Waarnemingen aan een ‘paupervorm’ van de Rode bies (Blysmus rufus (Huds.) Link) op het Groene Strand van Terschelling

A large population of a typical ‘pauper’ form of Blysmus rufus was found on the ‘Groene Strand’ of Terschelling in late August 2001. The ‘pauper’ form of B. rufus has a strikingly different appearance than the common form. Plants of the pauper form are tall and slender and have an inflorescence that consists of a single spike, one long bract, and sometimes a shorter second one. Identification of the ‘pauper’ form using Dutch Floras is impossible. Identification of the Terschelling material could only be ascertained by comparing it with herbarium specimens preserved in the ‘Nationaal Herbarium Nederland’ at Leiden. When monitoring the Terschelling population of B. rufus during 2002 and 2003 it was observed that the population has two separate flowering periods: i) the first one is from mid-May till late June, ii) the second one is from mid-August to late September. In the first flowering period, all plants in the population have the common form type inflorescences with 5 to 8 spikes and usually without bracts. In the second flowering period all flowering plants represent the ‘pauper’ form of B. rufus, which strongly suggests that the ‘pauper’ form is nothing more than a representation of late flowering in B. rufus in late summer.