A new species of Hypodematium (Hypodematiaceae) from China

Abstract Hypodematium confertivillosum J.X.Li, F.Q.Zhou & X.J.Li, sp. nov., a new species of Hypodematium from Shandong, China, is described and illustrated. It is similar to H. crenatum (Forssk.) Kuhn & Decken and H. glanduloso-pilosum (Tagawa) Ohwi, but differs greatly from them by its abaxial fronds sparsely covered with rod-shaped glandular hairs, its adaxial fronds without rod-shaped glandular hairs and spore reniform, with verrucate processes, surface with distinct finely lamellar rugae ornamentation. The description, photographs and a key to H. confertivillosum as well as their notes are provided.


Introduction
Described in 1833, Hypodematium Kunze is the only genus of Hypodematiaceae Ching (Ching 1975). Iwatsuki (1964) reviewed the genus and recognised four species including one subspecies. Recently, more than 16 species of Hypodematium, mainly distributed in subtropical and temperate areas of Asia and Africa, have been established (Shing et al. 1999). China, with 12 species of Hypodematium, is regarded as the centre of distribution for this genus (Zhang and Iwatsuki 2013). The genus is characterised by a distinctive swollen scaly stipe base and grows only on limestone habitat (Zhang and Iwatsuki 2013). Previous research on systematics and palynology of Hypodematium (Ching 1935, 1940, 1963, 1975, 1978a, b, Li et al. 1988, Shing et al. 1999, Zhou et al. 1999, Wang et al. 2010, Zhang and Iwatsuki 2013 provided an important background that allowed the recognition of the species new to science.

Materials and methods
The voucher specimens of the new species were collected from Tashan mountain, China and deposited in PE (herbaria acronyms according to Thiers 2016).
Scanning electron microscopy (SEM) was used to document the micromorphology of spore and fronds. Samples were dehydrated and were then placed on aluminium stubs using double-sided adhesive tape and sputter coated with gold in a Hitachi E-1010 Ion Sputter Coater, following Wen and Nowicke (1999). The materials were subsequently observed and photographed under a SUPRATM55 scanning electron microscope.  Kuhn & Decken and H. glanduloso-pilosum (Tagawa) Ohwi, from which it differs greatly by its abaxial fronds sparsely covered with rod-shaped glandular hairs, its adaxial fronds without rod-shaped glandular hairs and spore reniform, with verrucate processes, surface with distinct finely lamellar rugae ornamentation.
Distribution. This species is known only from the area around the type locality in Tashan, Shandong.
Ecology. Usually growing in limestone crevices of xeric areas. Discussion. The perispore is an important trait for identifying species under the scanning electron microscopy (Liu and Li 1999) and it contributes to the discovery of some new species, for example Dryopteris guanchica (Jermy 1980). There are significant differences between the perispore of H. confertivillosum that has verrucate processes, surface with distinct finely lamellar rugae ornamentation, H. crenatum having curved long ridges, surface with fine striae ornamentation and H. glanduloso-pilosum having tuberculate-massive ornamentation, providing an important micromorphological basis for establishment of the new species H. confertivillosum. A comparison of H. confertivillosum, H. crenatum, and H. glanduloso-pilosum is given in Table 1 and Figure 2.
It is commonly believed that Hypodematium, a very special group, has different types of glandular hairs and non-glandular hairs, which is an important basis for the identification and classification of species of Hypodematium (Zhang and Iwatsuki 2013). Hypodematium confertivillosum fronds are sparsely covered with rod-shaped glandular hairs abaxially, but its adaxial fronds without rod-shaped glandular hairs; H. crenatum fronds are sparsely covered with acicular hairs adaxially, densely covered with long hairs abaxially and without rod-shaped glandular hairs on both surfaces. Hypodematium glanduloso-pilosum fronds are mixed, densely covered with acicular and rod-shaped glandular hairs adaxially and long hairs and rod-shaped glandular hairs abaxially. Therefore, the types of hair and the degree of density of different types of hair support the establishment of the new species of H. confertivillosum. A comparison of H. confertivillosum, H. crenatum, and H. glanduloso-pilosum is given in Table 2 and the taxonomic key below (adapted from Zhang and Iwatsuki 2013), and Figure 3.