The histology and morphology of developing asparagus Asparagus officinalis L.) somatic embryos arising in callus cultures were examined and contrasted with that documented for zygotic embryos. Histological sections of lateral bud-derived callus cultured for 2 weeks on embryo induction medium consisting of Murashige and Skoog salts and vitamins (MS) with 1.5 mg NAA/liter and 0.1 mg kinetin/liter indicated the formation of distinct groups of embryogenic cells. At 4 weeks, the callus was comprised of embryos in the early and late globular stages and a few bipolar embryos. Within 2 weeks on embryo development medium consisting of MS with 0.05 mg NAA/liter and 0.1 mg kinetin/liter, the globular embryos developed a bipolar shape having an expanded upper region that formed the cotyledon and a smaller region that formed the radicle. Within 4 to 6 weeks on this latter medium, each mature bipolar embryo was opaque and had a large cotyledon, a distinct shoot apex at the cotyledon-hypocotyl junction, and vascular connections between the radicle, shoot apex, and cotyledon. Many mature somatic embryos resembled the asparagus zygotic embryos in having a crescent shape, whereas others had a short but wide cotyledon. Both somatic embryo types converted to plantlets at equal rates. Chemical names used: N- (2-furanylmethyl)-1 H -purin-6-amine (kinetin); 1-naphthaleneacetic acid (NAA).