http://orcid.org/0000-0002-5455-3925
ABSTRACT
The chromosomal observations were carried out on 66 taxa collected from Kolli Hills belongs to 38 genera and 20 families. Sixty two ferns were studied cytologically for the first time in this study area. The present study has revealed the presence of 32 sexual diploids, 20 sexual tetraploids, 2 apogamous tetraploids, 9 sexual octoploids, 2 apogamous triploids and one 12-ploid sexual species. The sexuality of polyploids has also been calculated. The maximum number of chromosomes (n=171) were observed in Adiantum hispidulum while a minimum number of chromosomes (n=30) were in Adiantum latifolium, Cheilanthes tenuifolia and Pellaea boivinii. About the 20 genera were observed to be with more than one base number and remaining 18 genera with a single base number.
Introduction
The pteridophytes consist of ferns and fern allies; of these, the ferns are much more predominant, considering the richness of genera and species in a wide range of distribution. Pteridophytes are one of the richest floras in India. More than 12,000 species of pteridophytes are estimated and distributed in various regions of India (Chandra Citation2000). Most pteridophytes are observed in the Himalayas, Western and Eastern Ghats. They grow in the moist tropical and temperate forests and their occurrence in different eco-geographically threatened regions from sea level to the highest mountains is of much interest. The increasing number of chromosomal data on the ferns has played a significant role in the identity and phylogenetic affinities of several species and genera of ferns (Jin Mei et al.Citation2006). The cytological changes like hybridity, polyploidy and aneuploidy have played an important role in the evolution (Bhavanandan Citation1981). Evolution in many ferns involves changes in ploidy level and reproductive system (Manton Citation1950). The grade of polyploidy and the percentage of polyploids are indicators of the rate of evolution of ferns and these considerations suggest that the rate of evolution is faster in the tropics than in the temperate latitude (Manton Citation1953). The present study deals with the determinations of the chromosome numbers, interspecific polyploids, apogamous and sexual reproduction, the base number of the genus, cytotypes distribution in various regions of India and the grade of polyploidy in fern species from Kolli Hills, Eastern Ghats, Tamil Nadu, India.
Materials and methods
The Kolli Hills are part of the Eastern Ghats, which is a mountain range that runs almost parallel to the east coast of Tamil Nadu. It is located in Namakkal District of Tamil Nadu. It extends to an area of about 503 km2 at 11°10ʹ–11°30ʹ N, 78°15ʹ–78°30ʹ E (). Its elevation ranges from 700 to 1600 m. The mean annual temperature in the hills ranges from 18°C to 29°C. The humidity is 80–98% during the rainy season. The average annual rainfall is 763–833 mm in the monsoon period. The vegetation is prominently open evergreen, dense evergreen and dry deciduous with patches of moist deciduous and semi-evergreen forests. Foothills have dry deciduous shrub forests. About 271 km2 is occupied by forest, mostly in sholas.
Figure 1. Map of the study area – Kolli Hills.
The fieldwork was undertaken throughout the study area from September 2013 to May 2017 comprising all the seasons. The ferns and fern-allies were identified with the help of previous floras including Pteridophytes of Karnataka State, India (Rajagopal and Gopalakrishna Bhat Citation2016) and Pteridophyte flora of the Western Ghats-South India (Manickam and Irudayaraj Citation1992). The meiotic chromosomal counts were done for the ferns of the present study area. Young sori were collected in the early morning between 6.00 and 7.15 am and fixed in Carnoy’s fluid (absolute alcohol, chloroform and glacial acetic acid in the ratio of 6:3:1). The preserved materials were used within a week for the experiment. Meiotic studies were based on the usual acetocarmine squash method (Manton Citation1950). The chromosome count was made in the spore mother cell at first meiosis. The slides were photographed using an Olympus-CX21i research microscope under 100× (oil) magnification (Uttar Pradesh, India). The present chromosome numbers were verified and confirmed with the help of previous floras including Cytology of ferns of the Western Ghats, South India (Manickam and Irudayaraj Citation1988) and Chromosome atlas of the Indian pteridophytes (Bir and Verma Citation2010). Voucher specimens were deposited in the Centre for Cryptogamic Studies Herbarium (CCSH), Department of Botany, St. Joseph’s College (Autonomous), Tiruchirappalli, Tamil Nadu, India. The taxon was arranged as per the classification of Christenhusz et al. (Citation2011).
