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Polyploidization plays an important role in generating the current high diversity of plants. Studies of the distributional patterns of diploid and derivative polyploid races have provided important insights into the evolutionary process and cryptic speciation by polyploidization within and between closely related taxa defined on the basis of their morphology. Allium thunbergii and A. sacculiferum, occurring throughout eastern Russia, eastern China, Korea, and Japan, are examples of closely related species with unsolved taxonomic relationships. A total of 97 and 65 individuals from 26 and 13 populations of A. thunbergii (including var. thunbergii, var. deltoids, and var. teretifolium) and A. sacculiferum, respectively, were studied to determine their ploidy. The geographic structure and habitat differentiation of the cytotypes were also analyzed. The main cytotype of A. thunbergii was diploid (92.3% in total; the rest were tetraploids). In contrast, the majority of A. sacculiferum plants were tetraploids (69.2% of the total; the rest were diploids). No populations of the studied taxa harbored both cytotypes. Allium thunbergii was more often found at higher elevations than A. sacculiferum, and it tended to occur more frequently on rocky slopes and below forests in mountainous areas. On the other hand, A. sacculiferum occurred at forest margins and in lowland pastures. The cytotypes differed with respect to the elevation; diploids were found more frequently at higher elevations than tetraploids. The results of this study and additional biosystematics data indicate that the morphological characteristics of A. thunbergii and A. sacculiferum may be influenced by polyploidization and by their adaptation to various habitat conditions and that A. thunbergii and A. sacculiferum do not clearly fulfill the requirements of any species concept. Consequently, we propose that A. sacculiferum be considered as an additional synonym of A. thunbergii. Additionally, Allium thunbergii var. deltoides is unified into A. thunbergii var. thunbergii.

Here we report a previously unrecorded species of Korean Myriophyllum L. (Haloragaceae). Thistaxon, M. oguraense Miki has been regarded as a Japanese endemic for some 60 years. Myriophyllum oguraenseand its closely related M. verticillatum L. share the characteristic of having pectinate emergent leaves that aresimilar in shape to, but much smaller than, the submerged leaves. However, the primary characteristic that dif-ferentiates these taxa is the turion shape (club shaped in M. verticillatum and linear in M. oguraense). The com-mon name, ‘Gin-dong-a-mul-su-sae-mi’ was also newly given considering its characteristic turion shape.Photographs and a key to Korean Myriophyllum species are provided in addition to complete descriptionsincluding information on nomenclatural types, distributions and specimens examined. Keywords: Haloragaceae, Myriophyllum oguraense, new record, Korea 적요: 물수세미속(개미탑과) 1분류군을 국내미기록종으로 보고한다. 이 분류군은 지금까지일본에만 분포하는 것으로 알려졌던 Myriophyllum oguraense Miki로서, 근연종인 물수세미(M. verticillatum L.)와 같이 공기중에서 발달된 잎이 빗살모양으로 갈라져 있으나 물 속에 잠겨있는 잎의 크기가 훨씬 작다. 무엇보다 동아가곤봉 모양으로 발달하는 물수세미에 비해 얇고 가느다란 선모양의 동아를 지님으로서 뚜렷이 구분된다. 새로운 국명 역시 이러한 동아의 특징을 고려해 ‘긴동아물수세미’로 신칭하였다. 한국산 물수세미속 분류군의검색키와 더불어 긴동아물수세미에 대한 생육지사진, 형태적 특징, 기준표본 정보, 국내 분포현황 및 관찰표본 목록을 제시하였다.