Double Flowers

Double Flowers differ considerably in structural origin. Most commonly they consist in an increased number of petals with entire loss of stamens and carpels, as in roses, bachelors' buttons, eranunculi, etc. Sometimes the carpels only or the stamens only are petaloid, or there may be, as in double stocks, an increased number of petals by chorisis (q.v.) without any change of stamens or carpels. Among gamopetalous flowers there may be a petaloid calyx, as is sometimes the case in Primula; or there may be a second corolla or "cata-corolla," as an outgrowth outside the normal one, as often occurs in Campanula; or both calyx and corolla may be repeated once or oftener one inside the other," hose in hose." The term double flower is le-,s accurately applied to the inflorescences of certain Composites in which either all the tubular disc florets become ligulate like those of the ray, as in the Dahlia; or, as in "quilled" chrysanthemums, their tubes are elongated; or, as in the "dragon" varieties, they are irregularly prolonged in distinct petalline segments. The so-called double Poinsettia (q.v.) has merely some extra coloured bracts below the inconspicuous inflorescences. Though double flowers do occur in a wild state they are far more common among cultivated plants, being produced by some check to vegetation, either by starvation; by plethora, i.e. an excess of food which the plant cannot assimilate; or by sterility, the removal or non-development of the sexual organs.

Double stocks are raised from plants weakened by starvation - i.e. drought, which produce short pods with few seeds, only the seeds from the lower part of the pods being sown. The tendency to form double flowers becomes hereditary.