLANTS. 323 



those plants each of which as a whole does not contain green- colouring 

 matter. A seed itself germinates in the dark ; and the work of 

 bulbs and tubers in producing their characteristic plants takes 

 place, as every one knows, independently of light. Even the annual 

 layers of new wood that increase the growth of a tree, are produced 

 beneath the bark, and necessarily in darkness. Again, the habits of 

 plants, like the habits of the highest life, may exhibit strange 

 contradictions in the matter of the necessity or demand for light. 

 Thus, the seed-leaves of many members of the pine order become 

 green notwithstanding the darkness, and the same remark holds good 

 of the fronds of ferns. But a far wider generalisation may still be ' 

 made regarding the question of light and no light in the habits of 

 plants. Any plant which in its natural state does not develop 

 green colour is, of course, practically independent of light as a 

 condition of successful vitality. A mushroom, toadstool, or other 

 fungus, for example, does not require light for the performance of 

 its vital functions. Many fungi grow in the dark. The familiar 

 " truffles " are underground livers, and "moulds " certainly love the 

 darkness rather than the light. These plants, curiously enough, and 

 low as they are regarded in the botanical scale, exhibit a nearer 

 relationship with the animal world than do their green and higher 

 plant- neighbours. For instance, a non-green fungus inhales oxygen 

 gas and exhales carbonic acid like an animal ; whereas, as we have 

 seen, its green neighbour absorbs the latter gas for food, and exhales 

 oxygen under the combined influence of light and its green-colouring 

 matter, and only at night, or in darkness, imitates the animal 

 respiration. And, whilst the green plant lives on water, minerals, 

 ammonia, and other lifeless material, ,the fungus, or non-green plant, 

 demands " organic " matter that is, matter which has been elabo- 

 rated by a living being for its support. As a matter of familiar 

 observation, fungi and their neighbours possess the habit of locating 

 themselves near decaying organic material, and in this respect prove 

 themselves possessed of a " selective " power to which more particular 

 reference will be made later on. 



The hidden currents of plant-life have, however, developed 

 certain remarkable instincts in the choice not merely of food, but 

 also of habitat, which clearly prove that the plant- world is the seat 

 of actions and habits that form a striking parallel to those of the 

 animal world. It might, for instance, form an interesting inquiry to 

 determine how and why certain fungi have come to select the human 

 skin and that of lower animals as a habitation. A very large number 

 of skin diseases are known to be the products of the growth and deve- 

 lopment, within the skin -tissues, of special forms of fungi. Even the 

 silkworm and the fly appear to be infested by specific and " unbidden 

 guests " in the form of lower plants, which firstly disease, and finally 



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