Abstract
GROWING plentifully among the grass on the coast hills of Natal is a small blue flower belonging to the Rubiaceæ. In this plant, generally speaking, there are two forms only, in one of which the five stamens are exserted considerably beyond the tube of the rotate corolla, and the stigma is included in the tube; in this form the tube is almost devoid of hairs. In the other common form the position of these essential organs is reversed, the stigma protruding to about the same extent that the stamens do in the first mentioned, and the stamens being included; here, however, the upper part of the corolla tube is thickly covered with downy hairs—of course this is an ordinary dimorphic plant. But I find lately a third form of the same species (only, however, rarely) in which both stamens and stigma are exserted and are of the same length, so that here self-fertilisation must take place, as the stamens and stigma touch at the time the former dehisce. I do not think this can be termed a cleistogamic form, as, although rather smaller and lighter in colour than the others, the difference is only trifling. The hairs which cover the corolla-tube in the form with included stamens serve to keep the pollen collected near the upper part of the tube, as, if it fell to the base it would not be so easily transferred by the proboscis of an insect as when lightly held by the hairs through which the insect must make way. As these hairs would be for this purpose useless when the stamens are exserted they do not occur in the other form.
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EVANS, M. Notes on Some Natal Plants . Nature 18, 543 (1878). https://doi.org/10.1038/018543a0
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DOI: https://doi.org/10.1038/018543a0