부산대학교 도서관

The family Fossombroniaceae Hazsilinszky, order Metzgeriales, includes three genera, two of which are found in the United States. Petalophyllum ralfsii (Wils.) Nees et Gott. is a monotypic, thallose species which has been reported from only four southern states: Texas, Louisiana, Mississippi and Arkansas. Fossombronia Raddi is a comparatively large genus with 14 leafy species of which eight are reported from Texas. On the basis of vegetative morphological characteristics, this family appears to occupy a pivotal position in the evolution of the Hepaticae between the leafy Jungermanniales and the purely thallose liverworts in the Marchantiales.The sperms of the bryophytes are the most structurally complex cell produced by the embryophytes. They consist primarily of the tetriole, elongated nucleus, two mitochondria, two flagella and an amyloplast. The ultrastructural characteristics of the sperms were found not to be useful for phylogenetic circumscription at the generic level but did provide good circumscription of the orders within the Hepaticae.