Certain trees, like the fir and the pine, flourish most in the mountains on account of the eager air, while in this region where it is more temperate the poplars and the willows thrive best. Again the arbute and the oak prefer the more fertile lands, while the almond and the fig trees love the lowlands.[61] The growth on the low hills takes on more of the character of the plains, on the high hills that of the mountains. For these reasons the kind of crops to be planted must be suited to the physical characteristics of the farm, as grain for the plains, vines for the hills and forests for the mountains. All these considerations should be weighed separately with reference to each of the three kinds of conformation. VII. "It seems to me," said Stolo, "that, so far as concerns the natural situation of a farm, Cato's opinion is just. He wrote, you will recall, that the best farm was one which lay at the foot of a mountain looking to the South." Scrofa resumed: "So far as concerns the laying out of the farm, I maintain that the more appearances are considered the greater will be the profit, as, for instance, orchards should be planted in straight lines arranged in quincunxes and at a reasonable distance apart. It is a fact that, because of their unintelligent plan of planting, our ancestors made less wine and corn to the acre than we do. The point is that if each plant is set with due reference to the others they occupy less land and are less likely to screen from one another the influence of the sun and the moon and the air. This may be illustrated by an experiment: you can press a parcel of nuts with their shells on into a measure having only two thirds of the capacity of what is required to contain them after they have been cracked, because the shells keep them naturally compacted. When trees are planted in rows the sun and the moon have access to them equally from all sides, with the result that more raisins and olives are developed and then mature more quickly, a double result with the double consequence of a larger crop of must and oil and a greater profit." _How character of soil affects agriculture_