Regarding identification of the other photo/plant in Jorun's posting of 5dec12...The plant captioned Viola collina on this page
http://botanika.prf.jcu.cz/materials/fotogalerie-nahledy.php?family=Violaceae&name=Rosidaelooks very similar to the MGS forum plant; I would say it is the same species.
But, unfortunately, that is not Viola collina.
The same page also features a plant captioned Viola riviniana; also matching the MGS forum plant. But the plant in that photo has petals that are too narrow for V. r..
It is almost definitely one of the caulescent rosulate species (forming rosettes of leaves plus foliar non-stoloniferous stems), examples being Viola riviniana, reichenbachiana.
It is not V. reichenbachiana (that has a dark spur).
It is not V. riviniana (that has broader petals) - or at least not typical V. r. ...
It is superficially similar to V. sieheana, which I know from Cyprus.
Have a look at V. sieheana in Marijn van den Brink's photos from NE Turkey -
http://photos.v-d-brink.eu/search/?searchWordsShort=viola+sieheana&searchType=InAlbum&AlbumID=10572637&x=0&y=0 - similar, but with purplish spurs, not white.
Yiannis Christofides has a typically excellent photo of it here -
http://www.treknature.com/gallery/Middle_East/Cyprus/photo256315.htm. The lateral petals are more heavily bearded and the petals broader than the MGS forum plant. Petal broadness/overlapping is known to be variable in this species.
Thomas Marcussen (relatively recent research) considers V. sieheana to be within V. riviniana.
...In which case, the plant from Montenegro might, after all, come under V. riviniana, in a broad sense.
Thomas wrote a useful paper:
"Species delimitation in the Ponto-Caucasian Viola sieheana complex, based on evidence from allozymes, morphology, ploidy levels, and crossing experiments"
Plant Systematics & Evolution; Feb2011, Vol. 291 Issue 3/4, p183.
http://connection.ebscohost.com/c/articles/58001744/species-delimitation-ponto-caucasian-viola-sieheana-complex-based-evidence-from-allozymes-morphology-ploidy-levels-crossing-experimentsThat includes NW Greece (Pinhos Mts.) in the range of V. sieheana sensu stricto - which is getting close to western Montenegro...
And in fact Wilhelm Becker (one of the great students and publishers of Viola), 1910, p.55, mentions some sites for it in Bosnia, Serbia, and Montenegro.
Thomas also shows that V. sieheana hybridizes with similar species.
The big problem with V. sieheana is the stipules. The ones on the MGS forum photo, even though not well shown, are much too small. I have to rule it out.
Considering other candidate species:
- V. dirphya occurs in Greece (endemic), not too far away, but its petals are consistently oval, unlike the MGS forum plant. (
http://1.bp.blogspot.com/_7n7qoWr2hv0/S-r43YhLV2I/AAAAAAAAKcM/y2CMa6kiRL8/s1600/Viola+dirphya+tiniakou.JPG)
The similar V. caspia is too far away (eg. Azerbaijan) from Montenegro to come into consideration.
- V. chelmea occurs in Montenegro and nearby, but flowers and foliage are wrong. The two sspp. were previously included in V. sieheana.
- V. rupestris occurs nearby, but foliage, etc. is wrong.
- V. mirabilis occurs in Bosnia, but wrong leaf shape.
- V. jordani, pumila, etc. are wrong re stipules, and other features; shame in a way because some of those have the necessary pale blue flowers.
- V. reichenbachiana occurs in Montenegro, and has a pale blue form (f. pallida), but other aspects of the flower don't match, eg. dark spur.
- V. oligyrtia is endemic to Greece, and not quite right (
http://www.srgc.net/forum/index.php?topic=3329.180)
In summary,
I am of the opinion that the plant is Viola riviniana, though it is a form with which I am not familiar.
As far as I can tell from the photo, the essential characteristics (many of which, such as petal venation, I have not mentioned here) are correct.
The narrowness of the petals may be a regional character, as may their paleness. That's based not just on this one plant, but on the similarity the plant to this one
http://botanika.prf.jcu.cz/materials/fotogalerie-nahledy.php?family=Violaceae&name=Rosidae (scroll down to the V. riviniana photo).
If it is a known forma/varietas, I have not discovered its diagnosis or supporting photographs.
I will email Thomas for his opinion.
Update, 25dec12:
I have discussed this with Thomas.
He cannot give a certain identification either, but leans towards V. sieheana (which would make your plant/observation in Montenegro an extension of its range, Jorun).
He says that the stipules of V. sieheana are very variable - making my comment about large stipules (above) invalid. Also, he uses the presence of a seed pod in your photo to rule out a hybrid (a bit prematurely, in my opinion: seed pods sometimes form but contain empty seeds).
Thomas points out that it would be useful to know the hairiness of the plant: V. sieheana is almost glabrous, whereas V. riviniana and reichenbachiana have hairs of ~1mm on the upper leaf surface.
Result: uncertain, but either V. riviniana or sieheana.
Refs:
Becker, W., 1910, 'Violae europaeae. Systematische Bearbeitung der Violen Europas und seiner benachbarten Gebiete'.