Taxonomy of wetland carices

Abstract

The genus Carex (Cyperaceae) is one of the largest and most widely distributed plant genera in the world. Most species in the genus are not true aquatics but wetland plants of littoral communities, peatlands and wet meadows. Carex is normally easily recognized because of the utricles or perigynia, which are unique structures surrounding the small, naked female flowers. To understand the variation within the genus, special attention must be paid to the inflorescence and flower structures. The genus Carex may be divided into four subgenera with ca. 70 sections. The important wetland Carices are found in the subgenera Carex and Vignea. In this paper the subgenera are characterized and a few important sections discussed. Cytologically, the genus is peculiar and difficult, not only because of the small size of the chromosomes but because they have a diffuse centromere. This is the reason for the presence of a series of aneuploid numbers of chromosomes in many taxonomically difficult Carex sections. Attention is drawn to the hybrid swarms which may be found in some sections. It is important for identification to use the characters of utricles and also to note the growth habit of the plant, its rhizone structure, structure of the basal sheaths and shape of the transverse section and epidermal characters of the leaf blades. Hybrids are in several respects (morphologically, anatomically, chemically and ecologically) intermediate between parent species but the degree of sterility varies greatly in various sections. References at the end of the paper include treatments of the genus from different parts of the world.