Name: Mycena adscendens
Author: (Lasch) M. Geest.
Citation: Proc. K. Ned. Akad. Wet., Ser. C, Biol. Med. Sci. 84(2): 211 (1981)
Preferred Synonyms:Mycena tenerrima (Berk.) Quél.
Thank you for your explanation! Since the time we joined Mushroom Observer, I have been calling for the deprecation of “deprecation” and removing it from MO vocabulary. There are many other strange terms, such as “Preferred Synonyms” (I guess that preferred synonyms are not in fact synonyms), but the MO officials thought I was joking. Never mind, I found MO being a magnificent tool that is not fully appreciated by professional mycologists and MO strange terminology is one of MO features that deter them from actively using MO for data basing their collections. That’s a pity!
Most of this debate centers around incorrect usage of the nomenclatural terms “invalid” and “illegitimate” and the term “deprecated” which if used really should replaced by “depreciated”, unless the desire is to belittle the poor synonyms. E.M. Fries in the Index (1832) to the Systema Fungorum lists three (not 2) uses of Agaricus adscendens and all were placed in synonymy so that none are sanctioned. Agaricus adscendens Bolton (1788), Agaricus adscendens Schumacher (1803), and Agaricus adscendens Lasch (1829). The latter two are illegitimate. Even Bolton’s use could be questioned because he used two names, Agaricus adscendentibus (vol. 2 p. 55) and in his index and key Agaricus adscendens. Be that as it may, A. adscendens Lasch is illegitimate. Therefore when M.A. Donk apparently proposed the name combination Mycena adscendens he inadvertently created a new name Mycena adscendens that should not be cited as “(Lasch) Donk” but be cited as was corrected by Paul Kirk in Index Fungorum, to be cited as Mycena adscendens Donk (1981). It, of course is a much later date from the names Agaricus tenerrimus Berk. (1836) and Mycena tenerrima (Berk.) Quel. (1872). The latter is correct when considered to be synonymous with M. adscendens Donk.
I have not seen the original publication (M. Geest. Proc. K. Ned. Akad. Wet., Ser. C, Biol. Med. Sci. 84: 211 1981) where Mycena ascendens was published and it’s not clear to me why M. Geest. did not accept Mycena tenerrima (Berk.) Quél. In the time when Maas Geesteranus described his Mycena adscendens none of the two "Agaricus adscendens " have been “published”, since the Fries’ starting point for fungi (Syst. Mycol. 1: xlvi. 1821) was still in effect. There might be some other glitch for which people prefer Mycena adscendens to M. tenerrima. At this point, Mycena tenerrima (Berk.) Quél. looks like a “better” name.
Article 53.1 applies here because when the basonym of Mycena adscendens (Agaricus adscendens) was published in 1829, the name Agaricus adscendens was already in use. In 1803, H.C.F. Schumacher published Agaricus adscendens.
53.1. A name of a family, genus, or species, unless conserved (Art. 14) or sanctioned (Art. 15), is illegitimate if it is a later homonym, that is, if it is spelled exactly like a name based on a different type that was previously and validly published for a taxon of the same rank (see also Art. 53.2 and 53.4).
Be careful with deprecation. Terms Deprecate or Deprecation is not mentioned (not speaking about defined) in the Code at all.
Mycena adscendens is an invalid name due to article 53.1. M. tenerrima is the oldest validly published name.