1. When fruiting, Ricciocarpus is essentially a free floating plant. 2. The genus is strictly monoecious, though a small number of plants fail to produce archegonia. 3. Sex organs are produced in single definite groups as in Asterella, etc. Antheridia are produced on very young plants, which later produce archegonia and sporophytes. 4. The basal cell of the archegonium develops a structure which is partially imbedded in the storage tissue and acts as the physiological equivalent of the sporophyte foot in higher forms. 5. There is no rudimentary integument of the archegonium. 6. The diameter of the male nucleus is about one-half that of the female nucleus. 7. The first division of the sporophyte is transverse or oblique. The early subsequent divisions are irregular. 8. A large quantity of nutritive material is excreted into the capsule among the mother-cells. 9. There is no indication of elaters or sporophyte foot of any kind, which fact is associated with the aquatic habitat. 10. The fruiting period occur...