Results and discussion
Cytological investigations were carried out for 66 taxa belonging to 38 genera and 20 families (, –). Sixty-two ferns have been studied cytologically for the first time from Kolli Hills and the remaining species have already been reported by Manickam and Irudayaraj (Citation1988). The chromosome number ranges from 30 to 171. The highest chromosome number was observed in Adiantum hispidulum while the lowest chromosome numbers were observed in Cheilanthes tenuifolia and Pellaea boivinii. Most of the species had n = 41, n = 72, n = 36, n = 144, n = 58 and n = 82. New chromosome counts were reported for Adiantum latifolium (diploid, n = 30), Leptochilus decurrens (octoploid, n = 144), Asplenium decrescens (octoploid, n = 144) and Pyrrosia porosa (diploid, n = 37) from Kolli Hills by Sahaya Sathish and Vijayakanth (Citation2015, Citation2016) and Vijayakanth and Sahaya Sathish (Citation2016, Citation2017). Thirty-two species were observed to have diploid cytotypes and 33 species were of various levels of intraspecific polyploidy. Triploid (3x) cytotypes were observed in two species (Cheilanthes viridis and Parahemionitis cordata), tetraploid (4x) in 22 species, octoploid (8x) in nine species, and one species (Adiantum hispidulum) had a 12-ploid (12x) cytotype. One species exhibited both tetraploid and octoploid cytotypes (Adiantum raddianum) (J, K).
Table 1. Data on meiotic chromosome numbers of ferns from Kolli Hills, with previous reports in India.
Figure 2. Meiosis in spore mother cell of ferns. (A) Botrychium daucifolium (n = 90). (B) Angiopteris helferiana (n = 80). (C) Abrodictyum obscurum (n = 33). (D) Crepidomanes latealatum (n = 36). (E) Dicranopteris linearis (n = 39). (F) Lindsaea heterophylla (n = 92). (G) Microlepia speluncae (n = 43). (H) Pteridium revolutum (n = 52). (I) Adiantum hispidulum (n = 171). (J, K) Adiantum raddianum (n = 57, n = 114). (L) Antrophyum plantagineum (n = 45). (M) Cheilanthes viridis (n = 90). (N) Cheilanthes tenuifolia (n = 56). (O) Doryopteris concolor (n = 30).
Figure 3. Meiosis in spore mother cell of ferns. (A) Parahemionitis cordata (n = 90). (B) Pellaea boivinii (n = 30). (C) Pityrogramma calomelanos (n = 116). (D) Pityrogramma austroamericana (n = 116). (E) Pteris argyraea (n = 58). (F) Pteris confusa (n = 58). (G) Pteris pellucida (n = 58). (H) Pteris quadriaurita (n = 58). (I) Pteris vittata (n = 58). (J) Asplenium aethiopicum (n = 144). (K) Asplenium crinicaule (n = 144). (L) Asplenium inaequilaterale (n = 72). (M) Asplenium laciniatum (n = 36). (N) Asplenium normale (n = 36). (O) Asplenium obscurum (n = 72).
Figure 4. Meiosis in spore mother cell of ferns. (A) Asplenium yoshinagae (n = 144). (B) Cyclosorus dentatus (n = 72). (C) Cyclosorus interruptus (n = 36). (D) Cyclosorus papilio (n = 72). (E) Cyclosorus parasiticus (n = 72). (F) Macrothelypteris torresiana (n = 62). (G) Pseudocyclosorus ochthodes (n = 35). (H) Pseudocyclosorus tylodes (n = 36). (I) Trigonospora caudipinna (n = 36). (J) Blechnum orientale (n = 33). (K) Athyrium hohenackerianum (n = 41). (L) Deparia petersenii (n = 80). (M) Diplazium cognatum (n = 41). (N) Diplazium polypodioides (n = 41). (O) Arachniodes aristata (n = 82).
Figure 5. Meiosis in spore mother cell of ferns. (A) Bolbitis appendiculata (n = 41). (B) Bolbitis prolifera (n = 41). (C) Bolbitis semicordata (n = 41). (D) Dryopteris cochleata (n = 41). (E) Dryopteris sparsa (n = 82). (F) Polystichum squarrosum (n = 82). (G) Nephrolepis cordifolia (n = 41). (H) Nephrolepis multiflora (n = 82). (I) Tectaria gemmifera (n = 41). (J) Tectaria wightii (n = 41). (K) Davallodes pulchra (n = 41). (L) Lepisorus nudus (n = 36). (M) Microsorum punctatum (n = 72). (N) Pyrrosia lanceolata (n = 37). (O) Pyrrosia porosa (n = 37).
