← Glossary Morphology rachis The main axis of a compound leaf or fern frond, from which the leaflets or pinnae arise. An extension of the petiole . Plants Using This Term (1) Toxicodendron vernix — Poison Sumac Related Terms achene acuminate aerial root alternate annual axillary basal berry biennial bract calyx capsule cauline clasping cordate corolla corymb crenate cyme cypsela deciduous dentate drupe entire evergreen fenestration follicle glaucous inflorescence lanceolate legume ligulate lobed opposite ovary palmate panicle papilionaceous pappus pedicel perennial petiole pinnate pubescent raceme rhizome rosette sepal serrate sessile silique spadix spathe spatulate stamen stipule succulent taproot ternate thallus trifoliate umbel undulate whorled