Class XV. Dicotylcdones, with stamens, in separate flowers, from the pistils.
Orders five. 96. Enphorbite, consists of Mercurialis, Euphorbia, Phyllanthus, Buxus, Croton, Hippomane, with several more, for the most part acrid, and often milky plants ; 97 the gourd tribe, Bryoniai Cucumis, Passi flora, with a few more; 98 Urticre, com posed of Ficus, Morus, Urtica, Humulus, Cannabis, to which, among others, Piper is subjoined, as an ally ; 99 .thnentacece, Salix, Populus, Betula, Quercus, Corydus, &c. to which tlimus, Celtis, and Fother gilla, are prefixed ; 100. Conifene, Ca suarina, Juniperus, Cupressus, are exam ples of this very distinct order.
At the end of this system is a large as semblage of genera, under the denomina tion of Planta. incerhe setlis, as not capa ble of being referred to any of the fore going orders. Some of them, perhaps, when better known, may be removed in to the body of the system, but many mast always remain in doubt. tor is this to be esteemed as a fault peculiar to the sys tem of Jussieu. It must be the case with all natural systems, unless it were possi ble for their contrivers to have all the genera of plants from every corner of the earth before them at one view.
As long as any remain to be discovered, or any that are discovered are imperfect ly known, every such system must be defective. Besides, it appears that plants are connected, not in one regular series, but, as it were, in a circle, touching or approaching each other by so many differ ent points, that no human sagacity can de tect which points of connection are most important, so as to obtain an infallible clue through so vast a labyrinth.
A natural system of botanical arrange ment being therefore probably unattaina ble in perfection, we are obliged to be content, for daily use, with an artificial one. When we meet with an unknown plant, we count its stamens and styles, or observe any other circumstance attend ing those organs, on which the characters of the Linnwan classes are founded. Hav ing easily determined the class of our plant, we in like manner ascertain its or der. We proceed to compare the parts of its flower and fruit with the characters of every genus in that order, till we find one that agrees with them. Having fixed
the genus, we in like manner read over the characters of the species, in case the genus consists of more than one, till we are satisfied we have met with the right. Thus we learn the generic and specific name of our plant, and are enabled to find any thing recorded concerning it.
Such isthe mode of applying the Lin mean system to use, and in ordinary cases no difficulties attend it. But it may happen, that we have found a plant whose number of stamens is variable in itself, or perhaps different from their usual number in the natural genus to which it belongs ; for all genera ought to be na tural, and no species must be divided from its brethren, on account of charac ters which only respect the artificial classes and orders. In this case Linnwus has provided us a remedy, by enumerat ing at the head of each class all such anomalous species, as far as he could re collect or determine them ; so that if our plan does not agree with any of the re gular genera of the class, we may seek it among these irregular species. If, after all our attempts, the plant under consider ation still proves refractory, the system of Jussieu comes to our aid. Not that we can hope, even though adepts in the science, to determine a plant by the same mode in this author ; beginning with the cotyledons, which, in many cases, we shall find it impossible to judge of, and which, when found, will often lead us astray in the more abstruse orders of Jus sieu.
The true way to use this system is, to consider what known genus or family our plant most approaches in its habit and leading characters. By turning to such, through the help of the index, and read ing the characters of the corresponding order, we shall be able to judge how far we are right, and shall, at any rate, grow familiar with natural orders and affinities. When we have determined the genus of our plant in Jussieu, as he has not treat ed of species, we must still recur to Lin wens for that part of the subject, as well as for synonyms of other authors, and re ferences to figures or descriptions.