Helping each other: the case of Sphagnum warnstorfii

I started this Project with the hope that we can help each other with the peculiar problems of identifying Sphagnum species microscopically. A discussion today about Sphagnum warnstorfii at https://www.inaturalist.org/observations/178222140 suggested to me a specific way this can work.

Sphagnum warnstorfii, in subgenus Acutifolia, is a northern species. It's a smallish, rather spindly plant of mineral-rich sites, best recognizable in the field by a bluish-purple color and long, strongly 5-ranked branches (though it can sometimes be green or mottled). However, the signature trait of this species is a microscopic feature of branch leaves, with "hyaline cells on convex surface with very small ringed pores (less than 0.25 cell width) along commissures near apex, changing abruptly to large elliptical pores (0.4 cell width or more) basally" (FNA).

What does this feature look like? We have different techniques and work under constraints of different quality of equipment, but I thought "Sphagnum with Slides" could offer some insight. I searched among our RG observations of this species and found some helpful images. These show the "very small ringed pores" in the apex of branch leaves. All these plants additionally have the purple color and 5-ranked branches that S. warnstorfii "should" have.

1. From Ontario, by @burke_korol:
2. From Nova Scotia, by @tomneily:
3. From Michigan, by @rroutledge:

4. From Maine, by me (@janetwright):
   .

If your observation has pores larger than these, or not ringed, you might want to check other subgenus Acutifolia species in your area. Or, we can engage in more discussion of how big S. warnstorfii pores "ought" to be! Thanks to everyone for stimulating ideas.

Posted on August 15, 2023 02:55 PM by janetwright