Dioon Lindley (1843:59)

Hernández-Tapia, Jessica E., Jiménez-Ramírez, Jaime & Vovides, Andrew P., 2020, Taxonomic revision of the genus Dioon (Zamiaceae), Phytotaxa 442 (4), pp. 267-290 : 273

Dioon Lindley (1843:59) . Type:— Dioon edule Lindley

= Platyzamia Zuccarini (1845: 23) .

Arborescent plants,dioecious.Stems epigeous,cylindrical,armed with persistent leaf petiole bases, without ramifications (sometimes with ramifications in older specimens), with grey bark, scales formed by persistent cataphylls and leaf petiole bases. Cataphylls lanate, triangular, acute, widely or normally caudate, cuspidate, apiculate, acuminate to aristate. Leaves pinnate, spirally arranged, forming an ascending crown, straight to conduplicate vernation, tomentose to glabrate, sometimes glabrescent, rigid-coriaceous. Leaflets linear-lanceolate, falcate to subfalcate, the apex acuminate, pungent, ascending, flat, convex-flat, ascending, convex, reclined to descending, imbricate or not, opposite to subopposite, the margin entire or spinose-dentate, veins parallel, with or without pinnacanths; rachis straight or twisted at the apex, terete to semiterete; petioles terete to semiterete, lanate at the base. Male strobili cylindrical to conic, the peduncles short and tomentose; microsporophylls slightly lanate to tomentose, cuneate, sori with 3–6 sporangia, the dehiscence longitudinal on each sporangium, pollen globose, smooth, yellow. Female strobili erect, semipendulous or pendulous, ovoid to cylindrical, stalked or occasionally sessile, densely lanate; megasporophylls petiolate, deltoid to trulate, subpeltate, flat to recurved at the apex, lanate on the outer surface, glabrate on the inner surface, sometimes lanate on both surfaces. Seed subglobose to ovoid, sarcotesta white-yellowish, sclerotesta hard, beige. Seedling with one single eophyll after germinating.