02381nas a2200253   4500008004100000245013000041210006900171260001200240300001600252490000700268520155900275653001501834653001101849653001201860653002101872653001201893653002301905653001501928653002201943100001701965700001701982700001201999856011602011       1996                        eng d00aBiosystematic studies on the genus Isoetes (Isoetaceae) in Japan. II. Meiotic behavior and reproductive mode of each cytotype0 aBiosystematic studies on the genus Isoetes Isoetaceae in Japan I  c1996///  a1309 - 13220 v833 aMeiotic behaviors and reproductive modes of Japanese Isoetes were studied. The hexaploid (2n = 66) and the octaploid (2n = 88) of I. japonica consistently formed 33 and 44 bivalents, respectively, at diakinesis and/or metaphase I in both micro- and megaspore mother cells. The tetraploid (2n = 44) of I. sinensis formed 22 bivalents and its hexaploid made 33 bivalents in both types of spore mother cells. At diakinesis and/or metaphase I of microspore mother cells in I. asiatica with 2n = 22, 11 bivalents were detected. Because behaviors of meiosis in all cytotypes mentioned above were quite regular and plants yielded normal-appearing spores, they should reproduce sexually. Aneuploids of I. japonica with 2n = 87 formed 43 bivalents and one univalent, and I. sinensis with 2n = 65 formed 32 bivalents and one univalent in microspore mother cells. Meiosis of both cytotypes was almost regular and yielded microspores of normal appearance. In the heptaploid (2n = 77) of I. japonica, a configuration of 22 bivalents and 33 univalents was detected in micro- and megaspore mother cells, and various irregularities were observed throughout the meiotic divisions. Therefore, the genomic formula of the heptaploid is symbolized as AABBCDE, and the heptaploid is a sterile F 1 hybrid between the hexaploid (AABBCC) and the octaploid (AABBDDEE) of I. japonica. Since diploid and even-numbered polyploids regularly formed bivalents and odd-numbered ones displayed irregularities, allopolyploidy should act as a significant speciation mechanism in this genus.10aChromosome10aHybrid10aIsoetes10amegasporogenesis10ameiosis10amicrosporogene sis10apolyplo id10areproductive mode1 aTakamiya, M.1 aWatanabe, M.1 aOno, K.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0030475989&partnerID=40&md5=996182a1723b75d447e3a2137006f7bd01157nas a2200205   4500008004100000245009000041210006900131260001200200300001400212490000800226520047700234653001100711653001500722653002800737653001600765653001700781100001800798700001800816856011700834       2006                        eng d00aIsoetes x novae-angliae (Isoetaceae), an additional hybrid quillwort from New England0 aIsoetes x novaeangliae Isoetaceae an additional hybrid quillwort  c2006///  a228 - 2410 v1083 aIsoetes x novae-angliae D.F. Brunt. & D.M. Britton, hyb. nov., represents a sterile hybrid between the tetraploid aquatic pteridophytes I. riparia and I. tuckermanii. It is known only from North Easton, Massachusetts although it formerly likely occurred across the state as well as in Connecticut and southern New Hampshire. Determination of the distribution and nomenclature of this taxon also clarifies the status of a number of early 20th century taxonomic innovations.10aHybrid10aIsoetaceae10aIsoetes x novae-angliae10aNew England10aPteridophyte1 aBrunton, D.F.1 aBritton, D.M.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-33750506895&partnerID=40&md5=cfb8fb103c449613c66501a4a452c5a6