Eragrostis tef (teff) is a crop native to Ethiopia that is becoming increasingly planted worldwide because of its nutritious grain and drought tolerance. Most cultivated cereals retain their grains on the plant until harvest, i.e., the floral parts do not abscise, or shatter.  In contrast, the grains in teff do abscise and are only retained on the plant because the surrounding floral bracts (lemmas and paleas) hold them in place. This mechanism is distinct from the shattering process in nearly all other grasses. In this study, we investigated the morphology, anatomy, cell structure, and gene regulation of the abscission zone in teff.  The abscission zone (AZ) of tef is a slender, non-lignified stipe below the caryopsis whose morphology is shared among many other species of Eragrostis including E. pilosa.  Cell walls in the AZ are thin and fracture at maturity, unlike the walls in the AZ of most other grasses, which separate at maturity, as shown by X-ray microscopy, scanning electron microscopy, transmission electron microscopy, and immunolocalization of cell wall components. The cells themselves die. Genes involved in cell wall modification and programmed cell death are upregulated in the AZ near seed maturity, as shown by RNA-seq, consistent with our cell-level observations. The lemma in the domesticated E. tef is thicker than that in E. pilosa, possibly explaining why the grains are clasped more tightly. Because shattering in many cereals is regulated in part by the YABBY transcription factor SHATTERING1 (SH1), we used CRISPR-Cas9 technology to disrupt it in E. tef.  Shattering was normal in the mutant, indicating that SH1 is not involved in AZ regulation. Together these results point to a previously undescribed mechanism of abscission in E. tef, identify genes that may be involved in its regulation, and note genes that may be targeted for crop improvement.