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Turczaninowia 21 (3): 5-11 (2018) DOI: 10.14258/turczaninowia.21.3.1 http://turczaninowia.asu.ru
ISSN 1560-7259 (print edition)
TURCZANINOWIA
ISSN 1560-7267 (online edition)
УДК 582.394.7:581.4(59)
Spore morphology of Taenitis, Syngramma and Austrogramme species (Pteridoideae, Pteridaceae) from South-Eastern Asia
A. V. Vaganov1, I. I. Gureyeva2, A. I. Shmakov1, A. A. Kuznetsov2, R. S. Romanets2
1 South-Siberian Botanical Garden, Altai State University, pr. Lenina, 61, Barnaul, 656049, Russia.
E-mail: vaganov_vav@mail.ru
2 Tomsk State University, pr. Lenina, 36, Tomsk, 634050, Russia. E-mail: gureyeva@yandex.ru
Keywords. Austrogramme, Pteridaceae, Pteridoideae, scanning electronic microscopy (SEM), spore morphology,
Syngramma, Taenitis.
Summary. A comparative study of spores of seven species. Taenitis blechnoides (Willd.) Sw., T. hookeri (C. Chr.) Holttum, T. pinnata (J. Sm.) Holttum, Syngramma alismifolia (Presl) J. Sm., S. lobbiana (Hook.) J. Sm., S. quinata (Hook.) Carruth., and Austrogramme boerlageana (Alderw.) Hennipman from South-Eastern Asia was performed using the method of scanning electronic microscopy (SEM). Spores of all examined species are trilete, tetrahedral or tet-rahedral-globose. Spores of Syngramma and Austrogramme are very similar to each other in shape and ornamentation. Ornamentation of both sides of spore is similar, verrucate (microverrucate), surface covered by rodlets and granulate deposits. Spores of Taenitis species with conspicuous cingulum (Taenitis blechnoides) or without it, ornamentation of both faces of spore could be tuberculate or baculate. Spores of Taenitis hookeri and Taenitis pinnata demonstrate tendency to forming of comissural ridges. Spore size of all studied species is close. equatorial diameter of spores of Taenitis species varies within 24-43 ^m, those for Syngramma species is 29.8-35.5 ^m, spores of Austrogramme boerlageana are smallest, their equatorial diameter varies within 22.5-29.4 ^m.
Морфология спор ТавпШБ, Зущгатта и Austrogramme (Pteridoideae, Pteridaceae) из Юго-Восточной Азии
А. В. Ваганов1, И. И. Гуреева2, А. И. Шмаков1, А. А. Кузнецов2, Р. С. Романец2
1 Южно-Сибирский ботанический сад, Алтайский государственный университет, пр. Ленина, 61,
г. Барнаул, 656049, Россия
2 Томский государственный университет, пр. Ленина, 36, г. Томск, 634050, Россия
Ключевые слова: морфология спор, сканирующая электронная микроскопия (СЭМ), Austrogramme, Pteridaceae, Pteridoideae, Syngramma, Taenitis.
Аннотация. Методом сканирующей электронной микроскопии (СЭМ) проведено сравнительное исследование спор Taenitis blechnoides (Willd.) Sw., T. hookeri (C. Chr.) Holttum, T. pinnata (J. Sm.) Holttum, Syngramma alismifolia (Presl) J. Sm., S. lobbiana (Hook.) J. Sm., S. quinata (Hook.) Carruth. и Austrogramme boerlageana (Alderw.) Hennipman из Юго-Восточной Азии. Споры всех исследованных видов трехлучевые, тетраэдрические или округло-тетраэдрические. Споры Syngramma и Austrogramme сходны по форме и характеру поверхности. Скульптура обеих сторон спор бородавчатая (до мелко-бородавчатой), с гранулами на поверхности. Споры Taenitis с хорошо выраженной экваториальной складкой (Taenitis blechnoides) или без нее, скульптура обеих сторон спор бугорчатая. Споры Taenitis hookeri и Taenitis pinnata проявляют тенденцию к формированию комиссуральных складок путем слияния бугорков, расположенных вдоль лучей лезуры. Размеры спор всех исследованных видов близки: экваториальный диаметр спор видов Taenitis варьирует в пределах 24-43 мкм, у видов Syngramma - 29,8-35,5 мкм, споры Austrogramme boerlageana самые мелкие, их экваториальный диаметр варьирует в пределах 22,5-29,4 мкм.
