Certain plants were deemed to represent some disease or morbid condition, and were judged to be helpful in its cure. Thus those were administered in cases of calculus which represented stones, such as Milium solis, the root of the White Saxifrage, the shells of Nuts, and Nuts themselves. Spotted plants and herbs were thought to eradicate spots, and scaly plants to remove scales. Perforated herbs were selected for the cure of wounds and perforations of the body. Plants which exude gums and resins were considered available for the treatment of pus and matter. Swelling plants were thought good for tumours; those that permit the cutting or puncturing of the stem were employed for closing up wounds; and those that shed bark and skin were thought adapted for the cleansing of the skin.
Accordingly as plants and herbs exhibited peculiarities in their actions, so were they supposed to operate on man. Thus, sterile plants, such as Lettuce, Fern, Willow, Savin, and many others, were believed to conduce to the procuring of sterility in men; whilst salacious and fecund plants were considered to confer fecundity. On the same principle, long-lived and evergreen plants were said to procure vigour for the human body.
Helvetius has left a list of classified herbs and plants which in his time were considered by experts in herbcraft to exhibit peculiar marks and Signatures by which they could be identified with the several parts and members of the human body. This may be said to have formed the basis of the system embraced in the Doctrine of Plant Signatures, and as it epitomises the results of the protracted and laborious researches of the old herbalists, who may fairly be said to have laid the foundations of our present system of Botany, it has been thought worth while to give an abbreviation of it.
The Doctrine of Signatures did not exclusively apply to the medicinal virtues of herbs and plants: for example, Hound’s-tongue Cynoglossum officinale, named from the shape and softness of its leaf, was (if we may believe William Coles) thought to “tye the tongues of hounds, so that they shall not bark at you, if it be laid under the bottom of your feet, as Miraldus writeth.” Garlic (from the Anglo-Saxon words gár, a spear, and leác, a plant) was, from its acute tapering leaves, marked out as the war plant of the warriors and poets of the North. The heavenly blue of the flower of the Germander Speedwell won for it the Welsh appellation of the Eye of Christ. Even abstract virtues were to be learnt by an attentive study of the Signatures of certain plants, according to the dictum of that loyal and godly herbalist Robert Turner, who naively tells us that “God hath imprinted upon the Plants, Herbs, and Flowers, as it were in Hieroglyphicks, the very Signature of their Vertues; as the learned Grollius and others well observe: as the Nutmeg, being cut, resembles the Brain; the Papaver erraticum, or red Poppy Flower, resembleth at its bottom the setling of the Blood in the Plurisie; and how excellent is that Flower in Diseases of the Plurisie, and Surfeits hath sufficiently been experienced.”
In the Heliotrope and Marigold subjects may learn their duty to their Sovereign: which his Sacred Majesty King Charles the First mentions in his Princely Meditations, walking in a Garden in the Isle of Wight, in the following words, viz.:—
“‘The Marigold observes the Sun
More than my subjects me have done,’ &c.”
That great naturalist, John Ray, whilst expressing his disbelief of the Doctrine of Plant Signatures as a whole, admitted that there were tangible grounds for the formation of the system. He wrote:—“Howbeit, I will not deny but that the noxious and malignant plants do, many of them, discover something of their nature by the sad and melancholick visage of their leaves, flowers, or fruits. And that I may not leave that head wholly untouched, one observation I shall add, relating to the virtues of plants, in which I think is something of truth; that is, that there are, by the wise dispensation of Providence, such species of plants produced in every country, as are made proper and convenient for the meat and medicine of the men and animals that are bred and inhabit therein. Insomuch that Solenander writes that, from the frequency of the plants that spring up naturally in any region, he could easily gather what endemical diseases the inhabitants thereof are subject to. So in Denmark, Friesland, and Holland, where the scurvy usually reigns, the proper remedy thereof, Scurvy-grass, doth plentifully grow.”