One interesting feature of Bacon’s Sylva Sylvarum is the constant attempt to naturalize explanations. Bacon stripes traditional theories of their vitalist and magic coat. He re-interprets the alchemical theory of the Paracelsians, criticizes the sympathies and antipathies of the natural magic and attempts to explain “sympathetic effects” through purely natural (and quantitative) mechanisms. Here is one example (and see the translation here):
493. Some of the ancients, and likewise divers of the modern writers that have labored in natural magic, have noted a sympathy between the sun, moon, and some principal stars, and certain herbs and plants. And so they have denominated some herbs solar, and some lunar; and such like toys put into great words. It is manifest that there are some flowers that have respect to the sun; in two kinds; the one by opening and shutting, and the other by bowing and inclining the head. For marygolds, tulippa’s, pimpernel, and indeed most flowers, do open or spread their leaves abroad when the sun shineth serene and fair: and again (in some part) close them or gather them inward, either towards night, or when the sky is over-cast. Of this there needeth no such solemn reason to be assigned, as to say that they rejoice at the presence of the sun, and mourn at the absence thereof. For it is nothing else but a little loading of the leaves and swelling them at the bottom with the moisture of the air; whereas the dry air doth extend them. And they make it a piece of the wonder, that garden claver will hide the stalk when the sun sheweth bright; which is nothing but a full expansion of the leaves. For the bowing and inclining the head, it is found in the great flower of the sun, in marygolds, wart-wort, mallow flowers, and others. The cause is somewhat more obscure than the former; but I take it to be no other, but that the part against which the sun beateth waxeth more faint and flaccid in the stalk, and therby less able to support the flower.
Bacon’s target here is Giovan Battista della Porta whose Phytognomonica (I, 18) offers precisely the kind of magical explanations criticized in the paragraph above. Della Porta’s Magia naturalis also deals with solar and lunar plants and various forms of cosmic sympathies (Magia naturalis, I, VIII).