Fern for Identification

Johnny81 · #1 (**permalink**) 09-02-2011, 04:23 PM

Taken today under beech in mixed woodland. I am a bit pants on ferns, this could be a common species, but something not right about it too me.

Many Thanks
John

aeshna5 · #2 (**permalink**) 09-02-2011, 04:26 PM

One of the Polypodium spp.

Johnny81 · #3 (**permalink**) 09-02-2011, 04:31 PM

I thought a polypodium initially. Good to know my first instinct was correct then. Looks like it is doing well for the time of year.

Dorts · #4 (**permalink**) 09-02-2011, 06:16 PM

Polypodium vulgare - (Common Polypody).

We have three Polpody Ferns native to Britain antd their three hybrids. Needs an expert eye to readily tell them apart.
Dorts.

Johnny81 · #5 (**permalink**) 09-02-2011, 07:06 PM

Cheers guys, a first for me (I must leave the county more)! Been a while since I have last terrorised the botanical section of WAB

pleb · #6 (**permalink**) 10-02-2011, 05:43 PM

This fern is almost certainly Polypodium interjectum (Intermediate Polypody). In Devon, it is by far the commonest of the three Polypodium species and can be recognised by the way that the frond has its widest point about half way up the frond and then tapers towards both top and bottom. Polypodium vulgare, (Polypody), has fronds with parallel sides for most of their length and is a smaller fern. Polypodium cambricum, (Southern Polypody) has a typically wider, shorter shape of frond and is calcicole.

Hope this helps you. After a while, with practice, it is possible to identify the three Polypodium species by eye although they are variable species and do hybridize so one can never be 100% sure.

Dorts · #7 (**permalink**) 10-02-2011, 08:45 PM

That's great Pleb, there's nothing like a bit of local knowledge.
It would be usefull to know where John recorded it.
Dorts.

JennyS · #8 (**permalink**) 10-02-2011, 11:26 PM

I agree with pleb that it's Intermediate Polypody, P. interjectum.
The spores are very helpful for identification as in P.interjectum the sori are oval (shown in John's photo) but circular in Common Polypody, P. vulgare.

Intermediate Polypody:
Irish ferns - Intermediate Polypody

The Woodman · #9 (**permalink**) 10-02-2011, 11:30 PM

That's a useful guide pleb, thanks.

Johnny81 · #10 (**permalink**) 11-02-2011, 09:16 AM

Dorts you wanted to know where I found it: Taken Northamptonshire Harlestone firs. It is a mixed woodland surround by agricultural land, that once was heath land I believe. The polypody fern was observed right underneath a huge beech tree. The trees have been planted in a type of avenue within the woodland.

Many thanks for the information from all of you.