Cleome (Siliquaria) Arabica, (Linn. sp. pl. ed. 2. p. 939. De. Cand. prodr. 1. p. 240), a supposed variety of which was found both in the neighbourhood of Tripoli and in Soudan, belongs to another subdivision of the genus, equally natural, and readily distinguishable. The species of this subdivision are included in M. De Candolle’s second section of Cleome, but are there associated with many other plants, to which they have very little affinity.
All the species of Cleome Siliquaria are indigenous to North Africa and Middle Asia, except violacea, which is a native of Portugal. Cleome deflexa of M. De Candolle (prodr. 1. p. 240.), founded on specimens in Mr. Lambert’s herbarium, which were sent by Don Joseph Pavon as belonging to Peru, seems to present a remarkable exception to this geographical distribution of the section. But on examining these specimens I find them absolutely identical with some states of violacea. I think it probable, therefore, either that they are erroneously stated to have come from Peru, or that this species may have been there introduced from European seeds.
Cadaba farinosa (Forsk. Arab. p. 68. De Cand. prodr. 1. p. 244) is in the herbarium from Bornou. The specimen is pentandrous, and in other respects agrees with all those which I have seen from Senegal, and with Strœmia farinosa of my catalogue of Abyssinian plants, collected by Mr. Salt, and published in his travels. M. De Candolle, who had an opportunity of examining this Abyssinian plant, refers it to his C. dubia, a species established on specimens found in Senegal, and said to differ from farinosa, slightly in the form of the leaves, and in being tetrandrous. Of the plant from Abyssinia I have seen only two expanded flowers, one of which is decidedly pentandrous, the other apparently tetrandrous. Mr. Salt, however, from an examination of recent specimens, states it to be pentandrous. It is probably, therefore, not different from C. farinosa of Forskal, whose specimens M. De Candolle has not seen. And as the form of leaves is variable in the specimens from Senegal, and not elliptical, but between oval and oblong, in those of Abyssinia, C. dubia is probably identical with, or a variety merely of farinosa, as M. De Candolle himself seems to suspect.
Crateva Adansonii (De Cand. prodr. 1. p. 243) is in the collection from Bornou. This species is established by M. De Candolle upon a specimen in M. de Jussieu’s herbarium, found in Senegal by Adanson, and is supposed to differ from all the other species in having its foliola equal at the base. I have examined the specimen in M. de Jussieu’s herbarium, in which, however, the leaves not being fully developed, I was unable to satisfy myself respecting their form. But in a specimen, also from Senegal, which I received from M. Desfontaines, the lateral foliola, though having manifestly unequal sides, are but slightly unequal at the base, and the inequality consists in a somewhat greater decurrence of the lamina on the anterior or inner margin of the footstalk. As well as can be determined, in very young leaves, this is also the case in the specimen from Bornou; and it is manifestly so in my specimen of C. læta, which appears to belong to the same species.
Crateva læta was founded by M. De Candolle on a plant from Senegal, communicated by M. Gay, from whom I also received a specimen in 1824, with the remark, that it was not different from C. Adansonii. In that specimen the flowers are male with an imperfect pistillum; in the plant from Bornou they are hermaphrodite, with elongated filaments; and in the specimen received from M. Desfontaines they are also hermaphrodite, but the stamina, though apparently perfect, are fewer in number and shorter than the stipes of the ovarium. I have observed, however, the flowers to be in like manner polygamous in some other species of Crateva, belonging both to India and America, a fact which materially lessens the dependence to be placed on characters taken from the number and length of the stamina in this genus.
Crateva Adansonii, it would appear, then, is the only known species of the African continent, for C. fragrans does not belong to the genus. And it will be difficult to distinguish this African Crateva from a plant which seems to be the most general species of India; except that in the latter, as in all the other species of the genus, the inequality of the lateral foliola, which is also more marked, consists in the greater decurrence of the lamina being on the outer or posterior margin of the footstalk. This Indian species, which may be named C. Roxburghii, is the Capparis trifoliata of Dr. Roxburgh’s manuscripts, but not Niirvala of Hortus Malabaricus (vol. 3. p. 49. t. 42), as he considers it. I have little doubt of its being also the plant described as C. Tapia, by Vahl, (symb. 3. p. 61.) his specific character well according with it, and not applying, as far as relates to the petals, to any known species of America. But as this character is adopted by Sir James Smith (in Rees’s Cyclop.), it may likewise be C. Tapia of the Linnæan herbarium; a conjecture the more probable as Linnæus has distinguished his Tapia by its ovate petals from gynandra, in which they are said to be lanceolate (Sp. pl. ed. 2. p. 637). This celebrated herbarium, however, is here of no authority, for Linnæus was never in possession of sufficient materials to enable him to understand either the structure and limits of the genus Crateva, or the distinctions of its species; and the specific name in question, under which he originally included all the species of the genus, ought surely to be applied to an American plant, at least, and if possible to that of Piso, with whom it originated. It is hardly to be supposed that the plant intended by Piso can now with certainty be determined; the only species from Brazil, however, with which I am acquainted, well accords with his figure and short description. This Brazilian species is readily distinguishable both from C. Adansonii and Roxburghii, by the form of its petals, which, as in all the other American species, are narrow-oblong or lanceolate; and from C. gynandra by the shortness of its stipes genitalium, or torus.
Crateva Tapia so constituted, is, on the authority of a fragment communicated by Professor Schrader, the Cleome arborea of that author, (in Gœtt. Anzeig. 1821, p. 707. De Cand. Prodr. 1. p. 242.); nor is there any thing in the character of C. acuminata of De Candolle (Prodr. 1. p. 243) which does not well apply to our plant.
C. Tapia, as given by M. De Candolle (op. cit.), is characterized chiefly on the authority of Plumier’s figure, in the accuracy of which, either as to the number or length of stamina, it is difficult to believe, especially when we find it also representing the petals inserted by pairs on the two upper sinuses of the calyx.
The genus Crateva agrees, as I have already stated, in the remarkable æstivation of its flower with Cleome Gymnogonia, by which character, along with that of its fruit, it is readily distinguished from every other genus of the order. Although this character of its æstivation has never before been remarked, yet all the species, referred to Crateva by M. De Candolle, really belong to it, except C. fragrans, which, with some other plants from the same continent, forms a very distinct genus, that I shall name Ritchiea, in memory of the African traveller, whose botanical merits have been already noticed.
Capparis sodada nob. Sodada decidua, Forsk. Arab. p. 81. Delile, Flore d’Egypte, p. 74. tab. 26. De Cand. Prodr. 1. p. 245.