21. (From Baer) Section of the chick in ovo on the fourth day. 22. (From Rathke) Embryo of the chick on the fifth day. Magnified one diameter. 23. (From do.) Longitudinal and vertical section of the head and neck of the chick on the fifth day, shewing the interior of the pharynx and the remains of the branchial apertures. 24. (From do.) Heart and anterior part of the neck of the same embryo, shewing the infer. maxilla and operculum. 25. Posterior view of the heart and interior of pharynx, at a corresponding period, shewing the branchial arches given off by the bulb of the aorta. A, Section of the extremity of the bulb. 26. (From Rathke) A, The lower, and B, The lateral view of the lungs and trachea of the chick on the fifth day, with the oesophagus. 27. (From do.) The same on the sixth day. 28. (From do.) The same on the seventh day. (From do.) The lungs, &c. on the eleventh day, shewing the trachea, aorta, pulmonary arteries, communicating vessels, and the union of the cellular, with the bronchial parts of the lungs. 30. (From Burdach, but reversed.) Diagram shewing the branchial divisions of the aorta of the chick on the lower side of the pharynx, and the mode of their transformation into the aortic and pulmon. ary vessels. 31. The position of the ductus arteriosi relatively to the œsophagus in the chick about the 12th day. MAMMALIA. 32. (From Bojanus) Sketch shewing the relative position, size, &c. of the allantois and yolk-sac, &c. in the foetus of the sheep about three weeks old. A, The foetus and umbilical vesicle magnified. B, A small part of the foetal placenta or cotyledon of the calf, shewing the processes of the chorion on which the umbilical vessels are ramified. 33. (From Bojanus) The same in the dog of 24 days. 34. The same in the rabbit of about fourteen days, with the placenta. A, The entire ovum. B, The chorion and umbilical vesicle opened, so as to shew the allantois and placenta. 35. The head and neck of the embryo of the dog of three weeks, represented by Baer, and copied from Fig. 8. of former Essay. 36. The human embryo of about six weeks, in which I found two branchial apertures at least on each side of the neck, the heart exposed. A, The natural size. 37. (From Rathke) Anterior view of the neck of the foetus of the pig, represented in Fig. 9. of former Essay, shewing the branchial aper tures and operculum. 38. Heart and branchial arches in the rabbit, Fig. 34. 39. Diagram of the branchial arches of mammalia, and their transformations, corresponding with that of birds by Burdach. A, Ductus arteriosus of mammalia when just formed. 40. Posterior view of the heart and commencing lungs and trachea of the rabbit, Fig. 34. Magnified three diameters. 41. (From Rathke) The tongue, trachea, and lungs of the foetal horse seen from above, twice the natural size. A, The same seen from below. B, Section. 42. (From do.) Lungs of the pig farther advanced, twice the natural size, seen from below. A, The same, seen from above. B, Section. 43. The heart, lungs, pulmonary and aortic vessels, and ductus arteriosus of the human embryo of ten weeks, twice the natural size. On the Characters and Affinities of certain Genera chiefly belonging to the Flora Peruviana. By Mr David Don, Librarian to the Linnean Society, Member of the Imperial Academy Naturæ Curiosorum, of the Royal Botanical Society of Ratisbon, and of the Wernerian Society of Edinburgh, &c. THE object of the present memoir is an attempt to illustrate some of the more obscure genera published in the Flora Peruviana et Chilensis, a work containing a rich fund of interesting materials; but which, from its plan, it is much to be regretted, is, in many instances, unavailable for the purposes of science, the descriptions being often too meagre, and the details of the plates rarely sufficient for determining satisfactorily the classification of the new genera therein proposed. The examination, however, of authentic specimens in the Herbarium of Ruiz and Pavon, has rendered a task comparatively easy, which otherwise would have been very difficult, if not wholly fruitless. To illustrate the characters of groups already established, and to determine their several stations in the system of Nature, is of much more importance to the advancement of science, than the discovery of new species, or the forming of new combinations. I cannot hope to have been equally fortunate in all cases; but if I have succeeded, even in an approximation to ascertaining the characters and affinities of these genera, my utmost expectations will be fulfilled. CLEOMELLA, Decand. Syst. Linn. HEXANDRIA MONOGYNIA. Ord. Nat. CAPPARIDEÆ, Juss. Calyx monophyllus! 