The discontinuous distribution of morphologically similar and presumably closely related plants between North America and eastern Asia is well known. Currently a flurry of research activity based on the employment of molecular methods is providing new evidence on relationships and times of divergence of some genera belonging to this phytogeographical pattern. With few exceptions, however, these recent studies seldom combine molecular techniques with rigorous examination of specimens and living plants using more traditional methods. Within the past 15 years or so, the herbaria in China, the country with the largest assemblage of these disjunct genera in Asia, have become increasingly more accessible. Many recent collections from China have been distributed through the exchange programs of several Chinese herbaria and from the results of collaborative field work by Chinese and foreign botanists. These specimens, both old and new, contain a wealth of morphological and distributional information for previously poorly represented taxa, and they can often provide supplementary information for even well known taxa. This paper reviews briefly the history of plants disjunctions between Asia and America, reviews the pattern of distribution of plants in Asia and suggests additional studies now possible because of the increased access to both preserved specimens in herbaria and living plants in the field.
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