Other Methods of Increase* 
43 
developed in the production of buds on various parts 
of their fronds. Experiments have conclusively 
proved that the barren Scolopendrium crisjniin, for 
instance, is much more readily propagated from sec- 
tions of the underground stem than the fertile species 
and varieties. Among British Eerns naturally 
barren, the most striking instance is that of the 
Welsh Polypody (I^olypodiiivi vulgare cambricum), 
which, although grown in great quantities, and con- 
sequently under very different circumstances, and 
subjected to various climatic conditions and in- 
fluences, has never been seen bearing any fertile 
fronds, either naturally or under cultivation. 
Permanent barrenness is equally well illustrated in 
the case of the lovely frilled or plumose form of the 
common Hartstongue, Scolopendrium vulgare cri.i- 
pum, which, although grown in enormous quantities 
and under various conditions, has invariably re- 
frained from producing spores. 
Numerous other instances of barren or partially- 
barren species and varieties might be adduced in 
exemplification of the characteristic referred to. 
Anyhow, it is only fair to assume that this absence 
of spores accounts for the rarity of such Perns in 
collections, as well as the comparatively high figures 
asked for them. Their propagation is necessarily 
a very slow process, particularly that of the plumose 
form of Aspidium (PoIysticJmm) aculeatiim ; this 
can only be increased by means of side growths, 
which are but sparingly produced at the base of the 
protracted trunk, and only after the plant has 
already attained a certain age. The barren forms of 
Poly podium and of Scolopendrium are more plenti- 
ful in collections, for this reason — that while, in the 
cases just described, one must patiently wait for the 
production of the offsets or of side buds, these species 
and their varieties may be — and, indeed, frequently 
are — propagated either by the sectioning of the 
underground stems, as previously explained, or by 
the division of the crowns, which are produced in 
greater abundance. In exotic Perns, we And the 
same barren character affecting to a similar degree 
