Checklist of the pteridophytes of Narsingdi District, Bangladesh

Bangladesh Abstract The occurrence of a total of 31 species of pteridophytes under 20 genera and 13 families in Narsingdi district were confirmed. Pteridaceae with 11 species was found as the largest family, which was followed by Salviniaceae and Polypodiaceae consisted of four species each and Thelypteridaceae with three species. Each of the rest nine families was represented by only one species. Pteris with six species was found as the largest genus, which was followed by Salvinia with three species, and Adiantum , Ceratopteris , Pyrrosia and Cyclosorus with two species each. Each of the rest 14 genera was represented by only one species. Among these species, 21 were found as terrestrial, two as both terrestrial and semiaquatic, four as aquatic and other four as epiphytic. The occurrence of Tectaria chattagrammica Ching, listed as DD (Data Deficient) in Red Data Book of Bangladesh, was common with natural regeneration in this


INTRODUCTION
Pteridophytes or the ferns and fern-allies are the most primitive vascular plants in the plant world. They were a major part of the earth's luxuriant vegetation during the Carboniferous period (The Columbia Electronic Encyclopedia, 2012). In the modern era, the pteridophytes are an important component of the flora of any area. They have been used as ornamentals and medicinals (Nayar, 1957;Benerjee & Sen, 1980;Dhiman, 1998;Dixit, 1974 and1975;Hodge, 1973;Kaushik, 1998;Singh, et al., 1989;Benjamin & Manickam, 2007;Kavitha et al., 2017;Singh & Rajkumar, 2017). Some pteridophytes of Bangladesh are used as vegetables (Sarker & Hossain, 2009). Many species of this plant group occurring in Bangladesh are also reported as ethno-medicinally useful (Uddin, et al., 1998;Uddin, et al., 2008;Sarker & Hossain, 2009). Prain (1903) was the first who reported 98 species of pteridophytes from the then East Bengal including the present Bangladesh. The nomenclature and taxonomic position of many pteridophytic taxa have been changed in last eleven decades. After Prain (1903) different studies have been done on the pteridophytes of Bangladesh (e.g., Pasha & Mallick, 1980;Pasha & Chakraborty, 1984;Pasha, 1985;Mirza & Rahman, 1997;Uddin & Pasha, 1997;Uddin, et al., 1998;Uddin, 2001;Uddin et al., 2001;Siddiqui et al., 2007;Uddin, et al., 2008. Uddin & Hassan, 2012, Hossain et al., 2015. Siddiqui et al. (2007) compiled 195 species of pteridophytes from Bangladesh. These works were conducted on specific area or taxon based on representative specimens collected through field inventories, examination of previously collected voucher specimens deposited at different herbaria and of Bangladesh or survey of available literatures. However, the pteridophytic flora of this country is still inadequately known and described and until now there is the scope, need and justification of exploring this plant group throughout this country to know their present status and distribution. This study was conducted to know the current status and distribution of pteridophytic flora in Narsingdi district.

MATERIALS AND METHODS
Narsingdi district is located in central Bangladesh, 50 km north-east of the capital city Dhaka and lies between 23º46' and 24º15ʹ north latitudes and between 90º34ʹ and 90º59ʹ east longitudes. This district with an area of 1140.76 sq km is a part of the Dhaka division and consisted of six upazilas, namely Belabo, Monohardi, Narsingdi Sadar, Palash, Raipura and Shibpur ( Fig. 1). Narsingdi is a densely industrial area, harbor many textile and jute mills and includes numerous agricultural fields. The northern region of the district is composed of both hillocks and plain lands and the rest of plain and low lands. It includes a total of 89045 hectares of cultivable land and 22154 hectares of fallow land. The maximum annual average temperature is 36°C, minimum 12.7°C, annual rainfall 2376 mm. Main rivers crossing this district are Meghna, Arial Khan, Haridhoa, Kalagachhia and Paharia.
This study was based on a thorough taxonomic inventory comprised of 29 field trips conducted in different seasons of 2014-2018 throughout the Narsingdi district. Standard herbarium methods and techniques were followed (e.g., Hyland, 1972, Jain & Rao, 1977 in collection, processing, drying and preservation of plant specimens. The representative herbarium specimens were examined at the Bangladesh National Herbarium (DACB), and Jahangirnagar University Herbarium (JUH). The specimens were identified by consulting Clarke (1880), Holttum (1968Holttum ( , 1991, Siddiqui et al. (2007). The relevant type images of pteridophytes available in the web pages of different international herbaria (e.g., Kew Herbarium Catalogue, Geneva Herbarium) were also matched. The voucher specimens have been preserved at JUH. Nomenclatural information of each taxon was verified following Larsen (1975 and, Wu et al. (1995Wu et al. ( -2013, IPNI (2016), The Plant List (2017) and TROPICOS (2017). The families have been arranged according to the classification system of Pichi (1977). The genera and species under each family have been arranged alphabetically. The valid name of each taxon has been mentioned with full original citation, followed by the basionym and synonym/s (if available). Each species is presented with minimum taxonomic description including comment on its present distribution in the study area and citation of representative specimens.

