Variétés agricoles du niébé et espèces immédiatement apparentées . orks que les fleurs sont jaunes ou ; jaunâtres. Dans presque toutes les variétés, un petit pot jaune en forme d'usuyW apparaît à la base de la norme, à la base de laquelle s'étendent plus ou moins les lignes de guidage visibles. De chaque côté de l'œilleton est une arête verticale vive qui apparatlyfonctionne pour élever la norme à une position verticale. À la base de la corolle se trouvent des nectaries qui sécrètent une petite quantité de miel. Ce miel ne peut être atteint que par des insectes à longue durée, comme les abeilles et les papillons. Il semblerait que cela

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Agricultural varieties of the cowpea and immediately related species . orks that the flowers are yellow or ; yellowish. In nearly all varieties a small, usuallyW-shaped, yellow eyespot appears at the base of the standard, to thebase of which more or less conspicuous guide lines extend. Oneach side of the eyespot is a sharp vertical ridge which apparentlyfunctions to raise the standard to a vertical position. At the base of the corolla are nectaries which secrete a smallamount of honey. This honey can be reached only by long-tonguedinsects, such as bumblebees and butterflies. It would seem that aheavy-bodied insect, such as a large bumblebee, could certainly pushdown the keel enough to expose the stamens and stigma, though noinstances are on record where such action has been observed. AtArlington Farm bumblebees have frequently been seen obtaining thenectar from the flowers, but in no case under observation was thestigma extruded as a result. Butterflies also can get the floral nectar 229 229, Bureau of Plant Industry, U, S. Dept. of Agricultur Plate VII.. Pods of Two Varieties of Cowpeas Having Curved or Coiled Pods: UpperFigure, No. 21296A; Lower Figure, No. 29278. (Two-thirds natural size.) THE ORIGIN OF NEW VARIETIES. 27 without bringing about the extrusion of the stamens and stigma.At Arlington Farm, during the season of 1909, a few of the flowershad their stamens and stigmas extruded. Whether such extrusion isdue to insects or not remains to be determined. It has never beenobserved in the hundreds of plants grown in the Department green-houses. THE ORIGIN OF NEW VARIETIES. The fact of the existence of numerous varieties of cowpeas callsfor some explanation of their origin. Mention has already beenmade (p. 15) of the fluctuations or fluctuating variations so markedin the cowpea. It is now the general belief that such variationsare not hereditable in any plants, and if such is true this type ofvariation can have had no effect in producing the large number ofvarie

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• bookcentury1900
• bookdecade1910
• bookpublisherwashi
• bookyear1912