There are some images of the aecia of the rust
Puccinia sessilis on this website (correctly named I hasten to add)
http://fungi.org.uk/viewtopic.php?f=9&t=9 . I would encourage others to check out
all rusts on Ramsons they see as there may be a second and (just possibly) a third species involved.
Recognising
P. sessilis aecia is relatively simple (when they are fully developed) as they have rather neat, usually circular, sori arranged with a distinctive "cup" around each element. That cup is made up of fungal material, of rather regular honeycomb-like pale cells - see accompanying images.
The thing to look out for is sori which are much more irregular - "caeomoid" is the technical term - and what pale margin they may have is simply remnants of the plant's leaf cuticle. These sori belong to species of
Melampsora. For a long time their presence in the UK was not accepted - perhaps they were genuinely absent, or (more likely) not recognised for what they were. Whereas
P. sessilis alternates with the grass
Phalaris arundinacea, if you find these caeomoid sori the likelihood is that you are in close proximity to
Crack Willow trees. I am now convinced (having seen this in numerous spots around SW Yorkshire) that aecia of
Melampsora allii-fragilis on Ramsons are not uncommon (they also seem to be attractive to molluscs and show "shot-holes" such as one rarely sees in
P. sessilis).
There is just one other possibility, again long doubted as being British; similar (indistinguishable, except apparently by colour - a bit subjective for me) but alternating with poplars
Melampsora allii-populina. This is not uncommon in its later uredinial and telial states on poplar leaves - the fungus does not need the
Allium to complete its life-cycle; I have yet to see caeomoid aecia on Ramsons where there was no Crack Willow in the area, only poplars. If you do find this possibility, make a note of the site and revisit in late summer and look for the later stages (the uredinial stage can often be seen from metres away as the leaves, covered in it and with orange undersides, blow in the wind).
Also, now that the leaves are starting to go over look for damp rotting areas on the Ramsons leaves, especially near the tips. On the underside and with a handlens you will probably see the extremely common "mouldy" anamorph of the ascomycete
Botryotinia globosa.
Good hunting
Chris
, so much to learn
