Stylidium armeria (trigger plant)

References: 

• Wege, Juliet A. (2017)
Stylidium miscellany 3:
A synopsis of Robert Brown’s Stylidiaceae types and occasional notes on associated names.
Nuytsia, 28 : most relevant here pages under Stylidium armeria 232–234 out of all the pages: 229–246 .
https://library.dbca.wa.gov.au/static/Journals/080057/080057-28.019.pdf 

Two short quotations for situation summary purposes : 
"
...
I recently conducted a very preliminary sort of material at CANB which indicated that there is considerably more variation in this species complex than has been accounted for in either study.
...
While both Raulings and Ladiges (2001) and Jackson and Wiltshire (2001) make insightful observations at a local scale, resolution of the taxonomy of the S. graminifolium complex demands a geographically comprehensive, modern and integrative approach that uses multiple lines of evidence (molecular, morphological, cytological and ecological) and includes examination and curation of the more than 2,500 specimens currently available in Australian herbaria. This is not something that I will be able to pursue from Western Australia.
" .

Hence, a lot of field study required to clarify human understandings of classifying the complex group of species which includes Stylidium graminifolium, S. montanum, S. armeria, S. productum, ... .
.

• Raulings, E. J. and Pauline Y. Ladiges (2001 December 18) 
Morphological variation and speciation in Stylidium graminifolium (Stylidiaceae), description of S. montanum and resinstatement of S. armeria.
Australian Systematic Botany 14(6) : 901–935 
https://doi.org/10.1071/SB99037 (pay-walled) .

Quotation: 

"
Key to Species 

1. Leaves strictly narrowly linear, up to 2.5 mm wide, glaucous, c. regularly serrate, midrib prominent on abaxial surface and leaves bifurrowed; flowers white to pale pink; in siliceous sands and well-drained soils   –   S. graminifolium 

Leaves linear to narrowly oblanceolate, greater than 3 mm wide, pale to dark green, serrations absent or towards apex only, lamina continuous over midrib and leaves not bifurrowed; flowers pink to deep magenta   –   2

2. Leaves 4–15 cm long, pale to mid-green, widely spreading to suberect; scape fine (< 2 mm wide), glabrous or glabrescent below lowest flowers; flowers 10–30; in water-retentive, peaty soils of montane to subalpine areas at high altitudes  –   S. montanum

Leaves 20–40 cm long, dark green, spreading to erect; scape robust (>2 mm wide), glandular–pubescent beyond lowest flower; flowers 30–120; widespread from coast to alps  –  S. armeria 

".

• Flora of NSW online PlantNet key to species has not been updated with Stylidium armeria after its reinstatement in 2001 .

• Jackson, W. D., & Wiltshire, R. J. E. (2001)
Historical taxonomy and a resolution of the Stylidium graminifolium complex (Stylidiaceae) in Tasmania.
Australian Systematic Botany 14 (6) : 937–969 .

Also: 
• Wege, Juliet A. (2009) 
Naming Stylidium (Stylidiaceae): an historical account, with specific reference to S. graminifolium and S. lineare .
Telopea 12 (3) : 321–332 .
https://scholar.archive.org/work/kraarhdcf5c5pg6ziwvjprfgfi/access/wayback/http://plantnet.rbgsyd.nsw.gov.au/emuwebnswlive/objects/common/webmedia.php?irn=55016&reftable=ebibliography 
.