Doctrine of signatures: (above) a plant with flowers resembling the human eye, and (below) a pair of eyes. Coloured ink drawing by C. Etheridge, 1906, after G.B. Della Porta.

Previous title, replaced September 2023 : Doctrine of signatures: (above) a plant with flowers resembling the human eye, and (below) a pair of eyes. Coloured ink drawing, c. 1923, after G.B. Della Porta.

In his Phytognomica, Della Porta discerns the hidden qualities of plants from the analogy of their forms with comparable features of animals. Those features of animals are "signs" which signify the same effects in plants which they have in animals: "ut cui signum competat, eidem et effectus: et cui effectio, pariter & signum: & quae signis vacent, & effectibus vacent" (Phytognomica, lib I, cap. xiii, Rouen 1650, p. 26); in English "That to which a sign belongs, to it also the effect belongs; and that to which the effect belongs, equally to it the sign belongs; and those which lack the signs also lack the effects"

The plant is described as having properties for healing the eye

1923

1 drawing : ink, with watercolour

Doctrine of signatures. Plant resembling the eyes. From a woodcut of the XVI. century.

Wellcome Collection 524852i

After: G.B. Della Porta, Phytognomica Io. Bap tistæ Neopolitani, octo libris contenta, lib. III, cap. xxxix (Rouen 1650 p. 233)