Long-Lived Fern Prothallia

Abstract

There is considerable evidence that fern prothallia are like many other plants in that they will extend their lifespan if kept from reproducing. Most fern gametophytes produce sporophytes within a few months after spore germination, and then die. In 1927, Mottier (5) reported keeping alive the prothallia of Osmunda Claytoniana L. and Pteretis nodulosa (Michx.) Nieuwl. for 3? and 4 years, respectively. He concluded from his study that the continuation shoots of prothallia are able to grow indefinitely. Further evidence at Marietta College substantiates this finding. In the fall of 1938 several kinds of fern spores (Adiantum pedatum L., Asplenium platyneuron (L.) Oakes, Camptosorus rhizophyllus (L.) Link, and Polystichum acrostichoides (Michx.) Schott) were sown on a sterile inverted flower pot filled with Sphagnum. The pot had been placed in a deep culture dish containing Knop's nutrient solution; over it a glass bell-jar was placed after the spores were sown. During the next few months, hundreds of prothallia appeared, forming a rather dense covering over most of the pot. At one time, in the early stages, the culture was invaded by molds; these fungi were eliminated by spraying the pot lightly with a fresh weak solution of potassium permanganate, and by occa. sionally adding a few small grains of the same chemical to the nutrient solution. Except for this spraying, the culture received all its moisture by capillarity from below. The bell-jar served not only to keep the atmosphere humid, but also to keep out air-borne contamination. Because of overcrowding, watering by subirrigation, and perhaps the application of potassium permanganate solution, very few gametophytes ever produced sporophytes. 109