Поступило в редакцию 19.06.2018 Принято к публикации 31.07.2018
Submitted 19.06.2018 Accepted 31.07.2018
Taenitis Willd. ex Schkuhr, Syngramma J. Sm. and Austrogramme E. Fourn. are paleotropical genera, which belong to taenitidoid ferns, and are classified as the members of Taenitideae tribe and Taenitidoideae R. M. Tryon subfamily of the large and diverse Pteridaceae E. D. M. Kirchn. family, or considered as distinct Taenitidaceae (C. Presl) Pic. Serm. family (Pichi Sermolli, 1977; Tryon, 1986; Tryon et al., 1990; Sanchez-Baracaldo, 2004; Smith et al., 2006). M. J. M. Christenhusz et al. (2011) and L. Zhang et al. (2015, 2017) classify these three genera to subfamily Pteridoideae C. Chr. ex Crabbe, Jermy et Mickel. E. Schuettpelz et al. (2007) considered them as the members of the pteridoid ferns within the Pteridaceae. However, R. E. Holttum, who studied the relationship between Taenitis and Syngramma, wrote "feel sure that Syngramma and Taenitis both belong to the Gymnogrammeoid ferns" (Holttum, 1975, p. 341).
R. E. Holttum (1975) recognized in Syngramma 17 species, including 6 species of Craspedodictium, that he transferred to this genus. Austrogramme includes five species (Hennipman, 1975). These species occur in South-Eastern Asia and Oceania on the Pacific islands and islands of Indian Ocean (Philippines, Borneo, Fiji, Malaya, New Guinea, Java, Sumatra, New Caledonia). Taenitis includes about 15 species occurring in Old World from India and Ceylon northward to China (Hainan Island), throughout Malesia eastward to New Guinea, southward to northern Australia (Queensland), and to Fiji in the Pacific (Holttum, 1975; Tryon, Lugardon, 1991).
Recently molecular-phylogenetic studies based on plastid DNA involving discussed genera were conducted. One of them carried out by P. Sanchez-Baracaldo (2004) based on sequences of rps4 region of plastid DNA demonstrates the close relationship between these three Old World genera, which form clade with Taenitis being basal to Syngramma and Austrogramme. Two species of Taenitis (T. blechnoides (Willd.) Sw. and T. interrupta Hook. et Grev.) were included in the molecular analysis of Taenitidoideae (9 species) based on four singlegene datasets (atpA, chlL, rbcL, and rps4). The combined analysis shows the relationship between Austrogramme, Syngramma, and Taenitis, and places a new genus Tryonia sister to them (collectively) (Cochran et al., 2014). Five species of Pteridoideae including two species (with seven patterns) of Taenitis, two species of Austrogramme, and single species of Syngramma were involved in the molecular-phylogenetic study based on six plastid
regions (the atpA gene, the atpB gene, the rbcL gene, the rps4 gene and rps4-trnS intergenic spacer, the trnL intron, and the trnL-F intergenic spacer). The monophyly of the Old World Austrogramme -Syngramma - Taenitis clade was confirmed; the sister genera Austrogramme and Syngramma are together sister to Taenitis (Zang et al., 2015, 2017). Thus, all molecular-phylogenetic study confirmed the close relationship between three paleotropic genera - Austrogramme, Syngramma, and Taenitis. In all published phylograms Austrogramme and Syngramma form a clade sister to Taenitis (Sanchez-Baracaldo, 2004; Cochran et al., 2014; Zang et al., 2015, 2017).
