Spicantopsis Nakai

Spicantopsis Nakai (Figure 9A‒C; Figure 10). Type:— Spicantopsis niponica (Kunze) Nakai. Plants terrestrial; rhizomes either creeping and slender or erect and thick, not stoloniferous, dark, covered with scales; scales concolorous or discoloured, light brown to dark brown, linear-lanceolate or ovate-lanceolate, membranaceous or papyraceous, with entire margins; fronds forming a rosette, dimorphic, sterile fronds with stipes slender, short, light brown or green, proximally covered with scales, laminae lanceolate, erect or arcuate, pinnate to pinnatisect to pinnate, apices conform to subconform, glabrous or with small triangular-lanceolate scales, pinnae adnate, oblong-linear to linear-falcate, with entire margins, reduced towards the base; veins free, simple or 1-furcate, catadromous, ending in very patent adaxial submarginal hydathodes, with a series of parallel intramarginal stomata not following secondary veins; fertile fronds erect and pinnate, pinnae contracted, rachis proximally with small filiform scales or glabrous (S. amabilis); sori linear and continuous, forming coenosori on both sides of the costa, occupying the entire length of the pinna, not decurrent towards the rachis; indusia linear, continuous, long and coiled, open towards the costa; sporangia with 19‒29 arc cells; spores monolete, perispore brown, irregularly reticulate or verrucose granular. Distribution:— Japan and Taiwan (Figure 5). Basic chromosome number:— 2 n = 31. Taxonomic notes:— The genus to which Spicantopsis is most closely related is Struthiopteris, and in fact has been considered part of it until recently (Gasper et al. 2016, 2017, PPGI 2016), subsequently being resurrected (Molino et al. 2019b). Spicantopsis has pale-brown stipes, sori with straight bases, glabrous epidermis, and stomata that do not follow a pattern following the veins, the latter character being the one that was used to propose its separation from Struthiopteris the first time (Nakai 1933). On the other hand, Struthiopteris has dark brown to atropurpureous stipes, decurrent sori, epidermis with red glandular hairs on the abaxial side, and stomata located following the veins. They can also be distinguished by the spores, which have a compact perispore in Spicantopsis (Figure 9A‒C) and are alveolate in Struthiopteris (Figure 9D‒H). The other two genera to which it is phylogenetically most closely related are Brainea Smith (1856: 5) and Blechnidium Moore (1860: 210) (Gasper et al. 2016, 2017, Molino et al. 2019b). However, morphologically they are not similar, these genera being monomorphic or subdimorphic plants with anastomosing venation (vs. dimorphic plants with free veins in Spicantopsis). Despite not being phylogenetically closely related, it has some resemblance to some species of the genus Austroblechnum Gasper & V.A.O. Dittrich in Gasper et. al. (2016: 202), but differs in the margins of the pinnae, which are crenulate to serrate in Austroblechnum and entire in Spicantopsis, however, the diagnostic value of this character is subtle as this difference is not always clear. They also differ in the spores, since in Austroblechnum the perispore is smooth and never has folds, while in Spicantopsis the perispore is reticulate or verrucose (Moran et al. 2018, Molino et al., 2020). In addition, Austroblechnum has an austral distribution (Gasper et al. 2016), while Spicantopsis is found only in Japan and Taiwan. Also in a different clade at the phylogenetic level, it is very similar to Cleistoblechnum Gasper & Salino in Gasper et al. (2016 a: 207). It differs in that the fronds of this genus are monomorphic or subdimorphic, the margins of the pinnae are strongly revolute (vs. straight in Spicantopsis) and the laminae are more leathery.