With thrifty and high cultivation it may, indeed, prove profitable to compensate defects of climate by the use of glass and artificial heat. The part played in the economy of Nature by fungi and bacteria—the new learning of the last half-century—is an addition to human knowledge which is destined to revolutionise our views of many natural phenomena. It has already exercised enormous propulsive power on human thought, and has stimulated our imagination scarcely less than when, to use the words of Froude, 'the firm earth itself, unfixed from its foundations, was seen to be but a small atom in the awful vastness of the universe.' This knowledge has provided us with a new world, peopled with organisms in numbers which, like the distances of the astronomers and the periods of the geologists, are really unthinkable by the human mind. Their variety also, both in form and function, is, for practical purposes, infinite. When, with the help of the many inventions of the optician and the dyer, we catch a glimpse of things which a few years back were 'undreamt of in our philosophy,' and when we reflect that these organisms are certainly the offspring of 'necessity,' and are probably mere indications of infinities beyond, we cannot be too thankful for the flood of light which these discoveries have shed upon the enormity of human ignorance. The lower animals and the lower vegetable organisms (fungi and bacteria) co-operate in a remarkable way in the circulation of organic matter. In the autumn the gardener, with a view to what is called 'leaf mould,' sweeps the dead leaves into a heap, where they are exposed to air and rain. This heap when thus treated gets hot, and last autumn I found that the temperature of such a heap had risen in the course of a week or so to 104° F., and remained at a temperature considerably above that of the surrounding air during the whole winter. On turning it over after a month or so one found in it a large number of earthworms and endless fungoid growths visible to the naked eye, and one felt sure that it was swarming with countless millions of bacteria, invisible except to the highest powers of the microscope. In the beginning of March this heap, much reduced in size, was spread loosely over a patch of ground which was previously dug. If one examined that ground to-day one would scarcely recognise the structure of leaves, and in a few weeks more it will have become nothing but ordinary garden mould, and anything planted in it will grow with vigour. This is a familiar everyday fact.