a plant with a single seed-leafseed-leaf – the first one or two leaves from produced by the…. A natural group of plants without secondary xylem, presence of parallel veinsthe arrangement of the veins of a leaf. and trimerous flowers. This includes all grasses, sedges, rushes, lilies, orchids and onions. See here and here and compare with dicotsflowering plants of which the embryo have two seed-leaves. T….