In a collection of tropical plants, where a few cisterns of aquatics are judiciously interspersed, the oppressive heat of the stove in which they grow, is as it were delusively alleviated, “in the mind’s eye,” by the simple, yet cooling sight of the little pools of water in which they float. Few are the number of observers who contemplate them without imbibing pleasure. This unquestionably arises from the strong but agreeable contrast that is exhibited to the eye, by the happy junction of the productions of the waters with those of the earth. They are vegetables of widely different orders--productions of very different natures--and inhabitants of elements diametrically opposite. The simple-spiked Aponogeton produces roundish tubers in various parts of its shoots; by the transplantation of which the plant is readily and speedily propagated. Our drawing of it was made in July last, at J. Vere’s, Esq. Kensington Gore, in whose collection it thrives very well. We have not as yet seen it in any other. [Illustration] PLATE CCCCVII. CALENDULA DENTATA. _Toothed-leaved Marygold._ CLASS XIX. ORDER IV. _SYNGENESIA POLYGAMIA NECESSARIA._ Tips united. Necessary Polygamy. ESSENTIAL GENERIC CHARACTER. RECEPTACULUM nudum. Pappus nullus. Calyx polyphyllus, subæqualis. Semina disci utplurimum membranacea. RECEPTACLE naked. Pappus none. Empalement many-leaved, nearly equal. The seeds of the disk chiefly membranous. SPECIFIC CHARACTER, &C. CALENDULA, foliis alternis linearibus remote et acute dentatis; caule fruticoso decumbente. MARYGOLD, with alternate linear remotely and acutely dentated leaves, and a decumbent shrubby stem. Calendula dentata. _Donn’s Hort. Cantab. ed. 3. 163._ REFERENCE TO THE PLATE. 1. The empalement. 2. A floret of the circumference. 3. A floret of the disk. 4. The same laid open and magnified, to show the situation of the chives. 5. The pointal, with the summit detached and magnified. Although this species of Calendula appears to have been introduced to the British gardens so long since as the year 1790, from the Cape of Good Hope, its native country; I do not find it enumerated either in Mr. Aiton’s Hortus Kewensis or Gmelin’s edition of Systema Naturæ; but it will in all probability be taken up in Willdenow’s Species Plantarum, when he arrives at that part of it which is to include the genus Calendula. It is well known in the gardens by the applicable name of dentata, but is not a common plant,--although, from the beauty and size of its flowers, highly worthy of general cultivation: its branches are weak, yet shrubby; and require support. It is a green-house plant, and is propagated by cuttings in the usual way. Our drawing was made from the Clapham collection in July last. [Illustration] PLATE CCCCVIII. DAHLIA PINNATA. _Pinnated Dahlia._ CLASS XIX. ORDER II. _SYNGENESIA POLYGAMIA SUPERFLUA._ Tips united. Superfluous Pointals. ESSENTIAL GENERIC CHARACTER.