Spore morphology of Pteridaceae species are discussed in the numerous works (Hennipman, 1975; Tryon, Lugardon, 1991; Kuznetsov et al., 2014; Palacios-Rios et al., 2016; Vaganov, 2016). Some authors emphasize the diagnostic value of spore ornamentation in different ferns at the specific level, which can help clarify infrageneric taxonomy (Passarelli et al., 2010; Wei, Dong, 2012; Palacios-Rios et al., 2016). For different fern genera on various examples the congruence of morphological characteristics of spores with the result of molecular-phylogenetic analyzes has been shown (Gureyeva, Kuznetsov, 2015; Vaganov et al., 2017a, b, c).
Spores of some species of Taenitis, Syngramma and Austrogramme with using of scanning electron microscopy were examined by A. Tryon and B. Lugardon (1991): Taenitis blechnoides, T. cordata (Gaudich.) Holttum, T. hookeri (C. Chr.) Holttum, T. interrupta, T. luzonica (Alderw.) Holttum, T. requiniana (Gaud.) Copel., Syngramma wallichii (Hook.) Bedd., S. cartilagidens (Bak.) Diels, S. alismifolia (Presl) J. Sm., Austrogramme decipiens (Mett.) Hennipman, and A. boerlageana (Alderw.) Hennipman. E. Hennipman (1975) studied spores of four species of Austrogramme (A. asplenioides (Holttum) Hennipman, A. boerlageana, A. decipiens, and A. francii (Rosenst.) Hennipman), two species of Syngramma (S. quinata (Hook.) Carruth., S. luzonica Alderw.), and ten species of Taenitis (T. blechnoides, T. cordata, T. flabelivenis, T. hosei (Baker) Holttum, T. interrupta, T. lanceolata Kaulf., T. marginata Holttum, T. requiniana (Gaud.) Copel., T. pinnata (J. Sm.) Holttum, and T. vittarioides Holttum). E. Hennipman (1975) allied Syngramma with Austrogramme and distinguished them from Taenitis on the basis of spore morphology. A. Tryon and B. Lugardon (1991) supported this disposition. It should be noted that Syngramma luzonica (in Hennipman, 1975) was considered by R. Tryon and B. Lugardon as Taenitis luzonica.
The aim of this study is to provide details of spore ornamentation and evaluation of its diagnostic value for Taenitis, Syngramma, and Austrogramme species using scanning electron microscopy (SEM).
Materials and methods
Spores were obtained from herbarium specimens of seven species: Taenitis blechnoides (Hainan, China), T. hookeri (New Guinea), T. pinnata (J. Sm.) Holttum (Papua New Guinea), Syngramma alismi-folia, S. lobbiana (Hook.) J. Sm. (both - Borneo), S. quinata (Hook.) Carruth. (Sulawesi), and Austrogramme boerlageana (Ambon) stored in PE (Herbarium of Institute of Botany, Chinese Academy of Sciences, Beijing). Only mature spores were used for SEM examination. Spores were mounted on SEM stubs using double-sided carbon adhesive tape and coated with gold in the "Quorum Q150R S" sputter-coater. Stubs were viewed and photographed with the scanning electronion microscope "MiniSEM SNE-4500M" in the Laboratory of Structural and Molecular Analysis of Plants (Tomsk State University, Tomsk, Russia). Spore surface was scanned in a high vacuum at voltage of 20 kV, through 2000* and 15000* of magnification.
Equatorial diameter (distal or proximal position of spore), polar axis (equatorial position of spore),
length and width of laesura arms (proximal position of spore) were measured for 10-20 spores of each species. All measurements were made on SEM-micrographs of spores using the computer program "Image J". For terminology of sculpture elements, we primarily followed A. Tryon, B. Lugar-don (1991), shape of the distal and proximal sides was described using terms by B. K. Nayar, S. Devi (1966). Spelling of the names of taxa and authors is given according to "The International Plant Name Index" (http://www.ipni.org).
