Oddities of the history of botanical terminology: how many cussate can phyllotaxis be?

The contemporary botanical terminology stems from a lasting tradition. Although some of the existing terms have a clear etymology, the others may comprise oddities. This paper is devoted to a series of terms describing phyllotaxis, such as decussate, tricussate and alike, up to hexacussate found in some sources. The first member of this series, decussate, has been used in human anatomy for a long time and originates from the Latin decussare “to intersect in X-shaped way”. However, tricussate was introduced in the 1870s by George Henslow who most likely reinterpreted the de- of decussate as denoting two and hence replaceable with other numerals. Such an innovation may seem surprising from the perspectives of etymology, but it remarkably gave rise to a series of related terms. These seem to have been implanted in the botanical lexicon, regardless of their eccentric origin. However, the terms describing the numbers of organs per floral whorl and leaves per verticil on a vegetative shoot might benefit from unification.