Ward's Accidental Discovery of the Terrarium

Below is how Ward described his 1829 discovery in his 1852 book On the Growth of Plants in Closely Glazed Cases (London: J. Van Voorst).

"The science of Botany, in consequence of the perusal of the works of the immortal Linnaeus, had been my recreation from my youth up, and the earliest object of my ambition was to possess an old wall covered with ferns and mosses. To obtain this end, I built up some rock-work in the yard at the back of my house, and placed a perforated pipe at the top, from which water trickled on the plants beneath; these consisted of Polypodium vulgare, Lomaria Spicant, Lastroea dilitata, L. Filix mas, Athyrium Filax foemina, Asplenium Trichomanes and a few other ferns, and several mosses procured from the woods in the neighborhood of London, together with primroses, wood-sorrel, &c. In consequence, however, of the volumes of smoke issuing from surrounding manufactories, my plants soon began to decline, and ultimately perished, all my endeavours to keep them alive proving fruitless.

When the attempt had been given up in despair, a fresh impetus was given to my pursuits, and I was led to reflect a little more deeply upon the subject, in consequence of a simple incident which occurred in the summer of 1829. I had buried the chrysalis of a sphinx [moth] in some moist mould contained in a wide-mouthed glass bottle, covered with a lid. In watching the bottle from day to day, I observed that the moisture which, during the heat of the day arose from the mould, condensed on the surface of the glass, and returned whence it came; thus keeping the earth always in some degree of humidity. About a week prior to the final change of the insect, a seedling fern and a grass made their appearance on the surface of the mould.

I could not but be struck with the circumstance of one of that very tribe of plants which I had for years fruitlessly attempted to cultivate, coming up sponte sua in such a situation, and asked myself seriously what were the conditions necessary for its well-being? To this the reply was -- a moist atmosphere free from soot or other extraneous particles; light; heat; moisture; periods of rest; and change of air. All these my plant had; the circulation of air being obtained by the diffusion law already described.

Thus, then, all the conditions requisite for the growth of my fern were apparently fulfilled, and it remained only to test the fact by experiment. I placed the bottle outside the window of my study, a room with a northern aspect, and to my great delight the plants continued to thrive. They turned out to be L. Filix mas and the Poa annua. They required no attention of any kind, and there they remained for nearly four years, the grass once flowering, and the fern producing three or four fronds annually. At the end of this time they accidentally perished, during my absence from home, in consequence of the rusting of the lid, and the consequent too free admission of rain water."

The mould Ward refers to was leaf mold, partly decomposed leaves which are often used in gardening. Ward's Poa annua (annual bluegrass) is a common introduced lawn weed in the United States, and his fern is the male fern, now called Drypoteris filix-mas. Ward mistakenly referred to the young fern as a seedling, however ferns grow from spores, not seeds. Ward also referred to the moth cocoon as a chrysalis, a term usually reserved for a butterfly pupa.

After his initial observations, Ward quickly began other experiments and soon constructed larger glass plant cases that filled his house and yard and even were placed on his roof. His largest was 2.4 m square and was named the Tintern Abbey case because it contained a model of the west window of Tintern Abbey, which was overgrown with 50 species of plants. He continually expanded the number of species successfully cultivated. In June 1833, he displayed a case at a meeting of the Linnean Society, a scientific organization in which he was an active Fellow.

The first publication of his work occurred in 1834, when John Loudon, leading horticulturist and publisher of the popular Gardener's Magazine, visited Ward's house. Loudon wrote enthusiastically of the house filled with fern cases and persuaded Ward to contribute an article. In December 1834, the influential Society of Arts requested further details on Ward's work resulting in another article, but not until 1836, when a letter from Ward describing his cases was also published in the Companion to the Botanical Magazine. This letter finally alerted the scientific community to Ward's invention, because also in 1836, the British Association for the Advancement of Science gave a grant for studying Wardian cases to a committee headed by James Yates. The 1838 committee report contained reports by Ward and several others.

Ward reported on his studies to the British Association in 1837. Michael Faraday, famed physical scientist and President of the Royal Society, gave a lecture on Wardian cases before the Royal Institution in April, 1838. In 1839, Daniel Ellis published a detailed 25-page report of experiments on Wardian cases conducted at the Royal Botanic Gardens in Edinburgh. At the Great Exhibition of 1851, Ward displayed a bottle containing a fern and mosses that had not been watered for 18 years.