It must be remembered that in some genera, where this separation of the petals has been met with, there are species in which a similar isolation occurs normally, as in Rhododendron. R. linearilobum, a Japanese species, offers a good illustration of this.
The following list contains the names of the genera in which this separation of the petals of an ordinarily gamopetalous flower takes place most frequently.
- Correa.
- Campanula! sp. pl.
- Polemonium.
- Phlox!
- Cobœa!
- Rhododendron!
- Erica!
- Rhodora.
- Azalea!
- Compositæ! sp. pl.
- Lonicera!
- Convolvulus!
- Pharbitis.
- Antirrhinum!
- Verbascum!
- Mimulus.
- Digitalis!
- Orobanche.
- Solanum.
- Nicotiana.
- Gentiana!
- Anagallis.
- Primula!
- Lamium!
- Convallaria!
- Lilium!
- Colchicum!
- &c. &c.
This list does not include those very numerous cases in which this change is associated with more or less complete frondescence or leafy condition of the petals.
Dialysis of the stamens.—A similar isolation of the stamens occurs occasionally; for instance, when Mallows (Malvaceæ) become double, one of the first stages of the process is often the disjunction of the stamens, and a similar dissociation occurs in Leguminosæ and Compositæ, as in Tragopogon, as related by Kirschleger, in Hypochæris by Wigand, and in Coreopsis by Schlechtendal.
Dialysis of the carpels.—In the case of the carpels this disunion is more frequent than in the stamens. M. Seringe[78] figures carpels of Diplotaxis tenuifolia more or less completely separated one from the other; indeed, this separation is very common amongst Cruciferæ and Umbelliferæ.
Generally speaking, the disunion is complicated with frondescence—but not always so. I have, in my herbarium, specimens of Convallaria majalis, Commelyna sp., and of Lilium auratum, in all of which the three carpels are completely disjoined, and present three styles, three stigmas, &c., without any other change. Engelmann[79] speaks of three classes of this malformation. 1st, that in which the carpels separate one from the other without opening, as in the lily just alluded to; 2nd, that in which the ovary remains closed, but loses its internal partitions, as in a case mentioned by Moquin in Stachys sylvatica, in which, owing to imperfect disjunction, the two bi-lobed carpels were changed into a nearly one-celled capsule;[80] and 3rd, those cases in which the carpels are open and foliaceous.
Fig. 32.—Anomalous form of orange.