Apogamy and sexual reproduction
There are two types of reproduction, i.e. sexual and apogamous. The mode of reproduction has been determined by the number of spores produced per sporangium. As a rule, a normally sexual species produces 64 spores while an apogamous one releases 32. There are four apogamous species collected in the present study, Lindsaea malabarica, Cheilanthes viridis, flora, Parahemionitis cordata, and Pteris confusa. The remaining 62 species are sexual. Manton (Citation1953) reported that 10% of fern species from Ceylon were an apogamous type. Abraham et al. (Citation1962) reported 8% of the ferns to be of an apogamous type from South India. Manickam and Irudayaraj (Citation1988) listed 18 apogamous fern species and have recorded 7.27% from South India. Vasudeva and Bir (Citation1983) observed 5.45% from Pachmari Hills of Central India. In the present study, 6.06% (four species) are apogamous.
Intraspecific polyploidy
Polyploidy is a common phenomenon in pteridophytes and the cytological diversity at intraspecific levels has not been kindled to the fullest levels in the present study area. In India many workers have reported more than one cytotype within the species. Thirty-eight species of ferns have more than one cytotype in the present study. Both tetraploid (n = 57) and octoploid (n = 114) cytotypes were observed in Adiantum raddianum. Bir and Irudayaraj (Citation2001) have reported three cytotypes, tetraploid (n = 57), octoploid (n = 114) and 16-ploids (n = 228) from Nilgiris, South India. Manton (Citation1953) also reported from Ceylon three cytotypes, diploid, tetraploid and octoploid, for Ploypodium vulgare. Vasudeva and Bir (Citation1983) recorded 28 species (50.9%) from Pachmari Hills of Central India to be polyploids. Similarly Manickam and Irudayaraj (Citation1988) have also reported seven species (11%) from South India with more than one cytotype. In the present study about 58.46% (38 species) are found to be with polyploids.
Grade of polyploidy
The present results are compared with the Himalayas, Western India, Eastern India and Central India to determine a grade of polyploidy. About 11 species have the higher grade of polyploidy: Angiopteris helferiana, Cheilanthes tenuifolia, Pteris quadriaurita, P. vittata, Asplenium yoshinagae, Cyclosorus papilio, Dryopteris sparsa, Polystichum squarrosum and Microsorum punctatum. Seven species of fern have shown a lower grade of polyploidy: Dicranopteris linearis, Antrophyum plantagineum, Asplenium laciniatum, A. normale, Cyclosorus dentatus, Dryopteris cochleata and Pyrrosia porosa.
Different base numbers of genera
Twenty genera of ferns were observed to have more than one base number:Adiantum (15, 29 and 57), Pellaea and Pityrogramma (29 and 30), Antrophyum (40 and 30), Asplenium (36 and 40), Blechnum (33 and 31), Davallodes and Dryopteris (40 and 41), Lepisorus (11, 13, 22, 23, 26, 35, 36, 37 and 47), Microsorum (36 and 37), Lindsaea (34, 37, 41, 42, 43 and 50), Microlepia (35, 43 and 44), Phymatosorus and Pyrrosia (36 and 37), and Pteris (28 and 29). Eighteen genera had a single base number: Angiopteris, Athyrium, Deparia (40), Abrodictyum (33), Diplazium, Arachniodes, Bolbitis, Polystichum, Nephrolepis (41), Botrychium (45), Cyclosorus, Trigonospora (36), Dicranopteris (39), Parahemionitis, Doryopteris (30), Macrothelypteris (31), Pseudocyclosorus (35) and Pteridium (52). The base number ranges from x = 9 to x = 57. The lowest base number was observed in Abrodictyum and Crepidomanes and highest base number in Adiantum. Most genera had base numbers of 29–30, 33–37 and 41–43. A few genera were recorded with more than two base numbers from the study area, e.g. Lepisorus with nine types, Lindsaea with seven and Microlepia with three.
Abraham et al. (Citation1962) reported that the base number 30 might have originated from 29 and Manton (Citation1953) is also of the view that the base number 36 might have originated from 35. The different base numbers within a genus are due to aneuploidy and dysploidy. Manickam and Irudayaraj (Citation1988) have reported 17 genera with different base numbers from South India. In the present investigation 20 genera showed multiple base numbers.
Cytotype distribution in different regions of India
The present cytological report of some species is similar to the reports from regions including Western Himalayas, Eastern Himalayas, Western India, Eastern India, Central India and South India. They are Blechnum orientale (2x), Dryopteris cochleata (2x), Nephrolepis cordifolia (2x) and Tectaria gemmifera (2x), Pteridium revolutum (2x), Cheilanthes tenuifolia (4x), Pteris vittata (4x), Cyclosorus parasiticus (4x) and Pityrogramma calomelanos (8x) ().
