De Agricultura

He therefore occupies himself with improving the character of wild trees, and making them fruitful, and with further improving the character of fruitful trees by his care, and with reducing by pruning those branches which through superfluity of nourishment are too luxuriant, and with inducing those which are contracted and crowded to grow by the extension of their young shoots. Moreover, those trees which are of good sorts, and which make many shoots, he propagates by extending them under the earth in ditches of no very great depth, and those which do not produce good fruit he endeavours to improve by the insertion of other kinds into their roots, connecting them by the most natural union. For the same thing happens likewise in the case of men, that they firmly unite into their own family adopted sons, who are unconnected with them in blood, but whom they make their own on account of their virtues.