Violets and others: Leontodon Achene Photos

Comparison of L. saxatilis ( Lesser Hawkbit) and L. hispidus (Rough Hawkbit) achene to see if they can be used to separate these close pair of species.

According to P. Sell in his section on L. saxatilis " The pappus of the outer achenes is the only characteristic that will always separate this species from L. hispidus. (Flora of Great Britain and Ireland Vol 4.) It would be nice to find an alternative difference, especially when confronted with
hybrids between the two species.

Previous blog on looking at hybrids between Leontodon saxatilis and Leontodon hispidus, see Hawkbits ( Leontodon) 22 Dec 2017 looked at various features of both species and their hybrids.
Shape of achene ( seed) was noted in the two following photos of the central achene.

In L.saxatilis the outer achenes have the pappus replaced with a short ring of scales. See photo below, with the outer achene lying in the bracts, often remaining long after all the other seeds have flown.

The achene shape of the outer ring of is usually curved and lacks the beaked attenuation of the central achenes.

As previously shown in the top two photos, the shape of the central achenes is different with the L. saxatilis achene being beaked or at least semi beaked. The achene has a upper section that is thinned down, unlike the L hispidus achene which gradually tappers down over two thirds of its length.

In practice there are complications. Many achenes are sterile and can be thin and pale (strange these non-viable pale seeds are often longer that the viable ones). Others are the normal colour brown but withered and thin. There is also variation with some curved and some straight. A more detailed look at the different shape of the achenes, showed with enough magnification, the upper end of the achene where the pappus hairs spread, has possible features that are more reliable than the overall shape.
Only thick and brown viable achenes could be checked, thinner ones need to be disregarded.

L. hispidus ( Rough Hawkbit)
Achene tapers down gently to an abrupt end where the pappus hairs radiate out from the outer edge of the achene cylinder. In this photo there is no necking ( thinning) at all.
The pappus hairs radiate out and up, being quite thick structures at their base but they thin down quite quickly with thin white side hairs sticking out. The pappus hairs are pale brown. The literature says there are two rows which I found a confusing comment, until I realised, what is being referred to as a 'row' is in fact not a row at all. It is an occasional short and thin hair which sticks out just below the main ring of pappus hairs. See the lower thin and short hair sticking out to the left in this photo.

L. saxatilis ( Lesser Hawkbit)
Achene is beaked ( thinned down ) but its termination before the pappus hairs is very different in that the achene diameter thickens slightly making a definite bulge which is a paler colour. I call this a sub-terminal bulge. Then the diameter reduces quite rapidly to where the pappus hairs radiate out. The structure of the pappus hairs seems to be the same as in L. hispidus and also have the lower 'row' of shorter hairs, which can be seen in this photo.

L. hispidus pappus showing how the pappus hair structure thins down quite rapidly into a thiner but long section that has very thin side hairs sticking out. This pattern is the same in saxatilis as far as I can see. The lower row of hairs is hardly a row but just the odd shorter hair, three visible in this photo.

This lower 'row' of shorter hairs is not present in Autumn Hawkbit ( Scorzoneroides autumnalis ) but easier differences are present to separate that species.

L. hispidus, Soham 28th October 2018

L. hispidus seed head showing the following features:-
Pale non- viable achenes, Thin brown achenes also probably not viable and healthy thick chestnut brown achenes.
The main feature is that the outer achenes have the full pappus so this is not L saxatilis.
None of the achenes have the sub terminal bulge and shape fits with normal pattern.

All looking good so far.

L.saxatilis ,7th September 2017, Cork Ireland

In comparison, An example of L. saxatilis shows outer achene with short ring of scales rather than the full pappus and central pappus with more of a semi-beaked thinning down and just visible is the pale sub-terminal ring. The achene shape is quite limited in terms of being beaked so this is a variable feature and this photo was taken in Cork, Ireland to add a bit of geographical variation.

L. saxatilis Picos, Northern Spain 6th July 2018

To go even further afield , next photo of L saxatilis was taken in the Picos Mountains of Northern Spain. The outer achenes are clearly showing the short scales but the more central achenes are not showing the beaked shape and are more like the shape of the UK hispidus with a gentle tapering down.

Enlarged , just shows sub-terminal pale bulge.

Conclusion. In Cambridgeshire there does seem to be a consistent difference in the shape of the achenes at the pappus end. In L. saxatilis the beaked achenes have a sub-terminal pale band that bulge out slightly. The problem with this feature is that it is reduced by variation when photos from Cork and Spain are considered. I suspect that if enough plants are examined in the UK some L. saxatilis will also not have beaked central achenes.
The enlarged photo above shows the achene shape is not a reliable separator as no beak is present but interestingly even this achene has a slight pale sub- terminal ring of a very subtle type, so maybe more investigation is required and the search should continue? Or maybe P. Sell was correct all along.

One possibility is that L. saxatilis not having the sub-terminal bulge are not pure and have some L. hispidus in them which might not always show up in having mixed scales/pappus hairs in the outer achenes. The relationship between these two species is complex. It does appear that plants which are hybrids, have achene shaped as in L.hispidus.

Peter Leonard

Rampton, Cambridgeshire, 12th November 2018
Some additional photos follow.

L. hispidus from Soham. (21st June 18) Although most of the achenes are sterile the good ones have logitudinal ridges more pronounced that the original example photo above. Another example of variation.

L. saxatilis taken in County Kerry, Ireland showing sub-terminal bulge.

Example of L. saxatilis in Southern Spain (near Ronda) show sub-species longirostris which has a much more beaked achene.

Achene much more beaked L.saxatilis subspecies longirostris

You can just about see an outer achene on the left of this photo (at 6 o'clock ) with the short scales indicating L. saxatilis but the normal achenes are much more beaked than the more widespread sub species L. saxatilis saxatilis which occurs throughout the whole range of the species, whereas sub-species longirostris is limited to Southern Europe.