CRYPTOCHLOROPHYLLOUS SPORES IN FERNS: NONGREEN SPORES THAT CONTAIN CHLOROPHYLL

In terms of color, fern spores have traditionally been classified as either green or nongreen. This study reports a new kind of spore, here termed cryptochlorophyllous. Such spores contain chlorophyll but do not appear green when examined with either the naked eye or a light microscope. Epifluorescence microscopy was used to detect chlorophyll in cryptochlorophyllous spores. To test one aspect of the reliability of this method, we examined whether chlorophyll degradation over time would give false negative results. We found that in two species with green spores (Osmundastrum cinnamomeum and Terpsichore asplenifolia), fluorescence weakened with but could still be detected in specimens that were 110 yr old. We surveyed the spores of species in three fern genera under white light and with epifluorescence microscopy. Under white light, green spores were seen in 10 (26%) of 39 species of Elaphoglossum, two (17%) of 12 species of Lomariopsis, and seven (25%) of 28 species of Pleopeltis. When spores from the same species were examined with epifluorescence microscopy, fluorescence was detected in 22 (56%) of 39 species of Elaphoglossum, 10 (83%) of 12 species of Lomariopsis, and 12 (42%) of 28 species of Pleopeltis. We also found conflicting results in nine of the 33 species represented in our study by more than one specimen. In these species with conflicting results, at least one specimen fluoresced whereas the other(s) did not. The specimens that failed to fluoresce might have been collected and dried before the chloroplasts in its spores had developed, or they may represent infraspecific variation in this characteristic. Chlorophyll-containing spores have probably been overlooked in Elaphoglossum and Lomariopsis because the dark perispore obscures the green contents of the cell. In some species of Pleopeltis, such spores have probably been overlooked because of their paleness and the short duration of their greenness. Chlorophyll-containing spores are probably more widespread than is currently suspected, especially in clades known to contain both green and nongreen spores. Overall, the dichotomy of fern spores into green and nongreen is too simplistic. It must be investigated experimentally whether cryptochlorophyllous spores behave like visibly green spores in terms of germination and viability times.