An Improved Block for Spore-Formation in Yeast

V. Hartelius and E. Ditlevsen1 recently directed attention to the fact that gypsum blocks used for spore-formation in yeast will not tolerate the strong heating necessary for adequate sterilization. After trials with various materials, they finally chose a block cast of Portland cement and kieselguhr, which after hardening in carbon dioxide is sufficiently porous.