Seed morphology of Iranian annual species of Euphorbia (Euphorbiaceae)

Euphorbia (Euphorbiaceae) is one of the largest and most diversified cosmopolitan genera of flowering plants. South‐west Asia is a major centre of diversity and contains c. 65 annual species, 35 of which occur in Iran. In this article, the seed morphology of all Iranian annual species was studied, including E. aulacosperma and E. rhabdothosperma, both new records for Iran. Quantitative and qualitative macro‐ and micromorphological features of seeds and caruncles were investigated using stereomicroscopy and scanning electron microscopy. Caruncle characters (shape, size, colour) and seed characters (shape, size, colour, ornamentation) are often constant and useful in identification and classification. An identification key and scanning electron micrographs are provided for all known Iranian taxa. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 167 , 212–234.