Among the Campyloneurum that occur entirely or primarily in the Atlantic Rain Forest of Brazil, three species have been previously referred to by the following six names: C. acrocarpon, C. crispum, C. herbaceum, C. lapathifolium, C. minus, and C. wacketii. We show that C. crispum and C. herbaceum are the correct names for two of the species, and we designate lectotypes for these two names. The third species, which ranges from Brazil to Argentina and Paraguay, lacks a name and is here newly described as C. atlanticum. Two of the previously used names, C. acrocarpon and C. wacketii, are considered synonyms of C. crispum. The remaining names, C. lapathifolium and C. minus, appear to be of uncertain application. Based on our field studies, C. atlanticum and C. herbaceum are primary hemiepiphytes. Our finding constitutes the first report of this growth habit in the genus. The third Brazilian species treated herein, C. crispum, varies in growth habit, being either terrestrial, primary hemiepiphytic, or holoepiphytic. The spores of the three species are uniform and typical of the genus; they do not provide any distinguishing characters for the species.

Light intensity is among the major environmental factors determining the ecological distribution of any plant. The effects of light availability on aquatic plants continue to be discussed, as some species show higher growth under full sun conditions and other species show reduced growth. The aim of this study was to test the effects of different shade levels on ramets and clonal growth of the fern Salvinia auriculata. We hypothesized that the ramets grow better under shade conditions over time as in most land ferns. We performed a greenhouse experiment, putting plants under three treatments: control (0% shade), 30% shade, and 70% shade. We monitored the growth of individual ramets as well as clonal spread for 30 days. The number of new ramets (clonal growth) increased exponentially in the three treatments, however this number was higher in shade than in full sun plots. The size of floating leaves, submerged leaves, and rhizomes was higher under shade treatments compared to individuals under sun treatment. Our results showed that S. auriculata has a high growth performance under shade environments, including both clonal growth and the size of individual ramets, similar to most land ferns. This species appears highly plastic as it also thrives under bright sun, which appears to be a consistent pattern among fern species in both terrestrial and aquatic environments. Because shade has been proposed as a treatment to control and manage aquatic plants, application of this treatment should be carefully considered depending of the species, especially when it involves aquatic fern species.

After a long history of taxonomic isolation, recent studies show that Hymenophyllopsis K.I.Goebel is nested within the tree fern genus Cyathea Sm. s.s.. We compare developmental stages of typical Cyathea with an anatomical survey of Hymenophyllopsis. Such comparisons should clarify how the distinctive features of Hymenophyllopsis are related to or derived from those of typical Cyathea. Hymenophyllopsis and Cyathea samples from field-preserved materials and herbarium specimens were examined using standard light microscopy techniques. Hymenophyllopsis species have simple stem anatomy: all have solenosteles or simple dictyosteles, and sclerenchyma and secretory strands are lacking. Only H. superba has as many as four vascular bundles in the petiole base. Leaf blades lack stomata, the epidermal cells contain chloroplasts and there are only one or two mesophyll layers. Typical adult Cyathea species have complex stelar anatomy with medullary bundles (some with cortical bundles) and complex stem histology. There are numerous vascular bundles in the petiole. Leaf epidermal cells other than guard cells lack chloroplasts and the mesophyll has multiple layers. In contrast to their differences from adult Cyathea plants, Hymenophyllopsis anatomy corresponds closely to early stages of young Cyathea sporophyte development. The origin of “Hymenophyllopsis” from typical Cyathea ancestors involved a drastic reduction in size and anatomical complexity, with the precocious production of spores. This is a clear example of paedomorphosis among pteridophytes, where Hymenophyllopsis adult plants represent precociously fertile, permanent “young sporophytes” of tree ferns.