formed of two lamellae, derived from the parietes of the fruit. These lamella? are in many cases easily separable, and where their union is more intimate, their existence is still evident from the want of correspondence, and consequent decussation, of their areolae. The lamellae, which are usually very thin and transparent, have their surface divided into areolae, in different genera of very different forms, some of which may, with sufficient clearness, be described. In many cases no other appearance exists; in some, however, the axis of the septum resembles either a single nerve, or two distinct parallel nerves ; and from this axis, whether formed of one or two nerves, tubes having the appearance and ramification of the veins of a leaf, and which generally terminate within the margin, not unfrequently proceed. This is remarkably the case in Farsetia, as I here propose to limit that genus; the central vessels in both its species being closely approximated, so as to form a single cord, extending from the apex to the base of the septum, and the veins being numerous and uncommonly distinct. Approaches more 01* less manifest to this structure of Farsetia exist in several other genera, as in Parrya, Savignya, and Koniga. But polyspermous parietal placentae, which is the usual structure of the order, to that of Isatis, where a single ovulum is pendulous from the apex of the unilocular ovarium; and, lastly, in the genus Bocconia, in the original species of which ( B.Jrutescens) , the insertion of the single erect ovulum has the same relation to its parietal placentae, as that of Compositae has to its filiform cords, a second species (JB. cordata) exists, in which these placentae are polyspermous.” From this quotation it is, I think, evident, that in 1818 I had published, in my Essay on Compositae, the same opinion, relative to the structure of the pistillum of Cruciferae, which has since been proposed, but without reference to that essay, by M. de Candolle, in the second volume of his ff Systems N a tu r a le a n d I am not aware that when the essay referred to appeared, a similar opinion had been advanced by M. de Candolle himself, or by any other author; either directly stated of this family in particular, or deducible from any general theory of the type or formation of the pistillum. I am persuaded, however, that neither M. de Candolle, when he published his Systems, nor M. Mirbel, who has very recently adverted to this subject, could have been acquainted with the passage above quoted. This, indeed, admits of a kind of proof; for if they had been aware of the concluding part of the quotation, the former author would probably not have supposed that all' the species referred to Bocconia were monospermous, (Syst. Nat. 2. p. 89) ; nor the latter that they were all polyspermous. (.Mirbel in Ann. des Scien. Nat. 6. p. 267). Respecting Bocconia cordata, though it is so closely allied to Bocconia as to afford an excellent argument in favour of the hypothesis in question, it is still sufficiently different, especially in its polyspermous ovarium, to constitute a distinct genus, to which I have given the name (M a c le a y a cordata') of my much valued friend, Alexander Macleay, Esq. Secretary to the Colony of New South Wales, whose merits as a general naturalist, a profound entomologist, and a practical botanist, are well known. in this last mentioned genus the nerve, which originates, as in all cases, at the apex, hardly extends, even in the polyspermous species, beyond the middle of the septum, and the veins, which are much less distinct, are descendent. As far as my observations on this subject at present extend, I expect, with great confidence, uniformity in the structure of the septum of strictly natural genera, and in many cases, though certainly not in all, I have founff^a resemblance in this respect in more extensive groups' Thus Draba, Arabrs, and Aubrietia, agree in having amorphous areola?, bounded by flexuose tubes or lines; while Alyssum, Berteroa, and Fibigia, have narrow linear areola?, bounded by parallel or slightly arched lines. Capsella bursa differs from Thlaspi and JEthionema, as Draba from Alyssum, and agrees with Lepidium procumbens, Larin, improperly referred to Hutchinsia, and which equally has incumbent cotyledons. Cochlearia differs in like manner from Kernera. And numerous other examples of the same agreement in nearly related plants, and of differences where the usual sources of distinction are less available, might be noticed. H e s p e r i s n i t e n s of Viviani is sparingly in the herbarium, both in flower and fruit. The seeds, though not ripe, are sufficiently advanced to show that the direction of the cotyledons is in this stage accumbent; and, as I have found in Cruciferas generally that the ultimate kgrees with the early state of cotyledons, I conclude they are likewise accumbent in the ripe seed. The plant is also abundantly different from Hesperis in other respects, and does not appear to be referrible to any genus yet published. This new genus * I have dedicated to the memory of Dr. Oudney, who found the present species in many of the wadeys between Tripoli and Mourzuk, and remarks that camels and mules eat it. * OUDNEYA. C h a r. Gen. Calyx clausus, basi bisaccatus. Filamenta distincta, edentula. Stigmata connata apicibus distinctis. Siliqua sessilis linearis rostrata, valvis planis uninerviis, funiculis adnatis, septo avenio areolarum parietibus subparallelis. Semina uniseriata. Cotyledones ac- cumbentes. Suffrutex (O. Africana nob. Hesperis nitens, Viv.lib.jt. 38. tab. 5 . f 3.) glaberrimus, ramosus. Folia integerrima sessilia avenia, inferior a obovata, superior a subline aria. Racemi terminates, ebracteati. Flores mediocns magnitudinis, petalorum laminis obovatis venosis. Obs. Oudneya ab Arabidi differt stigmatis forma, siliquae rostro, et dissepimenti areolarum figura. Parrya ad quam genus nostrum accedit diversa est dissepimento binervi venoso! calyce baud clauso, siliquae forma, et seminibus biseriatis testa corrugata.
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