On September 20, 1845, the polymathic Scottish mathematician Mary Somerville — the woman for whom the word scientist was coined — sent a letter to the polymathic English astronomer John Herschel, who six years earlier had coined the word photography for the radical invention of capturing light and shadow with chemistry. Somerville recounted her landmark experiments with an alternative image-making process, for which Herschel had laid the groundwork several years earlier.

Called anthotype, from the Greek anthos (“flower”) and typos (“imprint”), the process is kindred to cyanotype, but instead of using a solution of potassium ferricyanide and ferric ammonium citrate sensitive to the blue portion of the solar spectrum spilling into ultraviolet, it trades the laboratory for the garden, using the same photosensitive pigment compounds involved in how leaves change color and the entire spectrum.

To create an anthotype, a flat object is placed on paper coated with an emulsion made not of chemicals but of plant extracts — crushed petals, tinctures of roots — and then exposed to direct sunlight for a long period: days, weeks, even months, depending on the plant, season, and intensity of the light. Eventually, the sun bleaches out the parts of the paper not covered, leaving an imprint of the photopositive object in the color of the pigment used in the coating — a ghostly beauty with the chromatic quality of a watercolor and the feeling-tone of a poem.

On the first of January the following year, Somerville’s results were published as On the Action of the Rays of the Spectrum on Vegetable Juices in the Philosophical Transactions of the Royal Society — not under her own name, since women could not publish in scientific journals, but under Herschel’s, who gave her full credit.

Condensing the solar spectrum through a lens of flint glass and projecting it through a pinhole onto thick white letter paper washed with various pigments and compounds — from “the velvety petals of a scarlet geranium” to the juice of the beet-root — Somerville discovered that the juices of the same plant produce different colors depending on what portion of the spectrum they are exposed to and whether they are extracted with water or alcohol. Some of the results were entirely counterintuitive, rendering colors very different from those of the flower — the dark orange nasturtium, for instance, turned the paper Prussian blue when exposed to light. Somerville marveled at how “the action of the different parts of the spectrum seems very capricious” — a delightful unpredictability that recurred across all of her experiments. She wrote of one:

The juice of the petals of pale blue Plumbago auriculata in distilled water imparted its tint to writing-paper, which, after exposure to the action of diffused light, acquired a pale yellowish green hue. The part under the lavender and violet rays of the spectrum, repeatedly washed with the juice, assumed a pale brown colour: the indigo rays seemed to have no effect, although from their lowest edge to the distance of half the length of the spectrum below the red rays, a lavender blue image was formed. Under the orange rays a minute indigo-coloured spot appeared, and also a larger spot of the same colour under the yellow, which were soon blended into one, forming a single oblong figure of maximum intensity, surrounded by a halo of paler indigo

This was entirely new insight into the interaction of photons and organic molecules, into the materiality of beauty, into how nature works. Mary Somerville had chipped another fragment of knowledge from the monolith of mystery — the task and measure of the true scientist.

But as commerce interceded with creativity and the seeds of our insta-culture were planted, the much faster — and much more toxic — chemical imaging processes like daguerreotype and tintype became favored over the slow, gentle work of sunlit flowers.

Expelled from the realm of science and commercial technology, anthotypes became the province of artists.

Meanwhile in New England, around the time she sat for the daguerreotype that remains her sole surviving photograph, the teenage Emily Dickinson was discovering a kindred way of immortalizing flowers.

Not long after botany gave women a foothold in Victorian science, the young poet began pressing and arranging hundreds of wildflowers into her remarkable herbarium, on the pages of which she honed the art of composition and incubated her ecological poetry.

Two centuries later, photographers Amanda Marchand and Leah Sobsey pay an anthotype homage to Dickinson in their lovely collaboration This Earthen Door, titled after a line from her poem “We can but follow to the Sun.”

Painstakingly recreating all 66 pages of Dickinson’s herbarium in large-scale anthotypes made with juices from 66 species of plants the poet grew in her garden, they offer something uncommonly lyrical — part color study and part time travel, harmonizing the ephemeral and the eternal, radiating the quiet consolation of the dialogue between nature and human nature.

But there is also an elegiac undertone to the project: The evolution of flowering plants is what made mammals possible — creatures capable of photography and poetry — and yet flowers are now evolving to bloom less. Metabolically costly since the start, producing blossoms to attract pollinators is now becoming prodigal as pollinator populations are rapidly declining. Instead of relying on pollinators, many bisexual species — the botanical term for which is perfect flowers — are evolving to fertilize their own seeds with their own pollen: a process known as selfing. Its haunting downside is that, because diversity is nature’s fulcrum of resilience, flowers pollinated by selfing replicate their own genes in the next generation of seeds, amplifying their existing vulnerabilities to disease and drought — something cross-pollination prevents by mixing the DNA of different plants into new, adaptive combinations of genes. (I am reminded of Iris Murdoch’s lovely notion that beauty and art grant us an opportunity for unselfing, disrupting the ruminative replication of our beliefs and mental states with something magnificently other — and what is psychological resilience if not the ability to see beyond our suffering, and what is compassion if not the ability to step outside the self and take in the other with a gasp of tenderness.)

The less flowers bloom, the less nectar they are providing for the already endangered pollinators, foreboding a vicious cycle for the entire planetary ecosystem. Against this ecological backdrop, the ghostly loveliness of these anthotypes may one day read as a requiem for life — an echo of a time on Earth when flowers flourished and poetry was possible.

But amid a world increasingly famished for beauty as it careens into brutality, they are also a tender reminder that the human species is as capable of making art as it is of making war, that each day the Sun rises to shine its spectrum upon this lush wonderland of chemistry and chance, we begin again and get to choose afresh how to spend our light.

Complement with contemporary artist Rosalind Hobley’s stunning cyanotypes of flowers, created two centuries after Anna Atkins became the first person to illustrate a book with photographic images — her hauntingly beautiful cyanotypes of algae — and the story of the Victorian algae herbarium that brought the submarine wilderness to Earth, then delve into this excellent field guide to making your own anthotypes.