The specimen in the herbarium is marked by Dr. Oudney as belonging to a tree common on the boundaries of Bornou. It is probably the Suag, mentioned in his journal, observed first at Aghedem, and said to be “a tetrandrous plant having a small drupa, which is in great request in Bornou and Soudan, for removing sterility in females: it is sweetish and hot to the taste, approaching to Sisymbrium Nasturtium;” and that “in passing the plant a heavy narcotic smell is always perceived.”
I have here united Sodada with Capparis, not being able to find differences sufficient to authorise its separation even from the first section of that genus, as given by De Candolle.
Forskal describes his plant as octandrous, and M. De Candolle has adopted this number in his generic character. M. Delile (op. cit.), however, admits that the stamina vary from eight to fifteen; and, in the specimen which I received from M. Jomard, I have found from fourteen to sixteen. But were the number of stamina even constantly eight, this alone would not justify its separation from Capparis, several octandrous species of which, belonging to the same section, are already known.
Another species of Capparis, also from Bornou, exists in the herbarium. It appears to be undescribed, and to belong to M. De Candolle’s first section of the genus; but the specimen is too imperfect to be satisfactorily determined.
Both these species have aculei stipulares, and it may here be remarked that all the plants belonging either to Capparis, or to any of the genera of the order whose fruit is a berry, in which these aculei are found, are indigenous either to Asia, Africa, or Europe; while all the aculeated Cleomes, with the exception of perhaps a single African species, are natives of equinoxial America.
Mærua rigida. This plant, of which flowering specimens were collected at Aghedem, certainly belongs to Forskal’s genus Mærua, adopted by Vahl and De Candolle; and I believe it to be a species distinct from the three already published. It is very nearly related, however, to a fourth species (M. Senegalensis nob.), of which I received a specimen from M. Desfontaines. M. De Candolle has placed the genus Mærua at the end of Capparideæ, between which and Passifloreæ he considers it intermediate. This view of its relation to these two orders I cannot adopt. To me it appears truly a Capparidea, having very little affinity with Passifloreæ, to which it seems to approach in one point only, namely, the corona of the calyx. But of a similar corona rudiments exist in several other African Capparideæ, and from some of these the genus Mærua is with difficulty distinguished[97].
Resedaceæ. The herbarium contains two species of Reseda. The specimens of one of these are too imperfect to be determined. The other is probably undescribed, though very nearly related to R. suffruticulosa, and undata of Linnæus. This supposed new species (Reseda propinqua) was found near Tripoli by Mr. Ritchie, and between Tripoli and Mourzuk by Dr. Oudney. It is remarkable in having the ungues of all the petals simple; that is, neither dilated, thickened, nor having any process or appendage at the point of union with the trifid lamina, into which they gradually pass. We have here therefore a species of Reseda with petals not different in any respect from those of many other families of plants; and, although this is an exception to their usual structure in the genus, I shall endeavour to show that all the deviations existing, however complex in appearance, are reducible to this more simple state of the organ.
Resedaceæ, consisting of Reseda, divisible into sections or subgenera, and Ochradenus, which may perhaps be regarded as only one of these subdivisions, I consider very nearly related to Capparideæ, and as forming part of the same natural class. It differs, in the variable number of the parts of its floral envelopes, from the other orders of the class, in which the quaternary or binary division is without exception; and it is especially remarkable in having the ovarium open even in its earliest state. From Cruciferæ and Capparideæ, the two families of the class to which they most nearly approach, Resedaceæ also differ in the apparent relation of the stigmata to the placentæ. The stigmata in this order terminate the lobes of the pistillum, and as these lobes are open sterile portions of the modified leaves, from the union of which in the undivided part I suppose the compound ovarium to originate, they necessarily alternate with the placentæ. I have generally found, however, the upper part of each placenta covered by a fleshy or fungous process, which is connected with the margins of the lobes, and therefore with the stigmata, and is probably essential to the fecundation of the ovula. The singular apparent transposition of the placentæ in Sesamoides of Tournefort, so well described by M. Tristan in his ingenious Memoir on the Affinities of Reseda[98], appears to me necessarily connected with the extreme shortness of the undivided base of the ovarium; for in supposing this base to be elongated, the placentæ would become parietal, and the ovula, which are actually resupinate, would assume the direction usual in the order.
M. De Jussieu, in his Genera Plantarum, has included Reseda in Capparideæ, and to this determination I believe he still adheres. M. Tristan, in the memoir referred to, is inclined to separate it as a family intermediate between Passifloreæ and Cistineæ, but more nearly approaching to the latter. M. De Candolle, who first distinguished Reseda as an order under the name here adopted, in 1819[99] placed it between Polygaleæ and Droseraceæ, and consequently at no great distance from Capparideæ. He must, since, however, have materially altered his opinion respecting it; for the order Resedaceæ is not included in the first or second part of his Prodromus, and I can find no observation respecting it in these two volumes. It is probable, therefore, that he may either intend to place it near Passifloreæ, as suggested by M. Tristan, or, which is more likely, that he has adopted the hypothesis lately advanced, and ingeniously supported, by Mr. Lindley, respecting its structure and affinities[100].
According to this hypothesis, in Reseda the calyx of authors is an involucrum, its petals neutral flowers, and the disk or nectary becomes the calyx of a fertile floret in the centre: and, as a deduction from this view of its structure, the genus has been placed near Euphorbiaceæ.