Agnes Arber

Agnes Robertson Arber (1879-1960) was a renowned British plant morphologist and anatomist, historian of botany and philosopher of biology. She was born in London but lived most of her life in Cambridge, including the last 51 years of her life. She was the first woman botanist to be elected as a Fellow of the Royal Society (21 March 1946, at the age of 67) and the third woman overall. She has written some 218 publications and 8 books. Arber was draughts person and generally illustrated her later books and articles herself.

Among her books, The natural philosophy of plant form (1950) is a milestone on the way to a more open and dynamic approach on plant morphology and developmental genetics. In this book, Arber proposed the partial shoot theory of the leaf. According to this theory, each element of the plant is a shoot or a partial shoot. Leaves are partial shoots that show reduced growth capacity. She mentions: “the leaf is a partial-shoot, revealing an inherent urge towards becoming a whole shoot, but never actually attaining this goal, since radial symmetry and the capacity for apical growth suffer inhibition”. The parallelism of leaf and shoot dates back to Goethe, who first described compound leaves as in “reality branches, the buds of which cannot develop, since the common stalk is too frail”. For Arber, compound leaves are clusters of united partial-shoots.

Arber appreciated Goethe who was also more of a scientist than is generally believed. In Goethe’s botany (1946), she translated and tried to interpret Goethe’s Metamorphosis of plants (1790).

In opening the door to genetics to elucidate the underlying mechanism, Arber was ahead of her time. Recent developmental genetic evidence has supported aspects of the partial shoot-theory of the leaf, especially in the case of compound leaves.