Liverworts

Day 362: Scientists are driven to name things (via those pesky taxonomists, of course): to categorize, to distinguish, the better to understand where any given species fits into the grander scheme. To know that This and That are related gives us perspective from two angles, and so much the better if we also know they are related to Those. The morphological commonality here is obvious: This, That and Those all belong to the family "Th-," further divided into genus and species by "-is," "-at" and "-ose," and that method (superficial as it was) served us well for many years. Then came DNA analysis, and now our preconceptions are flying out the window at an astonishing rate. Observation of macroscopic and microscopic characteristics is proving to be insufficient. The liverwort shown above demonstrates my point.

There are two schools of thought regarding this Marchantia. Some will argue that it is M. polymorpha, a common pest in greenhouses and nurseries. Others will claim that it is M. alpestris, and may even cite as proof the fact that it lacks the black median line seen in its cousin. Yet another branch will defend it as a different variety (M. polymorpha var. alpestris) or subspecies (M. polymorpha ssp. montivagans). It's enough to drive you mad! To date, Santa Claus has declined my requests for a DNA sequencer and someone with the knowledge to run it, so given that my observations of this liverwort have both occurred in alpine locations where it is unlikely to have been imported from a lowland greenhouse, I'm calling it Marchantia alpestris, and I reserve the right to be wrong.