Studies on Vicia villosa Roth., with Special Reference to the Fertilization and Seed Production (Preliminary)

Abstract

Hairy vetch is one of the best winter legumes as green manure or as cover crop, especially for the dune or sandy field in the snowy Hokuriku district. However, the high cost of seed has been the greatest handicap to its more extended use compared with the other crops. In the past, before the war, large quantities of hairy vetch seed have been imported from Korea, and a little was produced in the Sado Island, Japan. But in recent, years, after the war, the home production of the seed has become of interest. In more recent years, however, it has been observed that seed production is almost impossible at several experimental farms in Japan. Therefore, a study was performed by the authors for the purpose of tracing the difficulty of seed production. In the present paper, the authors gave accounts first, on morphology of its flower and on the relation between its fertilization and flowering, and secondly on the relations between fertilization or seed formation and some environmental factors for cultivation, and also on insect's visitation during its flowering season. The results are summarized as follows: 1) Hairy vetch is a proterogynic plant, but the gynoecium and the antheridia preserve their ability of fertilization when the plant is isolated from insects. 2) the individual plant has about 2000 flower-clusters in a desirable conditions, and the floret number averages about 30 per flower-cluster, while the podding florets among them are less than one, and the number of full ripened grains averages 2 or 3 per pod. 3) In the past, it has been believed that the seed growing in the hairy vech plant is influenced by climate, especially, by high temperature and humidity during its flowering season. And the reasoning to attribute its sterility to over moisture, has been confirmed by the Sado comparison of the precipitation and the duration of sun-shine in Korea (Saishu-Island), and other districts in Japan. Moreover, it has been indicated that the Hokuriku district resembles to Korea (Saishu-Island) in the climatic conditions during the flowering season of hairy vech. 4) In general, the early flowers or those which have bloomed during a long spell of fine weather are fertile in high percentage, but the late or those in rainy weather are low. However, this relation somewhat differs according to the degree of thickness of the plant growth. 5) when the plant grows in a suitable condition, viz. being thinly seeded or supported with a fine crop, the fertilization percentage parallels to the number of blooming flowers in each stage of flowering. And the climatic conditions affect a little the fertilization. 6) When pollination is performed by hands or by the useful bumble-bees, the fertilization percentage is high in the fine weather, but it is very low or the flowers become sterile perfectly in the rainy weather. 7) it is not clear that the high temperature exerts a bad influence upon the fertilization of hairy vech during the flowering season in Hokuriku district. 8) the shaking of the plant body by sind or by hand has no effect on fertilization of hairy vech. 9) hairy vech is a close or self fertilizing plant, but the fertilization is impossible when the plant is isolated from insects in wire cage, notwithstanding the stigma being covered with pollen grains at the flowering time. This is an interesting problem and the fact that the insect's service in this case differs from that ordinarily found in the "insect-pollinated flower or entomophilae"is a noteworthy phenomenon when considered botanically. 10) The length of calcar of hairy vetch is longer than that of red clover, and the length is 11-14mm. [the rest omitted]