Fern will be sure to die at the end of a couple of years, if you prevent it from putting forth leaves; the most efficient method of ensuring this is to beat the branches with a stick while they are in bud; for then the juices that drop from it will kill the roots.[81] It is said, too, that fern will not spring up again if it is pulled up by the roots about the turn of the summer solstice, or if the stalks are cut with the edge of a reed, or if it is turned up with a plough-share with a reed placed[82] upon it. In the same way, too, we are told that reeds may be effectually ploughed up, if care is taken to place a stalk of fern upon the share. A field infested with rushes should be turned up with the spade, or, if the locality is stony, with a two-pronged mattock: overgrown shrubs are best removed by fire. Where ground is too moist, it is an advantageous plan to cut trenches in it and so drain it; where the soil is cretaceous, these trenches should he left open; and where it is loose, they should be strengthened with a hedge to prevent them from falling in. When these drains are made on a declivity, they should have a layer of gutter tiles at the bottom, or else house tiles with the face upwards: in some cases, too, they should be covered[83] with earth, and made to run into others of a larger size and wider; the bottom, also, should, if possible, have a coating of stones or of gravel. The openings, too, should be strengthened with two stones placed on either side, and another laid upon the top. Democritus has described a method of rooting up a forest, by first macerating the flower of the lupine[84] for one day in the juice of hemlock, and then watering the roots of the trees with it. CHAP. 9. (7.)—THE DIFFERENT KINDS OF GRAIN. As the field is now prepared, we shall proceed to speak of the nature of the various kinds of grain; we must premise, however, that there are two principal classes of grain, the cereals,[85] comprising wheat and barley, and the legumina, such as the bean and the chick-pea, for instance. The difference between these two classes is too well known to require any further description. CHAP. 10.—THE HISTORY OF THE VARIOUS KINDS OF GRAIN.