Re: Lowest pinnae length as ID clincher

Hello Larry,
    You did not respond to my previous e-mail regarding books that would be
helpful for identification so I hesitate to explain this but here goes.
    In the case of many dryopteris species it is the lowemost pinnule next
to the rachis or center stem, referred to as basiscopic, is often used in
the key and to help identify certain species.  It may be smaller than the
adjacent basiscopic pinnule or larger.  The uppermost one would be referred
to as the acroscopic
    Since botanists refer to the fact that Polystichums have an enlarged
acroscopic pinnule next to the rachis, the polystichum thumb, and that helps
beginners determine a polsytichum from a dryopteris when spores are not
present it seems likely that there are very few dryopteris with enlarged
acroscopic pinnules next to the rachis.
    Both dilatata and expansa (aemula does too but is quite rare) have
enlarged basiscopic pinnules nest to the rachis.  However expansa, at least
in its Northwestern form, is much more delicately dissected and of thiner
texture than sporling dilatata.
    "The Luustrated Fiel Guide to FErns and Allied Plants of the British
Isles" by Clive Jermy and Joesphine Camus has a very easy to use key that
might be helpful in your rambles through the countryside.
Judith I. Jones,
Gold Bar, WA, US
----- Original Message -----
From: "Larry Shone" <greenlarry@ntlworld.com>
To: <ferns@hort.net>
Sent: Monday, May 23, 2005 10:43 AM
Subject: [ferns] Lowest pinnae length as ID clincher


> I have been told when Identifying to possible dryopteris species that the
> lowest upper pinnae is longer than the one below it, is this what is
meant?:
> http://img.photobucket.com/albums/v11/Dawnrider/pinnae.jpg
>
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