Behavior of Certain Fern Prothallia under Prolonged Cultivation

Abstract

1. Prothallia of Osmunda claytoniana and Matteuccia nodulosa have been grown on soil for over three and one-half and four years respectively, under cultural conditions that prevented the production of sporophytes. When an occasional sporophyte appeared, it was amputated in such a manner as not to injure the gametophyte. 2. Prothallia thus grown branched both dichotomously and by the production of lateral shoots or proliferations. Proliferations, large and small, develop from the margins, from both surfaces of the midrib, and from the older proximal tissue, as well as from the growing point or apical sinus. 3. In older prothallia archegonia may be developed from both upper and lower surfaces. In such prothallia antheridia are borne chiefly on small marginal proliferations, or on small granular protuberances on older parts. 4. In some cases small protuberances are produced along the midrib upon the upper side. Such protuberances bear many archegonia. 5. The cell walls in older parts of the midrib are relatively thick, and are marked by numerous pits varying in size 6. An endophytic fungus is present in certain circumscribed areas of older midribs of Osmunda claytoniana. The fungus has a tubular, branched, multinucleated mycelium The hyphae may pass from cell to cell through the large pits in the cell walls No fungal spores were observed 7 A spinelike process developed from near the growing point in a few prothallia of Matteuccia nodulosa. These dried up as the prothallia grew older. 8. Apogamous sporophytes did not develop in any case. 9. If sporophytes are not produced, the continuation shoots of the prothallia seem to be able to continue growth indefinitely.