Results and discussion
Spores of all examined species of Taenitis, Syngramma and Austrogramme are tetrahedral or tet-rahedral-globose, trilete. In equatorial position the distal side is convex or hemispherical, proximal side is plane, convex or conical. In polar position spores are triangular, roundish-triangular or nearly roundish with straight or concave sides and rounded corners. Spores with cingulum (equatorial flange, equatorial wing) or without it. Ornamentation of both face of spore could be tuberculate, baculate or ver-rucate, spore surface covered by rodlets and granulate deposits. The main morphometrical characteristics of spores are shown in the Table.
Table
Spore size of Austrogramme, Syngramma and Taenitis species, mean (min-max)
Bug Equatorial diameter (Mm) Polar axis (Mm) Laesura length (Mm) Laesura width (Mm)
Austrogramme boerlageana 26.0 (22.5-29.4) - 13.2 (11.8-14.4) 0.8 (0.6-1.1)
Syngramma alismifolia 31.9 (29.8-33.4) 24.8 (24.2-25.3) 7.6 (6.9-8.3) 0.7 (0.4-0.9)
S. quinata 28.2 (25.4-29.8) 23.4 (21.2-25.5) 8.7 (7.5-10.2) 0.4 (0.2-0.7)
S. lobbiana 33.9 (31.2-35.5) 24.3 (23.3-25.0) 10.5 (8.6-12.6) 0.7 (0.4-1.0)
Taenitis blechnoides 40.4 (39.0-42.7) 26.2 (25.5-27.7) 14.7 (13.8-16.0) 1.0 (0.8-1.1)
T. hookeri 31.0 (30.2-32.4) 24.4 (23.5-25.6) 3.1 (2.1-4.6) 0.6 (0.5-0.7)
T. pinnata 26.5 (24.0-29.0) 28.4 (27.5-29.2) 10.3 (10.1-10.5) 0.9 (0.8-1.0)
1. Syngramma alismifolia (Presl) J. Sm. (Fig. 1A; Table). Spores are tetrahedral, roundish-triangular in polar position, with straight or slightly concave sides and wide-rounded corners. In equatorial position distal side is hemispherical, proximal side is convex. Proximal and distal sides are densely ver-rucate, with low, small, discrete or fused verrucae, 0.2-0.9 pm in width, covered by sparse rodlets. Laesura arms are straight, reaching the spore corners. Proximal side of spore is depressed between laesura arms.
Investigated specimen: Borneo E., 1953. № 01715222 (PE).
2. S. lobbiana (Hook.) J. Sm. (Fig. 1B, C; Table). Spores are tetrahedral-globose, roundish-triangular in polar position, with straight or slightly concave sides and wide-rounded corners. In equatorial position the distal side is hemispherical, proximal side is convex. Proximal and distal sides are irregular ver-rucate, surface covered by rodlets. Laesura arms are straight, reaching the spore corners. Spore may be depressed on the distal side.
Investigated specimen: № 933 Native collector. Plants of Sarawak, Borneo. Collected through the Museum for the Bureau of Science, Manila, P.I. № 01715231 (PE).
3. S. quinata (Hook.) Carruth. (Fig. 1D-F; Table). Spores are tetrahedral, roundish-triangular in polar position, with convex sides and wide-rounded corners. In equatorial position the distal side is hemispherical, proximal side is plane. Proximal and distal sides are verrucate, with small hemispherical verrucae 0.3-0.9 ^m in diam., surface is covered by granulate deposits, especially on the distal side. Laesura arms are straight, reaching the spore corners. Spore may be depressed on the distal side.
Investigated specimens: № 6943. V. Guinen Ja-pen, № 01715087; Selebes, G. Kjellberg, 1939, 500 alt. № 01715234 (PE).
