There are three main methods by whichare propagated—the first through root action, the second through leaf action, and the third through the spores which are found on the backs of the leaves, and which ripen in summer. In the case of the root it may be that the rootstock, like that of many rhizomatous plants, can be broken up, and each part with its rootlets and growing point set in to produce a new plant, as in the Polypody.
It may be that, after the bulb fashion, the central crown makes offsets which speedily make their own roots, and if left, develop into an association of plants. These crowns are, however, better prised away with a trowel and reset, to form finer single plants.
A really old rootstock, through exposure, may appear well-nigh dead, but if all the dead roots and dead surface are cut away, and the internal green part is well washed and potted in a goodunder glass, bulbils may appear as white pimples on its surface, and each will, if encouraged, develop into a new plant.
REPRODUCTION FROM LEAF BULBILS
It is the habit of some leaves, e.g. those of the Soft Shield fern, to grow bulbils on the axils or joints of the pinnae, and The Lady Fern will produce them on the backs of the fronds. If these are pegged down into fern mould, the bulbils will root, and can later be cut away from the parent plant.
PROPAGATION BY SPORES
This is the only method in which the raising of new varieties is possible. The spores are exceedingly small, and might easily be destroyed or lost, but Nature provides bountiful supplies. The spores themselves develop in moisture into tiny green scales known as prothalli, which in their turn produce a minute fertilizing body, and contain an embyro seed. The union of these produces the new young plant. Spores of hardy ferns can be propagated if laid on pieces of clean sandstone kept under a bell-glass on the ground in a moist corner of the garden.
In order to grow the more delicate ferns from spores in a greenhouse, it is essential to sterilize the compost. Take a small pot and put in the usual drainage crocks, fill it with good fern compost pressed flat, and sprinkle crumbs of loam or crushed flower pot on the surface, on which paper can be placed to prevent disturbance.
Thoroughly saturate the soil with boiling water till the pan is too hot to hold. All germs or spores are thus killed. Let this cool, then scatter very thinly the required spores, which have been previously collected on a glass slip and freed as far as possible from any unwanted matter.
Finally cover the pot with a glass slip—stand it in a saucer in a well-lighted place out of the direct sunshine. In a few weeks the green scales will appear. No watering must be done from the top—a little in the saucer will suffice. A month or so must elapse, and then the tiny fronds should open to the light, and all that remains is to prick them out, and bring them on in the usual way.