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The Embryo in Grass Systematics

John R. Reeder
American Journal of Botany
Vol. 44, No. 9 (Nov., 1957), pp. 756-768
Stable URL: http://www.jstor.org/stable/2438397
Page Count: 13
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The Embryo in Grass Systematics
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Abstract

Histological investigations were made of embryos of some 300 species of grasses representing over 150 genera and all tribes usually recognized. Previous reports that grass embryos are of two basic types (panicoid and festucoid) were confirmed. It is pointed out also that the embryo is small in proportion to the size of the caryopsis in festucoids, while usually relatively much larger in panicoids. Four important embryo characters are discussed, three of these evident in longitudinal section and one in transverse section. On the basis of these four characters, six distinctive embryo types may be recognized: true festucoids, true panicoids, chloridoid-eragrostoid, bambusoid, oryzoid-olyroid, and arundinoid-danthonioid. The embryo appears to offer unusual promise in suggesting relationships of anomalous genera, especially when employed in connection with other histological and cytological studies. In the majority of cases a striking correlation is found between the results of these embryo studies and those of the epidermis and anatomy of the leaves, as well as with size and number of chromosomes. All lines of evidence, including embryo studies, point to the fact that the Panicoideae, for the most part, is a natural and homogeneous group. The Festucoideae, on the other hand, appears to be extremely heterogeneous, many of its genera having much closer affinities with those of the Panicoideae. A tentative grouping of the genera studied, based on the embryo type, is suggested.

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