The last, and not the least concern in the cultivation of this plant, is the destruction of the worm that nature has given it for an enemy, and which, like many other reptiles, preys on its benefactor. To destroy these, which are the only insects that molest this plant, or at least to keep them under, for it is impossible totally to exterminate them, every leaf must be carefully searched. As soon as a wound is discovered, and it will not be long before it is perceptible, care must be taken to destroy the cause of it, who will be found near it, and from his unsubstantial texture, which I shall describe at the conclusion of this chapter, be easily crushed: but the best method is to pluck it away by the horn, and then crush it. Without a constant attention to these noxious insects, a whole field of plants may be soon destroyed; and even if any of them are left in the leaves, during the cure, they prove equally destructive. This is termed "worming the tobacco;" and as these worms are found most predominant the latter end of July, and the beginning of August, they must be particularly attended to at that season. As I have just observed, that it is impossible, without experience, to point out the due time for topping the plant, so it is equally as impossible to ascertain the time it will take to ripen in this climate. That can only be known by future observations; for as it is at present only cultivated in England as an ornament for the garden, no attention has, I believe, been hitherto bestowed on the preservation of its leaves. The apparent signs, however, of its maturity are these: The leaves, as they approach a state of ripeness, become more corrugated or rough; and when fully ripe, appear mottled with yellowish spots on the raised parts, whilst the cavities retain their usual green colour. They are, at this time, also thicker than they have before been, and are covered with a kind of downy velvet, in the same manner as the stalks are described to be, in the preceding chapter. If heavy rains happen at this critical period, they will wash this excrescent substance off, and thereby damage the plants. In this case, if the frosty nights are not begun, it is proper to let them stand a few days longer; when, if the weather be more moderate, they will recover this substance again. But if a frost unexpectedly happens during the night, they must be carefully examined in the morning before the sun has any influence on them; and those which are found to be covered with frosty particles, whether thoroughly ripe or not, must be cut up: for though they may not all appear to be arrived at a state of maturity, yet they cannot be far from it, and will differ but little in goodness from those that are perfectly so.