Mycelial growth in this study was far slower than the finding of Tan (1981) and Dahmardeh et al. (2010) that the spawn running took three weeks and fruiting bodies appeared after 2–3 days. The slower spawn running on cotton seed hull substrate may be due to the high nitrogen, which is known to inhibit mushroom growth in excessive amounts (Table 1). Narain et al. (2008) reported that mushroom mycelia growth and primordial development is dependent on the lignocellulosic materials especially the C:N ratio. Yang (2000) suggested that the C/N ratio favored the primordial formation about 22–30:1, higher C/N ratio favored the mycelial growth, and lower C/N ratio favored the fruiting bodies growth.