Bonjour tous
This time of year is not the best time to collect these fungi, but a recent species-rich collection has encouraged me to draw the attention (or remind) ASCOFrance members to this branch of mycological study (Alain G is clearly 'on the case'!). I know many on here have made excellent collections of teleomorphs of aquatic and semi-aquatic ascos.

All that is needed is naturally-formed foam in streams, or sometimes at the edge of standing water, and the simplest of materials:
~ a teaspoon
~ a water-tight container
~ a botanical fixative (otherwise the conidia start to germinate when they touch a solid object) Formol Acetic Alcohol is the one normally used
~ literature - this http://www.ascofrance.com/uploads/document/1989DescalsAquaticHyphos-0001.pdf which I have uploaded to ASCOFrance was produced for a workshop I helped organise many years ago, and is still the first one I consult when identifying conidia

Most of the fungi encountered are anamorphs of ascomycete fungi; for a number the teleomorph is also now known. Occasionally one comes across fungi from other groups: in the foam in these photographs were also the coronate conidia of a zygomycete (Erynia rhizospora) and those of a member of the tiny basidiomycete order the Classiculales http://en.wikipedia.org/wiki/Classiculomycetes. I have included images of three fungi here, before I submit them to the Database.

Nectria lugdunensis - these are conidia of the Heliscus anamorph, they are characteristically shaped like cloves (clous de girofle /Gewürznelken); once, many years ago, I collected a semi-submerged branch with both the anamorph and teleomorph growing together.

Culicidospora gravida - these remarkable conidia have been described by Ingold as looking like penguins, to me they also resemble hummingbirds. The granular contents are characteristic, I have not found a reference yet to the coloured contents - these are not stained.

Flabellospora acuminata - another species with large remarkably shaped (and large) conidia - an aquatic lifestyle evolves its own solutions.

I hope this may encourage others to dip their toes into this fascinating area of study.

Cordialement
Chris