22 BRITISH FERNS 



not only to dwarf the central one by competition at the roots, 

 but spoils the graceful effect afforded by an individual centre, 

 owing to the intermingling and consequent distortion of the frond- 

 age. In addition to these offset-forming buds, a number of our 

 abnormal Ferns, and especially the soft Shield Fern (Polystichum 

 angular e), produce bulbils, or small plants, on their fronds. In 

 most instances these are confined to the lower part of the frond, 

 where they appear as brownish scaly knobs within, or close to, 

 the axils of the lowest side divisions or pinnse. In some instances, 

 however, as in the "proliferum" section of this species, such bulbils 

 are produced in profusion, even to the very tip of the frond, and 

 for some distance up the lateral pinna as well, so that a dense, 

 moss-like growth occupies the centre of the frond, and consists of 

 many scores of young plants. Each of these bulbils, while still 

 attached, is nourished by the parent plant ; but if such a frond be 

 detached, pegged down on good compost, either in its entirety 

 or in short sections, and kept close, the bulbils will root into the 

 soil and produce fresh fronds, and in course of time the connecting 

 midrib may be cut apart by scissors or a sharp knife, and a large 

 batch of independent plants thereby secured. Where such bulbils 

 are few and close to the base, it is better to peg down the frond 

 which bears them and let them root in in situ, only removing them 

 when well established. In some rare cases bulbils are produced 

 on the frond backs in association with the spore heaps ; but 

 although this occurs as a specific character in one exotic, Lastrea 

 prolifera, it has so far only been noted as a varietal feature on 

 several plumose Lady Ferns, Athyrium filix faemina plumosum 

 divaricalum, Axminsterense, and its progeny, the superbum section 

 (see chapter on "Fern Selection," p. 29), and some others of the 

 same class, and also in one or two cases referred to hereafter. 

 Here, however, we are dealing with deciduous Ferns, the fronds 

 of which perish in the autumn, and hence such bulbils can only 

 occasionally be induced to persist long enough to root when layered 

 as described. Much depends on the season. In some years these 

 bulbils have appeared so early that by the autumn their fronds 

 have formed an obvious fringe to the parent ones, and were easily 

 rooted before the latter began to fade. Polypodium vulgare 

 elegantissimum also, under very favourable circumstances, pro- 

 duces bulbil plants also in conjunction with its spore heaps, but 

 only on its most finely cut fronds, and as a secondary growth in the 

 second year. Adiantum capillus veneris vars. daphnites and im- 

 bricatum both produce bulbils by spore transformation on the 

 frond margins, and with a little warmth can be easily propagated 

 by their means. Several forms of the Hartstongue (Scolopendrium 

 vulgare) are proliferous, sometimes, as in S. v. cristatum viviparum 

 0' Kelly, the surface of the frond is dotted with little clusters of 

 young plants. In S. v. Wardii, Coolingii, Kelwayii, and Cousensii, 



