1. The prothalli of Ceratopteris thalictroides (L.) Brongn. were hermaphroditic in culture as well as in nature (14). They were asymmetric and irregularly lobed. 2. Prothalli bearing only antheridia, as reported by Kny (12), were also obtained in cultures, but in extremely small proportions. Prothalli with archegonia only were not found. 3. Development of antheridia was normal. The number of androcytes varied between eight and thirty-two in different antheridia on the same prothallus. The antheridia were marginal or spread ventrally on the wings. 4. Development of the archegonium and embryo was normal, as reported by previous authors (12, 14). 5. The haploid number of chromosomes in the local plants was 78. 6. Since the chromosome number is different from that reported by some authors, it is suggested that there are many ecotypes of the species. The variable number of androcytes in the antheridia is perhaps also indicative of this.