CLEISTOG'AMOUS FLOWERS (Gk. xNeur T6s.•leistos, that which may be closed, from ,cXskzr, Oriel», to close -ydpos, gamos, marriage). Relatively inconspicuous and-never-open flowers, which Occur, along with the ordinary flowers, in many plants, representing all of the principal alliances of the flowering plants. Cleis togamous flowers are seldom in a conspicuous position. One of the best-known illustrations is in the stemless species of violets. In these, in addition to the well-known conspicuous flowers, cleistogamous flowers occur more or less con cealed near the base of the cluster of leaves and flower-stalks. Since these flowers are never Open, they are necessarily self-pollinated; but they are very fertile, and produce an abundance of seed. The significance of this dimorphism in the flow ers of so many plants is not clear. It has been suggested that, in case cross-pollination is not secured by the showy flowers, the presence of self-pollinating cleistogamous flowers makes seed production secure. However, some plants with cleistogamons flowers, as grasses and rushes, are anemophibms (wind-pollinated), so that it is not a habit entirely related to the uncertain ties of pollination by insects. In comparing the development of the eleistogamous and ordinary flowers, it is discovered that the former are like the latter at various stages of development.
The following quotation from Darwin's Dif ferent Forms of 17ourers presents some detailed differences: "In eleistogamous flowers. the petals are rudimentary or quite aborted; their stamens an. often reduced in number, with anthers of very small size, containing few pollen grains, wrier have remarkably thin, transparent coats, and generally emit their tubes while still inclosed within the anther-cells; and, lastly, the pistil is much reduced in size, with the stigma in some eases hardly at all developed. These flowers do not secrete nectar or emit any odor: from their small size, as well as from the corolla being rudimentary, they are singular ly inconspicuous. Consequently. insects do not visit them: nor, if they did. could they find an entrance. Such flowers are, therefore, invariably self-fertilized; yet they produce an abundance of seed. In several eases, the young capsules bury themselves beneath the ground, and the seeds are there matured. These flowers are de veloped before, or after, or simultaneously with the perfect ones."