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Mon Mar 8 20:17:44 CET 2004


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From: "Mellard, David" <dam7 at CDC.GOV>
Subject: Re: Trillium Trek
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>Those in bud being shorter than those in full flower. There was
certainly many "stocky" plants but also the occasional more graceful
mature  plant with slender leaves.  I assumed
these were extremes of T. underwoodii but how would we be able to tell
if a few T. decipiens were mixed in with the 1000's of T. underwoodii.
It seems that most of these traits are overlapping to at least some
degree.   Is there any difference in the rhizomes, or flower parts that
>might be a more independent trait? 

>It seems that most people familiar with these plants feel they are
distinct. 

Hi Kirk,

More field work......darn.  When I'm in doubt, I generally classify a
population as T. underwoodii, meaning that I give T. underwoodii more
variation when it comes to leaf/stem ratio than the standard (what is
it? ) < 2:1.  My experience has been underwoodii is far more common than
decepiens or at least I know of more underwoodii sites than decepiens
sites.  I know of a population in middle Georgia that are just giant
plants, very tall but generally falling within the <2:1 ratio.  Don
Jacobs has seen some of the plants from there and remarked about it
being a relic population (whatever that means).  I think it's
environmental in that the plants are on a slope down from a working
field and so they receive extra fertilizer as run off.  Hence, the
plants go grow bigger but still maintain the underwoodii
characteristics.  I understand your dilemma, though, when you say that
you find some portion of a population that is outside the
characteristics of what one would expect.  Jacobs and Case write about
hybridizing between the two species.  I'm less inclined to believe this
is happening to any great extent.  This is why looking at a population
is so important.  I classify a population as decepiens only when almost
all of the individuals are tall plants with a ratio that is usually >
3:1.  Finding a few plants that don't fit the >3:1 ratio doesn't bother
me in such a population.  It may be that next year they are >3:1.
Obviously, one would have to mark and follow individual plants to answer
that question.  

The keys use the ratio as to the diagnostic point between the two.  I
guess the only thing I can add is that when you're in the field and you
find a population where all the flowering plants are tall with
relatively short leaves, then you realize that you are looking at
something that quite's different from T. underwoodii (short or
tall/big).

Sorry, I can't answer your question any better than that.  

David
Atlanta
 

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