“…Their addition to the drying medium may thus be a relatively easy way of adapting the conditions of preservation to the needs of special groups of organisms. With few exceptions (CHOD and POLAK 1969, GILL 1973, HIDAKA and ToMARU 1960, there is a remarkable lack of quantitative assays in the work done with plant viruses along this line, presumably because of the difficulties encountered in evaluating viability of plant as compared to animal viruses. So the question whidi protectants are able to act satisfactorily on the retention of infectivity of plant viruses largely remains still to be answered.…”