The evolution theory . o primarj^ constituents whichhave long been present, but are usually suppressed, and so it is alsoamong the plants. I have in mind, for instance, the interesting-experiments of Vochting on the influence of light in the production T 2 276 THE EVOLUTION THEORY of flowers in phanerogams. These showed that the common balsam{hnpatiens noli rtie tangeve) produces its familiar open flowers ina strong light, but in weak light only bears small, closed, so-called cleistogamous flowers. But it would be utterly erroneous to supposethat the strong or weak light is the real cause, the

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The evolution theory . o primarj^ constituents whichhave long been present, but are usually suppressed, and so it is alsoamong the plants. I have in mind, for instance, the interesting-experiments of Vochting on the influence of light in the production T 2 276 THE EVOLUTION THEORY of flowers in phanerogams. These showed that the common balsam{hnpatiens noli rtie tangeve) produces its familiar open flowers ina strong light, but in weak light only bears small, closed, so-called cleistogamous flowers. But it would be utterly erroneous to supposethat the strong or weak light is the real cause, the causa materiality,of these two forms of flowers; the degree of illumination is merely thestimulus which provokes one or other of the primary constituentsto development, both kinds being present in the constitution of theplant. As has long been known, the balsam normally possesses twokinds of flowers, and the slumbering primary constituents of theseare so arranged that the open flowers develop where there is a prospect.

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Keywords: ., bookauthorthomsonj, bookcentury1900, bookdecade1900, bookyear1904