In 1942 the author published the so-called tetrazolium method for determination of the germinability of seeds (3). This method is based upon the reduction in germinability of the seeds due to a gradual dying-off of the embryo (2). The topographical spread of necrosis of embryo tissues can be demonstrated by means of 2,3,5-triphenyl-tetrazolium-chloride. This compound is colorless but is reduced (hydrated) into the stable but nondiffusible red formazan by living cells (3). Coloration of a cell by tetrazolium is a definite indication of its viability because necrotic cells remain uncolored. By means of extensive experiments conducted over a period of years, the procedure has been perfected to demonstrate which parts of the embryo are at least sufficiently viable to make germination possible (4). The recent publication of R. H. Porter, Mary Durrell, and H. J. Romm (1) concerning the topographical tetrazolium method does not, however, present the method correctly in relation to several essential points. In order to correct these errors, the present author submits a short description of his method (3). Use of the tetrazolium method merely involves preparation of the embryo of various species of seeds in such a way that all those parts which are decisive in the estimation of germinability be made visible. In most cereals the anterior face of the embryo must be visible. Since the pericarp is impermeable and opaque in most cereals, the embryo must be removed from the kernel with a lance-like scalpel or dissecting needle. Except in maize, a longitudinal section through the center of the embryo is not adequate because the lateral root primordia remain invisible. Only in oats is the pericarp sufficiently transparent to obviate excision of the embryo. The embryo of maize, however, possesses a simple root primordium, and the lateral root primordia (secondary radicles) in the mesocotyl are uniformly distributed. In this instance a longitudinal section provides the best preparation (5). The presoaking of the seeds in water is necessary only to facilitate the removal of the embryo. Initiation of germination is neither necessary nor significant for the test because even non-after-ripened cereals can reduce tetrazolium According to the method described below, the cross-sectioned grains of oats are placed in tetrazolium solution without pre-soaking. Only in the case of maize is the staining of the scutellum important in relation to germinability. This response of