Psilocybe cubensis (Earle) Singer is the most widely studied member of the genus and the reference species for most spore microscopy. It is a dung-associated, pantropical species, described from Cuba in 1906, and it is the species behind almost every named strain in circulation.
Under the microscope cubensis spores are subellipsoid to ellipsoid in face view, thick-walled, and carry a distinct germ pore at the apex. Reference measurements put them at roughly 11-17 x 8-11 micrometres, which makes them comfortably resolvable at 400x and straightforward to measure at 1000x under oil. The spore print is a dark purple-brown, dark enough that print colour alone separates the species from most lookalikes.
Work at 400x first to survey the field, then move to 1000x with oil for measurement against a stage micrometer. The germ pore is the feature worth finding: a distinct, flattened aperture at the apex of the spore, clearly visible as a lighter spot when the spore is oriented face-on.
Wall thickness is the other diagnostic. Cubensis spores are noticeably thick-walled compared with Panaeolus, which is the comparison most people are actually trying to make when they put both on a slide.
A strain name in this catalogue means one of two things. Either it is an isolate, a line taken down to a single stable phenotype from a parent population, or it is a documented cross between two named parents. Where we know the cross, it is printed in the product name in brackets.
This matters for microscopy because an isolate gives you a far more uniform sample. A multispore syringe from the same parent will show you the whole genetic spread instead, which is interesting for a different reason.