Chapter I: ANACROGYNÆ. The archegonia are situated on the upper side of the

thallus or stem, _placed laterally_, and covered by an “involucre,” formed by the calyptra together with the tissue of the stem or thallus.

a. ANELATEREÆ. Without any elaters: _Sphærocarpus_, _Riella_.

b. ELATEREÆ. α. Thalloid: _Aneura pinguis_, in damp situations; _Metzgeria furcata_, on trees; _Pellia epiphylla_, in damp situations; _Blasia pusilla_, on damp clay soil, in the shade (scales are present on the thallus). β. Foliose and not dorsiventral: _Haplomitrium hookeri_.