The Hawaiian Species of Cibotium

Abstract

The genus Cibotium (Dicksoniaceae) comprises approximately ten species ranging from Assam to China and Papua New Guinea in the Old World, to Central America and Mexico in the New World, and Hawaii. The genus is distinguished from Dicksonia by the cartilaginous texture of the valves of the indusium, which are strongly differentiated from the lamina. This paper will review the Hawaiian species of Cibotium. Hybrids between the Hawaiian species are known and will be discussed in a subsequent paper. The Hawaiian flora is noted for its many polymorphic species, and the Cibotium species are excellent examples. There are few clear-cut characters that separate the species, and while two of them (C. menziesii and C. glaucum) do have characteristics that are prominent and helpful, the other two taxa have more subtle and variable characters, especially the nature and color of the hairs on the abaxial surface of the segments. In attempting to understand Cibotium in Hawaii, it became obvious that serious problems existed in the clear definition of the species, how many there are, their nomenclature, and their distribution. The original descriptions are incomplete, sometimes do not correlate with the type specimens, and allow for overlapping interpretations. The resulting nomenclatural confusion has caused authors to assign the wrong name, or to identify incorrectly the plant being discussed (Wick & Hashimoto, 1971; Ripperton, 1924). Because of this confusion, the Hawaiian species of Cibotium have been seriously misunderstood (Rock, 1913; Skottsberg, 1942; Ogura, 1930). Another troublesome problem has been that herbarium specimens of Cibotium are frequently inadequate for identification, often consisting of no more than a single pinna. At the minimum, a good collection must include the base of the stipe, with its pubescence, as much of the stipe as possible, a middle pinna, and also the distal portion of the frond. Of value also is a basal pinna, including the adjacent stipe, and a crozier, if available. The stipe and crozier can easily be cut in half longitudinally to assure easier pressing, faster drying, and the use of less herbarium space. An adequate single collection may fill as many as three to five herbarium sheets. The practice of collecting only a single pinna for an herbarium specimen should be abandoned, since it will often have little taxonomic value. TAXONOMIC HISTORY