Thanks for taking a photo of the leaves Ian, with trigger plants they are the distinctive feature, the leaves of graminifolium are much thinner than those of ameria
OK. I picked up your need for a leaves photo from other comments you made elsewhere. Thanks for telling me the reason, although I'm not sure I see the difference as being 'thinner', rather armeria perhaps seems to have a 'ribbed', softer looking leaf to me. Is it a thickness or a width of leaf? Is there a key to their identification you are using which you can recommend? I'll have to look at trigger plants a lot more closely!
Neither PlantNET or Flora of Victoria online include Stylidium armeria in their keys. The key characters were described in Raulings, E.J. & Ladiges, P.Y. (2001), Morphological variation and speciation in Stylidium graminifolium (Stylidiaceae), description of S. montanum and resinstatement of S. armeria. Australian Systematic Botany 14(6): 928-931, Fig. 13. If you are a Friend of the Australian National Botanic Gardens, you can photocopy the whole paper in the Library. The characters in the key are: S. graminifolium: Leaves strictly narrowly linear, to 2.5 mm wide, glaucous (with a waxy bloom), regularly serrate (with small teeth), midrib prominent on abaxial (underneath) surface and leaves bifurrowed, flowers white to pale pink, in siliceous sands and well-drained soils (e.g. expect it on Black Mountain). S. armeria: Leaves 20-40 cm long, > 3mm wide, scape (flower stalk) robust (> 2mm wide), widespread. I have left out the bit in the middle about S. montanum. The only subspecies of S. armeria in the ACT is subsp. armeria.
I've just checked two papers relevant to Stylidium graminifolium and S. armeria: Raulings & Ladiges (2001) Australian Systematic Botany 14, 901-935, and Jackson & Wiltshire (2001) Australian Systematic Botany 14, 937-969. Both provided keys and descriptions for the two species (though Jackson & Wiltshire note they only examined Tasmanian herbarium specimens for S. graminifolium. It’s unclear how many specimens Raulings & Ladiges looked at, but they don’t cite any ACT specimens for S. graminifolium, and only one ACT specimen (from Mt Franklin) for S. armeria [all the other S. armeria specimens cited in their paper under the ACT are actually from NSW]. I’ve checked all the ACT specimens in ANH for both species against the keys and descriptions in the above two papers; the specimens include many from Black Mountain. Based on the herbarium specimens and relating it to my field knowledge of the genus on Black Mountain, I don’t believe S. armeria occurs on Black Mountain, Bruce Ridge or Mt Ainslie. The main obvious differences between the two species are the leaves: S. graminifolium leaves are linear, up to 3 mm wide, and the mid rib is clearly visible on the lower surface. S. armeria leaves are narrowly oblanceolate (ie broader in the upper half), usually 4 mm or more wide (rarely c. 3 mm) and the midrib is not obvious on the lower surface. These characters are difficult to tell from photos but are readily apparent in herbarium specimens (and fresh specimens).
Hi Rosemary, A somewhat more recent reference (albeit for Victoria and available online) has a key to the Stylidium graminifolium complex at the end of the paper: R.J.Best, D.E. Francis & N.G. Walsh, Muelleria 27(2): 174-178 (2009) A new subspecies of Stylidium armeria (Stylidiaceae) from the Macedon Range, Victoria. They also include Stylidium montanum which PlantNET does not which has me wondering about some of the plants I've seen in the Brindabellas Ken