Concluding remarks
The present study has revealed the presence of 32 sexual diploids (48.48%), 22 sexual and one apogamous tetraploids (33.33%), nine sexual octoploids (13.84%), two apogamous triploids (3.03%) and one 12-ploid (1.51%) sexual species. The sexuality of polyploids has also been calculated. 55.88% of species have more than one cytotype and 32.30% of species have more than one base number. In the totality of the cytotype ranges, the diploid is 48.48%, polyploids 45.45% and apogamy is 6.06%. The overall rate of polyploidy is 51.51%. The polyploidy result is similar to previous reports from South India (Abraham et al. Citation1962; Bir Citation1973; Bir and Irudayaraj Citation2001). All these polyploidy reports have shown that the fern flora of the present study area is in an active state of evolution. Polyploidy commonly occurs in various groups of plants and it is believed to have a specific role in the evolution of pteridophytes, according to the literature (Soltis and Soltis Citation1999; Otto and Whitton Citation2000; Soltis et al. Citation2003). Many hypotheses have been proposed to unfold the mystery behind the increased content of a duplicated genome. It was stated that genome doubling confers distinct advantages to a polyploid and these advantages allow polyploids to thrive in environments that pose challenges to the polyploid’s diploid progenitors(Madlung Citation2013). Morphological data alone will not help us to identify the plants at species level. Cytological information is more helpful to identify the species and for analysing the evolutionary relationship among several species.
Disclosure statement
No potential conflict of interest was reported by the authors.
References
- Abraham A, Ninan CA, Mathew PN. 1962. Studies on the cytology and phylogeny of the pteridophytes-VII. Observation on one hundred species of South Indian ferns. J Indian Bot Soc. 41:339–421.
- Ammal LS. 1990. Studies on the cytology and spore morphology of ferns [ Ph.D., Thesis]. Trivandrum (India): University of Kerala.
- Ammal LS, Bhavanandan KV. 1990. A note on the cytology of a tetraploid cytotype of Diplazium polypodioides Bl. from Idukki (Kerala), South India. Indian Fern J. 7:131–132.
- Ammal LS, Bhavanandan KV. 1991a. Cytological studies on some members of Polypodiaceae (Sensu Copeland). Indian Fern J. 8:154–158.
- Ammal LS, Bhavanandan KV. 1991b. Cytological studies on the genus Asplenium Linn. Indian Fern J. 8:69–73.
- Ammal LS, Bhavanandan KV. 1991c. Cytological studies on some member of Pteridaceae (Sensu Copeland) from South India. Indian Fern J. 8:87–92.
- Ammal LS, Bhavanandan KV. 1992. Cytological studies on the some ferns from South India. Indian Fern J. 9:94–101.
- Ammal LS, Bhavanandan KV. 1993a. Karyomorphological studies on three species of Diplazium Swartz. Indian Fern J. 10:30–34.
- Ammal LS, Bhavanandan KV. 1993b. Karyomorphological studies on three species of Tectaria Cav. Indian Fern J. 10:35–39.
- Ammal LS, Bhavanandan KV. 1994. Karyomorphological studies on Dryopteris Adanson. Indian Fern J. 11:89–93.
- Bhavanandan KV. 1968. Studies on the cytology of sixteen species of South Indian ferns. Caryologia. 21:333–338.
- Bhavanandan KV. 1971. Supernumerary cell division during meiosis in Rumohra artistata (Forst) Ching. Cytologia. 36:575–578.
- Bhavanandan KV. 1981. Studies on the cytology of South Indian Aspidiaceae. Cytologia. 46:195–207.
- Bir SS. 1953. Cytological studies of some members of Aspleniaceae [ M.Sc., Dissertation]. Solan Himachal Pradesh (India): Punjab University.
- Bir SS. 1960. Cytological observation on the East Himalayan members of Asplenium Linn. Curr Sci. 29:445–447.
- Bir SS. 1961. Chromosome numbers in Himalayan ferns. Vol. 12. Chandigarh: Research Bulletin of the Panjab University, Science; p. 139–164.
- Bir SS. 1962. Chromosome numbers in some Himalayan species of Vittaria. Am Fern J. 52:36–42.
- Bir SS. 1964. Taxonomic notes on some Himalayan ferns. J Indian Bot Soc. 43:556–572.
- Bir SS. 1964-1965. Chromosome numbers in some ferns from Kodaikanal, South India. Proceeding Combined 51st and 52nd Indian Science Congress Part-III, Calcutta; p. 340–341.
- Bir SS. 1965a. Chromosome numbers in some ferns from Kodaikanal, South India. Caryologia. 18:107–115.
