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Tue Jul 4 03:34:58 CEST 2006

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From: Mike Slater <mslater at VOICENET.COM>
Subject: Arisaema/Arisaema triphyllum ssp. pusillum green form)
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----- Original Message ----- >

> From:    "Mellard, David (ATSDR/OA/OD)" <dam7 at CDC.GOV>

> Is the bulbous tip to the spadix one of the distinguishing features of
> v. pusillum?
> David
> Atlanta

Hi David,

Not really. in A.t. ssp. pusillum the distinguishing physical characters =are
as follows:

1) the flower is small and the spadix us usually narrow and cylindrical (=not
slightly swollen as is usual for A.t.ssp. triphyllum.)

2) the underside of the spathe limb is almost never striped (it is usuall=y
dark red-purple to black (as in the picture I posted yesterday) but
occasionally plain green as in the picture I posted today.)

3) the flange of the spathe tube (the flared rim of the tube) is narrow.

4) the underside of the leaflets are shining green in A.t. ssp. pusillum =and
ssp stwardsonii and whitish/glaucous in A.t.ssp triphyllum.

5) (A harder to use character without plants for comparison) the lateral
leaflets of ssp. pusillum and stewardsonii are only slightly asymmetrical
about their mid-ribs, in ssp. triphyllum the lateral leaflets are very
significantly asymmetrical about their mid-ribs.

Other distinguishing features in the field are the later bloom time, (bot=h
ssp. pusillum and ssp. stewardsonii start blooming about at the end of th=e
blooming period for ssp. triphyllym) and the wetter habitat preferred by
both ssp. pusillum and ssp. stewardsonii .

And of course A.t.ssp. stewardsonii has it's very easlily seen  ribbing
which extends up the spathe tube and over the top of the spathe limb. Bot=h
ssp. pusillum and ssp triphyllum may have white ribbing on the spathe tub=e
but I have never seen it extend over the entire top of the spathe limb.

In addition the Chromosome counts are different
A.t. ssp. pusillum 2n=28 (diploid)
A.t.ssp. stewardsonii 2n=28 (diploiod)
A.t.ssp. triphyllum 2n=56 (tetraploid)

The ranges of all the subspecies overlap (i.e. they are sympatric at leas=t
in part)

(note that the descriptions in the Genus Arisaema by Guy and Liliane Gusm=an
is accurate and pretty thorough)

In his 1980 PhD thesis Miklos Trieber describes his attempt to interbreed
the subspecies.
He had no sucess with ssp pusillum x ssp triphyllum OR ssp. stewardsonii =x
ssp. triphyllum.
He got some seed set in his crosses of ssp. pusillum x ssp. stewardsonii =but
the germination was poor.

As a friend of mine said "Everything he found indicated them to be separa=te
species but he didn't call them such in his thesis."

There are some records of hybrids of suspicious appearance, especially th=ose
reported by Huttleston but compared to other genera where species can be
very difficult to diagnose and they hybidize like crazy, this seems to me
like it should be an easy call that we have at least three species as a
number of authors has proposed in the past.

Note that ssp. quinatum is another problem; Trieber lumped it into ssp.
pusillum. I have no opinion since I have never seen one of the southern
A.triphyllums with five leaflets all with petioles that I have heard abou=t
on this list and other places. I have only seen plant with very deeply lo=bed
basal leaves at Blackwaterfalls State Park in West Virginia two weeks ago.

Another as is the intriguing possibilty of finding a diploid population
(2n=28) of ssp. triphyllum!

I will post a picture of spp. stewardsonii awith its ribs and ssp.
triphyllum with the wide flange on the spathe limb for comparrison. I hop=e
other peoplpe have pictures of interesting A.triphyllum flowers to post t=oo!

Mike Slater

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