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The Genus Danthonia in Grass Phylogeny

J. M. J. de Wet
American Journal of Botany
Vol. 41, No. 3 (Mar., 1954), pp. 204-211
Stable URL: http://www.jstor.org/stable/2438974
Page Count: 8
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The Genus Danthonia in Grass Phylogeny
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Abstract

The genus Danthonia is among the most variable in the Gramineae in morphological as well as anatomical characters. The Gramineae are subdivided into four series, the Paniciformes, Eragrostiformes, Festuciformes and the Phragmitiformes. In such a subdivision, Danthonia is included in the series Phragmitiformes and placed in the neighborhood of the tribe Arundineae. The genus Pentaschistis, which is related to Danthonia, is similarly included in the Phragmitiformes rather than the Festuciformes as is done by most taxonomists. A basic chromosome number of n = 6 has definitely been established in Danthonia. A second basic chromosome number of n = 7 also appears to be present. In Pentaschistis the basic chromosome number is n = 7, in Danthoniopsis n = 9 and in Tristachya and Loudetia, apparently n = 12. In the majority of Danthonia species, and in Pentaschistis, the chromosomes are intermediate in size between the largest and the smallest chromosomes found in the Gramineae. In the genera, Danthoniopsis, Tristachya, Loudetia and in Danthonia forskalii R. Br., the chromosomes are small. In morphological, anatomical and cytological characteristics, Danthonia is intermediate between the series Festuciformes and the series Paniciformes. This leads the author to assume that the basic numbers of n = 10 and n = 9 in the Paniciformes are the result of a reduction in basic numbers from types with n = 12. The common basic number of n = 7 in the Festuciformes seems to be derived from a similar basic number in the Phragmitiformes. Evidence from the genera Tristachya and Loudetia, which are usually included in the Paniciformes tribe Arundinelleae, as well as the evidence from certain Danthonia species, indicates that the Paniciformes could have had its origin in the Phragmitiformes tribe Arundineae. These genera are regarded as transitional forms.

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