Although heterospory is rare among vascular cryptogams, all seed plants are heterosporous. Heterosporous plants produce microspores and megaspores. We discussed two of the five genera classified in the division. Its aerial stems are distinctive with their whorled leaves, which gives the stem a jointed appearance. The leaves are tiny, making the stem appear leafless.
Horsetails are homosporous.
Sporangia are borne on sporangiophores clustered in strobili. Gametophytes are photosynthetic. Ferns are a diverse group with about 10,000 extant species. Sporangia clustered in sori on lower surfaces of leaves. Sori my be naked or covered by an indusium of false indusium.