- Bir SS. 1965b. Cytomorphological studies in families Aspleniaceae, Blechnaceae and Vittariaceae [ Ph.D., Thesis]. Chandigarh (India): Punjab University.
- Bir SS. 1969. Cytological evolution in the Himalayan species of genus Diplazium Swartz. Seminar on morphology, anatomy and embryology of land plants [ Dissertation]. Department of Botany, University of Delhi; p. 6–8.
- Bir SS. 1971. Cytological Studies in the Himalayan species of Diplazium Swartz. Caryologia. 24:269–281.
- Bir SS. 1973. Cytology of Indian pteridophytes. In: Nair, Grover RK, Verghese TM. editor. New Delhi (India): Glimpses in Plant Research. Vikas Publication Pvt. Ltd; p. 28–119.
- Bir SS. 1983. Classification and taxonomy of pteridophytes with particular reference to the higher ferns. In: Bir SS, editor. Aspects of plant Science. New Delhi: Today and Tomorrow’s Printers and Publishers; p. 183–245.
- Bir SS. 1994a. Biosystematics of ferns: Himalayan Asplenoid and Athyroid genera from Himalayas: results of chromosomal analysis on population basis. Indian Fern J. 11:82–88.
- Bir SS. 1994b. Biosystematics of ferns: Himalayan Asplenoid and Athyroid ferns in retrospect. In: Sarma TA, Saini S, Trivedi ML, Sharma M, editeors. Current research in plant science. Dehara Dun (India); p. 105–118.
- Bir SS, Irudayaraj V. 2001. Cytology of some ferns from the Nilgiris, South India - IV. Fern Gazette. 16:177–190.
- Bir SS, Irudayaraj V, Manickam VS. 1996. Cytology of some ferns from the Nilgiris, South India III. Fern Gazette. 15:141–149.
- Bir SS, Trikha CK. 1979. Cytological evolution of Polypodioid ferns with particular reference to the Himalayan forms. In: Nair PKK, editor. Glimpses in plant research IV. New Delhi (India): Vikas Publication Pvt. Ltd; p. 98–130.
- Bir SS, Vasudeva SM. 1978. In IOPB Chromosome number reports LXII. Taxon. 27:523–524.
- Bir SS, Vasudeva SM. 1979. Cytological studies in some ferns of Kodaikanal (South India). In: Bir SS, editor. Recent researches in plant sciences. New Delhi: Kalyani Publishers; p. 221–228.
- Bir SS, Verma SC. 2010. Chromosome atlas of the Indian pteridophytes. Dehra Dun (India): Bishen Singh Mahendra Pal Singh; p. 1–346.
- Chandra S. 2000. The fens of India (Enumeration, synonyms & distribution). Dehradun (Uttarakhand (India)): International Book Distributors; p. 459.
- Christenhusz MJM, Zhang XC, Schneider H. 2011. A linear sequence of extant families and genera of Lycophytes and ferns. Phytotaxa. 19:7–54.
- Fabbri F. 1965. Secondo supplemento alle Tavole chromosomiche delle Pteridophyta di Alberto Chiarugi. Caryologia. 18:675–731.
- Ghatak J. 1961a. Some meiotic count on the ferns from Khasia - Jaintia Hills. Proceeding of the 48th Indian Science Congress; p. 270.
- Ghatak J. 1961b. Problems involved in the proper identification of ferns. Bull Bot Surv India. 3:79–82.
- Ghatak J. 1962. Observation on the cytology and taxonomy of some ferns from India. Nucleus. 5:95–114.
- Ghatak J. 1963. Observations on the cytology and taxonomy of some ferns from India. Proceeding 50th Indian Science Congress; p. 371–372.
- Ghatak J. 1964. A preliminary note on the peculiar chromosome-pairing in two species of filmy ferns from South India. Nucleus. 7:29–36.
- Ghatak J. 1977. Biosystematic survey of pteridophytes from Shevaroy Hills, South India. Nucleus. 20:105–108.
- Gibby M. 1985. Cytological observations on Indian subcontinent and Chinese Dryopteris and Polystichum (Pteridophyta: Dryopteridaceae). Bull Br Museum (Natural History), Bot Ser. 14:1–42.
- Irudayaraj V. 1998. IOPB chromosome data 13. Newsletter. 29:22–23.
- Irudayaraj V, Bir SS. 1994. Cytology of some ferns from the Nilgiris, South India - II. Fern Gazette. 14:301–312.
- Irudayaraj V, Bir SS. 1997. Note on some Pteridophyta from the Western Ghats of Goa State, South India. Indian Fern J. 14:113–117.
- Irudayaraj V, Bir SS, Manickam VS. 1993a. Cytology of ferns from the Nilgiris, South India. Proceeding 80th Indian Science Congress, Part - III Section 6 Botany. Abstract; p. 76.
- Irudayaraj V, Bir SS, Manickam VS. 1993b. Cytology of ferns from the Nilgiris, South India. Fern Gazette. 14:161–170.
- Irudayaraj V, Manickam VS. 1986. Chromosome number reports XCI. Taxon. 35:404–410.
- Irudayaraj V, Manickam VS. 1987. SOCGI plant chromosome number reports - V. J Cytol Genet. 22:156–163.
- Irudayaraj V, Manickam VS. 1995a. Biodiversity and conservation of ferns and fern allies of the Nilgiris. SB Acad Rev. 4:61–63.
- Irudayaraj V, Manickam VS. 1995b. IOPB Chromosome data 9. Newsletter. 24:12–13.
- Irudayaraj V, Rajkumar SD, Manickam VS. 1995. Studies on intraspecific variation in South India ferns: rediscovery of the rare diploid cytotype of Christella parasitica (Thelypteridaceae: Pteridophyte). Fern Gazette. 15:41–50.
- Jin-Mei L, De-Zhu L, Ding WU. 2006. Chromosome numbers of four genera in the Dryopteridaceae. Acta Phytotaxonomica Sinica. 44:516–522.
- Khare PB. 1980. A note on the chromosome number of the fern flora of Amarkantak Hills, Central India. Sci Cult. 46:138–139.
- Khare PB, Kaur S. 1979. Mating behavior in the homosporous ferns, Cyclosorus parasiticus (Linn.) Tardieu. Proceedings of the Indian National Science Academy; p. 243–347.
- Khare PB, Kaur S. 1982. New cytotypes of Pteris vittata L. from Lucknow, India. Proceedings of the Indian National Science Academy; p. 69: 67.
- Khare PB, Kaur S. 1987. Genetic load in tetraploid cytotype of Pteris vittata Linn. Indian Fern J. 4:82–85.
- Khare PB, Roy SK. 1977. Genetic aspect of capacity of colonization of Cheilanthes tenuifolia (Burm) Sw. (Pteridophyta). Genetica. 47:183–185.
- Khullar SP, Gupta SC. 1978. Cytotaxonomy of the genus Polystichum in the Western Himalayas. Plant Syst Evol. 129:269–275.
- Khullar SP, Mehra PN. 1972. Cytotaxonomy of Western Himalayan ferns - III Polypodiaceae. Nucleus. 15:156–162.
- Khullar SP, Sharma SS, Singh P. 1983. The Thelypteridaceae of West Himalayas. Nova Hedwigia. 38:617–667.
- Khullar SP, Sharma SS, Verma SC. 1988. In: Bir SS ed. SOCGI plant chromosome number reports - VI. J Cytol Genet. 23:38–50.
- Kuriachan PI. 1964-65. Cytology of some South Indian ferns. Proceeding of the 52th Indian Science Congress; p. 359.
- Kuriachan PI. 1965. Cytology of some Indian ferns. Proceeding of the 51st and 52nd Indian Science Congress; p. 359.
- Kuriachan PI. 1967. Cytological observations on some South Indian ferns. Cytologia. 32:500–506.
- Kuriachan PI. 1976. Cytological studies of two species and a triploid hybrid of Nephrolepis. New Botanist. 3:38–43.
- Kuriachan PI. 1978. Cytology of some South Indian ferns. New Botanist. 5:53–58.
- Kuriachan PI, Ninan CA. 1976. Cytological evolution in the fern family Pteridaceae (Sensu Copeland). Aspects Plant Sci. 1:127–154.
- Loyal DS. 1961a. Chromosomal studies on Himalayan Thelypteridaceae-I. Cytology of Thelypteris Schidel. Proceeding of the 48th Indian Science Congress; p. 225–266.
- Loyal DS. 1961b. Chromosomal studies in Himalayan Thelypteridaceae - II. Cytology of Cyclosorus Link., Abacopteris Fee and Ampelopteris Kunze. Proceeding 49th Indian Science Congress; p. 226–267.
- Loyal DS. 1961c. Chromosome number in Himalayan ferns. Res Bull Panjab Univ Sci Chandigarh. 12:139–164.
- Loyal DS. 1991. Cytomorphological studies in the Eastern Himalayan Thelypteridaceae. In: Bhardwaja TN, Gena CB, editors. Perspectives in pteridology present and future, Vol. 13. Aspects of Plant Science; New Delhi: Today and Tomorrow’s Printers and Publishers; p. 171–248.
