This is of great importance to Fern-growers not only on account of its character, but also of its cost. The best growers have to buy in hundreds of tons of top-spit or loamy soil, and this is stacked up until it has matured and is ready for use. It is often placed in layers 1 or 2 ft. thick, with an alternate layer of well-decayed manure 1 ft. or so thick between, and is thus left for two or three years to settle down and sweeten by exposure to the weather. When required for use it is chopped down with a spade, passed through a sieve, and may have some well-rotted leaf mould or a little peat mixed with it, and perhaps a dash of sharp silver sand. The whole is thoroughly mixed, and is then ready for use - at least for potting purposes.

Of late years the question of sterilizing the soil for Fern-growing has become prominent owing to the outcry made against eelworm and injurious bacteria - these being often the imaginary products of men who have never grown a Fern in their lives. Some growers make a point of sterilizing the soil in which spores are to be sown, others sterilize for all purposes, and others again never dream of sterilizing their soil; and each one produces good saleable plants. The sterilizing process may be done by placing the soil in iron receptacles which are heated in the furnace, or if steam or boiling water is available the soil may be saturated with one or the other. In this way it is possible to kill eelworm, injurious and perhaps also beneficial bacteria, and, what may be still more important, the spores of mosses, fungi, and the seeds of weeds. Thus, when the spores of a desired variety are sown on a sterilized soil, one may assume that the resulting vegetation is fairly clean and true to name.

According to Hornberger, Ferns generally are made up of 97.292 per cent of organic matter, and 2708 per cent of ash. The latter is made up as follows:-

It will be noticed that lime is apparently non-existent, while silica is the predominating constituent of the ash. Although not absolutely essential for plant growth according to experimental researches, the presence of silica (or flint) in the shape of sand is essential to give that rigidity and firmness to the stems of Fern fronds.