Typification of Blechnum spicant var. fallax Lange (Blechnaceae)

Blechnum spicant var. fallax Lange is a fern taxon endemic to Iceland where it occurs in the vicinity of hot springs on geothermally heated soils. The taxon was first described by a Danish botanist Johan Martin Christian Lange in 1880 on the basis of plant material collected by Christian Gronlund in Iceland. Because its holotype was not designated in the protologue, we examined the extant original material including illustrations from Flora Danica and a single plant on sheet C10021769 (deposited in C) that was the basis for the respective plate. We select this specimen as the lectotype of Blechnum spicant var. fallax .


Introduction
Blechnaceae is an important leptosporangiate fern family distributed mainly in tropical regions of America and Australasia that comprises around 220-250 taxa in an uncertain number of genera [1,2]. It is estimated that about 80% of the species within Blechnaceae belong to the genus Blechnum [3]. Blechnum is well known for a very complex taxonomy and huge uncertainty regarding species relationships within the genus [3,4].
Blechnum spicant (L.) Roth. is the only species from Blechnaceae with a circumpolar distribution that occurs in temperate and even cold regions of the Northern Hemisphere [5].
It Icelandic plants belonging to var. fallax are homophyllous, prostrate, with all the leaves in a rosette, which is pressed to the ground. Leaves are very short (2-5 cm), pinnatifid, lanceolate, and almost straight, with extremely short petioles on all the leaves, light green or inconspicuous brownish, with a few scales at the base. The rhachis is distinctly green up to the tip of the frond [6].
Plants belonging to this taxon were first found by a Danish botanist Christian Grønlund during his excursion to Iceland in 1876 [7]. He found the plant growing on the cone of a large hot spring called Deildartunguhver in western Iceland. According to our best knowledge, the taxon can be considered endemic to Iceland. Digital signature This PDF has been certified using digital signature with a trusted timestamp to assure its origin and integrity. A verification trust dialog appears on the PDF document when it is opened in a compatible PDF reader. Certificate properties provide further details such as certification time and a signing reason in case any alterations made to the final content. If the certificate is missing or invalid it is recommended to verify the article on the journal website.
Until now, the name Blechnum spicant var. fallax Lange has remained untypified according to modern nomenclatural practice, and our study aimed to designate a type for this name.

Typification
The protologue of B. spicant var. fallax can be found on page 11 of the 17th volume of Flora Danica [8] and includes a short morphological description and a geographic location: The Melbourne Code [9] states that original material comprises those specimens and illustrations (both unpublished and published either prior to or together with the protologue) upon which it can be shown that the description or diagnosis validating the name was based (Article 9.3). In the case described, the original material consists of at least several elements: ■ Illustrations (watercolor paintings) being a part of Plate 2983 that accompanies the protologue. The plate (see Fig. 1 It is almost certain that the above-mentioned elements of the original material do not constitute a comprehensive list, since two different (!) plants were depicted on the Plate 2983 in Flora Danica. Our research in the C herbarium also showed the presence of another sheet annotated as Blechnum spicant var. fallax Lange collected by Grønlund, but it cannot be proved that the description of the taxon was also based on it.
None of the above elements can be treated as a holotype as we cannot point out the only element upon which the validating diagnosis was based (Art. 9.1 Note 1 and Art. 9.3 of the Code [9,10]). Moreover, no specimens were explicitly cited in the protologue [8]. In such a case, Article 9.12 of the Code states that "the lectotype must be  chosen from among the uncited specimens and cited and uncited illustrations that comprise the remaining original material, if such exist". These three latter elements have equal priority. We decided to designate the specimen -plant No. 2 preserved on the herbarium sheet deposited in C (barcode C10021769) as a lectotype of the name. There is no doubt that it is the specimen depicted in one of the illustrations being a part of the Plate 2983 (that accompanies the protologue). Our choice ensures that all the important characters of the taxon (e.g., shape and color of scales) can be analyzed in detail. The formal typification may be thus summarized as follows: