Prothallia of the Cyatheaceae

Abstract

1. Under favorable conditions the plate stage follows very quickly after germination; there is ordinarily no filament left at the base of the prothallium. The mature prothallium usually is longer and the cushion heavier than in the Polypodiaceae. Forking of the cushion of the prothallium occurs frequently in old cultures, and in certain species may occur in relatively young prothallia. 2. Multicellular hairs were found to develop more or less abundantly on mature prothallia of all species of Alsophila, Hemitelia, and Cyathea, and to occur rarely on Lophosoria. None were found on Thyrsopteris, Culcita, Cibotium, or Dicksonia. The multicellular hair arises from a special initial, a wedge-shaped cell cut from the anterior face of a superficial cell near the apical meristem. The hairs are found on both dorsal and ventral surfaces, on or near the cushion, but not on the margin. The hairs may reach a length of 2 mm. 3. The wall of the antheridium typically consists of five cells: an oblique basal cell, a lower ring cell with a "binding wall" on one side; an upper ring cell, an opercular cell, and a crescent-shaped cell formed by the division of the cap cell. Many variations from this type occur. The antheridia of Lophosoria are larger and less symmetrical than those of Alsophila, Hemitelia, and Cyathea. Those of Thyrsopteris are the largest and least symmetrical of the family, ordinarily not conforming to the type just given. The antheridia of the Dicksonieae are usually larger than those of the Cyatheae. 4. The necks of the archegonia in the Cyatheae are straight or slightly curved; they have more cells in the neck and are longer than those of the Polypodiaceae. Those in the Dicksonieae and Thyrsopteris are longer than those of the Cyatheae, and are more apt to be recurved. The walls of the neck cells are more or less cutinized. The neck contains two neck canal nuclei not separated by a wall. Archegonia with four neck canal nuclei were found in all species. 5. Apogamous growths were found in Lophosoria quadripinnata, Alsophila excelsa, A. armata, Hemitelia parvula, Cyathea medullaris, C. dealbata, Thyrsopteris elegans, Dicksonia squarrosa, Cibotium barometz, and C. schiedii. 6. The evidence from the gametophyte indicates that the family Cyatheaceae, in the broader sense, is not a natural group, but is of polyphyletic origin.