A more frequent change among the monopetalous orders is the duplication or triplication of the corolla, in consequence of which there appear to be a series of corollas enclosed one within the other, the lobes of which generally alternate with one another, but which sometimes are superposed. This happens occasionally in the primrose (_Primula acaulis_), and constitutes the variety called by the gardeners "hose in hose." The same condition occurs frequently in some species of _Datura_ and _Campanula_. [Illustration: FIG. 191.--_Campanula rotundifolia_. "Double flowers" resulting from dialysis and multiplication of the petals.] In _Antirrhinum majus_ double flowers of this character sometimes occur; the outermost corolla is normal, the succeeding ones usually have their petals separate one from the other; the stamens are sometimes present, sometimes absent, and at other times petalodic. Similar occurrences may be met with in labiates and jasmines, and in _Erica hyemalis_. Mr. W. B. Hemsley has kindly furnished me with flowers of a similar kind occurring in wild specimens of _Epacris impressa_,[437] and there are analogous phenomena in the common honeysuckle (_Lonicera Periclymenum_), in which three corollas and no stamens often occur. This duplication may either be accounted for on the theory of chorisis above alluded to, or by supposing that the extra corolline whorl is due to a series of confluent petalodic stamens; that the latter is the true explanation, in certain cases at least, is shown by some flowers of _Datura fastuosa_, in which the second corolla was partially staminal in its appearance, and bore nearly perfect anthers, in addition to the five ordinary stamens, which were unaltered either in form or position. Some partially virescent honeysuckle flowers have a similar structure. There are other cases of apparent multiplication or duplication, due, probably, rather to the formation of outgrowths from the petals than to actual augmentation of their number. These excrescences occur sometimes on the inner surface of the petals, or of the corolla; at other times on the outer surface, as in some gloxinias, &c. This matter will be more fully treated of under the head of hypertrophy and enation. =Pleiotaxy of the androecium.=--An increase in the number of whorls in the stamens is very common, especially in cases where the number of circles of stamens is naturally large. The augmentation of the number of stamens is still more frequent where these organs are arranged, not in verticils, but in one continuous spiral line. In _Cruciferae_ there is always an indication of two whorls of stamens, and this indication is rendered even more apparent in some varieties accidentally met with. So in _Saponaria_, in _Dianthus_, and other _Caryophylleae_, three and four verticils of stamens have been met with. In _Lonicera Periclymenum_ a second whorl of stamens more or less petalodic sometimes occurs.