What discourse can touch all?  Can the human mind make an exact review, remark every distinctive property, exhibit all the differences, unveil with certainty so many mysterious causes?  The same water, pumped up through the root, nourishes in a different way the root itself, the bark of the trunk, the wood and the pith.  It becomes leaf, it distributes itself among the branches and twigs and makes the fruits swell—it gives to the plant its gum and its sap.  Who will explain to us the difference between all these?  There is a difference between the gum of the mastich and the juice of the balsam, a difference between that which distils in Egypt and Libya from the fennel.  Amber is, they say, the crystallized sap of plants.  And for a proof, see the bits of straws and little insects which have been caught in the sap while still liquid and imprisoned there.  In one word, no one without long experience could find terms to express the virtue of it.  How, again, does this water become wine in the vine, and oil in the olive tree?  Yet what is marvellous is, not to see it become sweet in one fruit, fat and unctuous in another, but to see in sweet fruits an inexpressible variety of flavour.  There is one sweetness of the grape, another of the apple, another of the fig, another of the date.  I shall willingly give you the gratification of continuing this research.  How is it that this same water has sometimes a sweet taste, softened by its remaining in certain plants, and at other times stings the palate because it has become acid by passing through others?  How is it, again, that it attains extreme bitterness, and makes the mouth rough when it is found in wormwood and in scammony?  That it has in acorns and dogwood a sharp and rough flavour?  That in the turpentine tree and the walnut tree it is changed into a soft and oily matter?