TAXONOMY OF THE GENUS CARDARIA WITH PARTICULAR REFERENCE TO THE SPECIES INTRODUCED INTO NORTH AMERICA

In the opinion of the authors, the genus Cardaria contains five species. They are described and a key is given. Two taxa are transferred from Lepidium to Cardaria, as C. PROPINQUUM and its variety AURICULATUM. Chromosome numbers reported for C. chalepensis, 2n = 80 and C. pubescens, 2n = 16, are new, as are those of naturally occurring and previously unrecognized hybrids between C. chalepensis and C. draba, 2n = 64. Three species, C. draba, C. chalepensis, and C. pubescens, are introductions to North America, where they have become prominent agricultural weeds. The morphological and specific limits of these three species are discussed in detail.