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Microscopy spores A-Strain cubensis: chestnut caps with white flecks and a small raised bump at the centre, close up

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Show: A-Strain cubensis: chestnut caps with white flecks and a small raised bump at the centre, close up

Show: Psilocybe cubensis spore print; a dark print of the underside of a mushroom where its spores have dropped on to a square piece of foil

Show: Psilocybe cubensis spore syringe inside labelled silver foil bag

Show: 3ml and 12ml Psilocybe cubensis mushroom spore syringes with secure tamper proof syringe caps

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Psilocybe cubensis

A Strain

The plainest, most old-school cube in the cabinet: a sharp little nipple on the cap, a heavy purple-brown print, and the pigmented parent that the famous Albino A+ was later isolated from.

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Sold for microscopy, taxonomy and collecting only. Not for cultivation.

UK lab-made
filled under laminar flow

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Straight talk

Fact vs. legend

There is a lot of folklore around this strain. Here is which bits are real, side by side.

What we actually know

It is a plain Psilocybe cubensis, not a hybrid and not a separate species, and it has circulated under the 'A-Strain' name for many years.
By most accounts its documented origin is simply unknown; the clearest thread on record is that it was originally supplied by a spore vendor based in Idaho.
Its standout field mark is a persistent acute umbo (a small nipple) at the centre of the cap, which often stays even after the cap flattens.
It is the pigmented line from which the leucistic Albino A+ (AA+) was later isolated, so the two are close relatives rather than unrelated strains.
It drops a heavy, dependable dark purple-brown print from subellipsoid spores on four-spored basidia, exactly what you want for study.

What the community says

The letter 'A' is often read as 'A for the original' or a vendor's grading mark, but nobody can actually say what it stands for. Treat it as guesswork.
The same anonymous hobbyist 'Mr. G' who attaches to B+ and A+ lore sometimes gets credited here too, but that link is unverified and may simply be the A+ story bleeding backwards onto its parent.
Various tellings place a tropical wild origin in South America or Southeast Asia. That fits the genus but is speculation, not a documented collection.
It is sometimes sold as a 'benchmark' or 'reference' cube. That is marketing framing for how ordinary and consistent it looks, not a measured ranking.

The story

The plain one that bred a famous ghost

Some cubes earn their fame with a wild backstory. A-Strain earned its place by being almost defiantly ordinary, and then quietly producing one of the most recognisable mushrooms in the hobby. The starting point is that nobody really knows where it came from. The clearest thread anyone can point to is that it was originally supplied by a spore vendor based in Idaho, and beyond that the paper trail simply runs out.

What it is best remembered for is what came after it. A-Strain is the pigmented parent line that the leucistic Albino A+ (AA+) was isolated from, so the pale celebrity and this plain workhorse are close family. People sometimes attach the anonymous "Mr. G" of B+ and A+ folklore to A-Strain as well, but by most accounts that is the later story bleeding backwards onto the older line, and it should be read as lore rather than record.

A-Strain is the rare case where the boring parent is the interesting one, because without it there is no Albino A+.

About that letter

As for what the "A" means, the truthful answer is that no one can tell you. It gets read as "A for original" or as an old distributor's grade, and both are guesses. You will also see it framed as a tropical South American or Southeast Asian line, which is plausible for the species but is speculation, not a documented wild collection. The interesting, verifiable thing is right there on the cap.

The species

Meet Psilocybe cubensis

A Strain is a collector's line of a single, well-travelled species. Psilocybe cubensis was first written up in 1906 by the American mycologist Franklin Sumner Earle, from a specimen found in a cattle field in Cuba, which is where the name comes from. He originally called it Stropharia cubensis; Rolf Singer moved it into the genus Psilocybe in 1948.

The genus name is a tidy bit of Greek: psilos ("bare") plus kubē ("head"), for the smooth, peelable skin of the cap, so the full name reads roughly as "the bare-headed mushroom from Cuba."

