Apostasis.—Engelmann made use of this term to express the separation of parts one from another by the unusual elongation of the internodes.[516] He drew a distinction between the separation of individual organs one from the other, and the corresponding displacement of whorls. The subject has already been, to a considerable degree, treated of in these pages under the head of dialysis, displacement, and prolification, and but little need here be added. With reference to the distance between one whorl and another, it will be remembered that, although in the majority of cases the floral whorls are packed closely together, yet in other instances the floral axis becomes elongated, and thus separates the whorls one from another, by structures such as the gynophores, androphores, &c., of Passifloreæ, Caryophylleæ, Capparideæ, &c. &c.
A similar elongation of the thalamus, bringing about the separation of the floral whorls, or of their constituent parts, is very commonly met with in association with median prolification. Where the individual floral elements are thus thrown out of their usual verticillate arrangement, they naturally assume a spiral disposition, and are, in some cases, united by their margins, so that a spiral sheet or tube is formed, surrounding the axis. This frequently occurs in double flowers of the Chinese primrose, Primula sinensis.
Engelmann[517] figures a case wherein the calyx of Anagallis phœnicea was separated by a rather long internode from the corolla, and a like illustration in Torilis Anthriscus.
Fig. 209.—Flower of Delphinium, showing apostasis of carpels, from lengthening of the thalamus, &c. (Cramer.)
A frequent change in Crucifers is due to the formation of a long stalk bearing the pod, and thus giving rise to the appearance met as a constant occurrence in Capparids.
In Tropæolum majus a similar elevation of the pistil may occasionally be seen.
The adjacent figure of a monstrous Delphinium taken from Cramer illustrates well the elongation of the floral axis and the apostasis of the carpels. In this instance the axis is terminated by a second flower (median prolification).