- Madlung A. 2013. Polyploidy and its effect on evolutionary success: old questions revisited with new tools. Heredity. 110:99–104.
- Mahabale TS, Kamble S. 1981. Cytology of ferns and other pteridophytes of Western India. Proceedings of the Indian National Science Academy; p. 260–278.
- Malhotra SK. 1961. Chromosome number in Himalayan ferns. Res Bull Panjab University, Sci Chandigarh. 12:132–164.
- Manickam VS. 1984. Cytology of thirty species of ferns from the Palni Hills (South India). Cytologia. 49:49–59.
- Manickam VS, Irudayaraj V. 1988. Cytology of ferns of the Western Ghats, South India. New Delhi: Today and Tomorrow’s Printers and Publishers; p. 81.
- Manickam VS, Irudayaraj V. 1989. Corrections to the cytology of ferns of the Western Ghats. Indian Fern J. 6:131–132.
- Manickam VS, Irudayaraj V. 1990a. Diplazium cognatum (Hieron.) Sledge - A new record from India. Indian Fern J. 7:54–57.
- Manickam VS, Irudayaraj V. 1990b. Thelypteridaceae of the Western Ghats, South India. Indian Fern J. 7:100–117.
- Manickam VS, Irudayaraj V. 1992. Pteridophyte flora of the Western Ghats - South India. New Delhi: B I Publications India Pvt Ltd; p. 1–653.
- Manickam VS, Irudayaraj V, Rajkumar SD. 1998. Studies on intraspecific variations in South India ferns-VI tripinnate form of Angiopteris evecta (Forst.) Hoffma. J Econ Taxon Bot. 22:139–144.
- Manton I. 1950. Problems of cytology and evolution in the Pteridophyta. Cambridge: Cambridge University Press; p. 316. doi:10.5962/bhl.title.4667
- Manton I. 1953. The cytological evolution of the fern flora of Ceylon. Evolution. 7:174–185.
- Mehra PN, Bir SS. 1957. Cytology of some Indian species of the Asplenium L. Curr Sci. 26:151–152.
- Mehra PN, Bir SS. 1958. Cytology of some Blechnoid ferns together with the note on the affinities of Stenochlaena palustris. Proceedings of the National Academy of Sciences, India Section B: Biological Sciences; p. 47–58.
- Mehra PN, Khanna KK. 1959. Cytology of some Himalayan ferns. J Genet. 56:1–14.
- Mehra PN, Khullar SP. 1980. Cytotaxonomy of West Himalayan ferns-II Gleicheniaceous series. Res Bull Panjab University, Sci Chandigarh. 25:135–178.
- Mehra PN, Loyal DS. 1965. Cytological investigations in the Himalayan Dryopteris Adanson. Caryologia. 18:461–498.
- Mehra PN, Palta H. 1971. Meiosis in sporophytes of different constitution of Pteris vittata L. produced In-Vitro. All India congress of cytology and genetics. Chandigarh: Panjab University; p. 97–98.
- Mehra PN, Singh G. 1956. Cytology of Indian Gleicheniaceae. Curr Sci. 25:168.
- Mehra PN, Singh G. 1957. Cytology of Hymenophyllaceae. J Genet. 55:379–393.
- Mehra PN, Verma SC. 1960. Cytotaxonomic observations on some West Himalayan pteridaceae. Caryologia. 13:619–650.
- Ninan CA. 1956. Studies on the cytology and phylogeny of the pteridophytes-I. Observations on the Marattiaceae. J Indian Bot Soc. 35:233–239.
- Otto SP, Whitton J. 2000. Polyploid incidence and evolution. Annu Rev. 34:401–437.
- Pal N. 1962. Studies on cytology of two species of Phymatodes. Proceeding 49th Indian Science Congress Association Part-III. Session 6 Botany, Abstract; pp. 328.
- Pal S. 1961. Chromosome number in some genera of Polypodiaceae. Sci Cult. 27:499–501.
- Pal S, Pal N. 1961. Studies on the cytology of two species of Phymatodes. Cytology. 26:460–467.
- Panigrahi G, Patnaik SN. 1962. Cytotaxonomic studies on Aglaomorpha coronans (Wall) Copel. Bull Natl Inst Sci India. 19:54–58.
- Punetha N. 1989. Cytological observations on ferns of Kumaon (North West Himalaya). Plant science research in India. New Delhi (India): Today and Tomorrow’s Printers and Publishers; p. 459–465.
- Punetha N, Sen A. 1989. Cytological observations on some species of Pteris from Kumaon (West Himalaya). Proceedings of the Indian National Science Academy (Plant Science); p. 131–134.
