As to the place of Savignya in the natural family, I believe, on considering the whole of its structure and habit, that it ought to be removed from Alyssineæ to a subdivision of the order that may be called Brassiceæ, but which is much more extensive than the tribe so named by M. De Candolle; including all the genera at present known with conduplicate cotyledons, as well as some others, in which these parts are differently modified.
There are two points in the structure of Savignya, that deserve particular notice. I have described the æstivation of the calyx as valvular; a mode not before remarked in this family, though existing also in Ricotia. In the latter genus, however, the apices of the sepals are perhaps slightly imbricate, which I cannot perceive them to be in Savignya.
The radicle is described by M. De Candolle as superior, with relation to the cotyledons. I am not sure that this is the best manner of expressing the fact of its being horizontal, or exactly centrifugal, the cotyledons having the same direction. This position of the seed is acquired only after fecundation; for at an earlier period the foramen of the testa, the point infallibly indicating the place of the future radicle, is ascendant. From the horizontal position of the radicle in this and some other genera, especially Farsetia, we may readily pass to its direction in Biscutella, where I have termed it descendant; a character which I introduced to distinguish that genus from Cremolobus. But in Biscutella the embryo, with reference to its usual direction in the family, is not really inverted, the radicle being still placed above the umbilicus. On the contrary, in Cremolobeæ, a natural tribe belonging to South America, and consisting of Cremolobus and Menonvillea, though the embryo at first sight seems to agree in direction with the order generally, both radicle and cotyledons being ascendant, it is, in the same sense, not only inverted, but the seed must also be considered as resupinate: for the radicle is seated below the umbilicus, and also occupies the inner side of the seed, or that next the placenta,—peculiarities which, taken together, constitute the character of the tribe here proposed. It appears to me singular that M. De Candolle, while he describes the embryo of these two genera as having the usual structure of the order, should consider that of Iberis, in which I can find no peculiarity, as deviating from that structure[90].
Lunaria libyca of Viviani[91] is the second plant of Cruciferæ, on which I have some observations to offer. This species was described and figured, by the author here quoted, in 1824, from specimens collected in 1817 by Della Cella. The specimens in the herbarium were found near Tripoli, where the plant had also been observed in 1819 by Mr. Ritchie, who referred it to Lunaria, and remarked that the calyx was persistent. Professor Sprengel, in his Systema Vegetabilium, considers it a species of Farsetia.
That this plant ought not to be associated either with the original species of Lunaria, or with Savignya, as now constituted, is sufficiently evident. And if it is to be included in Farsetia, it can only be on the grounds of its having a sessile silicule, with compressed valves, an indefinite number of seeds in each cell, and accumbent cotyledons. But in these respects it accords equally with Meniocus, a genus proposed by M. Desvaux, and with some hesitation received by M. De Candolle, and with Schivereckia of Andrzejowski, which he has also adopted. It does not, however, agree with either of those genera in habit, and it is easily distinguished from both by its simple filaments and other characters, which I shall notice hereafter. Is this plant, then, sui generis? ought it to be united with Alyssum, the character of that genus being modified to receive it? or does not Alyssum require subdivision, and may not our plant be referred to one of the genera so formed? A brief result of the examination of these questions, so far as they are connected with the subject under consideration, will be found annexed to the character which is given of the genus formed by the union of Lunaria libyca with Alyssum maritimum, a plant also in the collection, from the neighbourhood of Tripoli.
Alyssum maritimum, which is described both as an Alyssum and as a Clypeola by Linnæus, is the Konig of Adanson, who founded his generic distinction on the monospermous cells and supposed want of glands of the receptacle; and M. Desvaux, admitting Adanson’s genus, has named it Lobularia. In the second edition of Hortus Kewensis I included this plant in Alyssum, which M. De Candolle has also done in his great work.
For the genus here proposed I shall adopt Adanson’s name, altering only the termination, and wishing it to be considered as commemorating the important services rendered to botany by my friend Mr. Konig, of the British Museum[92]. In comparing these two species of Koniga, their agreement is very striking in habit, in leaves, in the closely pressed bipartite pubescence, in the calyx, petals, stamina, and stigma. They correspond also in some other points, less obvious but equally important, which I shall separately notice. The first of these is in having eight glands on the receptacle; a character peculiar, I believe, to these plants, and which first suggested the generic name Octadenia. The glands in Alyssum maritimum were entirely overlooked by Adanson, are not noticed by M. Desvaux, and M. De Candolle has described only the four that subtend the longer stamina. These certainly are much more conspicuous than the remaining four, which, however, occupy the place of the only glands existing in several of the most nearly related genera.
The number and position of the glands in this genus give some support, perhaps, to the hypothesis which I have formerly advanced, of the divisions of an hypogynous disk being in most cases formed of abortive filaments; an opinion more strikingly confirmed, however, in this family of plants, by their form and texture in Alyssum calycinum, and minimum.
The second point in which the two species of Koniga agree is in the structure of the septum. On this, which I consider as a new source of character in Cruciferæ, I shall offer some remarks in speaking of Farsetia.
The third point of agreement is the adhesion of the funiculi umbilicales to the septum. This adhesion, though really existing, is not very obvious in the monospermous cells of Koniga maritima; but in the supposed variety of this species from Teneriffe, in which the cells are occasionally dispermous, it is manifest, and is very remarkable in all states of Koniga libyca.