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1323 Views 4 Replies Last post: Oct 29, 2012 7:42 PM by Alan RSS
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Oct 11, 2012 8:41 PM

Fern species

could anyone help identify this fern, please. I'm thinking it is a Soft Shield Fern (Polystichum setiferum) but they are not common around here in South Yorkshire - willing to be proved wrong! photo taken 9 Oct

 

Alan

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    Oct 12, 2012 10:17 AM (in response to Alan)
    Re: Fern species

    Hi Alan,

    any chance you could send me a frond, or bit of a frond? Your first photo seems to show circular shield-like indusia with a central point of attachment which is characteristic of Polystichum - those of Dryopteris being kidney shaped. That said I can't see the photos too clearly and the close up of the foliage doesn't look typical.

    Any chance of some more photos - whole frond so one can see the lower portion of the frond, etc.

    What sort of habitat was the plant growing in?

    regards

    Fred

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        Oct 29, 2012 10:44 AM (in response to Alan)
        Re: Fern species

        Hi again Alan,

        yes you are quite correct with your ID - it is the Broad Buckler-fern (Dryopteris dilatata). The dark centred scales are a good way of telling this apart from some of its close relatives such as the Narrow Buckler-fern and the Northern Buckler-fern but one has to be a little careful as you do get some odd forms of the common plant that have paler scales. The difference between your two fronds is just a question of maturity. In the upper picture the sporangia are still blackish in colour as they are still packed with the spores - the covering protective indusia haven't dried ouit and shrivelled as they do later on - as in your lower photo. Here all of the spores have been shed - the sporangia have ripped themselves open and chucked the spores out and all that is left are the paler brown sporangial remains. Each of those little blackish dots that are packed together under the indusium is shaped like a boxing glove on a narrow stalk which attaches it to the frond around the indusium stalk. The knuckles of the glove are made up of slightly thicker walled cells - the annulus - but these are unequally thickened. That means as the ripe structure dries out it sets up an unequal tension which causes the thinner cells around to rip open and the whole thing thrashes around chucking the spores out. The sporangium ends up looking more like pac-man. In a sexual species like this there are 64 spores packed in each sporangium - a quick bit of maths and you realise just how many spores are going to be released by just this one frond!

        regards

        Fred

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