- Rajagopal PK, Gopalakrishna Bhat K. 2016. Pteridophytes of Karnataka State, India. Hemalatha Rajagopal,Vinayaka Prakashana, Udupi, Karnataka. India; p. 245.
- Rajkumar SD. 2001. IOPB chromosome data 17. Newsl, Int Organ Plant Biosyst. 33:25–26.
- Roy RP, Pandey SN. 1962. Cytotaxonomic studies of the fern flora of Parasnath Hills. Proceeding of the 49th Indian Science Congress; p. 333–334.
- Roy RP, Singh JB. 1973. Cytology and ecological notes on the ferns of Pachmarhi. Plant Sci. 5:1–16.
- Roy RP, Singh JB. 1975. A note on the chromosome numbers in some ferns from Pachmarhi Hills, Central India. Sci Cult. 41:181–183.
- Roy RP, Sinha BMB. 1961. Meiotic studies in the genus Adiantum. Caryologia. 14:413–428.
- Roy RP, Sinha BMB, Pandey SN. 1969. Cytotaxonomic studies in some epiphytic ferns of Parasnath hills. J Cytol Genet. 4:97–104.
- Roy RP, Sinha BMB, Sakya AR. 1971. Cytology of some ferns of Kathmandu Valley. British Fern Gazette. 10:193–199.
- Roy, Sakaya. 1963. Primo supplemento alle tavole chromosomiche delle Pteridophyta di Alberto Chiarugi. Caryologia. 16:237–335.
- Sahaya Sathish S, Vijayakanth P. 2015. Chromosome study on the fern species Leptochilus decurrens Blume (Polypodiaceae) of Kolli hills, Eastern Ghats, Tamil Nadu, India. Int J Res Eng Biosci. 3:7–13.
- Sahaya Sathish S, Vijayakanth P. 2016. New additions of fern flora to Kolli hills, Eastern Ghats, Tamilnadu, India. Indian J Plant Sci. 5:56–64.
- Singh VP, Roy SK. 1988. Cytology of forty four species from Sikkim, Himalaya. Indian Fern J. 5:162–169.
- Soltis DE, Soltis PS. 1999. Polyploidy: recurrent formation and genome evolution. Trends Ecol Evol (TREE). 14:348–352.
- Soltis DE, Soltis PS, Tate JA. 2003. Advances in the study of polyploidy since Plant speciation. New Phytol. 161:173–191.
- Srivastava RB. 1985. Ferns of the Indo-Nepal border. Proceedings of the Royal Society of Edinburgh. Section B. Biology; p. 471–472.
- Srivastava RB, Pandey SN. 1983. Cytotaxonomical investigation in the genus Pteris from Indo Nepal border region. Proceeding 70th Indian Science Congress; p. 37.
- Vasudeva SM, Bir SS. 1977. Cytological studies on ferns of Kodaikanal (South India). Symposium on recent research in Plant Science. Patiala: Punjabi University. Abstract; p. 16–17.
- Vasudeva SM, Bir SS. 1983. Chromosome numbers and evolutionary status of ferns and fern allies of Pachmarhi Hills (Central India). New Delhi (India): Today and Tomorrow’s Printers and Publishers; p. 66.
- Verma AK. 1973. Effect of X - radiation on morphology and chromosome parting in Pteris longifolia L. Proceeding of the 60th Indian Science Congress; p. 325.
- Verma SC. 1961. Chromosome numbers in Himalayan ferns. Res Bull Panjab Univ Sci Chandigarh. 12:139–164.
- Verma SC, Golaknath M. 1967. IOPB chromosome number reports X. Taxon. 16:146–157.
- Verma SC, Khullar SP. 1965. Cytotaxonomy and Cytogenetics of Onychium contiguum Complex in W. Himalayas. Caryologia. 18:555–566.
- Verma SC, Loyal DS. 1960a. Chromosome counts in some ferns from Nainital. Curr Sci. 29:69–70.
- Verma SC, Loyal DS. 1960b. Colchi - autotetraploidy in Adiantum capillus-veneris. Nature (London). 188:1210–1211.
- Vijayakanth P, Sahaya Sathish S. 2016. A new cytotype of Asplenium decrescens from Kolli Hills, Tamil Nadu. J Cytol Genet. 17:69–71.
- Vijayakanth P, Sahaya Sathish S. 2017. Pyrrosia porosa (C. Presl) Hovenkamp - a new diploid cytotype of South India from Kolli Hills of Eastern Ghats, Tamil Nadu, India. Int J Plant Biol Res. 5:1057–1058.