We described a freshwater filamentous zygnematacean species, Zygnema cruciatum (Vaucher) Agardh in Korea,based on light microscopy and scanning electron microscopy. Zygnema cruciatum is characterized by unbranched fil-amcnts of short cylindrical cells, two stellate chloroplasts per cell, a pyrenoid in each chloroplast. Cells are 32-39 $mu$m in width and 35-50 $mu$m in length, Conjugation is scalariform and female gametangia are cylindrical or slightlyenlarged. Zygospores are yellow-brown, spherical or broadly ovoid, 35-44 $mu$m wide and 40-47 $mu$m long. Under SEM, wall of zygospore has pitted mesospore and pits are 1.4-1.8 $mu$m in diameter and 3-4 $mu$m apart from each other.