The curious attribute of the petals is not to be considered simply as a reduction in size. On anatomical inquiry it has been found that these narrow petals bear some characteristics which, on the normal plants, are limited to the calyx. Stomata and hairs, and the whole structure of the surface and inner tissues on some parts of these petals are exactly similar to those of the calyx, while on others they have retained the characteristics of petals. Sometimes there may even be seen by the naked eye green longitudinal stripes of calyx-like structure alternating with bright yellow petaloid parts. For these reasons the cruciata character may be considered as a case of sepalody of the petals, or of the petals being partly converted into sepals. [587] It is worth while to note that as a monstrosity this occurrence is extremely rare throughout the whole vegetable kingdom, and only very few instances have been recorded. Two cases of sudden mutations have come to my knowledge, producing this same anomaly in allied species. One has been already alluded to; it pertains to the common evening-primrose or _Oenothera biennis_, and one is a species belonging to another genus of the same family, the great hairy willow-herb or _Epilobium _hirsutum_. I propose to designate both new forms by the varietal name of _cruciata_, or _cruciatum_. _Oenothera biennis cruciata_ was found in a native locality of the _O. biennis itself. It consisted of only one plant, showing in all its flowers the _cruciata_ marks. In all other respects it resembled wholly the _biennis_, especially in the pure green color of its foliage, which at once excluded all suspicion of hybrid origin with the purple _O. cruciata_. Moreover in our country this last occurs only in the cultivated state in botanical gardens. Intermediates were not seen, and as the plant bore some pods, it was possible to test its constancy. I raised about 500 plants from its seeds, out of which more than 100 flowered in the first year. The others were partly kept through the winter and flowered next year. Seeds saved in [588] both seasons were sown on a large scale. Both the first and the succeeding generations of the offspring of the original plant came true without any exception. Intermediates are often found in hybrid cultures, and in them the character is a very variable one, but as yet they were not met with in progeny of this mutant. All these plants were exactly like _O. biennis_, with the single exception of their petals.