Distal face of three spores of Riccia ciliifera Lindenb. from the same spore capsule (France, Haute-Loire, Cerzat, le Blot, herbarium Conservatoire Botanique National du Massif Central n. 3451, collector Hugonnot, non type specimen). 

Context in source publication

Context 1

... melitensis Massalongo (1913: 52) was described in 1913 by Caro Benigno Massalongo on the basis of material collected by Carlo Pietro Stefano Sommier in 1906. The collection date was mistakenly given as 1896 by Jovet-Ast (1983). It was collected on the island of Gozo, in the Mediterranean Sea. It is the second-largest island in the Maltese archipelago, a region which was at that time the subject of intensive floristic research (Massalongo in Sommier & Caruana Gatto 1910). Riccia melitensis is only known from the original publication (Massalongo 1913) and a unique specimen stored in G (G00067993). The specimen lacks a collection date but otherwise corresponds well with the protologue. Jovet-Ast (1983) did not formally designate a type because she only stated that the taxon “ n’est connu que par le type ”. Hence the holotype is here designated. Jovet-Ast travelled intensively in the Mediterranean during a number of expeditions. Riccia melitensis was the only Riccia Linnaeus (1753: 1138) species that she failed to collect during this time. Riccia melitensis was never mentioned again what raised doubts about the validity of the species and necessitated a reevaluation of the taxonomic status of R. melitensis . Other descriptions of R. melitensis have appeared in Zodda (1934), Müller (1954) and Jovet-Ast (1983, 1986). It is unclear whether all the published accounts are based upon examination of the type or literal transcriptions of the protologue. The account by Riccia’s worldwide expert, Madame Jovet-Ast is beyond doubt the most reliable publication on the species. She examined the original specimen in 1982 and left with the sheet a permanent slide allowing a close examination of the spores. She also published excellent SEM micrographs of spore proximal and distal faces (Jovet-Ast 1983). The material in G is otherwise very scanty but fully fertile so a reappraisal of this species was possible. According to my own observations, the thallus and spores are characterized by: a winged thallus with no marginal cilia and distinct overlapping hyaline marginal scales. The spores are 100–110 μm in diameter, with a wide, finely granulate and irregular wing. The distal face of the spores is concave, with a small group of areolae in the central part which are replaced by sinuose meshes toward the equator; the proximal face of spores lacks areolae but it is ornamented with sinuose meshes. The material seems to be dioicous (Jovet-Ast 1983). The sexual condition could not be fully assessed because no antheridia were found. The set of gametophytic and spore characters undoubtedly points to the material being a female thallus of R. ciliifera Link ex Lindenberg (1829: 119). Jovet-Ast (1983) discussed the affinity of R. melitensis with R. gougetiana Durieu & Montagne in Montagne (1849: 35) and R. ciliifera while refraining from synonymizing R. melitensis under any of these species because of supposed taxonomic informative characters which set R. melitensis apart. The thick “epidermis” made of 4–5 superimposed cells (Massalongo 1913; Zodda 1934; Müller 1954) ending in an oblong to pyriform cell is a common feature of most Riccia subg. Riccia and corresponds to the thread-like assimilation tissue. The violet-coloured median strip of tissue delineating the assimilative tissue from the storage tissue which is discernable in transverse section (Jovet-Ast 1983) is a highly plastic character in all Riccia subg. Riccia where anthocyanin pigments may or may not develop. As such, this character is also not taxonomically informative in this context. The whitish colour of the wings is an artifact due to the dessication of the plant. Jovet-Ast (1983) described the ventral scales as being “blanches” (white) but she used this term in most of her publications for such hyaline structures and this has caused some confusion regarding the taxonomic affinities of the species. Frey et al . (2006) keyed out Riccia melitensis in a couplet together with R. lamellosa Raddi (1818: 351), with which it bears no affinities based on sequence data (Wheeler 1998). Following Jovet-Ast (1971; 1986), R. ciliifera is characterized by the occurrence of a thallus with marginal cilia. In reality this character is immensely variable, with naked individuals being frequently found. The spore characteristics of R. melitensis match those of R. ciliifera . It is worth pointing out that the spore ornamentation in R. ciliifera is highly variable, the number of areolae being at times virtually confined to a small portion of the distal face or extending towards the periphery as incomplete areolae or meshes (see the illustration of the spores in Jovet-Ast 1983 and fig. 1). Clearly, the variability of the ornamentation of the spores in the genus Riccia invites further investigation. In most taxonomic publications on the genus variability of spore ornamentation is not included or is likely underestimated. The morphological characters allowing the separation of Riccia gougetiana , R. ciliifera and R. lamellosa are summarized in table 1. Riccia ciliifera exhibits a remarkable morphological plasticity in the gametophyte, which it is partially reflected in the high number of its heterotypic synonyms (Jovet-Ast 1986). This variability is confirmed by the examination of hundred of specimens of the Mediterranean by the author. The variability is exacerbated by its dioicous condition, with a marked differentiation between the sexes that is not always taken into consideration in morphological descriptions. Accordingly, there is no reason to segregate R. melitensis as a distinct species because all of its morphological characters observed herein, in addition to those published by other authors, are in agreement with the morphological variability of R. ciliifera . Hence, R. melitensis is here considered to be a synonym of R. cilifera . The occurrence of R. ciliifera on the Maltese Archipelago complies with the known range for this species (Bischler 2004; Ros et al. ...