The anatomical basis for the shrunken endosperm phenotype of eight recessive maternal effect mutants (seg1‐seg8) of barley (Hordeum vulgare L.) is described. Plants which are homozygous recessive for these nuclear genes produce only shrunken seeds regardless of pollen source. Light microscopy revealed that four of the mutants, seg1, seg3, seg6, and seg7, exhibited premature termination of grain filling because of the necrosis and crushing of the chalaza and nucellar projection of the pericarp early in the grain‐filling period, resulting in thin, wrinkled seed. Endosperm growth of these mutants before the occurrence of chalazal necrosis seemed normal. The other four mutants exhibited characteristic abnormalities in the endosperm growth pattern but normal development of matemal‐origin tissues. Endosperm size was severely reduced in seg2, in which two flat columns of tissue were present with no central endosperm. Seg4 and seg5 developed distorted, disorganized endosperms of variable size. Endosperms of seg8 developed as two well‐filled lobes with no central endosperm, resulting in a distinct dorsal crease. We suggest that the mutants are useful as probes to study maternal effects on endosperm development.