Dehiscence of the Capsules of Collomia

Abstract

IN Mr. Duthie's very interesting account (vol. xii. p. 494) of the mode of dehiscence of the capsules of this plant, he suggests that the purpose of the projection of the seeds on to the viscid hairs of the plant itself may possibly be found in its enabling the plant to live on its own seeds. Surely this is a superfluous and needlessly improbable hypothesis. The violent discharge cf the seeds is undoubtedly one of the modes adopted by nature for their dispersion to plots of ground where the mineral constituents of the soil which they mainly require have not been entirely used up by the parent plant. Their interception by the parent plant is no doubt accidental. The purpose served by the viscid hairs of this and other plants still remains to be discovered if we follow the clue afforded by Mr. Darwin's observations on insectivorous plants. The violent expulsion of the seeds from the ripe capsule is a much more common phenomenon than that which we have exhibited in Collomia, together with a few other plants, as Acanthus, Ruellia, Eschscholtzia, and Geranium, where the whole fruit is thrown off together. Mr. Duthie will find a good description of the phenomenon in Hildebrand's “Die Schleuderfrüchte und ihr im anatomischen Bau begründeten Mechanismus,” in Pringsheim's “Jahrbunh” for 1873–74. The author draws an interesting comparison between the structure of Collomia, with its single seed in each division, and its apparatus for projecting these to a distance, and that of the allied genus Gilia, with its numerous seeds in each division, which possess no such mechanism, but which, being much lighter, are consequently more easily dispersed by the wind.