Eragrostis virescens vs frankii

Nature Talk
1

During these days I have some Eragrostis at hand. https://www.inaturalist.org/observations/324711456
The most striking feature is the size of the spikelets, from (2)2,5 to 4,5(5) mm, and the number of florets per spikelet ranging from (2)3-7(8).
There are glandular rings on the culm below the nodes and glandular pits on panicle axis and branches.
The caryopses are either with or without a very shallow groove on one side.
Leaf blades are up to 8 mm broad.
I am using the key fo Flora of North America which would lead me to E. frankii but it also describes this latter species as having leaf blades no more than 4 mm broad.
On the other hand, E. virescens (as E. mexicana subsp. virescens) should have leaves up to 7(9) mm broad (so compatible with my specimens) but spikelets not less than (4)5 mm long.
So:

  • I wonder if spikelets length or leaf blades width is the character that better distinguish these two species.
  • Are possibly the number of florets/spikelet and spikelet length well below the smallest reported in FNA for E. mexicana s.l.? Or is leaf blades width well over the biggest reported for E. frankii?
  • Is there a work dealing in depth with the distinction of these two species?

Thanks

2

Why have you not considered Eragrostis pilosa?
To me it looks quite typical of that species. and with the key in flora d’Italia I reach it easily (note that while there are small spikelets, most of them have 5 or more flowers, excluding the species with small spikelets with spikelets mostly up to 3 flowered, and occasionally more - they also differ by the shape, pilosa always have this lanceolate shape, frankii and capillaris have ovate spikelets).
virscens is of the form of E. minor, lower whorls bear 1-2 branches, not many