Working Notes on Spring Corts

There are a number of spring Cortinarius that are similar and are mainly differentiated by subtle fatures in spore size, and extent and color of UV reaction. After recurrent confusion, I put together these notes to help you with ID. This is not a complete note. I will continue to add to it and welcome input.

Quick Takes:

• From current sequencing efforts Cortinarius ahsii and Cortinarius bridgei seem most common.

Species	# Seq on iNat	Main UV Color	Other UV	Veil color (not UV)	UV strength	Universal veil	Stipe base	Stipe surface UV rx
Cortinarius ahsii	10 [Link]	Bright yellow	No other	Yellow	Strong	Heavy	Yes	Yes,some
Cortinarius colymbadinus	0 [Link]	Bright yellow	No other	Greenish white to yellow, to buff	High	Heavy	Yes	Strongly yellow
Cortinarius vernalsierraensis	1 [Link]	Bright yellow	Pinkish gold	Yellowish (no basal remnants)	Less abundant	Less	Yes	No
Cortinarius bridgei	23 [Link]	Intense orange (base / mycelium)	Pale yellow (stipe)	Yellow	Strong (base)	Yes	Yes (Mycelium)	?
Cortinarius flavobasilis	0 [Link]	Orange (base / mycelium)	Pale yellow (stipe)	Yellow	No mention of intensity(base)	Yes	Yes	?
Cortinarius rumoribrunsi	0 [Link]	Orange (base / mycelium)	No yellow UV	White (but yellowish velar remnants on base?)	No mention of intensity	Yes	Yes	No
Cortinarius vernalishastensis	0 [Link]	Pale orange (base / mycelium)	No yellow UV mentioned	White (but base yellow)	Pale orange	Yes	Yes	No
Cortinarius clandestinus	11 (Link)	Bright yellow	None	No veil

• For Cortinarius ahsii, only the universal veil on the stipe and pileus surfaces and/or the stipe base are UV+ yellow, whereas the UV+ yellow reaction of C. colymbadinus is more extensive and includes the stipe surface, veil on the pileus surface, lamella edges, and entire context.
• C. vernalisierraensis: UV fluorescence: stipe base bright yellow to pinkish gold; flesh in base dull pinkish. KOH (5%): negative on basidiome context and surface.
• The UV fluorescence of Cortinarius vernalisierraensis is less extensive than in C. ahsii or C. colymbadinus in that the stipe base fluoresces bright yellow to pinkish gold and the flesh beneath is dull pinkish.
• C.bridgeii UV fluorescence: basal mycelium intensely bright orange, the universal veil on the pileus and stipe very pale yellow. KOH (40%): instantly bright red on stipe base.
• Cortinarius bridgei is very similar morphologically to C. flavobasilis and both have a UV+ orange fluorescent stipe base. They are sympatric throughout their range and often co-occur in the same habitat. These two species can be separated from one another by basidiospore length and width, the spores of C. bridgei (avg. 8 × 4.4 μm) being smaller than those of C. flavobasilis (avg. 9.4 × 5 μm).
• Cortinarius rumoribrunsi is a member of the rich vernal mycota of snowbank species in the Cascade-Sierra Mountains. The exsiccatae of this species have an UV+ orange stipe base, which it shares with C. flavobasilis, C. vernalishastensis, and C. bridgei. Mounts in 3% KOH of the exsiccatae; hyphae and basidia of C. rumoribrunsi have considerably more yellow pigment than in other species treated here. It also appears somewhat smaller in stature than the other members of this clade. Cortinarius rumoribrunsi has not been reported from north of Mt. Lassen
• C.vernalishastensis: UV fluorescence: light pale orange on stipe base.

References:

Joseph F. Ammirati et al., “Spring and Early Summer Species of Cortinarius , Subgenus Telamonia , Section Colymbadini and /Flavobasilis, in the Mountains of Western North America,” Mycologia 109, no. 3 (May 4, 2017): 443–58, https://doi.org/10.1080/00275514.2017.1349468.