Gynandria, the twentieth. The sta Monadelphia, the sixteenth, contains | be seen that each, especially fig. a, is a those plants whose flowers have their complete flower of itself. stamens united into one group, or as the word implies, brotherhood. The holly-mens in plants of this class proceed from hock is an excellent example. We have the pistil, as in the passion-flower, (fig.20.) given the meadow geranium, (fig. 16.) The orchis tribe belongs to this class. Fig. 16. Fig. 20. Syngenesia, the nineteenth. This class contains what are termed compound flowers, several small yet perfect florets composing one whole, and being enclosed in a common calyx. The essential character of this class is, that the anthers of the florets are united into a cylindrical form, and each floret has a single seed below the receptacle. The dandelion, chinaaster, marigold, and sunflower are familiar examples. We have given the common daisy, (fig. 19,) a a floret of the disk Fig. 19. a Diacia, the twenty-second class. In this class, not only are the stamens and the pistils found in separate flowers, but all the stamen-bearing flowers are on one plant, and all the pistil-bearing flowers on another plant, only the latter producing the fruit of the species. Example, the yew-tree, taxus baccata, (fig. 22,) a the Fig. 22, a. stamen bearing blossom, b the pistil Fig. 22, b. or centre, b a floret of the ray. It will bearing blossom, which is the rudiment | endeavour to understand what is here of a berry: both are magnified. To the twenty-third class, Polygamia, belong those plants whose flowers seem to be subject to no law of regularity, in the arrangement of the stamens and pistils. In some of the flowers are stamens only, in others pistils only, in others both stamens and pistils, (fig. 23.) Fig. 23. laid before you, by making it, as far as is practicable, matter of experiment. You may find even at this season of the year, when winter still lingers with us, many objects in the vegetable kingdom adapted to excite your admiration, in whatever direction you may feel disposed to rusticate; but the walk most prolific in objects of botanical nature will be along a lane, where the elevated hedgebank luxuriates in the morning sun. You should provide yourself with a tin botanizing box of convenient size, in which, if you have a garden for transplanting, you may carry a garden trowel. Thus equipped-and of such an accompaniment no one need be ashamed--you set out for your ramble, whether it be for The twenty-fourth class, Cryptoga-be either to find the locality of some paran hour, or for more; your object may mia, contains that branch of vegetation, ticular plant, or to fill a budget of whatwhose reproductive organs are undefined or indistinct, as the term implies. Fungi which you may bring home, and at leisure ever may be to you new and unexplored, the most despised leaf, or insignificant investigate. And you may be assured that morsel of moss, or a single bud of a tree, will amply reward the most diligent scrutiny. You will find a pocket lens to or mushrooms, moss of all varieties, ferns, sea-weeds, lichens, &c., belong to it. Now that the student may be able to determine to what class any plant belongs, let him pursue the following course. First, ascertain whether it has a simple or a compound flower: by the term compound, applied to a flower, is meant one that belongs to the class, Syngenesia. If simple, whether both stamens and pistils are present in every flower; if they are not, it will belong either to 21, 22, or 23. If in every flower there are present both stamens and pistils, observe whether the stamens are united into one or more sets; if so, it will belong either to 16, 17, or 18. If they are not united, nor are produced upon the pistil, count them, bearing in mind the difference between 12 and 13, 4 and 14, 6 and 15. This process simple enough, and cannot fail of conducting to a correct result. is assured be very serviceable in your examinations of the minute parts of the flower, &c., if you should not be fortunate enough to possess a proper botanical microscope. Such researches, besides the immediate pleasure they will impart to the student, will greatly assist his subsequent progress. flower in the course of this month :The following plants will probably CLASS DIANDRIA. *B. Veronica agrestis, wall speedwell. TRIANDRIA.— B. Crocus, of different varieties. HEXANDRIA.-B. Galanthus nivalis, the snowdrop. OCTANDRIA.-B. Daphne Mezereon, the mezereum. POLYANDRIA.— G. Helleborus niger, the Christmas rose. G.Helleborus hyemalis, the Winter aconite. G.Hepatica triloba, white, red, and blue. DIDYNAMIA.-B. Lamium album, white dead nettle. B.Lamium purpureum, purple do. TETRADYNAMIA.-B.Draba verna, early whitlow grass, grows on old walls. DIADELPHIA.