STUDIES ON THE GEOGRAPHICAL DISTRIBUTION OF THE WEEDS ON UPLAND FIELD IN JAPAN.

Abstract

(1) This investigation was carried out by the similar way as in the previous report dealing with the geogrophical distribution of the weeds on the paddy field in Japan. (2) The total number of kinds of weeds on the upland field which are distributed throughout the whole region of Japan except Hokkaido, amounted to 266 species of 50 families. Among them 61 species were recognized as the most noxious weed, 100 species as the moderately noxious and 150 species as the slightly noxious. These species of weeds were found to be widely destributed throughout Japan, but over 40 species of weeds other than these were regarded as the localized ones. (3) Hokkaido has considerably different kinds of weeds on the upland field from the other part of Japan; about 100 species of weeds which are distributed Honshu are not found in Hokkaido. On the other hand, some frigid plants which are not seen on the Main Land, grow even on the upland field in Hokkaido. (4) Most of weeds on the upland field are distributed throughout Japan, except Hokkaido, although among 266 species of weeds 24 are not seen in Tohoku, 28 in Hokuriku and 6 in southern region of Japan. (5) Among the weeds on the upland field, only a few species namely, Polygonum Reynoutria MAKINO, Achyranthes Fauriei LEV. et VNT, Allium nipponicum FRANCH et SAV., Pleioblastus spp. etc. are endemic to this country and the species other than these are common with the other parts of the world. (6) Number of spcies of the Japanese weeds in common with the following respective region are; China, about 220 species; Europe, 95; North America, 89; South eastern regions of Asia, 62; North Asia 30. etc.. It is known that about 80 species of the weeds on the upland field have naturalized in the recent part, and most of them are of European origion. In them are included a considerable number of the most troublesome weeds in Japan. (7) The number of weeds common to both the paddy field and upland field in Japan were 40 species belonging to 14 families. Among them, Echnochloa crusgalli BEAV., Alopecurus geniculatus L. and Cyperus Iria L. etc. were the most noxious.