4. Austrogramme boerlageana (Alderw.) Hen-nipman (Fig. 1D-F; Table). Spores are tetrahedral-
globose, nearly roundish in polar position. In equatorial position the distal side is hemispherical, proximal side is conical. Proximal and distal sides are verrucate with tiny hemispherical verrucae 0.2-0.4 ^m in diam. (microverrucate), surface is covered by dense granulate deposits over verrucae on the both sides. Laesura arms are straight, reaching the spore corners. Proximal side of spore is slightly depressed between laesura arms.
Investigated specimen: Ambon 1939. № 01715225 (PE).
5. Taenitis blechnoides (Fig. 2A-C; Table). Spores are triangular with concave sides and rounded corners in polar position. In equatorial position the distal side is hemispherical, proximal side is
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Fig. 1. SEM-micrographs of spores of Syngramma and Austrogramme: A - Syngramma alismifolia (Presl) J. Sm.; B-C - S. lobbiana (Hook.) J. Sm.; D-F - S. quinata (Hook.) Carruth.; G-I - Austrogramme boerlageana (Alderw.) Hennipman; A, F, H - proximal side; D, G - distal side; B, E, I - spore in equatorial-proximal position; C - close-up fragment of proximal side of spore and laesura arms. A-B, D-I - 20^m; C - 5 ^m.
plane. Spores are cingulate, cingulum is conspicuous, especially in proximal view, variable in width, narrower at the corners. Laesura arms are straight, without comissural thickness. Proximal and distal sides are densely tuberculate, with low, small, discrete tubercles 0.2-0.5 pm in diameter on proximal side and 1.8-2.5 * 1.1-1.4 pm on distal one. Tubercles are with fascicled rodlets on the top.
Investigated specimen: Hainan. Shan Mong, Fairly common. dry, gentle slope, clay, thicket, erect. Coll. Lau S.K., Det. ED. Merrill, Dec. 23, 1933. № 2935 (LE).
6. T. hookeri (Fig. 2D-F; Table). Spores in proximal-polar position are roundish-triangular, with concave sides and rounded corners; in distal-
polar position nearly roundish with convex sides. In equatorial view the distal side is hemispherical and proximal side is convex. Cingulum is absent. Laesura arms are straight, submerged for most of their length, with fused tubercles forming irregular ridges 1.0-2.2 pm width situated on both sides of each laesura arm parallel to it. Spore surface between submerged part of laesura arms is with small sparse verrucae. Both proximal and distal face are densely tuberculate, with elongate discrete tubercles (bacules), 1.8-2.9 * 0.9-1.8 pm in size. Tubercles with rodlets on the top.
Investigated specimen: Plants of Netherlands New Guinea. 1200 m alt. Feb. 1939. № 01715229 (PE).
Fig. 2. SEM-micrographs of spores of Taenitis species: A-C - T. blechnoides (Willd.) Sw.; D-F - T. hookeri (C. Chr.) Holttum; G-I - T. pinnata (J. Sm.) Holttum; A, D, G - proximal side; B, E, H - distal side; C, F, I - close-up fragments of sculpture (C, F) and laesura arms (I). Scale bars: A, B, D, E, H - 20pm, C - 1 pm; F, I - 5 pm.
7. Taenitis pinnata (J. Sm.) Holtt. (Fig. 1G-I; Table). Spores in proximal-polar and distal-polar position are roundish-triangular, with straight or slightly concave sides and rounded corners. In equatorial view the distal side is subconical and proximal side is conical. Cingulum is absent. Laesura arms are straight, with fused tubercles forming irregular ridges 0.6-2.2 pm width situated on both sides of each laesura arm parallel to it. Proximal face is densely tuberculate with discrete tubercles, distal face is densely rugulate-tuberculate with tubercles fused in short rugulae, 1.6-3.1 * 0.7-1.2 pm in size. Tubercles with sparse rodlets on the top.
Investigated specimen: Plants of Papua (British New Guinea) Lake Daviumbu. Rain forest. August, 1936. № 01715232 (PE).
