Detailed optical metallographic studies at room temperature on polycrystalline Gd₅Ge₄ are presented for two cases: (a) a sample in the as-cast condition and (b) the same sample subjected to a known number of temperature and magnetic field cycles. A herringbone- (criss-cross-) like pattern whose characteristic feature size extends to ≈20 µm is observed in the as-cast sample. The herringbone pattern at room temperature is interpreted as arising due to a long-lived (kinetically arrested) metastable phase. This herringbone pattern can be trained to form a pattern having a different morphology by cycling the sample through the low-temperature field induced magneto-structural transition. Training effects are also observed in magneto-transport and magnetization measurements as the sample is subjected to temperature and field cycles. Based on heuristic arguments, a model is proposed which self-consistently explains anomalies in transport and magnetization properties in terms of changes occurring in the microstructure of the sample. These results highlight the need for analysing the interesting properties of Gd₅Ge₄ and its family of alloys with microstructure as an important component.