Lucerne[301] is by nature an exotic to Greece even, it having been first introduced into that country from Media,[302] at the time of the Persian wars with King Darius; still it deserves to be mentioned among the very first of these productions. So superior are its qualities, that a single sowing will last more than thirty[303] years. It resembles trefoil in appearance, but the stalk and leaves are articulated. The longer it grows in the stalk, the narrower is the leaf. Amphilochus has devoted a whole book to this subject and the cytisus.[304] The ground in which it is sown, being first cleaned and cleared of stones, is turned up in the autumn, after which it is ploughed and harrowed. It is then harrowed a second and a third time, at intervals of five days; after which manure is laid upon it. This seed requires either a soil that is dry, but full of nutriment, or else a well-watered one. After the ground has been thus prepared, the seed is put in in the month of May;[305] for if sown earlier, it is in danger from the frosts. It is necessary to sow the seed very thick, so that all the ground may be occupied, and no room left for weeds to shoot up in the intervals; a result which may be secured by sowing twenty modii to the jugerum. The seed must be stirred at once with the rake, to prevent the sun from scorching it, and it should be covered over with earth as speedily as possible. If the soil is naturally damp or weedy, the lucerne will be overpowered, and the spot degenerate into an ordinary pasture; it is necessary, therefore, directly the crop is an inch in height, to disengage it from all weeds, by hand, in preference to the weeding-hook. It is cut when it is just beginning to flower, and this is repeated as often as it throws out new blossoms; which happens mostly six[306] times in the year, and four at the very least. Care should be taken to prevent it from running to seed, as it is much more valuable as fodder, up to the third year. It should be hoed in the spring, and cleared of all other plants; and in the third year the surface should be well worked with the weeding-hook. By adopting this method, the weeds will be effectually destroyed, though without detriment to the lucerne, in consequence of the depth of its roots. If the weeds should happen to get ahead of it, the only remedy is to turn it up repeatedly with the plough, until the roots of the weeds are thoroughly destroyed. This fodder should never be given to cattle to satiety, otherwise it may be necessary to let blood; it is best, too, when used while green. When dry, it becomes tough and ligneous, and falls away at last into a thin, useless dust. As to the cytisus, which also occupies the very foremost rank among the fodders, we have already spoken[307] of it at sufficient length when describing the shrubs. It remains for us now to complete our account of all the cereals, and we shall here devote a portion of it to the diseases to which they are subject.