RESULTS AND DISCUSSION
In this study a total of 31 species belonging to 20 genera of 13 families of pteridophytes have been found in Narsingdi district. For each species, up-to-date nomenclature, plant habit, ecology, distribution in Bangladesh, distribution in Narsingdi and the examined representative specimens collected from Narsingdi district has been mentioned below.  (Pasha, 1985). In Narsingdi it was found as common in Monohordi.  (1753). Terrestrial herb, rhizomes erect. In hilly forest areas, on moist soil. In Bangladesh it occurs in Chittagong and Sylhet district. In Narsingdi it was rarely found in Shibpur. Cyclosorus dentatus (Forssk.) Ching, Bull. Fan Mem. Inst. Biol., Bot. 8(4): 206-209 (1938).
Polypodium dentatum Forssk.  fig. (1931). Terrestrial herb, rhizome short, stout. In hill slope, on moist soil. In Bangladesh it occurs in Chittagong district. In Narsingdi it was occasionally found in Shibpur and Raipura. Representative specimen: Narsingdi: Shibpur, 25 December 2014, Robayda 98 & 99 (JUH); 7 April 2015, Robayda 373 & 413 (JUH). Raipura, 18 July 2017, Robayda 2408 (JUH). Among the total 31 pteridophyte species recorded from Narsingdi district 21 were terrestrial, two species were both terrestrial and semiaquatic, four species were aquatic and other four species were epiphytic. A total of 19 species were found in each of Monohordi and Shibpur upazilas, which was followed by 14, 13, 11 and 9 species, found respectively in Belabo, Palash, Narsingdi Sadar and Raipura upazilas. Selaginella ciliaris (Retz.) Spring was found only in Monohordi upazila, whereas Adiantum philippense L. in Palash upazila and Pteris biaurita L. in Belabo upazila only. Seven species, viz. Dicranopteris linearis (Burm. f.) Underw., Adiantum tenerum Sw., Pteris griffithii Hook., P. pellucida C. Presl, P. semipinnata L., Lindsaea ensifolia Sw., and Blechnum orientale L. were found only in Shibpur upazila. These data indicate that Monohordi and Shibpur upazilas harbors most of the pteridophytes of Narsingdi district recorded during this study. Pteridaceae with 11 species was found as the largest family, which was followed by Salviniaceae and Polypodiaceae, each with four and Thelypteridaceae with three species. The rest nine families consisted of one species each. Only four families, namely Pteridaceae, Salviniaceae, Polypodiaceae and Thelypteridaceae constituted 70.96% of total pteridophytic flora of the area, whereas, remaining nine families 29.03%. Pteris with six species was found as the largest genus, which was followed by Salvinia with three species, Adiantum, Ceratopteris, Pyrrosia and Cyclosorus, each with two species. The rest of the 14 genera consisted of one species each. Uddin & Pasha (1997) recorded 16 fern allies, Mirza & Rahman (1997) listed 161 species of fern and fern allies & Siddiqui et al. (2007) compiled 195 species of pteridophytes from Bangladesh. Considering Siddiqui et al. (2007), the Narsingdi district harbors 15.89 percent of the pteridophyte species of Bangladesh, which indicate that this district is an important area for harboring the pteridophytes of this country. Uddin & Hassan (2012) reported 41 species from Rampahar & Sitapahar and Rahman et al. (2016) 24 species from Sundarbans. In respect to the size of land area, the species composition of the pteridophytes of Narsingdi district seems higher than that of Sundarbans (Rahman et al., 2016), whereas it is relatively poorer than that of Rampahar & Sitapahar (Uddin & Hassan 2012). The species Tectaria chattagrammica Ching. has been enlisted as DD (Data deficient) in Red Data Book by Khan et al. (2001). During this study, it has been found as common in Narsingdi district with normal natural regeneration.