It is curious to observe in these flowers how precisely one sepal occupies the position of the labellum, and how the lateral petals are displaced from the position they usually occupy, so as to form a regular flower, the segments of which decussate, thus giving rise to a species of regular peloria. The genus _Maelenia_ was established on a malformed flower of _Orchis_ of similar character to those above mentioned. =Meiotaxy of the calyx.=--As already mentioned, this term is here employed to denote those illustrations in which entire whorls are suppressed. Complete deficiency of the calyx in a dichlamydeous flower seems seldom or ever to occur; the nearest approach to it would be in those cases where the calyx is, as it is termed, "obsolete," but here it is chiefly the limb of the calyx which is atrophied, the lower portion being more or less adherent to the ovary. In what are termed monochlamydeous flowers both calyx and corolla are wanting, as in _Salicineae_ and many other orders. =Meiotaxy of the corolla.=--Deficiency of the entire corolla occurs in conjunction with similar reductions in other organs, or as an isolated phenomenon in the many apetalous varieties of plants recorded in books. Deficiency of the corolla was observed in _Campanula perfoliata_ and _Ruellia clandestina_ by Linne, who calls such blooms _flores mutilati_.[480] Drs. Hooker and Thomson relate a similar occurrence in _Campanula canescens_ and _C. colorata_. Some plants seem as a normal occurrence to produce flowers of different construction, and are hence termed dimorphic, as in many _Malpighiaceae_, _Violaceae_, _Oxalidaceae_, in some of the flowers of which the petals are altogether wanting, while in others the corolla is developed as usual. This deficiency of the corolla is frequently, but not invariably, associated with an increased fertility. Thus, in some violets the flowers produced in summer, and in which the petals are either entirely suppressed or are more or less atrophied, are always fertile, while the blossoms developed in spring, and in which the petals are always present, are much less fertile. In _Oxalis Acetosella_ there are two forms of flower, the one with, the other without, petals, but both seem equally fertile. Linne remarks that many plants which, in warm latitudes, produce a corolla, do not do so when grown in colder climates. Thus, certain species of _Helianthemum_ are apetalous in Lapland. In the Pyrenees, according to Bentham, the flowers of _Ajuga iva_ are constantly deprived of their corolla.[481] Apetalous flowers have been noted most frequently in the following plants: