Taxonomic Studies of Cirsium (Asteraceae) in Japan XIII. Three New Species from Tohoku District, Northern Japan

摘要

Three new species of Cirsium are here described from Tohoku District, northern Japan. Cirsium horiianum is characterized by having nodding small capitula, larger lowermost cauline leaves at anthesis, deeply pinnate cauline leaves with sharp spines, narrowly cylindric involucres, strongly incurved involucral phyllaries without glandular bodies and the chromosome number 2n=34 and is an endemic of Oga Peninsula, Akita Prefecture. Cirsium uzenense is characterized by having nodding small capitula, larger lowermost cauline leaves at anthesis, shallowly pinnate cauline leaves with weak spines, narrowly cylindric involucres, broadly ovate involucral phyllaries with well developed glandular bodies and the chromosome number 2n=34 and is distributed in Ya-magata, Miyagi and Niigata Prefectures. Both C. horiianum and C. uzenense belong to Sect. Onotrophe (DC.) Cass. Subsect. Reflexae (Kitam.) Kadota (the C. kagamontanum complex). Cirsium ashinokuraense is characterized by the absence of basal leaves at anthesis, oblique to suberect capitula, cylindric involucres, recurved or patent involucral phyllaries without glandular bodies and the chromosome number 2n=68 and is also an endemic of Oga Peninsula, Akita Pref. A new subsection, subsect. Ogapeninsulae, is proposed for C. ashinokuraense. The subsect. Ogapeninsulae is a monotypic subsection.