The Doctrine of Signatures he accepts unquestioningly. "Though Sin and Sathan have plunged mankinde into an Ocean of Infirmities Yet the mercy of God which is over all his Workes Maketh Grasse to grow upon the Mountaines and Herbs for the use of Men and hath not onely stemped upon them (as upon every man) a distinct forme, but also given them particular signatures, whereby a Man may read even in legible Characters the Use of them. Heart Trefoyle is so called not onely because the Leafe is Triangular like the Heart of a Man, but also because each leafe contains the perfect Icon of an Heart and that in its proper colour viz a flesh colour. Hounds tongue hath a forme not much different from its name which will tye the Tongues of Hounds so that they shall not barke at you: if it be laid under the bottomes of ones feet. Wallnuts bear the whole Signature of the Head, the outwardmost green barke answerable to the thick skin whereunto the head is covered, and a salt made of it is singularly good for wounds in that part, as the Kernell is good for the braines, which it resembles being environed with a shell which imitates the Scull, and then it is wrapped up againe in a silken covering somewhat representing the _Pia Mater_." Of those plants that have no signatures he warns the reader not to conclude hastily that therefore they have no use. "We must cast ourselves," he says, "with great Courage and Industry (as some before us have done) upon attempting the vertues of them, which are yet undiscovered. For man was not brought into the world to live like an idle Loyterer or Truant, but to exercise his minde in those things, which are therefore in some measure obscure and intricate, yet not so much as otherwise they would have been, it being easier to adde than invent at first." He then gives his own curious but naïvely interesting theory of plants "commonly accounted useless and unprofitable." "They would not be without their use," he argues, "if they were good for nothing else but to exercise the Industry of Man to weed them out who, had he nothing to struggle with, the fire of his Spirit would be halfe extinguished in the Flesh." After pointing out that weeding them out is in itself excellent exercise, he proceeds:--"But further why may not poysonous plants draw to them all the maligne juice and nourishment that the other may be more pure and refined, as well as Toads and other poysonous Serpents licke the venome from the Earth?... So have I seen some people when they have burned their fingers to goe and burne them again to fetch out the fire. And why may not one poyson fetch out another as well as fire fetch out fire?" "For should all things be known at once," he wisely concludes, "Posterity would have nothing left wherewith to gratifie themselves in their owne discoveries, which is a great encouragement to active and quick Wits, to make them enquire into those things which are hid from the eyes of those which are dull and stupid."