organogenic cultures were induced from zygotic embryo and megagametophyte explants of the chiapas state (méxico) endangered cycad species, dioon merolae. the litz induction medium consisted of b5 major salts, ms medium minor salts and the organics glutamine (400mg·l-1), arginine (100mg·l-1), asparagines (100mg·l-1), sucrose (60g·l-1), gellan gum (4g), and supplemented with 0, 0.45, 2.26, 4.52 and 9.05μm 2,4-dichlorophenoxyacetic acid (2,4-d) and 0, 2.32, 4.60, 9.30, 13.90μm kinetin (k), arranged as a 5′5 factorial in a randomized block design. cultures were maintained in darkness at 25°c, and callus was subcultured onto fresh medium at 4 week intervals. callus initiation occurred on a wide range of plant growth regulators (pgr) combinations from megagametophyte explants. in comparison, callus initiation from explanted zygotic embryos occurred on few pgr combinations. adventitious shoot induction occurred from callus on formulations with k and 2,4-d. through the histological analysis of longitudinal sections of zygotic embryos were detected apical meristematic cells of the shoot and root and in megagametophytes the formation of elements similar to tracheids and coralloid roots. this technique has a great potential for preservation of the highly endangered cycads.