The Virginian Tobacco (_Nicotiana tabacum_) is an example of an inflated tube to the corolla (see _fig._ 70, _a_); the limb is small and divided into five pointed segments; and the capsule (_b_), which opens at the point into four valves when ripe, contains numerous seeds. The whole plant is covered with a clammy down, particularly the leaves, which are large and flabby, and which have their footstalks dilated at the base, so as partly to enfold the stem. There are many species of Nicotiana, some of which are very ornamental. It is the dried leaves that are used as tobacco, or ground into snuff. The Petunias are so well known, that I need say very little of the general form of their flowers, except to point out the connexion between them and the Tobacco. The corolla is salver-shaped, with a cylindrical tube, wider at the top than at the base, and a five-lobed limb. There are five stamens of unequal length, which are hidden in the tube of the corolla. The stigma has a broad head which is slightly two-lobed; and the calyx remains on the ripe capsule, which is two-celled, and opens in the upper part with two valves. The seeds are numerous and very small, and the leaves are pubescent and slightly clammy. If my readers will take the trouble to compare the Petunia and the Tobacco, they will be surprised to find how much the flowers are botanically alike. The differences are, that the calyx is more leaf-like in the Petunia than in the Tobacco; and the corolla of the Petunia is somewhat oblique, that is, two of the segments are smaller than the others; the filaments, also, are thickened at the base. It will appear extraordinary to every one acquainted with the flowers of the purple and the white Petunias, to find that some botanists have placed them in different genera. Such, however, is the case. On cutting open the delicate little seed of the white Petunia (_P. nyctaginiflora_), which it must have been very difficult to do, and examining it in a very powerful microscope, the embryo or germ of the future plant was found to be curved like that of most of the other Solanaceæ; whereas when the seed of the purple Petunia (_P. phœnicea_ or _violacea_) was examined in the same manner, the embryo was discovered to be straight. This purple Petunia has consequently puzzled botanists as much as some of the other plants I have had occasion to mention; and it has been called successively _Petunia violacea_, _Salpiglossis integrifolia_, _Nierembergia phœnicea_, and _Petunia phœnicea_.