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Floral Evolution in the Family Gramineae

H. T. Clifford
Evolution
Vol. 15, No. 4 (Dec., 1961), pp. 455-460
DOI: 10.2307/2406313
Stable URL: http://www.jstor.org/stable/2406313
Page Count: 6
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Floral Evolution in the Family Gramineae
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Abstract

It has been assumed that the Arundinaria-type flower is primitive in the family Gramineae. On the basis of this assumption the number of bilaterally symmetrical flowers that may be derived solely by reduction from this flower has been calculated and compared with the known number. Only about a quarter of the theoretically possible flowers are known, and five reasons are given to account for those that are missing. They may yet be discovered, or may have been discovered but overlooked by the writer; they may have existed in the geological past or may yet evolve; finally, they may be developmentally impossible through involving incompatible arrangements of organs. The primitive grass flower is assumed to have possessed a well-developed perianth and to have been insect-pollinated. In the course of evolution it has lost most of its perianth and become wind-pollinated. It is suggested that the transition from insect to wind pollination, and the reduction in stamen number within the flower in the course of evolution, has been accompanied by the development of the paniculate inflorescence, the marked tendency for vegetative reproduction, and the strong development of cleistogamy and apomixis in the family.

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