Here
is one method for creating the remaining
joint chains. Switch to the top viewport
and select your chain.
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Duplicate
the chain the move the pivot point into
another leaf stem.
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Rotate
the chain until you get a good match
to the orientation of the stem.
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Rotate
the chain again vertically to match
the stem. I prefer to create each chain
individually the same way I created
the first chain. It adds a little bit
of random placement and rotation, so
when animation they will not look like
clones. This is a minor detail though.
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Select
the main joint of your stem chain and
shift select the top joint of the tree
trunk.
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Hit
'p' to parent the new stem joint chain
to the top of the tree trunk.