The previously undescribed sporophyte of Leucobryum boivinianum [≡ Cardotia boiviniana] has inclined, weakly curved (but nearly symmetric), ovoid capsules that are lightly ribbed when dry and strumose. The 16, bifid peristome teeth are vertically striolate on the outer (dorsal) lamellae surface, and papillose on the inner (ventral) lamellae surface, with thick trabeculae. These sporophyte features add support to the synonymy of Cardotia with Leucobryum; the two names had been previously considered synonyms based on gametophyte characters alone. The peristome of L. boivinianum differs from other Leucobryum species in its paler color, less prominent striae, and thicker, crowded, brownish yellow trabeculae.