Hypogymnia nedfalds-lav (Hypogymnia Lichen Windfall)

I return from many of my walks with pockets full of lichen windfall. One of the common finds under trees is two slightly different species of Hypogymnia, a good dye lichen.

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Nedfalds-lav er perfekt at farve med, da det ikke gør nogen skade at samle nedfaldet op. Jeg har skriver derfor en lille serie af indlæg om de forskellige arter af lav, der typisk findes i nedfaldet, og har tidligere skrevet om Ramalina fastigiata.
Lichen windfall is perfect for dyeing, since it does no damage to just pick up the fallen lichens. I’m therefore writing a small series of posts on the different species of lichens typically found in windfall, and I’ve already written about Ramalina fastigiata.

Denne gang skal det handle om Hypogymnia physodes (almindelig kvistlav) og Hypogymnia tubulosa (finger-kvistlav), to almindelige arter, som er tæt beslægtede (og derfor har delvist samme navn). De ligner da også hinanden meget – begge er grå-grønne og foliose (fladtrykte, bladagtige). Hypogymnia physodes, som her gror ud over en lille gren, har flade lober, evt. med soredier på den yderste del. Soredier er en af lavets måder at formere sig på (se mere her), og gennembryder lavets overflade mange små steder, så den ser grynet eller pulveragtig ud. Hos Hypogymnia-arter sidder soredierne på undersiden, som er foldet op yderst på loberne, så den grynede overflade kan ses:
This time, I’ll have a look at Hypogymnia physodes and Hypogymnia tubulosa, two common species that are closely related (that’s why part of the name is the same). Also, they do look alike – both are grey-green and foliose (flattened, leaf-like). Hypogymnia physodes, here seen covering a small branch, has flat lobes, sometimes with soredia on the outer part. Soredia is one of the way that lichens can reproduce (see more here), and break through the surface in lots of little dots, making the surface look grainy or powdery. In Hypogymnia species, the soredia are found on the bottom side, which folds up on the tips of the lobes, making the grainy lower surface visible:

Hypogymnia physodes dækker en lille gren. Detalje til højre, hvor den grynede overflade pga. soredierne på de opfoldede lober kan ses. Hypogymnia physodes covering a small branch. Detail on the right shows the lobe tips folded up, displaying the graininess because of the soredia.

Hypogymnia tubulosa ligner physodes meget, men har hule lober. I højre side af dette billede har jeg skåret en lobe over, så man kan se at det er tilfældet:
Hypogymnia tubulosa looks a lot like Hypogymnia physodes, but has hollow lobes. In the right side of the image below, the hollowness is visible since I cut one of the lobes:

Hypogymnia tubulosa med en overskåren lobe til højre. Hypogymnia tubulosa with a cut lobe on the right side.

Begge arter er meget almindelige, og gror mange steder, inklusive på træer, sten og træværk. De kan lide at gro på sure underlag, og Dobsons “Lichens, An Illustrated Guide to the British and Irish Species” fortæller, at Hypogymnia physodes er en af de arter, der er mindst følsom overfor svovldioxid-forurening. Hypogymnia tubulosa er lidt mere følsom.
Both species are very common, and grow in many places, including on trees, stones, and wooden surfaces. They like growing on acidic substrates, and Dobson’s “Lichens, An Illustrated Guide to the British and Irish Species” mentions that Hypogymnia physodes is among the species least sensitive to sulfur dioxide pollution. Hypogymnia tubulosa is a bit more sensitive.

Nogle gange kan der være stor forskel på farveindholdet i arter, der ellers ligner hinanden meget. Jeg bestemte mig for at teste, om de to arter giver samme farve.
The dye content sometimes differs a lot even for species that are otherwise very similar. So I decided to test if the two species give the same color.

Jeg brugte ubejdset garn, for lav-farver er jo substantive. I et farvebad fra 9 g Hypogymnia tubulosa røg der et 12-grams Fenris (ren uld) og et 5-grams Bestla (merino-silke) testnøgle. Jeg lavede et farvebad af 15 g Hypogymnia physodes, og deri 2 12-grams Fenris og et 5-grams Bestla testnøgle. Altså halvt så meget lav som garn i begge tilfælde. Det ene nøgle Fenris modificerede jeg så i et efterbad med jern.
I used unmordanted yarn, since lichen colors are substantive. I made one dyebath with 9 g of Hypogymnia tubulosa, and put a 12-gram skein of Fenris (pure wool) and a 5-gram skein of Bestla (merino-silk) in. Another dyebath was 15 g of Hypogymnia physodes, and two 12-gram Fenris skeins and one 5-gram Bestla skein went into that one. So half the weight of lichen compared to fiber in both cases. I modified one of the Fenris skeins in an iron afterbath.

Begge slags lav giver samme farve, den fine, støvede gule, som er helt klassisk for bwm lav. Der er altså ingen grund til at sortere Hypogymnia physodes og tubulosa. Merino-silken tager en lille smule mindre imod end den rene uld, mens et efterbad i jern gør farven meget mørkere og drejer den over i det grønne.
Both lichens give the same color – a fine, dusty yellow, the completely expected shade from bwm lichens. So in conclusion, no reason to sort Hypogymnia physodes and tubulosa. The merino-silk takes the color a little less well than the pure wool, and an iron afterbath does significantly darken/sadden the color at turn it green.

Til venstre: ren uld og merino-silke farvet med Hypogymnia tubulosa. Til højre: ren uld og merino-silke farvet med Hypogymnia physodes, yderst til højre et nøgle ren uld hvor sidstnævnte farve er modificeret med jern. Left: pure wool and merino-silk dyed with Hypogymnia tubulosa. Right: pure wool and merino-silk dyed with Hypogymnia physodes, further right a pure wool skein dyed with the ladder, modified with iron.

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