Spores of all examined species of Syngramma and Austrogramme are very similar to each other in shape and ornamentation and very different in these characteristics with spores of Taenitis species. Spores of species of the first two genera have the simple verrucate (microverrucate) ornamentation, whereas those of Taenitis species have a very clear tuberculate or baculate ornamentation on the distal side and tendency to forming of comissural ridges through the fusion of tubercles arranged in a row along the laesura arms. Comparison with published data on other species of Syngramma and Austrogramme shows that the spores of the different species of these genera are very similar or have insignificant differences in shape and ornamentation. Spores of Syngramma and Austrogramme species may be depressed on the distal side or between laesura arms; E. Hennipman (1975), A. Tryon and B. Lugardon (1991) indicated the same peculiarity for other species of these genera. E. Hennipman (1975) has concluded that properties of spores together with chromosome number indicate a relationship between Austrogramme and Syngramma.
Spores of three studied species of Taenitis are distinctive to each other. The main distinguished feature in Taenitis blechnoides spores is conspicuous cingulum. E. Hennipman (1975), A. Tryon and B. Lugardon (1991) also denoted presence of prominent cingulum (equatorial flange) in spores of T. blechnoides and its absence in T. hookeri. Ornamentation of spores of T. hookeri in compare with spores of other two species represents by elongate tubercles (bacules). Spores of two species - T. hookeri and T. pinnata demonstrate tendency to formation of comissural ridges through the fusion of tubercles arranged in a row along the laesura arms. In com-
pare with data by A. Tryon, B. Lugardon (1991), who mentioned fascicled rodlets on tubercles in Taenitis blechnoides and Taenitis hookeri spores we observed sparse (not dense) rodlets on the tubercles of the spores of all examined species. E. Hennipman (1975) and A. Tryon, B. Lugardon (1991) also indicated the significant differences in ornamentation of spores of Taenitis and Syngramma - Austrogramme. Judging by our study and the photos published by E. Hennipman (1975) and A. Tryon, B. Lugardon (1991), spores of the same species collected in different localities retain their characteristics.
The size (equatorial diameter) of spores of studied Taenitis species varies within 24-43 pm. Spores of T. blechnoides have the largest and T. pinnata -the shortest equatorial diameter. In the same time spores of T. pinnata are characterized by the largest polar axis, the cause of which is the shape of spore -subconical in distal and conical in proximal side. Due to submerged laesura, spores of T. hookeri have the shortest laesura arms: visible parts of laesura arms are 3.1 pm, whereas length of laesura arms in two other species is 10.3 and 14.7 pm in average. Spores of studied Syngramma species are similar to each other in size (equatorial diameter varies from 25.4 to 35.5 pm), spores of Austrogramme boerlag-eana are smaller 22.5-29.4 pm (Table). E. Hennipman (1975) indicated larger spore size for all studied genera: 45-70 pm for Taenitis, 40-50 pm for Syngramma, and 35-40 pm for Austrogramme. A. Tryon and B. Lugardon (1991) indicated the spore size for Taenitis and Syngramma species as 33-53 pm, for Austrogramme - 30-40 pm.
Similarity of spore morphology of Syngramma and Austrogramme species confirms close relationship between these genera revealed as a result of molecular-phylogenetic studies (Sanchez-Baracal-do, 2004; Cochran et al., 2014; Zhang et al., 2015, 2017). Differences of spore morphology of Taenitis species confirm topography of this genus as sister to Syngramma and Austrogramme (collectively) in the common clade (Syngramma - Austrogramme -Taenitis).
Acknowledgements
We are grateful to curators of the Herbarium of Institute of Botany, Chinese Academy of Sciences (PE, Beijing) and Botanical Institute of Russian Academy of Sciences (LE, Saint-Petersburg) for the possibility of obtaining of spores from the herbarium material. The study was supported by RFBR (project No. 16-04-00513) and by the Tomsk State University competitiveness improvement program.
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