日本産ヒルムシロ属植物の細胞学的研究

1. The plants which were used as materials in the present investigation are 26 species and 6 formae of Potamogeton.
2. The chromosomes numbers determined by the author are as folloes : Potamogeton orientalis (2n=26), P. sibiricus (2n=28), P. zosterifolium (2n=28), P. porsildiorum (2n=28), P. cristatus (2n=28), P. miduhikimo (2n=28), P. limosellifolius (2n=28), P. asiaticus (2n=28), P. Fauriei (2n=27), P. Kamogawaensis (2n=27), P. numasakianus (2n=28), P. Friyeri (2n=42), P. subsessiliofolius (2n=42), P. torquatus (2n=42), P. miyakezimaensis (2n=52), P. subfluitans (2n=52), P. teganumensis (2n=52), P. leptocephalus (2n=52), P. anguillanus (2n=52), P. Tepperi (2n=52), P. Francheii (2n=52), P. longipetiolatus (2n=52), P. alatus (2n=52), P. polygonifolius (2n=52), P. malainoides (2n=52), P. grameans (2n=52), P. morongii (2n=52), P. Tenuifolius (2n=52), P, filiformis (2n=78), P. vaginatus (2n=78), P. flabellatus (2n=78).
In the following 17 species the reports of other investigations are confirmed by the author: P. oxyphyllus (2n=26), P. panormitanus (2n=26), P. pusillus (2n=26), P. monoginus (2n=28), P. vaseyi (2n=28), P. apertus (2n=42), P. malianus (2n=52), P. dentatus (2n=52), P. nipponicus (2n=52), P. perfoliatus (2n=52), P. crispus (2n=52), P. praelongus (2n=52), P. Maackianus (2n=52), P. biwaensis (2n=52), P. distinctus (2n=52), P. natans (2n=52), and P. pectinatus (2n=78).
The karyotypes and meiosis in all these species were observed. Moreover, some interspeciecific hybrids were cytologically studied.
3. From the view point of phylogeny and cytology, the species of this genus studied can be classified into two groups : (a) the 7 chromosomic group, (b) the 13 chromosomic group.
The following species being to the 7 chromosomic group: P. monoginus, P. crispus, P. vaseyi and P. numasakianus are tetraploid (2n=28), while P. apertus and P. Friyeri are hexaploid (2n=42).
The following species belong to the 13 chromosomic group : P. oxyphyllus, P. panormitanus, P. pusillus and P. orientalis are 2n=26. while P. fluitanus, P. malaianus, P. dentatus, P. nipponicus, P. perfoliatus, P. crispus, P. praelongus, P. Maackianus, P. biwaensis, P. alpinus, P. anguillanus, P. distinctus and P. natans have 2n=52 chromosomes.
4. The following species are interspecific hybrids : P Fauriei. P. orientalis P. numasakianus, P. biwaensis, P. malainoides, P. anguillanus, and P. nipponicus. In these interspecific hybrids, the irregularities in the meiosis, such as the occurrence of univalents, lagging of some univalents in the anaphase, and formation of restitution nuclei and dwarf nuclei, ets. are found to a greater or less extent.