Family: Hymenogastraceae (older books say Strophariaceae)
Genus: Psilocybe (Fr.) P. Kumm., 1871
Species: Psilocybe cubensis (Earle) Singer, 1948
Basionym: Stropharia cubensis Earle, 1906
This product: A Strain, a collector's cultivar of the species
Type locality: Cuba (where it was first named)

How you'd know it

Field marks

These describe the mature mushroom for reference and identification.

Nippled cap

The signature mark. Reddish cinnamon when young, maturing to golden brown and light yellow with nearly white edges, and keeping a small acute umbo (a nipple) at the centre even as it flattens. The surface is dry, without the veil spots some cubes carry.

Tall yellowish stem

A long stipe, often well past 150 mm, whitish to yellowish and fibrous. A leftover partial veil leaves a persistent membranous ring (annulus) that ends up dusted purple-brown once the spores ripen.

Greying to black gills

Adnate to adnexed and crowded, pale grey when young and darkening to nearly black as the spores mature, which is what gives the heavy print its colour.

Blue bruising

Handle the white flesh and it bruises bluish green, the classic Psilocybe reaction as enzymes convert psilocybin and the products oxidise into blue pigment.

Where it comes from

A dung-lover with a wanderer's history

Psilocybe cubensis is coprophilic, a fancy word for dung-loving. In the wild it lives on the droppings of big grazing animals, classically cattle and water buffalo, fruiting from warm, humid pasture. It does not grow on wood and it does not partner with tree roots.

You'll find it across the warm parts of the world: the Gulf Coast of the United States, Mexico, Central and South America, Southeast Asia and Australia. It was named from Cuba, but where the lineage truly began is an open question. A 2026 study describing its closest wild relative in southern Africa suggests the deep roots are Old-World, the mushroom having apparently travelled with grazing herds long before anyone gave it a Latin name.

The main event

Under the microscope

This is what you actually bought the spores for. Put a print or a drop from a syringe on a slide and here's what shows up.

Shape & size. Smooth, thick-walled and subellipsoid, like a slightly squashed rugby ball, roughly 11.5–17 µm long by 8–11 µm wide (the figures Paul Stamets settled on).
The germ pore. Look for a single pale, flattened dot at one end. That's the one thin spot in the wall where, in nature, a mushroom would begin, and a real cubensis hallmark.
Pale alone, dark in a crowd. A single spore looks honey-amber with the light behind it; only in a mass do they read deep purple-brown to black. So a near-black print but pale spores on the slide is normal optics, not a dud.
What you'll need. Find the field at 100×, study shape and the germ pore at 400×, and get the wall crisp at 1000× under oil. A touch of methylene blue or KOH lifts the contrast.
The legal bit, and why it's true. A dormant spore carries no psilocybin or psilocin at all; that chemistry only appears later in living tissue. That is exactly why the spores are legal to own and study in the UK.

Choose your format

Print, syringe, vial or swab?

Same lab-grade genetics in every option. The honest difference is shelf life versus how soon you're at the scope.

Spore print

Keeps longest

Spores dropped straight onto sterile foil. Stored cool and dry it outlasts everything else here, so it's the one to reach for if you're building a collection to keep for years.

Spore syringe

Ready tonight

Spores suspended in sterile water, ready to go straight onto a slide. The quickest way to be looking down the microscope this evening. Comes in 3 mL and 12 mL.

Vial & swab

Compact

A sealed glass vial is a tidy middle ground; a sterile swab is the most travel-friendly, robust little format for adding a strain to your reference set.

At a glance

The spec sheet

Species: Psilocybe cubensis
Strain: A Strain (collector's cultivar)
Spore print: Dark purple-brown to near-black, heavy depositor
Spore shape: Subellipsoid, smooth, thick-walled, with a germ pore
Spore size: ~11.5–17 × 8–11 µm
Basidia: Mostly 4-spored, ~20–30 × 7–10 µm
Wild habitat: Coprophilic, on herbivore dung & warm pasture
Climate: Subtropical to tropical
Intended use: Microscopy, research & collecting only

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