Again, we may thus say, that where we require now three acres, one acre would be sufficient for growing the same amount of food, if planting wide apart were resorted to. And there is, surely, no more objection to planting wheat than there is to sowing in rows, which is now in general use, although at the time when the system was first introduced, _in lieu_ of the formerly usual mode of sowing broadcast, it certainly was met with great distrust. While the Chinese and the Japanese used for centuries to sow wheat in rows, by means of a bamboo tube adapted to the plough, European writers objected, of course, to this method under the pretext that it would require too much labour. It is the same now with planting each seed apart. Professional writers sneer at it, although all the rice that is grown in Japan is planted _and even replanted_. Everyone, however, who will think of the labour which must be spent for ploughing, harrowing, fencing, and keeping free of weeds three acres instead of one, and who will calculate the corresponding expenditure in manure, will surely admit that all advantages are in favour of the one acre as against the three acres, to say nothing of the possibilities of irrigation, or of the planting machine-tool, which will be devised as soon as there is a demand for it.[97] More than that, there is full reason to believe that even this method is liable to further improvement by means of _replanting_. Cereals in such cases would be treated as vegetables are treated in horticulture. Such is, at least, the idea which began to germinate since the methods of cereal culture that are resorted to in China and Japan became better known in Europe. (See Appendix O.) The future--a near future, I hope--will show what practical importance such a method of treating cereals may have. But we need not speculate about that future. We have already, in the facts mentioned in this chapter, an experimental basis for quite a number of means of improving our present methods of culture and of largely increasing the crops. It is evident that in a book which is not intended to be a manual of agriculture, all I can do is to give only a few hints to set people thinking for themselves upon this subject. But the little that has been said is sufficient to show that we have no right to complain of over-population, and no need to fear it in the future. Our means of obtaining from the soil whatever we want, under _any_ climate and upon _any_ soil, have lately been improved at such a rate that we cannot foresee yet what is the limit of productivity of a few acres of land. The limit vanishes in proportion to our better study of the subject, and every year makes it vanish further and further from our sight. FOOTNOTES: [71] The researches of Tisserand may be summed up as follows: