Online Encyclopedia


Online Encyclopedia
Originally appearing in Volume V02, Page 14 of the 1911 Encyclopedia Britannica.
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SEMINEAE. Unitegmineae. Bitegmineae. The most remarkable feature here is the class of Liorhizal Dicotyledons, which includes only the families of Nymphaeaceae and Gramineae. It is based upon the fact that the histological differentiation of the epidermis of their root is that generally characteristic of Monocotyledons, whilst they have two cotyledons—the old view of the epiblast as a second cotyledon in Gramineae being adopted. But the presence of a second cotyledon in grasses is extremely doubtful, and though there may be ground for reconsidering the position of Nymphaeaceae, their association with the grasses as a distinct class is not warranted by a comparative examination of the members of the two orders. Ovular characters determine the grouping in the Dicotyledons, van Tieghem supporting the view that the integument, the outer if there be two, is the lamina of a leaf of which the funicle is the petiole, whilst the nucellus is an outgrowth of this leaf, and the inner integument, if present, an indusium. The Insemineae include forms in which the nucellus is not developed, and therefore there can be no seed. The plants included are, however, mainly well-established parasites, and the absence of nucellus is only one of those characters of reduction to which parasites are liable. Even if we admit van Tieghem's interpretation of the integuments to be correct, the diagnostic mark of his unitegminous and bitegminous groups is simply that of the absence or presence of an indusium, not a character of great.value elsewhere, and, as we know, the number of the ovular coats is inconstant within the same family. At the same time the groups based upon the integuments are of much the same extent as the Polypetalae and Gamopetalae of other systems. We do not yet know the significance of this correlation, which, however, is not an invariable one, between number of integuments and union of petals. Within the last few years Prof. John Coulter and Dr C. J. Chamberlain of Chicago University have given a valuable general account of the morphology of Angiosperms as far as concerns the flower, and the series of events which ends in the formation of the seed (Morphology of Angiosperms, Chicago, 1903). AurxoxlTIEs.—The reader will find in the following works details of the subject and references to the literature: Bentham and Hooker, Genera Plantarum (London, 1862–1883) ; Eichler, Bluthendiagramme (Leipzig, 1875–1878) ; Engler and Prantl, Die naturlichen Pflanzenfamilien (Leipzig, 1887–1899) ; Engler, Syllabus der Pflanzenfamilien, 3rd ed. (Berlin, 1903) ; Knuth, Handbuch der B?utenbiologie (Leipzig, 1898, 1899) ; Sachs, History of Botany, English ed. (Oxford, 189o) ; Solereder, Systematische Anatomie der Dicotyledonen (Stuttgart, 1899) ; van Tieghem, Elements de botanique; Coulter and Chamberlain, Morphology of Angiosperms (New York, 1903). (I. B. B.; A. B. R.)
End of Article: SEMINEAE
SEMINARY (Lat. seminarium, from semen, seed)

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