紊蒿属一新种和对该属分类及演化的讨论

对新种多头紊蒿(Elachanthemum polycephalum Z.Y.Zhu et C.Z.Liang)的形态特征进行了描述，并从形态和生态特征、地理分布及其区系起源等方面探讨了紊蒿属(Elachanthemum Y.Ling et Y.R.Ling)的分类地位。结果表明：紊蒿属与百花蒿属(Stilpnolepis Krasch.)在形态上虽有相近之处，但花、果实和花粉等形态差异明显，因而不能并入百花蒿属，而应独立成属。该属起源于第三纪亚洲北部的古蒿类群(Pro-Artemisia L.)，是蒿类中较为原始的属，为古地中海东部残遗的旱生成分，也是现代亚洲中部荒漠(戈壁荒漠)的持有属；多头紊蒿新种的发现，使紊蒿属从单种属变成寡种(双种)属，表明荒漠植物区系的物种分化仍在进行。

A NEW SPECIES OF ELACHANTHEMUM AND DISCUSSION ON THE CLASSIFICATION AND EVOLUTION OF THE GENUS

A new species - Elachanthemum polycephalum Z. Y. Zhu et C. Z. Liang, - is de-scribed in detail and the problem of the classification position of Elachanthemum is discussed by mor-phological characteristics, ecological properties, geographical distribution, and flora origin. Morpho-logically, although Elachanthemum is similar to Stilpnolepis, there are obvious differences on the mor-ph and structure of flowers, achenes and pollen grains between two genera. Therefore, the Elachanthemum is an independent genus and can not be merged into Stilpnolepis. The genus is a primitive genus in the category of Artemisia, and it, perhaps, come from the Pro - Artemisia that distributed in the northem part of Asia in tertiary. It is a relict xerophytic element in the eastern part of Tethys, and is an endemic genus in the desert of Asia Media ( Gobi desert). The discovery of the new species in Elachanthemum manifest that the species differentiation are stili progressing in desert flora, and make the Elachanthemum from a monospecific genus to olig - specific one (2 species).