About Euphorbia hyssopifolia L.
Euphorbia hyssopifolia L. is an arching annual species that grows up to 80 cm tall, with oblique leaf bases. Its flowers and fruits are arranged in small, loose clusters. This species is easily confused with Euphorbia nutans, which is typically slightly hairier, so fruit capsules should always be opened to examine the seeds for accurate identification. Compared to the more irregular, rounder-edged seeds of E. nutans, the seeds of E. hyssopifolia are cross-ridged and have relatively square edges. The seeds are described as brown to grayish white, ovoid, slightly 4-angled in cross section, with convex abaxial faces and slightly concave to slightly convex adaxial faces. They measure 1–1.4 × 0.7–1.1 mm, and have 2–3 prominent transverse ridges that do not interrupt the adaxial keel, or are coarsely and inconspicuously pitted-reticulate, per FNA (see also FNA entry for E. nutans).
