Robert Lloyd Praeger's work on Crassulaceae (Aeonium, Aichryson, Monanthes, Sedum, Sempervivum) is outlined; he studied living and cultivated plants and did not collect and preserve herbarium specimens. The existence of some of the original drawings made from living plants by Miss Eileen Barnes for Praeger's publications is noted, and their significance as likely types is discussed. A new combination is published, Aichryson × aizoides (Lam.) E. C. Nelson, for the plant commonly named Aichryson × domesticum (Praeger) Praeger.