REGIONAL MEETINGS - Natural History Museum

had checked Janet’s Foss Wood over the winter months, finding mostly Polypodium
interjectum and P. vulgare. But interestingly, with confirmation by Ken and Rob Cooke, we
consider the three Polypodium hybrids to be present here also. The nearest colony of
P. cambricum grows a kilometre away, west of Gordale Scar.
On our current visit we noted that the P. vulgare colonies were well developed with ripening sori,
whereas the P. interjectum was still producing new fronds and any sori present were very green,
so the colonies were nowhere near as luxuriant as they had appeared over the winter. Dropping
down to the fall pool (34/911633), we saw both species growing on the rocks and epiphytically
on several trees. A little further downstream the path wends its way beneath a ten-metre high
crag with some Polypodium fronds visible but unreachable along the top (34/910632). From a
previous examination of fallen fronds this is considered to be a P. x font-queri colony, based on
its complete infertility and characters relating to both P. cambricum and P. vulgare.
But with nothing to examine now, we continued further downstream to a site where a crag
with a large cave mouth at its base was visible up the valley side, requiring a slippery climb
(34/909632). Barry Wright produced his patent Mk 2 ‘Polypodium-gathering tool’ (a pair of
string-operated rose-gathering snips on the end of two camera monopods joined together),
which was a much-improved version of my tent poles and scissors that we had field-tested
in November (see photo p. 289). The fronds were large and elegantly adorned with doubly
serrated edges and have been identified as P. x shivasiae. Ken Trewren took a sample with
green sori for chromosome squashing. Near the bottom of the wood another slippery climb
took us up to a small craggy face with several clumps of P. interjectum, but one colony was
noticeably different, with fronds containing both ripening and aborting sori (34/909631).
This was confirmed as P. x mantoniae.
Other limestone pteridophytes noted as we returned back up the wood were Polystichum
aculeatum, Dryopteris filix-mas, Cystopteris fragilis, Asplenium scolopendrium and
A. trichomanes subsp. quadrivalens. There were a few Dryopteris dilatata plants growing
on old stumps and even a lone Athyrium filix-femina.
We returned to Street Gate for lunch in the cars with the rain still beating down, then,
undaunted and clad in waterproofs, we set off for the two-mile walk up to the watershed
between Malhamdale and Littondale. Fortunately, the cloud base lifted and the rain
gradually eased. We reached a wet flush near the top (34/908690), which yielded Equisetum
palustre and E. fluviatile. However, our main objective was the limestone pavement nearby
(34/911693) at a height of 460 metres. This habitat is typical for Polystichum lonchitis in
the Yorkshire Dales, although over many acres of seemingly suitable terrain it tends to crop
up only very occasionally. On my reconnaissance I had counted 51 plants but members
noted a further 11 plants on the day, which makes this site second only to Moughton in
terms of numbers. We were much impressed by the active growth of new fronds and baby
plants. Only one or two had that brown leathery appearance of aged plants. Most grew
protected in the grykes with a few frond tips bitten off here and there, but many were in
pristine condition. Perhaps the sheep-grazing regime is still low following the foot and
mouth disease outbreak in 2001. No signs of hybrids with the commonly occurring
Polystichum aculeatum were suspected.
Other associates in this splendid area of limestone pavement were Asplenium viride,
A. trichomanes subsp. quadrivalens, A. ruta-muraria, A. scolopendrium, Cystopteris fragilis,
Dryopteris filix-mas, and an occasional D. affinis subsp. borreri. One Polystichum aculeatum
was notable for its cristate form. Gymnocarpium robertianum was also well represented but
Dryopteris submontana was absent. A weak-looking Athyrium filix-femina was also present.
The sky was rapidly turning blue as we returned to visit our last site just five minutes walk east
of Street Gate (34/910656). This flush consists of small runnels flowing gently over calcareous
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