Practice question

Cycads along with Ginkgo represent most primitive extant gymnosperm lineages retaining ancestral flagellated motile spermatozoids coiled helically with thousands flagella derived from blepharoplast, produced within pollen tube tip and swimming short distance within viscous fluid-filled archegonial chamber to reach egg, condition termed zoidogamy combining siphonogamy tube and zooidogamy swimming. This contrasts siphonogamy of conifers gnetophytes angiosperms where non-motile sperm nuclei delivered via tube cytoplasmic fusion. Persistence motile sperm indicates phylogenetic link to fern allies Marattiopsida, supporting retention primitive traits like circinate vernation and stout pachycaulous trunk and coralloid roots cyanobacteria symbiosis, justifying primitive descriptor.