These are my notes for Usnea in the area, compiled from a few sources in an abbreviated form for quick identification. I wrote some tips below the tables as well.
cma | cortex medulla axis; a measurement of the relative lengths of each of these sections |
m/c | medulla / cortex; ratio |
a/m | axis / medulla; ratio |
b. | base |
sor | soralia |
isid | isidia |
>1/2 bw | “more than half the branch width”, in reference to the size of soralia |
tub | tuberculate (slightly raised) |
a.d. | anisotomic dichotomous (branching unevenly) |
i.d. | isotomic dichotomous (branching evenly) |
These are distinguished by chemistry typically, but in our area location is normally all you need:
sp | cma | m/c | a/m | size cm | branching | fibrils | branches pitted | base | annular cracks | papillae | soralia/isidia | UV |
---|---|---|---|---|---|---|---|---|---|---|---|---|
cavernosa | 7/28/32 | 4.0 | 1.1 | 60 | not often | few-none | very | some | none | none | - | |
chaetophora | 10/19/42 | 1.9 | 2.2 | 30 | few | few-no | no | black | >6/cm | sparse, low-none | none | - |
dasopoga | 16/9/49 | 0.6 | 5.4 | 30+ | often | often | no | few, small | tall | <1/2 bw, isid on sor, tub | - | |
pacificana | 19/16 (compact)/33 | 0.8 | 2.1 | 20 | yes | few-no | no | conspicuous near b. | common, near b. | <1/2 bw, isid on sor, tub | + | |
scabrata | 8/17/49 | 2.1 | 2.9 | 70 | often | many | weakly | few, small | sparse, low | usually | - | |
silesiaca | 19/9/50 | 0.5 | 5.5 | 25 | many | many | no | 6-15/cm | yes | >1/2 bw, isid on sor | - | |
subgracilis | 15/10 (<C)/38 | 0.6 | 3.8 | 50+ | some | variable | no | never black | >6/cm | none | few-none | - |
sp | size cm | fibrils | base | papillae | soralia/isidia | UV |
---|---|---|---|---|---|---|
cornuta | 5-15 | many | not black | yes | <1/2 bw, isid on sor | - |
fragilescens | 20 | few | black | yes, low | >1/2 bw, isid on sor | +/- |
flavocardia | <7 | yes | encircling, cortex peels back, isid or not | - | ||
esperantiana | 8 | many | not black | many | >1/2 bw, no isid | - |
glabrata | no | encircling, cortex peels back, no isid |
Photos of this type of soralia
sp | cma | m/c | a/m | size cm | branching | isidia | papillae |
---|---|---|---|---|---|---|---|
fulvoreagens | 10/22/27 | 2.2 | 1.2 | 20 | tips long+straight | none | yes/no |
lapponica | 9/28/30 | 3.1 | 1.1 | 8 | tips contorted by sor | few-none | |
wasmuthii | 11/13/53 | 1.2 | 4.1 | 10 | tips contorted by sor | few, on young sor | yes |
sp | cma | m/c | a/m | size cm | branching | fibrils | annular cracks | papillae | soralia/sidia | UV |
---|---|---|---|---|---|---|---|---|---|---|
diplotypus | 9/23/37 | 2.6 | 1.6 | 10 | tips sinuose | inconspicuous | short-tall | <1/2 bw, isid on sor, some oval | - | |
hirta | 9/24/35 | 2.7 | 1.5 | 10 | main foveolate | many | none | only isid, dense | - | |
nidulans | 9 glossy/15/55 | 1.7 | 3.7 | 10 | groups of 2-4 | often, small | low | when sor tub w/ isid | - | |
subfloridana | 10/20/40 | 2.0 | 2.0 | 15 | i.d. | some | yes, obvious | common near b. | small-large, tub, isid on young sor | +/- |
pacificana | 19/16 (compact)/33 | 0.8 | 2.1 | 20 | a.d. | few-no | yes, obvious | common near b. | small, tub, isid on young sor | + |
This can be a little tricky. Using a double edged razor blade that's been broken in half (like you might use for sectioning apothecia) is best. Find a well exposed, large branch near the base, and make a cut, trying to keep the razor blade level with the branch. If the cut isn't far enough into the branch to cross section the axis, scrape a bit more off. Less is better so you don't cut the branch all the way through (not the end of the world, if you still got a good level section exposed). I find this easier with dry thalli but completely possible with wet thalli too. A 1:1 macro lens with flash should be powerful enough to get a good photo for the CMA measurement. Rotate and crop so the branch makes up the lower 2/3rds of the photo and is horizontal in the frame.
Bruce McCune and Linda Geiser's Macrolichens of the Pacific Northwest; McCune's website has good photos
Daphne Stone's Usnea in the Pacific Northwest (available here)
Clerc (1987) Systematics of the Usnea fragilescens aggregate and its distribution in Scandinavia. (describes CMA measurements)
Clerc (1987) On the morphology of soralia in the genus Usnea.
iNaturalist currently doesn't have a lot of good observations, and computer vision is almost completely useless for Usnea.
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