Themale flowers of the cucumber, melon, and other monoecious plants, are popularly known as barren flowers; and the plants of the asparagus, mercury, and other dioecious plants bearing only male plants, are usually termed barren. These are naturally unfruitful; but there is also a barrenness arising from disease or other consequences of bad cultivation. If a tree, or any other plant, does not yield the desired produce of fruit of which it is capable, the gardener may be assured that the soil,or the want of drainage, or the manuring, or the pruning, is injurious. Even a blind or barren cabbage may be made productive; for its barrenness arises from the central bud being abortive, and it will produce lateral buds, if all but one leaf and the place of the abortive bud be cut away.

Temperature has a great influence over the sex of the flowers produced by a given plant. A very high temperature caused a water-melon to bear male blossoms only; and a very low temperature made cucumber plants yield female flowers alone. Mr. Knight had little doubt that the same fruit stalks might be made, in the plants just noticed, to support flowers of either ses in obedience to external causes.