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Many ferns have specialized fronds that bear sporangia, whereas sterile fronds lack reproductive structures. Although a strong case can be made that the presence of the sporangia will affect the physiology of the frond, only one study could be located that investigated this phenomenon. Thus, ecophysiological (and some morphological) features of fertile fronds were compared with those of sterile fronds of the subtropical epiphytic fern Pyrrosia lingua in Taiwan. Fertile fronds were thicker than sterile fronds, a result of the presence of the large sori. Stomatal sizes and densities did not differ between the two types of fronds. The osmotic potential of liquid expressed from the fertile fronds was more negative than that of the liquid of sterile fronds, although this may be an artifact due to a matric effect of the released spores. No differences in chlorophyll concentrations (area basis only) and a/b ratios were found between sterile and fertile fronds. In situ rates of net CO2 exchange of the fertile fronds were substantially lower than those of the sterile fronds. Similar stomatal conductances and internal CO2 concentrations in the sterile fronds indicated that the efficiency of the photosynthetic apparatus was lower in fertile relative to sterile fronds. The results of this study indicate that the presence of sori on fronds of the epiphytic fern Pyrrosia lingua reduces the photosynthetic capacity of these fronds and, most likely, the productivity of plants harboring many fertile fronds.
The gametophyte development and morphology of five Mexican species of Tectaria were documented and compared with what is know from literature reports of the Old world species of Tectaria. Both Old and New World species had the following characteristics in common: spores monolete, ellipsoidal and with a rugose surface; the perine is folded, brown to dark brown, with wing-like folds, and the laesurae measure 1/2 to 3/4 the length of the spore. The germination pattern is of the Vittaria-type and the developmental pattern of the prothallus is of the Aspidium-type. Gametangia are of the common type for the advanced leptosporangiate ferns. The presence of multicellular uniseriate hairs on the gametophytes may represent a synapomorphy for the family.
Spores of Lycopodiella lateralis germinate rapidly in illuminated cultures as is typical for most Lycopodiella spores. The young gametophyte develops into a solid, green, spherical primary tubercle. Mature gametophyte development occurs at the top of the primary tubercle by the formation of a crown with photosynthetic lobes. An intermediate shaft reported for other Lycopodiella gametophytes fails to form. Comparisons were made between intermediate shafts of Lycopodiella gametophytes growing in nature and in culture. In well illuminated conditions the intermediate shaft does not form as it does on poorly illuminated gametophytes. If the gametophyte development starts partially covered by soil, long intermediate shafts can be produced. The intermediate shaft raises the top of the young gametophyte to the top of the soil where a sexually-mature gametophyte develops and sexual reproduction can take place. The intermediate shaft provides the possibility for a young gametophyte in unsuitable illumination to grow into more suitable illumination for gametophyte maturation.
In 1853 J. R. Riddell validly published seven binomials of pteridophytes for species from Alabama, Louisiana and Texas that were missed by the standard indices. Only one of these names, Lycopodium corallinum, is the first name validly published for a currently recognized species replacing Selaginella riddellii. The six other binomials prove to be later synonyms of species of Adiantum capillus-veneris, Cheilanthes alabamensis, Dryopteris ludoviciana and D. kunthii, Pellaea ovata and Thelypteris hispidula.