4-fidus: laciniis ovato-oblongis, mucronatis (ut in foliis!) integerrimis. Petala hypogyna, laciniis calycinis alterna, ellipticooblonga, obtusa, subcarnosa, venosissima, integerrima: ungue brevissimo. Stamina 6, æqualia, glandulæ elevatæ magnæ truncatæ inserta: filamenta subcapillaria, glabra: anthera longa, lineares, subtetragonæ, obtuse, biloculares, basi insertæ, ad floris expansionem spiraliter revoluta! loculis parallelis, bivalvibus, suturâ longitudinali exteriùs dehiscentibus. 2 Ovarium pedicellatum, ovatum, compressum, uniloculare: ovulis pluribus. Stylus brevissimus, glaber. Stigma simplex, truncatum. Capsula pedicellata, compressa, triangularis, truncata, unilocularis, bivalvis, decasperma valvis navicularibus, in angulum prominentem productis (compressione cauli contrario), quasi transversis : suture intùs magis prominulæ, funiculis umbilicalibus, complanatis persistentibus instructæ. Semina simplici gyro cochleata, extremitatibus connatis! umbilico in sinu; testa exterior crustacea, lævis; interior cartilagineo-membranacea: albumen nullum. Embryo flexurâ arctâ teres, luteus: cotyledonibus incumbentibus, semicylindricis: radicula his parùm longiore, basi acutâ. Planta (Mexicana) suffruticosa, procumbens, glaber, glauco-virens. Caules plurimi, teretes, ramosissimi. Folia alterna, petiolata, ternata: foliolis breviter stipitatis, cuneiformibus, retusis cum mucronulo reflexo, integerrimis, 3--4linearibus. Petioli semicylindrici, 3-6 lineas longi. Stipulæ 2, setaceæ, brevissimæ. Flores axillares, solitarii, pedunculati, albi. Pedunculi subcapillares, semipollicares. 1. C. mexicana. Cleomella mexicana, Decand. Prod. 1. p. 237. Cochlearia trifoliata, Sesse et Mocinno MSS. Hab. in Mexico. Sesse et Mocinno. 4 (V. s. sp. in Herb. Lamb.) A genus first proposed by my candid and learned friend M. De Candolle, in the second volume of his Prodromus Systematis Naturalis Regni Vegetabilis, where the essential characters are given; but I have thought that a detailed description, derived from the examination of several complete specimens, might be desirable, especially as it is probable M. De Candolle had not an opportunity of seeing specimens of it, but had derived his knowledge of the genus from the unpublished drawings of the Flora Mexicana. This genus is interesting, as exhibiting, both in its habit and structure, an evident affinity to the Tropaolea, which I have elsewhere proposed to place near to Crucifera and Capparidece. The Balsamineæ, which I also formerly proposed to add to this class, I am now fully persuaded must be arranged near to Violec-to which, even in the nervation and dentation of their leaves, they exhibit a closer affinity. The placenta in Cleomella are very prominent, and extend sometimes considerably within the capsule, constituting a sort of partition; and as the rudiment of a connecting membrane, analogous to the dissepiment in Cruciferæ, is occasionally observable in the young ovarium, it is probable that that organ is wholly absorbed in the very early stage of the ovarium, in Capparideæ. OCTOBER-DECEMBER 1830. H PARNASSIA, L. Syst. Linn. PENTANDRIA TETRAGYNIA. Ord. Nat. HYPERICINÆ, Nobis. Calya 5-phyllus, persistens: foliolis obtusissimis, æstivatione imbricatis. Petala 5, calycinis foliolis alterna, persistentia. Stamina hypogyna; fertilia 5, petalis alterna, filamentis subulatis, compressis, glabris; sterilia 15 v. plurima, filamentis basi in 5 phalanges connatis! apice distinctis, antherarum rudimentis minimis! Anthera incumbentes, biloculares: loculis parallelis, bivalvibus, suturâ longitudinali dehiscentibus, connectivo latiusculo distinctis: valvulis coriaceis: receptaculo dilatato: pollen farinaceum. Ovarium uniloculare: ovulis erectis, numerosissimis. Stigmata 4, crassiuscula, obtusa, densè papillosa, recurvula. Capsula (è folliculis 4 marginibus connatis constituta) unilocularis, 4-valvis, rimâ in medio cujusque loculi quadrifariam dehiscens: valvulorum marginibus connatis, intùs prominentibus et