plural noun
Psi·​lop·​si·​da | \ sīˈläpsədə\

Definition of Psilopsida

: a subdivision of Tracheophyta comprising vascular plants with no roots, leaves only partially differentiated or lacking, no leaf traces, a usually protostelic vascular cylinder, and the sporangia merely terminal enlargements of the stem — compare lycopsida , pteropsida , sphenopsida

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History and Etymology for Psilopsida

New Latin, from psil- + -opsida (as in lycopsida)

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to corrupt or become corrupted

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