A study on achene macro- and micromorphological characters of Polish species of the Senecio jacobaea group

摘要

A study on achene macro- and micromorphological characters of the following five Polish species of the Senecio jacobaea group was carried out by LM and SEM: S. aquaticus (var. aquaticus and var. barbareifolius ), S. erucifolius (subsp. erucifolius and subsp. tenuifolius ), S. jacobaea , S. paludosus , and S. subalpinus . The achenes differed in several characters, but the most distinctive differences concerned their indument, especially the length and morphology of hairs. The study clearly shows that two morphologically similar species, S. jacobaea and S. erucifolius , which are often confused can be easily distinguished based on the morphological characters of achenes. Additionally, we showed differences between the achenes of S. erucifolius subsp . erucifolius and subsp. tenuifolius , the two taxa which were not distinguished in floristic studies and herbarium collections from Poland. The key to determine Polish species of the Senecio jacobaea group, based on the morphological characters of achenes, is also given.