XL. In the first place, the seed, which is the principle of all germination, is of two kinds, that which is not appreciable by our senses and that which is. Seed is hidden from us when it is disseminated in the air, as the physicist Anaxagoras holds, or is distributed over the land by the surface water, as Theophrastus maintains. The seeds which the farmer can see should be studied with the greatest care. There are some varieties, like that of the cypress, which are so small as to be almost invisible, for those nuts which the cypress bears, that look like little balls covered with bark, are not the seed but contain it. Nature gave the principle of germination to seed, the rest of agriculture was left for the experience of man to discover, for in the beginning before the interference of man plants were generated before they were sown, afterwards those seeds which were collected by man from the original plants did not generate until after they had been sown. Seed should be examined to ascertain that it is not sterile by age, that it is clean, particularly that it is not adulterated with other varieties of similar appearances: for age has such effect upon seed as in some respects to change its very nature, thus it is said that rape will grow from old cabbage seed, and vice versa.[90] _b. Transplanting_ In respect of transplanting, care should be taken that it is done neither too soon nor too late. The fit time, according to Theophrastus, is spring and autumn and midsummer, but the same rule will not apply in all places and to all kinds of plants: for in dry and thin clay soil, which has little natural moisture, the wet spring is the time, but in a rich and fat soil it is safe to transplant in autumn. Some limit the practice of transplanting to a period of thirty days. _c. Cuttage_ In respect of cuttage, which consists in planting in the ground a live cutting from a tree, it behooves you especially to see that this is done at the proper time, which is before the tree has begun to bud or bloom: that you take off the cutting carefully rather than break it from the parent tree, because the cutting will be more firmly established in proportion as it has a broad footing which can readily put out roots: and that it is planted promptly before the sap dries out of it. In propagating olives select a truncheon of new grown wood about a foot in length and the same size at each end: some call these _clavolae_ and others call them _taleae_. _d. Graftage_