-B. Ulex Europœus, the common furze or gorse. SYNGENESIA. B.Senecio vulgaris, the common ground The substance of this paper well considered, as it may be in a few hours, the student has made an important acquisition, and may cheerfully proceed, that he is going an easy way to obtain rational pleasure and improvement. In the next paper we purpose illus-sel. B. Bellis perennis, the daisy.B. Tustrating the first subdivision of this tem, called the Orders. In the meantime, kind reader, if you are disposed to view nature with an intelligent eye, and if you deem the present attempt in any measure calculated, to assist you, sys silago petasites, the white butter bur. The investigation of these, and whatever may ocur in the class Cryptogamia, will afford abundant employment for the present month to the lover of botany. B. British or wild. + G. grows in gardens. ELECTRICITY FROM MAGNETS. Ir is commonly supposed that electricity resides in all substances, each kind of matter having it in a fixed amount, and in a particular condition. When thus united with material existence, as a necessary element, it is, in reference to all our sensations, latent; and if it had not been separated from the matter with which it is combined, we could not possibly have been acquainted with its existence. We may illustrate our remarks on this subject by a comparison of electricity and heat. When we place a liquid over the fire, and expose it to a temperature greater than its own, the effect produced is soon made evident to the sense of touch. When the finger is plunged into a liquid thus acted upon by heat, we become conscious of a different state, and are accustomed to say, that its temperature has increased, or, in other words, that it is hotter. This is an effect produced, when heat is acting as a free agent; but there are times when it is so intimately connected with matter as to be altogether incapable of affecting the sense of touch, and is then said to be latent. Thus a vapour or a gas possesses a certain amount of heat necessary to support its condition, the removal of which will, in fact, change its state. Let us take steam as an example. Steam is formed by the addition of heat to water at the boiling point, that is 212 degrees. Under the common pressure of the atmosphere, water cannot be raised to a temperature greater than 212 degrees, and yet heat may be communicated to the liquid long after this has been done, and must produce some effect. Every one knows that it causes the formation of steam. But the steam is not hotter than the water, so that the heat must be in some manner connected with the particles of water in a latent state. For a further explanation of this subject, the reader may refer to a paper on "The Tea-kettle," Visitor, 1837, p. 91. Now, electricity exists in all substances in this latent state, but may be disturbed or set free in various ways, and it is only then that we can acquire any knowledge of its properties and effects. When two substances are rubbed together, their electric condition is disturbed. This means of obtaining free electricity was first discovered; and the agent thus developed is called common or ordinary electricity. For many years scientific men were experimenting with the elec trical machine without suspecting that any other means of obtaining the agent could be found. It was, however, discovered accidentally, that by the contact of metals and chemical action, the same agent was developed, producing effects sufficiently analogous to those of the common electricity to identify it as the same agent, yet vastly superior in many respects in its powerful control over matter. In the year 1824, Seebech discovered that when a circuit of perfect metallic conductors is formed, and unequally heated, the electrical condition is disturbed. This effect does not depend on any peculiarity in the metals, their contact or juncture. In the same year Yelin succeeded in an attempt to obtain electricity from a single metal. From his experiments it appears that electricity may be obtained from any metallic substance, when unequally heated. To distinguish the agent derived from this source, it is called thermo-electricity. Another and a fourth source of electricity has long been known; we refer to the electrical fishes. It appears that certain fishes are furnished with organs by which they are able to accumulate and discharge electricity. Such is the power of some of them in this respect, that it would be unsafe to receive a discharge from a full-grown and active fish. (See Weekly Visitor, for 1834, p. 447, 455.) We come now to the fifth source of electricity, and that which is the immediate object of our attention in this paper. Many of our readers are aware that electrical effects have been obtained from magnets. A large apparatus has been long exhibited in the Gallery of Practical Sciences, by which many curious experiments were shown. This arrangement, however, has been superseded by one invented by Mr. Clarke, the philosophical instrument maker. But before we proceed to a description of this instrument, and the experiments which may be performed with it, a few remarks will be required upon the means by which we may identify the electric agent. The effects obtained by the rotation of the armature of a magnet, forming and breaking contact with the poles, has been called magneto-electricity. How do we know that electricity is the cause? To this question we reply, because it produces results similar to those obtained from that agent, in whatever manner it may be developed. The effects of elec F nets, and therefore we are justified in tricity are the evolution of heat, the exhibition of magnetic properties, chemical decompositions, and an effect upon the animal system, when made the me-trical machine, that is, the instrument by dium of its transit from one substance which the magneto-electricity is obto another. Now, all these are the tained, may be understood by reference results of that agent developed by mag- to fig. 1. A is the magnetic battery, |