placentiferis. Semina numerosa, parva; testa exteriori membranaceâ, nucleo ampliori, punctatâ, in alam extensâ ; interiori crassiori, subcoriacea: albumen nullum. Embryo erectus, teres: radiculâ longâ, cylindraceâ, inferâ, centrifugâ. Herba (in paludosis regionum temperatarum provenientes) perennes, glabræ, copiosè lentiginosa ! Caules erecti, sulcati, uniflori, folio unico amplexicauli muniti. Folia petiolata, cordata, radicalia, integerrima, nervosa, pellucidopunctata! Flores albi, magni. Petala cum calyce multinervia, pellucidopunctata et densè lentiginosa. OBS. Tota ferè planta sub lente pellucido-punctata et lentiginosa ! _Structura fructificationis partium omninò cum Hypericinis convenit Parnassia, atque nervatione foliorum, calycis petalorumque. * Staminibus sterilibus in singulâ phalange plurimis. 1. P. palustris, petalis subrotundis unguiculatis; nervis extimis ramulosis, foliis cordatis. Parnassia palustris, L. Hab. in Europææ borealis paludosis, et in Sibiriâ. (V. v. sp.) Petalorum unguis brevissimus, contractus. Nervi intermedii subsimplices. ** Staminibus sterilibus in singulâ phalange definitis (3 v. 5). 2. P. ovata, petalis ellipticis ungue dilatatis; nervis extimis ramulosis, staminibus sterilibus ovario longioribus, foliis ovalibus. Parnassia ovata, Ledeb. in Act. Petrop. 1815. p. 514? P. ovata 6, Decand. Prod. 1. p. 320. Hab. in Sibiriâ orientali (Ledebour), in Canadâ. Pursh. (V. s. sp.) Sequenti proxima, sed duplò triplòve minor, nervis intermediis petalorum subsimplices, staminibus sterilibus ovario longioribus. 3. P. caroliniana, petalis oblongis: nervis omnibus ramulosis, staminibus sterilibus ovario brevioribus, foliis cordatis. Parnassia caroliniana, Mich. Fl. Amer. Bor. 1. p. 184. Pursh Fl. Amer. Hab. in Americâ boreali. Petala oblonga, ungue dilatato. (V. v. c. et s. sp.) 4. P. asarifolia, petalis oblongis; nervis extimis pulchrè divaricato-ramulosis, staminibus sterilibus ovario ter longioribus, foliis reniformibus. Parnassia asarifolia, Vent. Malm. t. 39. Pursh, Fl. Amer. Sept. 1. p. 208. Hab. in Americâ boreali. (V. v. c. et s. sp.) Omnium maxima. Folia radicalia reniformia, bipollicem lata; caulinum subrotundo-cordatum. Petala uncialia; nervis extimis pulcherrimè ramulosis; cæteris simplicibus, basi connatis. OBS. P. grandifolia, Decand. huic videtur maximè affinis, an satis differt? 5. P. fimbriata, petalis obovato-oblongis tripli-nerviis basi fimbriatis, staminibus sterilibus 25 ovario duplò brevioribus, foliis reniformibus. Parnassia fimbriata, Kon. in Ann. Bot. 1. p. 391. Smith, in Rees' Cyclop. in loco. Decand. Prod. 1. p. 320. Hook. Bot. Misc. 1. t. 23. Hab. in orâ occidentali America borealis. Menzies. (V. s. sp. in Herb. Smith.) Petala obovata, unguiculata, trinervia: nervis basi connatis; lateralibus trichotomis. Botanists have long been divided in opinion respecting the affinities of this highly interesting and curious genus of plants. Jussieu included it along with Drosera among his Capparides, and his opinion has been adopted by De Candolle, who has placed it in his family Droseraceae; and by the late Sir James Edward Smith and Mr Lindley it has been referred to Saxifrageæ. I am satisfied, however, that neither of these views is correct; and after a most careful examination, it appears to me that its true place in the natural system is among the Hypericina, with which it agrees in every essential point of structure, even to the nervation of its leaves and petals. The capsule is formed on precisely the same plan; the ovula are attached to the marginal placenta of the valves, whose inflected edges in both are united; but they are considerably more extended interiorly in the true Hypericinæ, and constitute the dissepiments of the capsule. The seeds of Parnassia, like those of Hypericina, are destitute of albumen, and otherwise their structure is precisely similar. The embryo is erect and cylindrical, having a long radicle pointing towards the hilum, and very short cotyledons. The anthers are bilocular, and incumbent with parallel cells; and the stigmata are like those of Hypericinæ, simple and papillose. In Sarothra, the stamina seldom exceed five; and in some others of the normal group of Hypericina, their number is also definite: but I do not mention these examples of reduction of stamina, to show that there necessarily is any |