The seed is generally divided into two compartments, called _lobes_, or _cotyledons_, as is exemplified by this bean (PLATE XV. Fig. 1.)--the dark-coloured kind of string which divides the lobes is called the _radicle_, as it forms the root of the plant, and it is from a contiguous substance, called _plumula_, which is enclosed within the lobes, that the stem arises. The figure and size of the seed depend very much upon the cotyledons; these vary in number in different seeds; some have only one, as wheat, oats, barley, and all the grasses; some have three, others six. But most seeds, as, for instance, all the varieties of beans, have two cotyledons. When the seed is buried in the earth, at any temperature above 40 degrees, it imbibes water, which softens and swells the lobes; it then absorbs oxygen, which combines with some of its carbon, and is returned in the form of carbonic acid. This loss of carbon increases the comparative proportion of hydrogen and oxygen in the seed, and excites the saccharine fermentation, by which the parenchymatous matter is converted into a kind of sweet emulsion. In this form it is carried into the radicle by vessels appropriated to that purpose; and in the mean time, the fermentation having caused the seed to burst, the cotyledons are rent asunder, the radicle strikes into the ground and becomes the root of the plant, and hence the fermented liquid is conveyed to the plumula, whose vessels have been previously distended by the heat of the fermentation. The plumula being thus swelled, as it were, by the emulsive fluid, raises itself and springs up to the surface of the earth, bearing with it the cotyledons, which, as soon as they come in contact with the air, spread themselves, and are transformed into leaves. --If we go into the garden, we shall probably find some seeds in the state which I have described-- [Illustration: Plate XV. Vol. II. p. 250 Germination. Fig. 1 & 2. A.B Cotyledons. C Envelope. D Radicle. Fig. 3. A.B Cotyledons. C Plumula. D Radicle. Fig. 4. A.B. Cotyledons. C Plumula. D Radicle. Fig. 5. Apparatus to illustrate the mechanism of breathing. A.A Glass Bell. B Bladder representing the lungs. C Bladder representing the Diaphragm.] EMILY. Here are some lupines that are just making their appearance above ground. MRS. B. We shall take up several of them to observe their different degrees of progress in vegetation. Here is one that has but recently burst its envelope--do you see the little radicle striking downwards? (PLATE XV. Fig. 2.) In this the plumula is not yet visible. But here is another in a greater state of forwardness--the plumula, or stem, has risen out of the ground, and the cotyledons are converted into seed leaves. (PLATE XV. Fig. 3.) CAROLINE. These leaves are very thick and clumsy, and unlike the other leaves, which I perceive are just beginning to appear. MRS. B.