Cover illustration: The inset cover photograph shows a cross-section of the velamen and exodermis of a root of Manniella gustavi, a geophytic orchid. Microscopical features of the velamen such as secondary cell-wall thickenings, tilosomes and supraendodermal spaces have proved useful in phylogenetic reconstructions in combination with DNA sequences. Supraendodermal space is associated with seasonally dry environments. See Figueroa et al. (pp. 509-520).
[Table of Contents]