This species was described by Smith and Singer in 1964. At that time it described as having lightly marbled to smooth spores, and having sub-capitate cystidia, along with no clamp connections, and both 2 and 4-spored basidia.
In the early 1970’s Kuhner said that this species was the same as his G. clavata that he discribed from the 1930’s. And for some reason, all obs. of these were moved to G. heterocystis, and became the accepted name.
In the late 1990’s new studies of Galerina looked at these again, to see if the 2-spored and 4-spored versions should get split into separate species. At this time the accepted description of this species also included spores which were lightly warted, and cystidia which are tibiiform, although that is not what was drawn in illustrations for the species in the Smith and Singer monograph. This is one reason I’ve had trouble find an id for this species, what is seen here in California has lightly warted spores, and clearly capitate, tibiiform cystidia.
As part of the new study, samples of G. heterocystis and G. clavata were looked at, and it was seen that the type of G. heterocystis does not have tibiiform cystidia, or lightly warted spores, but that G. clavata does, and that G. clavata matches the common obs. of this species.
At this point G. heterocystis has been deprecated for the older description of G. clavata. With the differences in the type samples seen, I would assume there might be a rare species out there that matches G. heterocystis, but there isn’t enough observations of this to say at this point.
The 2-spored form of the species has been split off to an also older described species of G. subclavata.
This is all from private conversation with Prof. Gro Gulden of Univ. of Oslo, with more details filled in by me. At some point I’ll try to find a better source for this.