University of arizona herbarium's illustration collection -
drawings by evelyn thornber

In addition to the many botanical drawings by Lucretia Hamilton, the University of Arizona Herbarium's illustration collection also includes 450 pen and ink works by artist Evelyn Thornber, the niece of John James Thornber, UA biology professor and botanist for the Agricultural Experiment Station from 1901 to 1942. Cactus lovers may be familiar with Professor Thornber’s 1932 work The Fantastic Clan – The Cactus Family, which he co-authored with Frances Bonker. The book contains a few watercolor paintings by Ella Howard Estill and drawings of several prickly pears and chollas by Evelyn Thornber. (The UA Herbarium’s collection also includes nearly 600 watercolors by Estill.)

Ms. Thornber used a style in her drawings that is simpler than Hamilton’s. These are basically straightforward line drawings that are useful for clearly showing the structures of the plant with no frills. None of the pen and ink techniques used to create three-dimensional form are used in these drawings.

One of the more intricate drawings in the Thornber collection is of Clematis drummondii, the desert clematis or old man’s beard. This is a tough, fibrous vine with slightly fuzzy, bright green leaves that can be found in canyons and washes from southern California to southern Texas and into Mexico. The vine has no actual tendrils for climbing, but the leaf petioles are modified to do the work of tendrils, allowing the plant to climb or trail to 30’.

Desert clematis is a dioecious plant. In Thornber’s illustration, the female fruiting plant is shown at the top of the page with the male flowering plant below. The numerous stamens and styles of the flowers are a greenish white, with four pale yellow sepals (no petals) at the base of each flower. The fruit of the female plant is a small dry seed, or achene, attached to a delicate silky white plume that becomes feathery as it matures. These fruits can be seen in the top drawing, but the female flower itself is not represented. Once these fruits become airborne, they can be a formidable opponent in the garden.

Clematis drummondii was named to honor the Scottish botanist and plant collector Thomas Drummond (c.1790–1835). In 1825, Drummond made his first extended collecting trip as assistant naturalist on the second arctic expedition of Sir John Franklin (whose third arctic voyage resulted in the tragic loss of the entire crew of the Erebus and Terror). Drummond’s collections in Canada were given to the botanist Sir William Jackson Hooker who, in 1830, funded Drummond’s excursion to the United States, where he collected primarily in Louisiana and Texas. In spite of constant ill health during his travels, he continued on to Florida and Cuba for further collecting. The exact circumstances of Drummond’s death in Havana are not known, other than that he died from a fever, in 1835.

Several of Evelyn Thornber’s illustrations of plants can be seen here. A number of her drawings of cacti were compiled by Margaret Pope in Cacti of the Sonoran Desert, a coloring book compiled for the Florilegium Program’s 2013 exhibit Botanical Art of the Sonoran Desert. — Cindy Hartwell

This article appeared in the April 2019 issue of the Desert Breeze, the monthly newsletter of the Tucson Cactus and Succulent Society.