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The anatomical comparative study of petiole and pinnule cross-sections of nine species from Plagiogyria was performed using light microscopy for the first time. The results showed that the epidermis, the basic tissue and middle column of middle petiole transection and epidermis, mesophyll and main vein of the vegetative leaf pinnule of nine species of Plagiogyria were similar, for example, the epidermis of the transverse section of the middle petiole was not covered with hair or squamas, the epidermis was round in shape with thick-walled tissue, and the central cylinder was a amphicribral vascular bundle; the stomatas of trophyll pinnule transection were only distributed in the lower epidermis, the shape of epidermal cells was flat, and the type of the main vein belongs to the peripheral vascular bundle, which supports for the viewpoint that Plagiogyria was a natural taxonomy. In the evolution of the system, Plagiogyria had a certain relationship with the Alsophila spinulosa and both of them had similar characteristics and also showed certain differences. However, the petiole central transverse section of these nine species of Plagiogyria were trapezoidal, oval or triangular. The shape of the vascular bundle including “U” shape, “V” shape or triangle. The number of vascular bundles in the central transverse section of the petiole was one or three. The arrangement of xylem in vascular bundles including Chinese character “Eight” shape, “U” shape or “-” shape; The underside protuberances of the pinnule main veins were curved, triangular or trapezoidal. The xylem of the petiole had two forms: typical hippocampus and atypical hippocampus. The typical hippocampus was characterized by obvious hook state at both ends of the xylem. The atypical hippocampus was characterized by no obvious hook state at the two ends of xylem or one of the xylems had no hook at one end. These morphological anatomical features are stable and cluster specific, which provides a new reference for taxonomy and systematic studies of Plagiogyria. Finally, a key to the Plagiogyria species is given based on the anatomical characteristics of the transverse section of petiole and pinnule. [ABSTRACT FROM AUTHOR]

The chromosome numbers and reproductive biology of eight species from fern genus Plagiogyria (Plagiogyriaceae) from China were investigated, finding seven of the eight species ( P. adnate , P. assurgens , P. euphlebia , P. glauca , P. japonica , P. pycnophylla , and P. stenoptera ) had chromosomal complements of n  = 66 (66II), while P. falcata had a chromosomal complement of n  = 62 (31II + 31I). The chromosome numbers of three species— P. assurgens , P. falcata , and P. pycnophylla —are here reported for the first time, while other assayed species revealed new cytotypes. Based on observations of homologous chromosome pairing in diakinesis stage meiosis I of spore mother cells, P. falcata is an agamospermous triploid with 64 haploid spores per sporangium. The remaining species are sexual diploids. Three basic chromosome numbers (i.e., x  = 62, 65, 66) are found in Plagiogyria . The distribution of species with different basic chromosome numbers indicates the basic chromosome number x  = 66 was plesiomorphic, while x  = 62 and x  = 65 are apomorphic, indicating aneuploidy events have occurred in this genus and showing an evolutionary trend of decreasing chromosome numbers. The distribution of the sexual diploid and tetraploid species and agamospermous triploid species confirmed the origin of this genus to be southwest China, with apparent diffusion into northeast Asia (e.g., Taiwan) and Japan. However, a few species appear to have originated in America. [ABSTRACT FROM AUTHOR]