﻿Lectotypification, epitypification and history of the name Plagiotheciumneglectum Mönk. (Plagiotheciaceae)

﻿Abstract In the protologue of Plagiotheciumneglectum, Mönkemeyer (1927) does not indicate any herbarium specimen as a type. The author only gave a short description and attached a figure illustrating selected features of this taxon. The original materials from the Mönkemeyer collection were deposited in the HBG herbarium; however, it is not currently possible to determine their location. Furthermore, one specimen of P.neglectum, currently known from the original Mönkemeyer collections, was found in the Herbarium B (B 30 0105646). The features given in the diagnosis of this taxon are consistent with those of the lectotype of Stereodonnemoralis Mitt.; only the leaf apex from Figure 207c (Mönkemeyer 1927) is different and thus suggests mixed material. According to Art. 9.1 of the Shenzhen Code, Figure 207c represents a holotype of P.neglectum. However, due to differences in the leaf apex and according to Art. 9.3 of the Shenzhen Code, the part representing the apex should be excluded from the holotype, and the remainder of Figure 207c is consequently designated as a lectotype of the name P.neglectum. However, because the lectotype does not include a complete set of significant distinguishing features, an epitype (B 30 0105646) was designated.

In the diagnosis, Mönkemeyer (1927) did not indicate any herbarium specimen as a type; the only original element is Figure 207c. The taxon is characterized, e.g., by shrunken turf in a dry condition, dense foliage, strong costae, and a very loose areolation of cells. In addition, Mönkemeyer (1927) compared this species with P. silvaticum and P. succulentum (Wilson) Lindb., also describing that the cell areolation in P. neglectum is as wide as that of the former, and the appearance of the turf and the leaves and habitat are similar to the latter.
Considering the above facts, efforts have been made to revise the original herbarium materials of P. neglectum from the collection of Wilhelm Mönkemeyer to confirm the correctness of the previous synonymization, which was made in the absence of herbarium specimens.

Materials and methods
Before starting the research, efforts were made to find all herbaria in which W. Mönkemeyer collections are deposited. Sayre (1977) pointed out that his materials are deposited in the HBG, H-BR, and S herbaria. Additionally, an analysis of the Index of Botanists (https://kiki.huh.harvard.edu, accessed 15 th of May 2021) found some of his herbarium specimens to be stored in the B, H, M and MANCH herbaria.
To find the original materials of P. neglectum, contact was made with the staff of all the above-mentioned institutions. All curators indicated that the original materials of the analyzed taxon had been deposited at the Herbarium HBG. This was also confirmed in a paper by Walter and Martienssen (1976) describing the bryological collection of this herbarium.

Results
In the diagnosis, Mönkemeyer (1927) did not designate any specimen or collection as a type, or identify any original material or even geographical locations of the collection sites of the analyzed specimens. He added only a figure (207c) to the description of the taxon (Fig. 1A). An analysis of the bryological collection of the HBG herbarium (Walter and Martienssen 1976) revealed the presence of 13 "syntypes" of P. neglectum (Fig. 2); however, these specimens are incorrectly defined as syntypes because none is cited in the protologue P. neglectum (Mönkemeyer 1927). Nevertheless, based on contact with the curator of the bryological collection in the HBG herbarium, it was found that the original material of this taxon has been lost and their location is currently unknown and cannot be determined (Herbarium staff, pers. comm.).
Nevertheless, our research yielded only one currently known original specimen of P. neglectum collected by Mönkemeyer (Wesergebirge: in Erlenbrüchen bei Eschershausen, Juli 1900, Mönkemeyer s.n., B 30 0105646). However, like the other ones, this is also not mentioned in the protologue (Fig. 1B).
The characteristics given in the diagnosis (e.g., shrunken turf; strong costae; loose cell areolation) and figures (e.g., rather flat, symmetrical, ovate leaves; straight apex; short, wide, hexagonal, or narrowly hexagonal cells) are consistent with those of the Stereodon nemoralis Mitt. lectotype . Only the leaf apex from the Mönkemeyer (1927) figure is not serrate, as should be in this case. Nevertheless, based on the other features given above, the proposal by Nyholm (1965), Ireland (1969), and Iwatsuki (1970) that P. neglectum is the plant currently understood as P. nemorale (syn. P. sylvaticum) appears correct.
Due to the existence of Figure 207c of this taxon, to which Mönkemeyer (1927) only refers to in the protologue, and according to Art. 9.1 of the Shenzhen Code (Turland et al. 2018), it should be assumed that Figure 207c is the holotype of that name. However, because the leaf apex of the holotype is not serrate, this suggests that the material used to make Figure 207c was derived from two different taxa (mixed material).
According to Art. 9.3 of the Shenzhen Code (Turland et al. 2018), "A lectotype is one specimen or illustration designated from the original material (Art. 9.4) as the nomenclatural type, in conformity with Art. 9.11 and 9.12, (...) if a type is found to belong to more than one taxon (see also Art. 9.14)". Therefore, the part of the figure representing the leaf apex, which is not serrate, should be excluded from the holotype, this being Fig. 207c (Mönkemeyer 1927: 862) (Fig. 3), and the rest of Figure 207c should be designated as the lectotype of P. neglectum.
However, due to the fact that the newly designated lectotype does not include the figure of the leaf apex, which is an important taxonomic feature, a specimen recently found in Herbarium B (B 30 0105646) should be designated as the epitype; it is the original material (as stated in Article 9.4 of the Shenzhen Code), collected by Mönkemeyer and signed by him as "P. neglectum". The plants of specimen B 30 0105646 also show a serrate leaf apex (Fig. 4), which indisputably indicates an association with P. nemorale. This is an excellent choice because this specimen comes from the original Mönkemeyer collection; this way, it is practically impossible to change the understanding of the name P. neglectum. In addition, it is not possible to find the remaining original materials, which, however, are not quoted in the protologue of P. neglectum but listed in the Walter and Martienssen (1976) catalog.