The kindness of Dr. GOETHART has enabled me to investigate all the Myxomycetes (Myxogasteres, Mycetozoa) which are kept in the Rijks-Herbarium at Leyden. Among the older collections I found those of PERSOON, V. HALL, HANKARL, BUSE, JUNGHUHN, WAGNER. Only a little part of these collections remains, owing to the way, in which the above-mentioned collectors used to conserve their materials.