No earlier letter has been found in which Müller mentioned enclosing seeds of any species of the leguminous genus Cassia. In Movement in plants, p. 34, CD mentioned that Müller had sent seeds of Cassia tora (a synonym of Senna tora), which grew by the sea; he noted that the seedlings were identified at Kew. It is unlikely that the identification was correct since Cassia tora is not native to the Americas; the specimen was probably Senna obtusifolia, a South American species often confused with C. tora.

CD worked on movement in Cassia from 1873 (see Correspondence vol. 21, letter to W. T. Thiselton-Dyer, 4 December 1873).

Müller’s three-part article on Brazilian butterflies had appeared in the September, October, and December issues of Kosmos (Fritz Müller 1877a). CD’s lightly annotated copies are in his collection of unbound journals in the Darwin Archive–CUL.