1	Basidiospores acicular, Q>4.5	2
–	Basidiospores cylindrical, fusiform, allantoid to reniform, Q<4.5	5
2	Basidiospores 12–16 × 2–3 µm, Q=4.5–7	longisporum
–	Basidiospores longer, Q>7	3
3	Basidiospores spirally curved, 27–35 µm long	curvisporum
–	Basidiospores straight or only slightly curved, shorter	4
4	Basidiospores 20–27 × 2–3 µm, cystidial crystalline sheath ends with a bundle of needle-like crystals	cochleum
–	Basidiospores 16–25 × 1.5–2.5 µm, cystidia with regular ornamentation (rows of rectangular crystals)	perlongisporum
5	Basidiospores fusiform	6
–	Basidiospores cylindric to broad cylindric (straight or curved)	11
6	Basidiospores 4–5 µm wide	naviculatum
–	Basidiospores narrower	7
7	Cystidia almost smooth, without regular rectangular crystalline protrusions	inornatum
–	Cystidia with regular ornamentation (rows of rectangular crystals)	8
8	Cystidia with large crystalline protrusions	9
–	Cystidia with small to moderately large crystalline protrusions	10
9	Basidiospores 2.5–3.5 µm wide	robustius
–	Basidiospores broader than 3.5 µm	ryvardenii
10	Basidiospores 8.5–11.5 × 2–2.5 µm wide	tedersooi
–	Basidiospores 10.5–12.5 × 2.5–3.5 µm wide	fusisporum
11	Basidiospores broad cylindric, Q=1.5–2.5	12
–	Basidiospores cylindric, Q=2.5–4.5	14
12	Cystidia covered with irregularly shaped large crystalline plates, 80–150 × 5.5–10 µm, basidiospores 8–11 × 4.0–5.5 µm	oberwinkleri
–	Cystidia with regular ornamentation (rows of rectangular crystals) and smaller, basidiospores also smaller	13
13	Basidiospores 7–9 × 3.5–4.5 µm	nikau
–	Basidiospores 6–8 × 2.8–3.5 µm	boidinii
14	Basidiospores 3–4 µm wide	15
–	Basidiospores 2–3 µm wide	17
15	Basidiospores 10–15 µm long	grandisporum
–	Basidiospores shorter	16
16	Basidiospores 9–13 µm long, cystidia with regular rows of rectangular crystals	obtusisporum
–	Basidiospores 8–10.5 µm long, cystidia bear rectangular to rounded, rather sparse and irregularly arranged crystals	rarocrystallinum
17	Basidiospores 5.0–6.2 µm long	parvisporum
–	Basidiospores longer	18
18	Basidiospores 7–10.5 µm long	brachysporum sensu Boidin and Gilles (1988)
–	Basidiospores 6–8 µm long	19
19	Crystal protrusions on cystidia are short rods that project backwards under acute angle, giving cystidia the resemblance of a harpoon	harpagum
–	Cystidia with regular ornamentation (rows of rectangular crystals)	20
20	Basidiospores elliptic with attenuated base, usually straight	brachysporum sensu Talbot (1958)
–	Basidiospores cylindric, straight to regularly curved	meridense