1 Branches ascending typically vigorously.
2 Branch sheath teeth attenuate & slightly spreading.
3 Common plants of disturbed wet to dry open sites.
4 Branches coarse, greater than or equal to 1mm diameter.
5 Branches 4 or 3-sided.
6 Branches 6-18 per whorl.
7 Stem internodes smooth or slightly rough to touch.
8 Fertile stems ephemeral disappearing by summer.
9 Reproductive stems without stomata.
10 First internode (including sheath and teeth) of branches of the second lowest branch-bearing main stem node clearly longer than the length of the sheath (plus teeth) on that main stem node.
1 Branches spreading from slightly ascending to slightly drooping.
2 Branch sheath teeth deltate & slightly clasping.
3 Occasional plants most often in moist upland forests.
4 Branches delicate, less than or equal to 1 mm diameter.
5 Branches 3-sided.
6 Branches 4-14 per whorl.
7 Stem internodes rough to touch (scabrous).
8 Fertile stems persistent becoming green and distinguishable by truncated tip.
9 Reproductive stems with stomata.
10 First internode (including sheath and teeth) of branches of the second lowest branch-bearing main stem node slightly to clearly shorter than the length of the sheath (plus teeth) on that main stem node.
While these two species are fairly easy to differentiate, there are substantial contradictory or ambiguous statements in the literature. It is important to distinguish stem versus branch and sheath versus teeth. Due to ambiguities, it seems prudent to pay attention only to branch teeth shape difference and ignore the other characters of teeth when comparing these 2 species. Central canal diameter varies and overlaps between these species too much to be truly useful.
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last update 2024-Jul-29