Sentence:  ("b") sporophyte with foot reduced, the entire sporophyte enveloped by the <WSD>calyptra</WSD>, which is ± stipitate at the base. 
Meaning of the word marked with <WSD> tags:  In bryophytes, a thin, hood of tissue that forms from the archegonium and covers the developing sporophyte and is shed as it ripens.<ref name= "BotGloss">Jackson, Benjamin, Daydon; A Glossary of Botanic Terms with their Derivation and Accent; Published by Gerald Duckworth & Co. London, 4th ed 1928</ref>