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Many plants are the hosts and are seriousluy damaged by the parasitic plants of Cuscuta and Cassytha. The distribution and their hosts of each species of these two genera in Taiwan were investigated. Special attention was paid to the ecological attribtutes and taxonomic characteristics of these parasitic plants. During the research period from July 1988 to April 1990, four taxa of Cuscuta and one species of Cassytha were found. They are Cuscuta australis R. Br, C. chinensis Lam., C. japonica Choisy var. formosana (Hay.) Yunker, C. japonica Choisy var. japonica, and Cassytha filiformis L. Among them, Cuscuta australis and C. chinensis were very similar in appearance and the two varieties of Cuscuta japonica are also similar. Flower characters are the critical differences between these two taxa pairs. These parasitic plants mostly grow at the sunny sites and are not selective for the hosts. The host plants include ferns, gymnosperms, dicotyledons, and monocotyledons. Each species may show self-parasitism and some taxa could possess the phenomenon of hyperparasitism. The younger tissues of one parasitic plants, with a stronger capicity in cell division, may produce a haustorium to invade the more mature and older stem of another parasitic plant which becomes the host. From anatomical observation, the vessels of haustorium are contacted to that of host and obtain water and minerals. However, the filiform cells at the apex of haustorium can take the nutrients from the host. Based on electrophoresis, the banding patterns of peroxidase isozymes of the parasitic plants were influenced by the hosts.
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