Rossolis

In an 1860 letter to geologist Charles Lyell, Darwin wrote that he "care[d] more about Drosera than the origin of all the species in the world." With a keen naturalist's eye, Darwin observed Drosera rotundifolia's capacity to capture insects, its sensitivity to touch, and its ability to secrete enzymes not unlike the digestive juices of animals. These observations would lay the groundwork for Insectivorous Plants, which appeared in 1875. Today, sundews are among the most recognizable carnivorous plants.

Yet long before Darwin hypothesized the insectivorous nature of the sundew, the plant's glistening tentacles captured the imagination of herbalists, who named it ros solis or "dew of the sun" because it appeared covered in dew even as the heat of the sun evaporated the moisture from surrounding plants. In turn, it was surmised that the sundew was useful for combating dehydration as well as for pulmonary problems, including asthma and "dry" cough. Modern studies suggest that the sundew may indeed have antitussive properties. 

Illustration from Jacques Daléchamps Histoire générale des plantes (Lyon, 1615)

But the sundew was more than medicine to early modern minds. Madeleine de Scudéry, celebrated seventeenth-century novelist, wrote of the sundew: "une fleur appellée rossolis qui vient d'une montagne de Languedoc, est toujours couverte de rosée pendant la grande ardeur du soleil, dans le même temps qu'elle sèche sur les herbes qui l'environnent." [A flower called rossolis that comes from a mountain in Languedoc is always covered in dew in the heat of the sun, which dries the surrounding vegetation.] This passage appears in her moral essay "On Flowers and Fruits," where the seemingly never-ending variety of botanical wonders, including the sundew, offers proof that "it pleased God to decorate the earth with such beauties."
For theologians, the sundew's marvelous ability to conserve its dew in the heat of the day was nothing short of miraculous. In a devotional book titled Les plaisirs de la vie spirituelle (1682), the Carmelite Dorothée de Saint-René assimilated the Virgin Mary, "Dew of Heaven" (Ros Coeli) to the sundew (ros solis). The plant "is marvelous in that, when exposed to the most ardent rays of the sun, it conserves dew in its leaves, which are fashioned like little spoons, such that it appears always covered in bright drops like pearls." The preacher's poetic description of the sundew sets the stage for the theological analogy he wishes to make: "Such was the humble Virgin, who [...] attracted the dew of the divine Word."
Of course, approaching Nature as a "great book" to be read in light of Christian doctrine was common practice. One of the most striking examples is found in Augustin Chesneau's emblem-book, Les Emblèmes sacrez sur le tres-saint et tres-adorable sacrement de l'Eucharistie (1667), a French translation of the original (much better titled, if you ask me) Orpheus eucharisticus (1657). The Latin title reveals the cleric's aspirations: like Orpheus, whose music calmed wild animals and coaxed rocks and trees to dance, God makes all of Creation sing. The book, a collection of one hundred emblems designed to encompass the vastness of the natural world (divided into sections on plants, animals, birds, stones, and so on) thus functions a the "great book of Nature" writ small, a theological field guide. The sundew appears as the 92nd emblem:

Humble souls, Chesneau explains, are like the little sundew (Rossolis) that grows in low, wet places. They are always "moistened with drops of heavenly grace's dew," especially when they are near the altar, where the "heat" of charity increases the production of heavenly dew (much like the heat of the sun appeared to increase the sundew's dewy appearance). Ultimately, the sundew is for Chesneau a figure of humility, contrasted with the "heights of self-esteem" that are exposed to "the most tempestuous vices" and "the winds of ambition."

There are probably many more references to sundews as marvelous, miraculous plants. Indeed, sundews continue to fascinate us not only by virtue of their insectivory, but also because of their unique and enchanting appearance. 

Leaf of Drosera anglica