Mon, 03 May 2004 11:47:24 -0500 Monique Reed wrote:
Look at a leaf scar--where a leaf has fallen. If you can't find one,
snap off a leaf at the base. White Ash, Fraxinus americana will have
leaf scars shaped like a U--rounded on the bottom and quite concave on
the top. Green Ash, F. pennsylvanica, has leaf scars round on the
bottom and nearly straight across the top, like a sideways D. This
usually works. Fruit characters are helpful too, but fruit aren't
always handy.

M. Reed

Archimedes Plutonium schreef
I wonder if the difference of a species of trees can come so close as to
be a small visual difference of between whether a leaf has convex shape or
concave shape.

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You are confusing identification with species delimitation.
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What I am getting at is whether scientists have yet quantified as to how
much at minimum must the A,C,T,G vary in order for there to be 2 different
species.

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Easy: 1. Theoretically a single base pair should do it.
On the other hand hundreds of base pairs could vary without any effect
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If Ash trees were intelligent life and went around inspecting humans, it
would be puzzling that ash of pennsyl and americ are different species yet
virtually identical in shape form and physical attributes, yet humans come
in a huge range of physical attributes yet all one species.

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Probably the other way about. Any species is most alive to their own
species. If Ash trees were intelligent, they would wonder why humans are all
so alike (driving cars, cutting down trees, etc) and that Ash trees are so
wonderfully recognisable. Intelligence is relative, anyway.
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Instead of leaf scars, I wonder if green ash and white ash can be
discerned from the leaf tip itself.

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For starters leaf scars can be observed year round, while leafs are
available only part of the year. Also there are lots of species known for a
wide variety of leaf shape, sometimes within a single tree.
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I wonder if that tip inspection is a true rule to follow.

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This would only be relevant if you want to start a church.
Do you know the Church of the Living Tree? [www.tree.org]
or this church http://www.therowantreechurch.org/
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I would have to
inspect alot of mature green and white ash but I encounter mostly only
green ash in the wild.

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Perhaps you should start with the difference between green and red ash?
PvR