Abstract
The nuclear DNA content of secretory trichome cells of Solanum nigrum has been studied by microspectrophotometry from initiation of the trichome up to the fully differentiated and functioning organ. Some initials become 4C by endoreplication, while others remain 2C. All those which turn out to be secretory are with a 4C DNA content and, when become active, show a partial amplification of their genome. An endoreplication therefore occurs in all trichomes at a given stage of their differentiation.